THE INFLUENCE OF MINERALOGY, CHEMISTRY AND PHYSICAL

ENGINEERING PROPERTIES ON SHEAR STRENGTH PARAMETERS OF

THE GOATHILL ROCK PILE MATERIAL,

QUESTA MOLYBDENUM MINE, NEW MEXICO

by

Luiza Aline Fernandes Gutierrez

Submitted in partial fulfillment of the requirements for the Degree of Master of Science in Mineral Engineering

with Specialization in Geotechnical Engineering

New Mexico Institute of Mining and Technology Department of Mineral Engineering

Socorro, New Mexico March, 2006

ABSTRACT

This thesis develops information regarding the engineering characteristics (direct

shear, Atterburg Limits, particle size) of the Goathill North (GHN) rock pile material at

the Questa molybdenum mine in New Mexico and examines correlations with chemistry,

mineralogy, particle size distribution and weathering indexes (SWI – simple weathering

index, WPI – weathering potential index, MI – Muira index). Results of peak internal

friction angle () ranged from 40º to 47º and residual friction angle varied between 37º

and 41º. These high values of peak internal and residual friction angle are attributed to

grain shape (subangular to very angular) and relative density of the test specimens.

Correlations of from GHN samples with chemistry and mineralogy are shown to be

weak or absent. Correlation of with lithology was not observed. Negative correlations

were observed for %Fines, liquid limit, plasticity index, LOI (lost of ignition), SWI, WPI,

and MI. The decreased as these parameters increased.

Direct shear tests were performed using a 2-inch square shear box and air-dried

samples with a maximum particle size of 3.36 mm (U.S standard sieve No. 6). A

displacement rate of 0.5 mm/min (0.02 in/min), and normal stress varying from 159 to

800 kPa (23 to 116 psi) were adopted for all the tests. These tests were conducted on

disturbed samples. The values determined from these tests should not be used for slope

stability considerations.

GHN rock pile samples were classified according to the United Soil Classification

System (USCS as poorly- to well-graded gravel with fines and sand). The percent of fines

(silt + clay size) and percent of clay varied from 3 to 19 and 0.3 to 6, respectively. Most

of the fines were identified as CL-group (inorganic clay with low swell potential).

ACKNOWLEDGEMENTS

Support for this research was provided by the Molycorp Corporation. in the form

of a Research Assistantship, by the WAAIME (The Woman’s Auxiliary to the American

Institute of Mining, Metallurgical, and Petroleum Engineers), and by the New Mexico

Bureau of Geology and Mineral Resources. I gratefully acknowledge this support.

I would like to express my sincere appreciation to Dr. McLemore and Dr.

Aimone-Martin for providing guidance, insight, and support throughout the course of this

research. Appreciation is also extended to Dr. Mojtabai who is on the thesis advisory

committee and who encouraged me to do my thesis research at New Mexico Tech.

I would like to thank many people who provided insight and suggestions on this

research: Dr. Virgil Lueth, Kelly Donahue, Erin Phillips, Fernando Junqueira, Dr.

Fakhimi, Dr. Gundiler, Prof. Ward Wilson, Mike Smith, and other members of the

Molycorp project weathering study. I especially want to thank Rick Lynn, Lynne

Kurilovitch, Farid Sariosseri, Pedro Martin Moreno, Erico Tabosa, Vanessa Viterbo,

Heather Shannon, Claudia Duarte, Alexandre, Igor, Armando and Jario for assistance

with the laboratory testing program. Last but not least, I would like to thank Remke van

Dam for all his support by reviewing my thesis thousand times, and literally going

through this experience with me.

This thesis is dedicated to my parents Marta Gutierrez and Zenon Gutierrez,

my sisters Norma Gutierrez Ventura, Kelly Gutierrez Alves, Adela Gutierrez Branco, and

to my lovely husband.

i

TABLE OF CONTENT

List of Tables………………………………………………………………...…………...iv

List of Figures…………………………………………………………………...………...v

1. INTRODUCTION ...................................................................................................... 1

1.1. Background ......................................................................................................... 1

1.2. Thesis Objective.................................................................................................. 2

1.3. Site Description ................................................................................................... 3

1.4. Thesis Outline ..................................................................................................... 8

2. REVIEW OF STUDIES AT GOATHILL NORTH ROCK PILE .............................. 9

2.1. Past Geotechnical Studies (Before Regrading) ................................................... 9

2.2. Present Work and Preliminary Results ............................................................. 14

3. LITERATURE REVIEW OF CONCEPTS RELATED TO THIS RESEARCH .... 20

3.1. Strength of Granular Materials ......................................................................... 20

3.2. Weathering Process ........................................................................................... 27

3.3. Effect of Weathering on Geotechnical Properties of Mine Rock ..................... 30

3.4. Published Grain Size distribution and Shear Strength Parameters for Mine Rock

........................................................................................................................... 34

4. METHODOLOGY ................................................................................................... 38

4.1. Sampling ........................................................................................................... 38

4.2. Particle Size Analysis ....................................................................................... 39

4.3. Direct Shear Test Under Consolidated Drained Conditions ............................. 44

4.3.1. Initial Test ................................................................................................. 47

4.4. Index Properties and Mineralogy ...................................................................... 54

5. RESULTS AND DISCUSSIONS ............................................................................. 55

ii

5.1. Indices Testing .................................................................................................. 55

5.2. Direct Shear Test Results .................................................................................. 59

5.3. Verification of Direct Shear Test Results ......................................................... 61

5.4. Correlations of Direct Shear Results with Geological and Geotechnical

Parameters ..................................................................................................................... 64

5.5. Correlations of Direct Shear Test Results with Weathering Indices ................ 73

6. CONCLUSIONS AND RECOMENDATIONS ................................................... 7978

REFERENCES ............................................................................................................. 8180

APPENDIX A – SAMPLE LOCATION ...................................................................... 8685

APPENDIX B – GRAIN SIZE DISTRIBUTION CURVES AND SUMMARY TABLE .. ............................................................................................................................... 8887

APPENDIX C – DIRECT SHEAR STRESS-STRAIN DIAGRAMS ..................... 118117

APPENDIX D – MOHR COULOMB DIAGRAMS................................................ 156154

APPENDIX E – DESCRIPTION OF GEOLOGIC UNITS, SUMMARY OF GEOLOGICAL AND GEOTECHNICAL DATA USED FOR CORRELATIONS 176174

APPENDIX F – STANDARD OPERATING PROCEDURES ............................... 186184

LIST OF TABLES

iii

Table 2.1. Summary of geotechnical properties at GHN rock pile ................................... 10

Table 2.2. Summary of friction angle of Molycorp mine rock piles and “weak zone” at GHN and their gradation results. ...................................................................................... 10

Table 3.1. Weathering field survey used to characterize the weathering sequence in the gneiss................................................................................................................................. 32

Table 3.2. Main engineering-geological features of weathered horizons near Acri (after Calcaterra et al., 1998). ..................................................................................................... 32

Table 3.3. Shear strength parameters of sedimentary residual soil with weathering grades varying from III to V. ........................................................................................................ 34

Table 3.4. Grain size distribution of rock piles around the world. ................................... 35

Table 3.5. Summary of mine rock values of friction angle and cohesion. ....................... 37

Table 4.1. The minimum specimen size required for particle size analysis according to the diameter of the largest particle (U.S. Army Corps of Engineers, 1970). .................... 41

Table 4.2. Summary of results of the 3 methods for particle size analyses. ..................... 43

Table 4.3. Summary of the results from direct shear tests using different maximum particle size and shear box size. ........................................................................................ 50

Table 4.4. Summary of the results from direct shear test using different maximum particle size. ................................................................................................................................... 52

Table 4.5. Summary of direct shear test results for samples at dry and moist state. ........ 52

Table 5.1. Summary of particle size analysis of samples from GHN by geologic unit. ... 56

Table 5.2. Summary of Atterberg limits results of samples from GHN by geologic unit. 57

Table 5.3. Summary of moisture content and paste pH results of samples from GHN by geologic units. ................................................................................................................... 57

Table 5.4. Summary of direct shear test results of samples from GHN by geologic units............................................................................................................................................ 60

iv

LIST OF FIGURES

Figure 1.1. Location of Molycorp Questa mine, northern Taos County, New Mexico. ..... 4

Figure 1.2. Aerial photo of Questa mine showing the nine rock piles adjacent to the open pit. ....................................................................................................................................... 4

Figure 1.3. Goathill North rock pile before regrading. ....................................................... 6

Figure 1.4. One of the trenches (LFG-004) excavated on stable portion of Goathill North rock pile during the regrading. ............................................................................................ 6

Figure 2.1. Friction angle of GHN mine rock based on triaxial test results ..................... 12

Figure 2.2. Grain size distributions from triaxial samples from Sugar Shack rock piles and typical Goathill North mine rock. .............................................................................. 13

Figure 2.3. Friction angle versus confining stress. ........................................................... 14

Figure 2.4. Example of a geologic map. ........................................................................... 15

Figure 2.5. Geologic cross section of bench 9, trench LFG-006. ..................................... 15

Figure 2.6. Plot of QSP hydrothermal alteration intensity. ............................................... 17

Figure 2.7. Plot of authigenic gypsum across bench 9, trench LFG-006. ......................... 18

Figure 2.8. Results of paste pH and NAG pH across bench 9, trench LFG-006. ............. 18

Figure 3.1. Examples of sphericity and roundness charts. ................................................ 23

Figure 3.2. The effect of particle shape on internal friction angle for sand. ..................... 24

Figure 3.3. Correlations between the effective friction angle and relative density for different soil type. ............................................................................................................. 25

Figure 3.4. Variation of peak internal friction angle with effective normal stress for direct shear tests on standard Ottawa sand.................................................................................. 26

Figure 3.5. Physical break up of a boulder by transformation of anhydrite to gypsum minerals at Questa mine site. ............................................................................................ 29

Figure 3.6. Evidence of chemical weathering process (oxidation) at Questa mine site. .. 30

v

Figure 3.7. Correlation of weathering grade with dry density and porosity. .................... 33

Figure 4.1. Generalized geologic cross section of GHN showing the location of the samples analyzed in this thesis. ........................................................................................ 39

Figure 4.2. Comparison of three different approaches for estimation of particle size distribution using sample GHN-LFG-0003. ..................................................................... 43

Figure 4.3. Manually direct shear equipment. .................................................................. 46

Figure 4.4. Example of a shear stress versus shear strain plot.. ........................................ 47

Figure 4.5. Example of a shear diagram showing the best fit line for the peak internal friction angle and the residual internal friction angle. ...................................................... 47

Figure 4.6. Shear box size effects on direct shear test. ..................................................... 49

Figure 4.7. Results of effect of particle size on direct shear test using a 2-inch shear box............................................................................................................................................ 51

Figure 4.8. Results of influence of moisture on direct shear test. ..................................... 53

Figure 5.1. Range of grain size distribution for samples from GHN rock pile. ................ 58

Figure 5.2. Distribution of the samples from GHN rock pile on the plasticity chart........ 58

Figure 5.3. Direct shear test results for a dry sample versus a sample with gravimetric moisture content of 12.4%. ............................................................................................... 61

Figure 5.4. Mohr-Coulomb diagram for sample GHN-KMD-0014 using two direct shear test equipments. ................................................................................................................. 62

Figure 5.5. Mohr-Coulomb diagram for sample GHN-KMD-0017 using two direct shear test equipments. ................................................................................................................. 63

Figure 5.6. Mohr-Coulomb diagram for sample GHN-KMD-0027 using two direct shear test equipments. ................................................................................................................. 64

Figure 5.7. Stratigraphic position of the geologic units for bench 9 (Trench LFG-006). . 65

Figure 5.8. Cross plots of internal friction angle versus paste pH.. .................................. 65

Figure 5.9. Cross plots of internal friction angle versus NAGpH .................................... 65

Figure 5.10. Cross plots of internal friction angle versus percent of fines.. ..................... 66

Figure 5.11. Cross plots of internal friction angle versus plasticity index.. ..................... 66

Figure 5.12. Cross plots of internal friction angle versus liquid limit.. ............................ 67

vi

Figure 5.13. Cross plots of internal friction angle versus percent Amalia Tuff.. ............. 67

Figure 5.14. Cross plots of internal friction angle versus percent Andesite.. ................... 68

Figure 5.15. Cross plots of internal friction angle versus quartz-sericite-pyrite (QSP) alteration.. ......................................................................................................................... 69

Figure 5.16. Cross plots of internal friction angle versus propylitic alteration. ............... 69

Figure 5.17. Cross plots of internal friction angle versus LOI (lost of ignition). ............. 70

Figure 5.18. Cross plots of internal friction angle versus percent epidote. ...................... 70

Figure 5.19. Cross plots of internal friction angle versus percent illite...... ...................... 71

Figure 5.20. Cross plots of internal friction angle versus percent MgO.. ......................... 71

Figure 5.21. Cross plots of internal friction angle versus percent CaO. ........................... 72

Figure 5.22. Cross plots of internal friction angle versus percent Al2O3. ......................... 72

Figure 5.23. Plot of WPI and MI with distance across bench 9, trench LFG-006. ........... 75

Figure 5.24. Plot of WPI and MI for all GHN samples. ............................................... 7675

Figure 5.25. Cross plot of Friction angle versus simple weathering index (SWI) for bench 9 samples, trench LFG-006. .............................................................................................. 76

Figure 5.26. Cross plot of Friction angle versus weathering potential index (WPI) for samples from bench 9, trench LFG-006. .......................................................................... 77

Figure 5.27. Cross plots of Friction angle versus Miura Index (MI) for samples from bench 9, trench LFG-006. ................................................................................................. 77

This thesis is accepted on behalf of the Faculty of the Institute by the following committee:

_________________________________________________________ Research Advisor

__________________________________________________________ Academic Advisor

__________________________________________________________ Committee Member

___________________________________________________________ Date

I release this document to the New Mexico Institute of Mining and Technology.

_____________________________________________________________ Student's Signature Date

1

1. INTRODUCTION

1.1. Background

This thesis develops information regarding the engineering characteristics of

Goathill North rock pile material at the Questa molybdenum mine in New Mexico and

examines correlations of internal friction angle with mineralogy, chemistry and

weathering indexes. Molycorp Inc. is funding a multidisciplinary study to investigate the

potential effects of chemical and physical weathering on the slope stability of Goathill

North rock pile, one of the nine rock piles at the mine. The project is a unique

opportunity to sample and study the internal material of this rock pile. The ultimate goal

of the study is to assess the risk of mass failure of the mine rock pile over at least 100

years. Another way to state this goal simply is to ask: Will the mine rock piles become

gravitationally unstable with time due to weathering? The weathering aspects of the rock

pile and stability analyses are being studied by other members of the team to the same

end. This thesis research will complement the weathering studies by examining the shear

strength using a direct shear apparatus with a 2-inch shear box.

Rock piles are disposal facilities for overburden (also termed “mine rock”).

Overburden or mine rock is the barren or uneconomic mineralized rock that must be

removed in order to mine the mineral resource. Surface mine operations create rock piles

that by weight, volume, or height represent some of the largest structures built by man.

Compared with other engineered structures, little or no characterization of the material

has been performed before, during, or especially after construction of the rock piles

(Robertson, 1982). Since the 1980s, environmental regulations forced mine operators to

2

consider the design of rock piles and in some cases enforced requirements for maximum

slope angles, factors of safety for slope stability, and site reclamation. These

considerations have led to the need for information on the strength characteristics of the

materials that comprise rock piles. Unfortunately, little detailed information has been

published on this topic. Thus, a secondary goal of this thesis is to add to the base of

knowledge in this area.

1.2. Thesis Objective

The purpose of this work is to interpret data on the engineering characteristics of

the Goathill North (GHN) rock pile at the Molycorp Questa Molybdenum mine, and to

examine correlations of internal friction angle with mineralogy, chemistry and

weathering indexes. The key elements of this research are to:

Investigate the variation of shear strength within the GHN rock pile by

performing a series of direct shear tests.

Investigate the variation of Geotechnical index properties within the GHN rock

pile by performing particle size analyses and by measuring Atterberg limits,

specific gravity, and moisture content.

Investigate the effect of gradation, chemistry, and mineralogy on shear strength

by correlating mineralogy, chemistry, and the data from particle size analyses

with friction angle.

3

1.3. Site Description

The Questa molybdenum mine (Figure 1.1), owned and operated by Molycorp,

Inc., is located 5.6 km (3.5 mi) east of the Village of Questa, in Taos County, northern

New Mexico, in the western portion of the Taos Range of the Sangre de Cristo

Mountains. The mine site is located in an area of high relief with elevations varying from

2,310 to 3,295 m (7,580 to 10,812 ft) in an area of about 15.54 km2 (6 mi2). The main

headframe of the mine is located on the south-facing slopes of the Red River Valley at

approximately 2,438 m (8000 ft) above sea level.

The Questa molybdenum mine has been in operation, though not continuously,

since 1918, during which time several mining methods have been used to extract

molybdenite (“moly” - MoS2) from this “Climax-type” porphyry molybdenum deposit.

Initially, the mine was a small underground working, with donkey-hauled ore cars

delivering ore to the surface that was broken up by workers. Later, from 1965 to 1982,

large-scale open pit mining methods were used to extract the ore. Currently the mine

operates underground using block caving mining methods.

During the open-pit period of mining, approximately 320 million tons of

overburden rock overlying and surrounding the ore body were excavated and deposited in

steep valleys adjacent to the open pit (URS Corporation, 2000). The resulting nine rock

piles are shown in Figure 1.2. In general, the mine rock piles are at the angle of repose

(35º to 40º) and have long slope lengths (up to 600.5 m or 1970 ft) and comparatively

shallow depths (~30-60 m or ~98-196 ft) (Shaw et al., 2002).

4

Figure 1.1. This image shows the location map of Molycorp’s Questa molybdenum mine, which is in northern Taos County, New Mexico.

Figure 1.2. This image shows an aerial photo of Questa mine showing the nine rock piles adjacent to the open pit.

Goathill North & Goathill South Rock Piles

Sulphur Gulch Rock Pile

5

The GHN rock pile is one of the nine rock piles created during open-pit mining.

Before reclamation GHN contained approximately 4.2 million m3 (5.5 million yds3) of

overburden material with slopes similar to the original topography (Norwest Corporation,

2004).

Studies by Norwest Corporation (2003) revealed that the GHN rock pile was

constructed in an area characterized by hydrothermal alteration scars. These

hydrothermal alteration scars are natural, colorful (red to yellow to orange to brown),

relatively unstable landforms that are characterized by steep slopes (greater than 25

degrees), moderate to high pyrite content (typically greater than 1 percent), little or no

vegetation, and extensively fractured bedrock (McLemore et al., 2004; Meyer and

Leonardson, 1990). The toe of the GHN rock pile is founded on a colluvium bench

underlain by pre-sheared material. Foundation movements associated with the initial

development of the slide occurred between 1969 and 1973 (Norwest Corporation, 2003;

Norwest Corporation, 2004), and continued to occur for more than 30 years untilthe

initial reclamation of that pile was completed in 2005.

GHN rock pile can be divided into two areas - a stable area and an unstable area,

as shown in Figure 1.3. In 2004-2005, Molycorp stabilized this rock pile by removing

material off the top portion of both areas to the bottom of the pile (Norwest Corporation,

2003). This regrading decreased the slope, reduced the load, and created a buttress.

During the progressive down-cutting (regrading) of the top of GHN, trenches were

constructed to examine, map, and sample the undisturbed internal geology of the rock

pile as shown in Figure 1.4. Samples collected from these trenches form the basis for this

thesis.

6

Figure 1.3. This image shows Goathill North rock pile before re-grading, looking east. Solid line indicates approximate location of trenches completed in summer-fall 2004; dashed line indicates the boundary between the stable and unstable portions of the rock pile (after McLemore et al., 2006).

Figure 1.4. This image shows one of the trenches (LFG-003) excavated on the stable portion of the Goathill North rock pile during the re-grading.

7

The geology at the Questa mine includes four main lithologies, all of which are

hydorthermally altered to varying degrees: andesite porphyry, aplite porphyry, andesite

to quartz latite porphyry flows, and rhyolite tuff (Amalia Tuff). Most of the mined rock-

pile material consists of andesite, rhyolite tuff and porphyritic aplite. Several studies of

the Questa mine have used the term ‘mixed volcanics’ to describe the lithology of the

rock piles. These ‘mixed volcanics’ consist of andesite, latite, quartz latite, and

volcaniclastic rocks all of which have been subjected to varying amounts of hydrothermal

alteration (Shaw et al., 2002).

The climate at the mine is semi-arid with mild summers and cold winters(Wels et

al., 2002). The long-term average annual precipitation at the mill site (located at the base

of the mine site) is approximately 401 millimeters (15.8 in). Temperatures vary greatly

both annually and diurnally. The average daily maximum temperatures range from 2.7º to

25º C (37º to 77º F) with average daily minimum temperatures ranging from -14.4º to 5º

C (6º to 41º F). During five months of the year (November through March) the average

monthly temperature is below freezing (Robertson GeoConsultants Inc., 2000). Hot days

and cool nights characterize summer. The rainy season is during July and August. Heavy

localized rainfalls during July and August often cause flash floods and mudflows, which

sometimes block the highway between the Village of Questa and the Town of Red River

(Molycorp Inc., 2002).

8

1.4. Thesis Outline

Chapter 2 contains a critical literature review of past and present studies on the

Goathill North rock pile. Chapter 3 discusses the factors that influence strength of a

granular soil, such as those found in the GHN rock pile. Chapter 4 presents the

methodology used in this thesis. Chapter 5 presents both the results of the physical

measurements and a discussion of those results. Chapter 6 contains conclusions and

recommendations. Appendices and references are located at the end of this thesis.

9

2. REVIEW OF STUDIES AT GOATHILL NORTH ROCK PILE

Past Geotechnical Studies (Before Re-grading)Past evaluations of the

geotechnical properties of the GHN rock pile were completed by several consulting

companies hired by Molycorp, Inc. These projects included stability evaluations and the

development of closeout and mitigation plans. The characterization of geotechnical

properties included laboratory tests of particle size distribution, Atterberg limits, dry unit

weight, specific gravity, moisture content, and shear strength. Samples were collected

from the surface in test pits or from deeper in the pile from drill holes. Drill hole depths

range from 9 to 70.4 m (30 to 231 ft). Drill hole logs indicated four different units, listed

in descending order as follows (Norwest Corporation, 2004):

Mine rock

Colluvium (and “weak zone”)

Weathered bedrock

Bedrock

Laboratory results from different projects are summarized in Table 2.1 and Table

2.2. Although the laboratory results included all four units, this thesis research examined

only the mine rock (first unit). Therefore, this document will be focused on describing the

mine rock.

The previous studies’ particle size analyses indicate that the GHN rock pile has a

wide variation in gradation ranging from cobble-sized material to silty sands and clayey

sands. The mine rock is mostly sandy gravel with less than 20% fines, clay contents less

10

than 12%, and plasticity indexes (PI) less than 10%. Dry unit weights of 21 mine rock

samples indicate an average of 1.82 g/cm3 (113.3 pcf) with standard deviation of 0.13

g/cm3 (8 pcf) (Norwest Corporation, 2004). The specific gravity of the mine rock based

on 15 samples ranges from 2.66 to 2.80 g/cm3 (166 to 175 pcf) (Norwest Corporation,

2004; URS Corporation, 2003).

Table 2.1. Summary of geotechnical properties at GHN rock pile

% Gravel %Sand %Fines % ClayLiquid limit

(%)Plasticity

index

Norwest Corporation, 2004

mine rock

55.1 (Ave.) 19.2

(STDEV) 42

(#samples)

33.9 (Ave.) 13.9

(SDTEV) 42

(#samples)

11.1 (Ave.)

6.6 (SDTEV)

42 (#samples)

5.6 (Ave.)

2.5 (SDTEV)

17 (#samples)

27.7 (Ave.)

3.6 (SDTEV)

36 (#samples)

9.5 (Ave.)

3.4 (SDTEV)

36 (#samples)

6.7 (Ave.)

3.9 (SDTEV)

42 (#samples)

sandy gravel with cobbles

Norwest Corporation, 2004

colluvium - -

24.1 (Ave.) 10.7

(SDTEV) 91

(#samples)

8.5 (Ave.)

4.8 (SDTEV)

50 (#samples)

11.2 (Ave.)

3.6 (SDTEV)

84 (#samples)

- -

Norwest Corporation, 2004

"weak zone" of the colluvium

- -

36-65 (range)

7 (#samples)

11-34 (range)

7 (#samples)

14-25.3 (range)

7 (#samples)

- -

URS Corporation, 2003

mine rock

35-54 (range)

28 (#samples)

36-49 (range)

28 (#samples)

6-28 (range)

28 (#samples)

2.1 -12.8 (range)

28 (#samples)

24-37 (range)

28 (#samples)

4-18 (range)

28 (#samples)

2.6-13.1 (range)

28 (#samples)

sandy and clayey gravel with cobbles

URS Corporation, 2003

bedrock (highly

altered/weathered andesite)

- -

30-49 (range)

4 (#samples)

30-36 (range)

4 (#samples)

12-21 (range)

4 (#samples)

11.4-12 (range)

4 (#samples)

-

Robertson GeoConsultants Inc., 2000

drill hole mine rock59

( 1 sample)19

(1 sample)5

(1 sample)2

(1 sample)28

(1 sample)12

(1 sample)2.7

(1 sample)sample (GT-18)

CommentsSample description

Particle size distribution Atterberg limitsNatural

Moisture Content, w

(%)

split tube drill

test pits

ReferenceSampling method

Table 2.2. Summary of friction angles of Molycorp mine rock piles and the “weak zone” at GHN and their gradation results.

11

Reference Sample location % Fines

(-0.75mm)%Clay

(-0.002mm)Plasticity

index

Friction angle

(degrees)Cohesion Test Comments

SSW-3 Sugar Shack

West rock pile18.8 6.6 8 -

Consolidated undrained triaxial test

SSM-6 Sugar Shack

Middle rock pile29.1 7.7 11 -

Consolidated undrained triaxial test

Mine rock/ Robertson GeoConsultants Inc., 2000

GT-18 GHN rock pile

5 2 12 31 561psf direct shear test

Shear box size= 2.4" diameter Test conditions=saturated # of tests considered = 3 different normal load

TH-GH-04S 60.0-61.0'

36 11 16.6 39.8 0.0 direct shear test

Sample size= 2.41" diameter Test conditions= saturated # of tests considered = 3 different normal load

TH-GH-04S 69.0-71.0'

65 34 25.3 22.3 0.0 direct shear test

Sample size= 2.41" diameter Test conditions= saturated # of tests considered = 3 different normal load

TH-GH-02S 137.5-138.5'

49 21 18.5 19.7 - direct shear test # of tests considered = 3 different normal load

TH-GH-02S 141.0-141.8'

44 18 15.6 30.0 - direct shear test # of tests considered = 1 normal load

TH-GH-10S 44.7-45.5'

39 20 24.8 27.0 - direct shear test # of tests considered = 1 normal load

TH-GH-14S 90.5-91.0'

39 15 18.2 25.0 - direct shear test # of tests considered = 2 different normal load

TH-GH-14S 94.2-95.0'

40 14 14 29.5 - direct shear test # of tests considered = 2 different normal load

Weak Zone/ Norwest Inc.,

2004

Mine rock / Norwest Inc.,

2004 and URS

Corporation Inc., 2003

Norwest suggested friction angle of GHN rock pile is the same as the average friction angle of this two samples from Sugar Shack rock piles at Questa. The tests were

performed by URS Corporation Inc., 2003.

36 average

Robertson GeoConsultants (RGC) Inc. (2000) performed a series of fourteen 12-

inch saturated direct shear tests on Questa rock pile material including one mine rock

sample from the GHN rock pile. Their results showed a range of friction angles and

cohesion from 41º to 47º and 9.6 to 96 kPa (200 to 2000 psf). Results from a 2.4-inch

saturated direct shear test on a mine rock sample from the GHN rock pile showed an

average friction angle of 31º and cohesion of 26.9 kPa (561 psf) (Robertson

GeoConsultants Inc., 2000).

Robertson GeoConsultants Inc. (2000) reported that all direct shear tests exhibited

evidence of strain hardening. The effect of strain hardening is that shear strength

12

continues to increase at very large strains under the conditions of the test and no sudden

reduction in shear strength as strain occurs (Robertson GeoConsultants Inc., 2000).

A study performed by Norwest Corporation in 2004 on GHN concluded that the

friction angle of the mine rock is an average of two triaxial test results performed on

samples from the Sugar Shack rock piles at Questa mine (Norwest Corporation, 2004).

The Mohr Coulomb diagram combined for the two samples gives a friction angle of 36º

as is shown in Figure 2.1. The assumption was justified by the similarity in particle size

distribution of these samples with the particle size distribution of the mine rock from

GHN as can be seen in Figure 2.2. The testing was conducted over a confining stress

range up to about 2,750 kPa (57,435 psf). The results show that the friction angle

decreases somewhat with confining stress from about 40º at low stresses to 35º at 2,750

kPa or 57,435 psf as shown in Figure 2.3.

Figure 2.1. This graph shows the friction angle of GHN mine rock based on triaxial test results for samples from Sugar Shack rock piles that have gradations lying towards the finer range of materials sampled at GHN rock pile (from Norwest Corporation, 2004).

13

Figure 2.2. This graph shows the grain size distributions from triaxial samples from Sugar Shack rock piles and typical Goathill North mine rock (from Norwest Corporation, 2004).

14

Figure 2.3. This graph shows friction angle versus confining stress showing a decrease in friction angle as confining stress increases (from Norwest Corporation, 2004).

2.1. Present Work and Preliminary Results

The present work on the GHN rock pile is being performed by a multidisciplinary

group of engineers and scientists with the following main objectives:

1. Understanding weathering processes, both at the surface and within the

mine rock pile which could affect the geotechnical properties of the pile.

2. Measuring the rate at which such weathering processes occur over time.

3. Determining the effect of these processes on the geotechnical properties of

the pile (e.g., grain size, grain shape and textures, cementation, shear

strength, moisture content) for further long-term stability analyses. (This

thesis research is complementing this work by providing initial

geotechnical data).

During the regrading of the GHN rock pile, several trenches were excavated into

the interior of the pile. For every trench, geologic maps and logs of each bench were

created to describe the different subsurface mine rock units. Subsurface units were

defined based on grain size, color, texture, stratigraphic position, and other physical

properties that could be determined in the field. Examples of a geologic map and the

subsurface units for trench LFG-009 are shown in Figures 2.4 and 2.5, respectively. Units

were correlated between benches and on each side of a trench, and several units were

correlated downward through the series of five successively excavated trenches. A

detailed description of each unit for all the trenches is presented in McLemore et al.

(2006) and in Appendix E.

15

Figure 2.4. This figure shows an example of a geologic map like those created for each trench at GHN rock pile. Geologic map of trench LFG-009 (from McLemore et al., 2005).

Figure 2.5. This figure shows a geologic cross section of bench 9, trench LFG-006 showing the identified subsurface units. See Appendix E for description of the subsurface units.

Field and laboratory analyses reveal that the GHN rock pile consists primarily of

hydrothermally altered andesite and Amalia Tuff (McLemore et al., 2005). The andesite

and Amalia Tuff rock fragments are comprised primarily of quartz and feldspar.

However, andesite contains less quartz and more plagioclase than the rhyolitic Amalia

16

Tuff. In addition, Amalia Tuff commonly contains quartz phenocrysts, which are usually

absent in the andesite. The andesite and Amalia Tuff have been subjected to variable

intensities of hydrothermal alteration as well as weathering. Hydrothermal alteration is

the change in original composition of the rock in place by hydrothermal (warm to hot

aqueous) solutions associated with mineralization and associated ore-forming events such

as granitic intrusions. Hydrothermal alteration is a pre-mining condition and includes

both hypogene (primary) and supergene (secondary) processes. Hypogene alteration

occurred during ore-formation. Supergene alteration, a type of weathering, occurred at

low temperatures near Earth’s surface after the formation of the ore deposit, but before

mining commenced. The major hypogene alteration types at GHN include quartz-sericite-

pyrite (QSP), propyllitic, argillic, and potassic alteration (Carpenter, 1968). Weathering

can be defined as the process of rock and mineral alteration to more stable forms under

the variable conditions of moisture, temperature, and biological activity that prevail at the

surface (Birkeland, 1999). Most rocks and minerals exposed at and immediately beneath

the earth’s surface are in an environment quite unlike that under which they are formed

(Birkeland, 1999).

Preliminary results of petrographic analysis of samples from bench 9, trench

LFG-006, show that both hydrothermal alteration of fragments within the pile varies

according to the predominant lithology (rhyolite typically shows more QSP alteration

than andesite) and that weathering increases from the interior of the pile to the edge of the

pile, as shown in the Figures 2.6 and 2.7. The QSP alteration intensity was defined by the

percentage of hydrothermal alteration minerals (quartz, sericite, pyrite))that have

replaced primary minerals and ground mass. A major indicator of weathering is the

17

abundance of authigenic gypsum crystals, which indicates that some weathering of

sulfide minerals (essentially all pyrite) and calcite occurred after emplacement of the rock

pile (Campbell et al., 2005).

Results from paste pH and net acid generation (NAG pH) show a range from 2.1

to 10. Paste pH and NAG pH typically increase with distance from the outer, oxidized

zone (west) towards the interior, unoxidized zone (east) of the GHN rock pile as shown in

Figure 2.8 (Tachie-Menson, 2006). These results can be attributed to a number of factors,

including (1) the different lithologies of the stratigraphic units that comprise the rock pile,

(2) the amount of weathering and leaching that had occurred before the material was

mined and dumped (deposited) onto the pile, and (3) the differences among variables,

such as oxygen concentration, moisture content, and presence of bacteria, that influence

weathering of the rock pile both at the surface and within the pile (Tachie-Menson,

2006).

Figure 2.6. This graph shows a plot of QSP hydrothermal alteration intensity (defined by the percentage of hydrothermal alteration minerals that have replaced primary minerals) across bench 9, trench LFG-006 (from McLemore et al., 2005). Refer to Figure 2.5. for geologic units.

18

Figure 2.7. This graph shows a plot of authigenic gypsum across bench 9, trench LFG-006 (from McLemore et al., 2005). Refer to Figure 2.5. for geologic units.

Bench 9, LFG-006

0

2

4

6

8

10

12

0 20 40 60 80 100Distance from 9NW (ft)

pH

Paste pH

NAG pH

Figure 2.8. This graph shows the results of paste pH and NAG pH across bench 9, trench LFG-006 (after Tachie-Menson, 2005).

19

A post-mining weathering index for the rock pile is currently being developed. A

weathering index is a measure of how much the sample has weathered. McLemore (2005)

described a simple, descriptive weathering index (SWI) that is based upon field

observations (color, grain size, mineral texture, and the presence or absence of certain

minerals indicative of weathering) for the purpose of identifying the relative intensity of

weathering of samples collected for the project. Other weathering indexes found in the

literature are being evaluated as well. Most weathering indexes are based on geochemical

parameters that restrict their applications to the type of environment that they were

developed for.

20

3. LITERATURE REVIEW OF CONCEPTS RELATED TO THIS RESEARCH

3.1. Strength of Granular Materials

A granular soil is composed of particles larger than approximately 0.075 mm or

No. 200 standard U.S. sieve size. Typically it is assumed that these soils do not exhibit

significant effective cohesion (resulting from electrostatic particle attractions) and are

free-draining (water not bound inside particle structure), with low retention of water

between particles. Coarse granular soil is composed of at least 50 percent by weight of

gravel (1/4-inch diameter) or larger particles (Holtz and Kovacs, 2003; Quine, 1993). The

shear strength of a granular soil can be defined by equation 3.1,

tan c (3.1)

where c is cohesion (in kPa, MPa or psf), is total stress ( in kPa, MPa or psf), and is

the internal angle of friction of the soil (in degrees) (Das, 1983). This equation is

generally referred to as the Mohr-Coulomb failure criteria. For saturated soils, the stress

carried by the soil solids is the effective stress and equation 3.1 is modified to equation

3.2:

tan''tan)( cuc (3.2)

21

where u is the pore water pressure, c’ is the effective cohesion, and ’ is the effective

stress on the failure plane at the failure. Since it is assumed that granular material does

not present any effective cohesion, equation 3.2 is generally simplified to equation 3.3 in

many references (Das, 1983; Holtz and Kovacs, 2003; Terzaghi et al., 1996).

tan' (3.3)

Therefore, the shear strength of granular soil is frequently characterized by its

internal friction angle (). The internal friction angle is a function of the following

characteristics (Hawley, 2001; Holtz and Kovacs, 2003):

Particle size (friction angle increases with increase in particle size)

Grain quality (weak rock such as shale verses strong rock such as granite)

Particle shape and roughness of grain surface (friction angle increases with

increasing angularity and surface roughness)

Grain size distribution (well graded soil has a higher friction angle than a

poorly graded soil)

State of compaction or packing (friction angle increases with increasing

density or decreasing void ratio)

Applied stress level (decreasing with increasing stress, resulting in a

curved strength envelope passing through the origin)

Various studies have successfully evaluated how the parameters listed above

affect internal friction angle. Findings from these studies are presented in the following

paragraphs.

22

It has been recognized (Holtz, 1960; Holtz and Gibbs, 1956) that an increase in

the proportion of coarse material in an otherwise fine-grained granular soil can result in

an increase in friction angle. Typical values for medium-dense sand can range from 32º

to 38º, while typical values for medium-dense sandy gravel can range from 34º to 48º

(Das, 1983). Triaxial strength testing of large-size (up to 200 mm or 7.87 in) rockfill

particles suggested that rock piles are expected to have internal friction angles in the

range of 40º to 50º, the lower end of the range corresponding to fine-grained material,

and the upper end of the range corresponding to coarse-grained material (Leps, 1970).

Particle size and shape reflects material composition, grain formation and release

from the mineral matrix, transportation, and depositional environments. Chemical action

and physical abrasion increase with weathering and more weathered sands tend to be

rounder regardless of particle size (Cho et al., 2004). Particle shape is characterized by

three dimensionless ratios (Barrett, 1980; Krumbein, 1941): sphericity (eccentricity or

platiness), roundness (angularity), and smoothness (roughness). Sphericity and roundness

can be estimated visually using the comparison charts shown in Figure 3.1. The use of

these charts makes it easier to examine the influence of particle shape on geotechnical

properties (Cho et al., 2004). The relationship between particle shape and friction angle is

presented in Figure 3.2. Open circles are for sand with sphericity > 0.7, and closed circles

are for sand with sphericity < 0.7. The plot shows a negative correlation between internal

friction angle and roundness. As roundness varied from 0.1 (very angular) to 1 (well

rounded), the internal friction angle decreased from 40º to approximately 28º. Particles

with a higher sphericity generally had lower friction angles. Surface roughness will also

have an effect on internal friction angle, although surface roughness is very difficult to

23

measure. Generally, the greater the surface roughness, the greater will be the internal

friction angle (Holtz and Kovacs, 2003).

(a)

(b)

Figure 3.1. This figure shows examples of sphericity and roundness charts (a) from (Cho et al., 2004) and (b) from AGI (American Geological Institute) data sheet 18.1 comparison chart for estimating roundness and sphericity, by Maurice C. Powers, copyright 1982. These charts were used for this project.

24

Figure 3.2. This graph shows the effect of particle shape on internal friction angle for sand ( from Cho et al., 2004). Open circles and closed circles are for sand with sphericity higher than 0.7 and sphericity lower than 0.7, respectively.

The effects of grain size distribution on internal friction angle can be observed on

samples with the same relative density. Figure 3.3 shows the correlation between the

effective friction angle from triaxial compression tests and both relative density and soil

classification. When two sands have the same relative density, the soil that is better

graded (for example, an SW soil as opposed to an SP soil) has a larger (Holtz and

Kovacs, 2003).

25

Figure 3.3. This graph shows the correlations between the effective friction angle and the relative density for different soil types (from Holtz and Kovacs, 2003). ML: Silt, SM: Silty sand, SP: Poorly graded sand, SW: Well-graded sand, GP: Poorly graded gravel, GW: Well-graded gravel.

The influence of void ratio (state of compaction or packing) and of applied stress

level are illustrated in Figure 3.4 (Das, 1983). Figure 3.4 is a plot of the results of direct

shear tests on standard Ottawa Sand. For loose sand (initial void ratio approximately

0.66), the value of decreases from about 30º to less than 27º when the normal stress is

increased from 45 to 766 kPa (0.5 to 8 ton/ft2). Similarly, for dense sand, decreases

from approximately 34.5º to about 30.5º due to an increase in normal stress from 45 to

766 kPa (0.5 to 8 ton/ft2).

26

Figure 3.4. This graph shows the variation of peak internal friction angle with effective normal stress for direct shear tests on standard Ottawa sand (from Das, 1983).

The determination of the internal friction angle () and the effective cohesion (c)

is commonly accomplished by the direct shear test or the triaxial test. The direct shear

test is preferred because of its simplicity and lower cost. The advantages and

disadvantages of direct shear tests are given below.

Advantages of direct shear testing are as follows:

The test is relatively inexpensive and quick to perform.

It requires less sophisticated equipment than other methods and it is easier

to reduce the data and interpret the results.

27

It has been found that soil parameters and c obtained by direct shear

testing are nearly as reliable as triaxial values. Typical values obtained

with the direct shear test are 1 to 2 degrees larger than values obtained

with the triaxial test (Bowles, 1979).

It is good for measuring residual strength values (Quine, 1993).

Disadvantages or limitations of the direct shear test (Holtz and Kovacs, 2003) are

as follows:

Shearing stress is not uniformly distributed across the sample. Initial

failure occurs at the corners and ends of the box, and propagates towards

the center.

The test forces failure to occur along a fixed zone or plane.

There is an uncontrolled rotation of principal planes and stresses that

occurs between the start of the test and failure.

Pore water pressures for fine-grained soils are neither controlled nor

monitored.

3.2. Weathering Process

Weathering is the process of rock and mineral alteration to more stable forms

under the variable conditions of moisture, temperature, and biological activity that prevail

at or near the surface (Birkeland, 1999). Two main types of weathering are recogonized:

physical weathering, in which the original rock disintegrates to smaller-sized material

with no appreciable change in chemical or mineralogical composition, and chemical

28

weathering, in which chemical and/or mineralogical composition of the original rock and

minerals are changed (Clark and Samall, 1982).

The mechanism common to all processes of physical weathering is the

establishment of sufficient stress within the rock so that the rock breaks (Clark and

Samall, 1982). The most common processes associated with physical weathering are

unloading by erosion of overlying material; by expansion of cracks or along grain

boundaries by crystallizing open-space-filling minerals or freezing water; and by thermal

expansion (associated with fire, for example) and contraction of the constituent mineral

(Birkeland, 1999). Physical weathering results in a decrease in grain size, which increases

surface area that in turn leads to greater chemical reactivity and the exposure of fresh

mineral surfaces. As shown in Figure 3.5, the fragments of andesite within the rock piles

at the Questa mine are affected by a physical break up of the rock caused by the volume

change produced by the transformation of anhydrite to gypsum or other crystal growth

along fractures.

29

Figure 3.5. This image shows the progressive physical break up boulders by the transformation of anhydrite to gypsum common at the Questa mine site.

Chemical weathering processes include dissolution, carbonation, hydration,

hydrolysis, oxidation and reduction (Birkeland, 1999; Clark and Samall, 1982; Gerrard,

1988). Evidences of chemical weathering are shown by several field and laboratory

criteria including: (1) change in color due to oxidation of iron-bearing minerals as shown

in Figure 3.6, (2) depletion of original minerals (non-clay and clay), (3) alteration of

original clay minerals or neo-formation of clay minerals, (4) neo-formation of iron or

aluminum oxides and oxyhydroxides, (5) changes in major-element chemistry versus that

of the assumed parent material, (6) the chemistry both of the waters that move through

the soil and that of the streams draining a particular basin (Birkeland, 1999).

30

Figure 3.6. This image shows evidence of chemical weathering process (oxidation of iron ) at Questa mine site.

The rate of weathering is complex; it involves not only particle size, but also

types of material, climate, moisture, exposure conditions, and plant, animal, and

microbial activities. Generally, in an acidic environment, both the rate and the amount of

weathering increases with time due to the reduction of grain size, which allows more

surface area of the material to be exposed to the process (Bowles, 1979).

3.3. Effect of Weathering on Geotechnical Properties of Mine Rock

Few studies exist on the effect of weathering on the geotechnical properties of

material found in mine rock piles. However, natural hillslopes and rockfill dams have

general similarities to rock pile material (Leps, 1970; Quine, 1993; Robertson, 1985;

31

URS Corporation, 2003). Therefore, in this literature review of the effect of weathering

on the geotechnical properties of mine rock, studies on natural hillslope and rockfill

material will be included as well.

Seedsman and Emerson (1985) studied the role of clay-rich rocks in spoil pile

failures at the Goonyella Mine in Australia. They observed a reduction of the friction

angle by 6º to 12º due to chemical weathering and by 2º to 3º caused by the presence of

fines generated by physical weathering. According to Seedsman and Emerson, the

reduction of the friction angle caused by physical weathering does not occur gradually as

the fines fraction (silt + clay) increases but, insteadrelatively suddenly at a fines content

of about 10%. At this fines content, the larger particles in the spoil are no longer in direct

contact with each other but instead tend to be supported in a matrix of silt- and clay-sized

particles.

Calcaterra et al. (1998) studied the weathering processes in crystalline rocks of

the Sila Massif, Calabria, Southern Italy. Weathering grades were identified using a

weathering field survey classification scheme proposed by the Hong-Kong Geotechnical

Control Office. Descriptions of completely to moderately weathered gneissic rocks are

presented in Table 3.1. Laboratory results of geotechnical properties in Table 3.2 showed

that strength, density, specific gravity, and porosity decreased as weathering grade

increased. Specific gravity did not significantly decrease with an increase in weathering

grade. Thuro and Scholz (2003) presented density and porosity results in agreement with

the findings from Calcaterra et al. (1988) shown in Figure 3.7.

32

Table 3.1. This table shows the weathering field survey used to characterize the weathering sequence in the gneiss (after Calcaterra et al., 1998). Weathering grades I, II, and VI were unavailable to survey.

Table 3.2. This table shows the main engineering-geological features of weathered horizons near Acri (after Calcaterra et al., 1998).

Weathering grade

Parent rockSpecific gravity

(kN/m3)

Bulk density

(kN/m3)

Dry density

(kN/m3)

Saturated density

(kN/m3)

Porosity (%)

Point load strength (MPa)

VGranitoids

(soil)26.3-27.6

(7)19.3-20.0

(7)18.3-19.4

(7)21.4-22.2

(7)28.7-32.2

(7)n.d.

VGneiss

(corestones)26.0-26.5

(5)22.1-25.2

(5)21.2-24.4

(5)23.0-25.5

(5)8.2-15.5

(5)0.7-1.1

(4)

IV Gneiss 26.1-26.7

(6)23.1-25.4

(6)22.7-25.2

(6)24.0-25.7

(6)5.0-13.1

(6)0.4-2.9

(6)

III Gneiss26.3-29.9

(5)25.3-28.6

(5)25.2-28.6

(5)25.6-29.0

(5)2.2-4.7

(5)0.5-4.1

(4) The numbers in brackets refer to the number of samples tested, and n.d. = not determined

Weatheringgrade

Parent rock

VGneiss

(corestones)

IV Gneiss

III Gneiss

brownish to reddish-orange coarse-grained soils, retaining original mass structure and material fabric (less than 30% rocks, as

"corestones"); slake in water, easily crumbled by hand and finger pressure into grains, indented by geologic hammer. Relict

discontinuities are recognizable. completely discolored (brownish-red) weak rocks. Do not slake in

water, can be broken by hand into smaller fragments. Discontinuities are clearly visible, original fabric is present.

greenish-grey rocks stained and discolored along discontinuities and

original fabric are wholly preserved.

Field survey

33

Figure 3.7. This graph shows the correlation of weathering grade with dry density and porosity. High/mean/low values are plotted for each grade (from Thuro and Scholz, 2003).

Huat et al. (2005) studied the strength parameters in a profile of sedimentary

residual soils of various weathering grades. The weathering grades varied from III to V,

where the lower end is for less weathered material and the higher end is for more

weathered material. The site comprised residual soil of weathered sandstone, overlying

schist and quartzite. The soils were generally yellowish brown and consisted mainly of

fine sands, silt and clay. Results of triaxial tests are shown in Table 3.3. The results show

an increase in cohesion but a decrease in angle of friction as the soil/rock becomes more

weathered. An increase in fines content with weathering grade was also observed, which

according to the authors was the reason for a decrease in friction angle.

Lumb (1962; 1965) conducted extensive work on residual soils in Hong Kong.

They successfully used particle size parameters to indicate the degree of weathering

based on field observations that most soil profiles exhibit trends of decreasing particle

size and increasing clay content towards the surface.

34

Even though most literature presents similar results and indicates a reduction of

strength with increasing weathering, it cannot be generalized that weathering will always

decrease mine rock/soil strength. Most of these studies are based upon soil profiles that

ranged from unweathered rock to weathered soil that formed over a long period of time.

Cementation was not a factor in these studies. Chemical weathering can produce cements,

such as hematite, that will join grains together and that are not easily dissolved in water.

According to (Pernichele and Kahle, 1971) field studies of rock piles indicate that the

cementing action of iron precipitates formed within the piles as a result of natural or

production leaching tends to improve the strength of the piles over time. Generally, the

cementation is so complete that vertical cuts are capable of standing for years without

signs of failure.

Table 3.3. This table shows the shear strength parameters of sedimentary residual soil with weathering grades varying from III to V. The lower end is for less weathered material and the higher end is for more weathered material

Weathering grade Cohesion, c Angle of friction,

(kPa) (degrees)

V 10 26

IV 8 28

IV-III 4 31

III 0 33

3.4. Published Grain Size distribution and Shear Strength Parameters for Mine

Rock

35

Table 3.4 summarizes values of grain size distribution for different rock piles

from around the world. Percentages of gravel, sand and fines in the mine rock piles range

from 45 to 70, 20 to 43, and 3 to 29, respectively. These distributions support the

generalized classification “sandy gravel with cobbles” attributed to rock piles in the

literature (Hawley, 2001; Leps, 1970; Quine, 1993; Robertson, 1985). Table 3.5

summarizes values of internal friction angle and cohesion from different rock piles.

Typical values of cohesion vary between 0 to 239 kPa (0 and 5000 psf) and friction

angles vary between 21º and 55º, with most values reported between 38º and 45º.

Table 3.4. This table shows the grain size distribution of rock piles from around the world.

36

Mine and Location Cobbles

(%)Gravels

(%)Sand (%)

Fines (%)

Silt (%)

Clay (%)

reference

Ajo mine, Arizona Copper mine

5 67 20 8 7 1Savci and

Williamson (2002)

Aitik Mine, Sweden Copper mine

6 45 34 15 n.d. n.d. URS

Corporation (2003)

Midnite Mine, Washington

Uranium Minen.d.

50-65 (range)

21-43 (range)

11-29 (range)

n.d. n.d. URS

Corporation (2003)

Bonner Mine San Juan County,

Coloradon.d. 70 20 10 8 2

Stormont and Farfan (2005)

Kidston gold mines, Australia

30 37 30 3 n.d. n.d. URS

Corporation (2003)

Morenci mine, Arizona

Copper minen.d.

50-56 (range)

30-34 (range)

10-20 (range)

n.d. n.d. URS

Corporation (2003)

n.d.= not determined

37

Table 3.5. This table shows a summary of mine rock friction angle and cohesion data from around the world.

Mine and locationMine rock material/

rock type or Deposit type

Internal friction angle

(degrees)

Apparent cohesion (kPa)

Comments References

Fresh 32-55

20-32

5 years old 34-35

21-35

7 years old 27-37

25-40

Fresh 36-41

18-23

8 years old 21-29

27-37

Bouganville Copper Ltd., Papua New

Guinea

Fractured rock (Panguna andesite)

29-45 0

Triaxial test 6-inch diameter dmax=3/4"

samples comprised of moderately to slightly

weathered rock with 20% fines

URS Corporation (2003)

Endako British Columbia,

Canada Molybdenum mine

100% Quartz monzonite

36 24Material properties 30% > 300mm and 2% < No.200 sieve

British Columbia Mine Waste Rock Pile

Research Committee (1991), URS (2003)

Bald Mountain gold, Nevada

Dundrberg Shale 39 172Direct shear test

shear box size 15in x 15in dmax = 3 inch

Quine (1993)

Barrick gold, NevadaArgillized

granodiorite38-40.3 83-139

Direct shear test shear box size 15in x 15in

dmax = 3 inchQuine (1993)

Big Spings gold, Nevada

Argillaceous siltstone 47-50 206-239Direct shear test

shear box size 15in x 15in dmax = 3 inch

Quine (1993)

Candelaria gold, Nevada

Siltstone and shale 43-47 90-239Direct shear test

shear box size 15in x 15in dmax = 3 inch

Quine (1993)

Newmont gold, Nevada

Siltstone/sandstone Siltstone/ argillized

sandstone35-51 69-205

Direct shear test shear box size 15in x 15in

dmax = 3 inchQuine (1993)

Round Mountain gold, Nevada

Rhyolitic tuff 40-41.5 77-96Direct shear test

shear box size 15in x 15in dmax = 3 inch

Quine (1993)

37.6-42.2 34-64 Direct shear test

39.6-40.4 0-11Triax compression

consolidated, undrained

Bonner Mine San Juan County,

Coloradon.d. 37 5

direct shear test shear box size 30in x 30in x 16in tall

Stormont and Farfan (2005)

32.6-43.7 0-29trixial test 4-inch diameter

dmax =3/4"

37 31trixial test 6-inch diameter

dmax =1 1/2"

Lubelskie, PolandFriction angle decreases,

cohesion increases with ageFilipowicz and Borys

(2005)

Upper Silesian, Poland

Friction angle decreases, cohesion increases with age

Filipowicz and Borys (2005)

n.d.

n.d.

PT Freeport Indonesia’s Gasberg

Open –Pit Mine

Walker, W.K. and J. M.J (2001)

URS Corporation (2003)

Midnite Mine, Washington

Uranium Mine

n.d.

Porphyritic quartz monzonite, and calc-

silicate rock and marble

n.d. = not determined

38

4. METHODOLOGY

4.1. Sampling

A multifaceted sampling program was carried out by the principal investigators of

the Molycorp Project Weathering Study. The sampling program was conducted from

Spring 2004 through April 2005. A total of 36 samples from the GHN rock pile were

analyzed during this thesis project. Samples were comprised mainly of a combination of

Amelia Tuff and andesite mine rock.

The sampling occurred during the re-grading period of the GHN rock pile when

the trenches were excavated. Approximately 5 gallons of solid material was collected for

geotechnical analyses for each sample. Samples for gravimetric moisture content,

mineralogy, and chemical analyses were also collected at the same locations. All samples

were collected as disturbed material Samples examined for this thesis project were used

to determine the effects of physical and chemical properties on the direct shear test and

were not used to calculate slope stability. Because all samples are a subset of the original

material, the resulting shear tests are not representative of the entire rock pile and cannot

be used to calculate friction angle for the pile.

Figure 4.1 shows a cross section of the GHN rock pile before re-grading including

locations of the samples that were analyzed in this thesis. A list of all the samples and

their respective coordinates (UTM easting, UTM northing, and elevation) is given in

Appendix A.

39

Figure 4.1. This figure shows a generalized cross section of GHN with the location of the samples analyzed for this thesis project.

4.2. Particle Size Analysis

Particle Size Analysis was performed to evaluate the sieving procedure most

appropriate to the samples from the GHN rock pile. Generally, the distribution of particle

sizes larger than 75 m (retained on the No. 200 U.S. standard sieve) is determined by

sieving, while the distribution of particle sizes smaller than 75 m is determined by a

sedimentation process with a hydrometer. This combined particle size analysis can be

performed using different approaches, such as dry sieve and wet sieve (or wash sieve).

Wet sieving is used instead of dry sieving when the material is not soluble in water and is

difficult to screen due to the presence of extremely fine particles that either agglomerate

or cause binding on the coarser sieves (U.S. Army Corps of Engineers, 1970). To

2750

2800

2850

2900

2950

3000

0 50 100 150 200 250 300 350 400 450

Easting (m)

Ele

vati

on

(m

)

2003 profile 1967 profile Sample locationOriginal Topographic profile 1967

40

determine the most appropriate procedure for the samples from the GHN rock pile, initial

tests of wet and dry sieving were performed, with separations made on the No. 10 (2 mm)

and No. 200 (75 m) U.S. standard sieves using sample GHN-LFG-0003. The results

were compared and the influence of aggregate fines on particle size distribution for this

kind of material was studied. All sieves used in this thesis research were U.S. standard

sieves.

Method 1, “Dry sieving with separation made on No. 200 sieve,” consisted of

mechanical dry sieving for particles larger than 75 m, and applying a sedimentation

process using a hydrometer for particles smaller than 75 m. These combined particle

size analyses (mechanical sieving and hydrometer) were performed in accordance with

U.S. Army Corps of Engineers (1970) methods.

Method 2, “Dry sieving with separation made on No. 10 sieve,” consisted of dry

sieving for particles larger than No. 10 sieve (2 mm). The material smaller than 2 mm

was analyzed using a sedimentation process (hydrometer) followed by the dry sieving for

the part larger than 75 m. First, hydrometer analysis was performed on all material

passing the No. 10 sieve (2 mm). The weight used was approximately 115 g for sandy

soils and approximately 65 g for silt and clay soils. The dry sieving of oven-dried

material between 75 m and 2 mm was performed after the fines (passing No. 200 sieve)

were washed out using wet sieving. The method No. 2 combined particle size analysis

was performed in accordance with the American Society for Testing and Material

standard procedures (ASTM, 2002a).

Method 3, “Wet sieving,” consisted of washing particles larger than 75 m

through a series of sieves, and performing a sedimentation process using a hydrometer for

41

particles smaller than the No. 200 sieve. This combined particle size analysis for method

3 was performed in accordance with the U.S. Army Corps of Engineers (1970) method.

All three methods were applied to the same sample in order to compare the

procedures. First, the sample was air dried and two representative splits were taken by the

method of cone and quartering (ASTM, 1987). The minimum mass of the sample used

for particle size analysis was related to the maximum particle size present in the bucket.

Table 4.1 shows different size particles and the corresponding minimum mass of sample

necessary to perform the test (U.S. Army Corps of Engineers, 1970).

One sample split was used for dry sieving (method 1, followed by method 2); the

second split was used for wet sieving. The sample preparation for dry sieving consisted

of breaking up the aggregates thoroughly with a mortar and pestle. The sample

preparation for wet sieving consisted of soaking the specimen in water for 24 hrs.

Table 4.1. This table shows the minimum specimen size required for particle size analysis according with the diameter of the largest particle (U.S. Army Corps of Engineers, 1970).

Nominal diameter of the largest particle

Approximate minimum mass of the sample

inches (mm) (g)

3 (76.2) 6000

2 (50.8) 4000

1 (25.4) 2000

1/2 (12.7) 1000

0.18 (4.75) 200

0.079 (2mm) 100

42

Results of the three methods are summarized in Table 4.2. The coefficient of

curvature (Cc) is defined as the ratio (D30)2/(D10 x D60), where D60, D30, and D10 are the particle

diameters corresponding to 60, 30, and 10% fines on the cumulative particle size distribution

curve. The coefficient of uniformity (Cu) is defined as the ratio D60/D10.

Figure 4.2 is a plot showing a comparison of the particle size distributions for the

three methods. A comparison of methods 1, 2 and 3 shows that wet sieving analysis

provided more fines than the other two methods. The fines are removed from the surface

of coarse grains by water. These results indicate that wet sieving is the best method for

particle size analysis. However, the duration of method 3 was a concern because it

required more time (about 6 hours) than either method 2 (about 2 to 3 hours) or method 1

(about 2 hours). Method 2 is preferred over method 1 because method 2 produced results

that were considerably closer to method 3 (e.g., % of fines: method 1 = 2.53, method 2 =

11.59, and method 3 = 17.78). Furthermore, no problems were encountered during the

testing using method 2. Using method 1, it was observed that aggregates of fines were

plugging the sieve openings, and this condition was even worse for sieves smaller than

No.10 sieve (2 mm).

Based on the results of these tests, method 2, “dry sieving with separation on No.

10 sieve” (ASTM, 2002a), was selected for particle size analysis of all the samples

described in this thesis.

43

Table 4.2. This table is a summary of results of the 3 methods for particle size analyses.

Dry sieve w/ separation on No200 sieve

Dry sieve w/ separation on No10 sieve

Wet sieve

Fines (%) 2.53 11.59 17.80

Sand (%) 67.05 42.59 65.51

Gravel (%) 30.42 31.00 16.69

D10 (mm) 0.27 0.019 0.004

D30 (mm) 1 0.59 0.35

D60 (mm) 3.1 3.1 1.5

Cu 11.48 163.16 375.00

Cc 1.19 5.91 20.42

USCS classification

SW well graded sand

with gravel

SP-SC Poorly graded sand with clay

and gravel

SC Clayey sand with gravel

GHN-LFG-0003

U.S. STANDARD SIEVE SIZE

0

10

20

30

40

50

60

70

80

90

100

0.00100.01000.10001.000010.0000100.00001000.0000

GRAIN SIZE MILLIMETERS

PE

R C

EN

T F

INE

R B

Y W

EIG

HT

COBBLES GRAVEL SAND SILT OR CLAYBOULDERS

Coarse Fine Coarse Medium Fine

6 4 3 2 1/4 4 81-1/2 1 101/2 3/83/4 16 20 30 40 50 60 140 200100

Wash sieve, Fines= 17.41%

Separation No10, Fines = 11.59%

Separation No200, Fines = 2.53%

Figure 4.2. This graph shows a comparison of the grain size distribution for the three different approaches tried for the estimation of particle size distribution using sample GHN-LFG-0003.

44

4.3. Direct Shear Test Under Consolidated Drained Conditions

All direct shear tests were conducted at the Soils Mechanics Laboratory in New

Mexico Institute of Mining and Technology following Standard Industrial Practice

(ASTM, 1998) and using standard manual equipment as shown in Figure 4.3. Prior to

testing, all samples were air-dried and a mortar and pestle was used to break up the

aggregates. Samples at field moisture contents were created by adding water and then

allowed to cure for 24 hrs. Strain rates of 1% and 0.5% were used to perform direct shear

tests on dry samples and samples at field moisture contents, respectively.

The sample density for the direct shear tests was based on measurements from a

nuclear gauge. The dry density ranged from 1.06 to 2.31 g/cm3 (66.5 to 144.8 pcf) with

an average of 1.69 g/cm3 (106 pcf) and standard deviation of 0.15 g/cm3 (9.6 pcf). The

wet density ranged from 1.16 to 2.43 g/cm3 (72.4. to 151.9 pcf) with an average of 1.8

g/cm3 (112.5 pcf) and standard deviation of 0.18 g/cm3 (11 pcf). Therefore, a dry density

of 1.7 ± 0.2g/cm3 (106 ± 10pcf) or a wet density of 1.8 ± 0.2 g/cm3 (112.5 ± 11 pcf) was

selected for the shear box tests. The purpose of using only one value of dry density or wet

density for all samples was to reduce the number of variables that could affect the friction

angle. The specimens were prepared by lightly compacting the soil in three lifts so that

each lift had the same relative compression.

Normal stresses required for testing were estimated by dividing the applied load

by the area of the shear box. Loads represented the weight of the rock pile overburden

45

consistent with the depth of the sample in the rock pile. Using a 2-inch shear box, the

normal stress varied between 50 kPa (1044.27 psf) and 800 kPa (16708 psf). These

values duplicate depths in the rock pile between 3 m and 48 m (9.8 ft to 157.6 ft)

considering sample density of 1.7 g/cm3 (106 pcf). For a 4-inch shear box the maximum

normal stress that could be applied (due to equipment limitations) was less than half of

the value ( 350 kPa or 7310 psf) obtained for a 2-inch shear box. This value duplicates a

maximum depth in the rock pile of 21 m (69 ft) considering sample density of 1.7 g/cm3

(106 pcf).

Peak shear strength and residual shear strength were determined from plots of

shear stress versus shear strain. One example is shown in Figure 4.4. Internal friction

angle was obtained using a linear best-fit line from the plot of peak shear strength versus

normal stress. An example plot is given in Figure 4.5. The residual friction angle was

obtained using a similar best-fit line.

46

Figure 4.3. This image shows the manual direct shear equipment used, with views showing the 2-inch square shear box, displacement dials and load frame.

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

stre

ss (

kPa)

Normal stress = 754kPa

Normal stress = 562kPa

Normal stress = 356kPa

Normal stress = 159kPa

Peak shear strength Residual shear strength

47

Figure 4.4. This graph shows an example of a shear stress versus shear strain plot. The test was conducted at four different normal stresses 159, 356, 562, and 754 kPa. The arrows indicate the peak shear strength and the residual shear strength.

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Shea

r st

rength

(kP

Peak internal friction angle Residuall friction angle

peak

residual

Figure 4.5. This image show an example of a shear diagram showing the best fit line for the peak internal friction angle and the residual internal friction angle.

4.3.1. Initial Test

A series of trial direct shear tests were performed to define the best conditions for

testing. Results of the effect of shear box size, maximum particle size, and moisture

content were studied to define the appropriate test conditions. The effects of particle size

and shear box size on friction angle were investigated using dry samples and three

maximum particle sizes: material passing the No. 3/8 (9.5 mm)sieve, material passing the

No. 4 (4.75 mm) sieve, and material passing the No. 6 (3.35 mm) sieve. The investigation

on the effect of shear box size was performed on dry samples passing the No. 4 and the

No. 6 sieves. Each sample was tested in 2- and 4-inch square shear boxes. The direct

48

shear tests for samples at field moisture content were performed using a 2-inch shear box

on material passing a No. 6 sieve.

The effects of shear box size, maximum particle size, and moisture are presented

in plots of shear stress versus normal stress shown in Figures 4.6 through 4.8 and in

summary Tables 4.3 through 4.5. Figure 4.6 shows the results of initial direct shear tests

for two samples from GHN, using 2- and 4-inch shear boxes. Table 4.3 summarizes the

results for both samples. The difference in internal peak friction angle with shear box size

was statistically insignificant as shown by the high correlation (R2) values. Therefore, the

selection of the shear box size was based on the surface area of shearing that provided the

range of normal stresses that encompassed the field normal stresses. The 2-inch shear box

provided a range of normal stress between 50 kPa (1044.27 psf) to 800 kPa (16708 psf).

The 4-inch shear box provided a range of normal stress between 50 kPa (1044.27 psf) to

350 kPa (7310 psf). Therefore, the 2-inch shear box size was selected for this study rather

than the 4-inch shear box.

49

(a)

= 1.03 n

R2 = 0.99

peak = 45.8o

0

100

200

300

400

500

600

0 100 200 300 400 500 600

Normal stress (kPa)

Sh

ear

stre

ss(k

Pa

)

4inch shear box

2inch shear box

Sample ID: GHN-KMD-0056dmax = 4.76mm

(b)

= 0.95 nR2 = 0.98

peak = 43.2o

0

100

200

300

400

500

600

0 100 200 300 400 500 600

Normal stress (kPa)

Sh

ear

str

ess

(kP

a)

4inch shear box

2inch shear box

Sample ID: GHN-LFG-0003dmax = 4.76mm

Figure 4.6. Shear box size effects on direct shear test (a) for sample GHN-KMD-0056 with dmax = 4.76 mm, (b) GHN-LFG-0003 with dmax = 4.76 mm.

50

Table 4.3. Summary of the results from direct shear tests using different maximum particle size and shear box size.

2 46.12º 0.9955

4 45.57º 0.9978

2 43.5º 0.9858

4 43.5º 0.9913

GHN-KMD-0056 4.76

4.76GHN-LFG-0003

Sample IDMaximum

particle size mm

Shear box Size (in)

Peak internal friction angle

(degrees)R2

Figure 4.7 shows the effects of maximum particle size for samples GHN-KMD-

0056 and GHN-LFG-0003. There was little difference in internal peak friction angle with

variations in maximum particle size (dmax). Both samples showed correlation (R2) values

of 0.98 for the best fit lines. When each series of direct shear tests are considered

separately, the results show an increase in correlation (decrease of data scatter) with a

decrease in dmax as shown in Table 4.4. Based on these results, a conservative maximum

particle size of 3.36 mm was selected for testing the remainder of the samples to

minimize possibility of data scatter.

51

(a)

R2 = 0.98

peak = 47.4o

0

100

200

300

400

500

600

0 100 200 300 400 500 600

Normal stress (kPa)

Sh

ear

stre

ss(k

Pa)

dmax = 9.52 mm

dmax = 4.76 mm

dmax = 3.36 mm

Sample ID: GHN-KMD-00562-inch shear box size

(b)

R2 = 0.98

peak = 45o

0

100

200

300

400

500

600

0 100 200 300 400 500 600

Normal stress (kPa)

Sh

ear

stre

ss(k

Pa

)

dmax = 4.76 mm

dmax = 3.36 mm

Sample ID: GHN-LFG-00032-inch shear box size

Figure 4.7. This figure shows the results of the effect of particle size on direct shear tests using a 2-inch shear box for (a) sample GHN-KMD-0056 with maximum particle sizes (dmax) of 9.52, 4.76, and 3.36 mm and (b) sample GHN-LFG-0003 with dmax of 4.76 and 3.36 mm.

52

Table 4.4. This table summarizes the results from direct shear test using different maximum particle sizes.

9.52 48.8º 0.9654

4.76 47º 0.9901

3.36 46.05º 0.9963

4.76 43.5º 0.9840

3.36 45.5º 0.9891

Peak internal friction angle

(degrees)R2

2GHN-KMD-0056

Sample IDShear

box Size (in)

Maximum particle size

(mm)

GHN-LFG-0003 2

Direct shear results for different moisture contents are given in Table 4.5 and

Figure 4.8. Adding water decreased the peak internal friction angle and increased the

apparent cohesion component, as shown in Table 4.5. The cohesion component is

estimated from the plot of shear stress versus normal stress by the interception of the

trendline with the y-axis. Measurements of pore water pressure were not done because of

limitations of the testing equipment. The remaining tests were conducted on dry samples.

Table 4.5. This table is a summary of direct shear test results for samples at dry and moist states.

GHN-KMD-0017 42.15º 0 14.97 12.40 34.27º 34.09

GHN-KMD-0018 44.43º 0 13.45 11.00 33.9º 41.33

Sample ID

samples air-dried

Peak internal friction angle

(degrees)

Apparent cohesion

(kPa)

Trying to achieve field moisture content

Field moisture content (%)

Moisture content

achieved (%)

Peak internal friction angle

(degrees)

Apparent cohesion

(kPa)

53

(a)

GHN-KMD-0017

R2 = 1.00

peak = 34o

R2 = 0.96

peak = 42o

0

100

200

300

400

500

600

700

0 100 200 300 400 500 600 700

Normal stress (kPa)

Sh

ear

stre

ss (

kPa)

dry

moisture 12.4%

note: shear box size: 2 inchesmax. part. Size: 3.36mm

(b)

GHN-KMD-0018

R2 = 0.99

peak = 44.4o

R2 = 0.96

peak = 33.9o

0

100

200

300

400

500

600

0 100 200 300 400 500 600

Normal stress (kPa)

Sh

ear

stre

ss (

kPa)

dry

moisture 11%

note: shear box size: 2 inchesmax. part. Size: 3.36mm

Figure 4.8. This figure compares the results of the influence of moisture on the direct shear test for samples (a) GHN-KMD-0017 and (b) GHN-KMD-0018.

54

The remaining direct shear tests were performed in a 2-inch shear box using dry

samples. Samples were first sieved on a No. 6 sieve (3.35 mm), then a minimum of four

fractionsof approximately 120 g (~ 4 oz) ofeach specimen were used for the tests. A dry

density of 1.7 ± 0.2g/cm3 (106 ± 10pcf) was achieved for all samples. A small density

range was desired to reduce the number of variables affecting the friction angle. All the

specimens were prepared by lightly compacting three lifts to attain the same relative

compression. A strain rate of 1% and normal stress varying from 159 to 800 kPa (23 to

116 psi) were adopted for all the tests.

4.4. Index Properties and Mineralogy

Other physical properties characterized in this study include moisture content,

liquid limit (LL), plastic limit (PL), plasticity index (PI), and specific gravity. Definitions

of theses terms as used in this document are given in appendix G. Tests were conducted

according to ASTM standard procedures (ASTM, 2001a; ASTM, 2001b; ASTM, 2002b).

Mineralogy of the samples was determined using a modal mineralogy analysis provided

by geoscientists at the New Mexico Bureau of Geology and Mineral Resources. The

modal mineralogy combines results from various chemical and mineralogical analyses,

including petrography, electron microprobe, clay mineralogy, pyrite concentrations using

the Reitveld method, and whole rock chemistry from X-ray fluorescence (XRF)

spectrometry. More information regarding the methodologies used to determine the

modal mineralogies can be found in project reports (McLemore et al., 2006) and project

standard operating procedures (Appendix F).

55

5. RESULTS AND DISCUSSIONS

Results of the measurements performed for this study are found in Appendices B

through E. Particle size analyses are located in Appendix B. Appendix C contains direct

shear stress-strain plots. Mohr Coulomb diagrams are given in Appendix D. In Appendix

E, sample mineralogy, measurements of Atterberg limits, direct shear test results, specific

gravity, particle size distribution, and moisture content are summarized.

5.1. Indices Testing

Tables 5.1 through 5.3 present results of particle size analysis, measurements of

Atterberg limits, moisture content, paste pH, and direct shear test results for samples

from the GHN rock pile arranged according to geologic units. Geologic units were

defined based on grain size, color, texture, stratigraphic position, and other physical

properties that could be determined in the field. Their characteristics are described in

Appendix E and in McLemore et al. (2005, 2006).

Based on gradation and Atterberg limits, the majority of samples from the GHN

rock pile are classified as poorly- to well-graded gravels with fines and sand according to

the United Soil Classification System (USCS). The table given in Appendix B shows the

USCS symbols for all soils that were classified. Soil ranged from GW, GW-GC, GW-

GM, GP, GP-GC, GP-GM, SC, SM, SW-SC, and SP-SC. Figure 5.1 shows the range of

particle size distributions for all the samples listed in Appendix B. Most of the fines were

56

identified as CL-group using the plasticity chart shown in Figure 5.2. The CL-group is an

inorganic clay with low swell potential. The remaining samples fall in the ML category,

which is an inorganic silt.

Table 5.1. This table is a summary of particle size analyses for samples from GHN indexed by geologic unit.

Geologic unit

Ave Max Min Ave Max Min Ave Max Min Ave Max Min Ave Max Min

Oxidized, outter zone

C 41.83 - - 46.95 - - 11.22 - - 5.51 - - 5.57 - - 1

I 46.45 55.69 37.21 37.99 43.66 32.32 15.56 19.13 11.99 12.72 14.57 10.87 2.84 4.56 1.12 2

J 56.77 63.40 49.84 35.29 41.01 29.36 7.94 10.70 4.70 6.25 8.34 4.42 1.69 3.97 0.28 5

Intermediate zone

N 54.55 57.57 51.53 35.88 38.95 32.80 9.45 9.99 9.36 8.13 8.18 8.07 1.46 1.46 1.45 2

Unoxidized, internal zone

K 54.90 69.62 45.06 35.24 44.20 24.97 9.86 12.54 5.41 6.16 7.97 3.12 3.69 5.71 2.28 4

O 55.25 70.45 41.56 35.45 47.93 24.21 9.31 12.64 5.34 6.26 8.20 3.23 3.04 4.89 2.10 10

M 61.18 - - 28.83 - - 9.99 - - 5.58 - - 4.41 - - 1

R 54.51 63.12 45.90 35.09 41.12 29.07 10.40 12.98 7.82 7.41 8.78 6.05 2.89 4.20 1.77 2

S 64.90 74.83 54.98 26.64 33.68 19.59 8.46 11.34 5.58 5.87 7.04 4.70 2.59 4.31 0.88 2

U 69.49 87.39 60.06 24.10 32.33 9.66 6.41 8.66 2.95 3.77 5.05 1.70 2.63 3.61 1.25 3

V 61.44 65.12 58.75 30.69 33.31 28.11 7.87 8.90 6.77 4.97 5.31 4.57 2.90 3.58 2.20 3

Gravel (%) Fines (%)Number

of Samples

Sand (%) Silt (%) Clay (%)

57

Table 5.2. This table is a summary of Atterberg limit results for samples from GHN indexed by geologic unit.

Geologic unit

Average Maximum Minimum Average Maximum Minimum Average Maximum MinimumOxidized,

outter zone

I 23.28 24.67 21.88 32.62 35.28 29.95 11.60 17.91 5.28 2

J 19.84 22.08 17.96 34.12 38.44 28.73 14.29 17.24 9.26 3

Intermediate zone

N 22.66 24.88 20.44 34.73 35.58 33.88 14.72 15.14 14.29 2

Unoxidized, internal zone

K 19.30 19.56 19.04 30.60 34.68 26.51 11.80 15.13 8.47 3

O 20.09 23.50 16.55 33.21 37.81 29.55 13.34 17.82 9.15 7

M 19.02 - - 30.03 - - 11.01 - - 1

R 16.80 - - 35.51 - - 18.76 - - 1

S 20.94 - - 28.11 - - 11.01 - - 1

U 22.39 26.45 18.33 33.62 34.52 32.71 11.23 14.38 8.07 2

V 22.00 25.64 18.36 32.44 35.34 29.54 10.44 16.98 3.90 2

Number of Samples

Liquid limit, LLPlastic limit, PL Plasticity index, PI

Table 5.3. This table is a summary of moisture content and paste pH results for samples from GHN indexed by geologic unit.

Geologic UnitNumber of

samplesNumber of

samples

Average Maximum Minimum Average Maximum Minimum

Oxidized, outer zone

C 6.97 9.33 5.48 3 2.85 3.43 2.33 12

I 15.47 23.89 10.72 5 3.07 4.77 2.19 28

J 10.39 17.13 6.61 16 3.37 5.75 2.14 52

Intermediate zone

N 13.13 17.25 9.6 17 3.39 4.71 2.15 58

Unoxidized, internal zone

K 10.16 11.77 8.34 9 4.83 7.2 2.36 36

L 8.62 1 6.46 8.74 2.25 9

O 11.2 18.01 6.15 50 5.49 8.98 2.43 163

M 10.45 15.09 5.54 13 4.45 9.56 2.41 57

R 10.51 11.46 9.91 3 6.05 9.6 3.17 16

S 10.43 13.36 7.43 6 6.25 9.47 2.61 20

U 10.61 13.23 7.99 2 3.86 5.52 2.45 15

V 9.23 9.6 8.59 3 4.39 5.77 3.37 11

W 9 9.58 8.41 2 6.65 6.68 6.62 2

Paste pH (s.u.)Moisture Content (%)

58

U.S. STANDARD SIEVE SIZE

0

10

20

30

40

50

60

70

80

90

100

0.00100.01000.10001.000010.0000100.00001000.0000

GRAIN SIZE MILLIMETERS

PE

R C

EN

T F

INE

R B

Y W

EIG

HT

COBBLES GRAVEL SAND SILT OR CLAYBOULDERS

Coarse Fine Coarse Medium Fine

6 4 3 2 1/4 4 81-1/2 1 101/2 3/83/4 16 20 30 40 50 60 140 200100

range of grain size distribution

Figure 5.1. This graph shows the range of grain size distribution for samples from the GHN rock pile.

A - LI

NE

U - LI

NE

0

10

20

30

40

50

60

0 10 20 30 40 50 60 70 80 90 100

Liquid limit (LL)

Pla

sti

cit

y i

nd

ex

(P

I)

CL

ML

CL-ML

CL or OL

MH or OH

CH or OH

ML or OL

Figure 5.2. This graph shows the distribution of samples from the GHN rock pile on the plasticity chart.

59

5.2. Direct Shear Test Results

The peak internal friction angle () and the residual friction angle (residual) were

measured by direct shear tests using dry samples with maximum particle sizes of 3.36

mm (0.13 in). The test results are given in Table 5.4. The peak internal friction angle

ranged from 40º to 47º and the residual friction angle varied between 37º and 41º.

Correlation coefficients (R2) for tests on peak angles ranged from 0.95 to 1.00 and

averaged 0.99 for a minimum of four tests. High correlations demonstrated that

individual test conditions were reproducible, therefore high confidence can be placed on

the results.

Dry densities obtained during the tests ranged from 1.48 to 1.82 g/cm3 (92.4 to

113.6 pcf). The maximum dry density obtained for the relative density test was 1.82g/cm3

(113.6 pcf). Therefore, the maximum and minimum relative test densities were 100% and

81%, respectively. The average test relative density was 95%. Typical values of internal

friction angle and residual friction angle for sand-sized material are 28º to 60º (Holtz and

Kovacs, 2003) and 26º to 35º (Das, 1983), respectively. The lower range applies to round,

loose sand and the higher range is for angular, dense sand.

The values for internal friction angle are higher than the values reported for

saturated conditions ( average = 31º and 36º) in past geotechnical studies conducted on the

GHN rock pile (Norwest Corporation, 2004; Robertson GeoConsultants Inc., 2000). The

difference in between dry and saturated conditions is to be expected. Figure 5.3 shows

normal stress versus shear stress for one sample tested both dry and at 12.4% moisture

content. It is clear that the addition of water to soil with an appreciable amount of non-

60

clay fines (19.3% in this case) produced an apparent cohesion. As such, was reduced

from its value in the dry soil case.

Table 5.4. This summary table shows direct shear test results of samples from GHN indexed by geologic unit.

G eolog ic un it

Average M ax im um M in im um Average M ax im um M in im umO xid ized ,

ou tte r zone

I 43 43 42 38 38 38 2

J 44 43 45 39 39 38 3

In te rm ed ia te zone

N 44 44 44 38 39 37 2

U nox id ized , in te rna l zone

K 44 47 42 38 39 37 3

O 44 47 42 38 41 37 13

M 44 - - 41 - - 1

R 44 45 43 40 40 39 2

S 45 - - 37 - - 1

P 46 - - 37 - - 1

U 44 46 43 38 39 37 4

V 46 47 44 40 40 39 2

N um ber o f S am ples

In te rna l fric tion ang le (degrees ) R es idua l fric tion ang le (degrees )

61

GHN-KMD-0017

R2 = 1.00

peak = 34o

R2 = 0.96

peak = 42o

0

100

200

300

400

500

600

700

0 100 200 300 400 500 600 700

Normal stress (kPa)

Sh

ear

str

ess

(kP

a)

dry

moisture 12.4%

note: shear box size: 2 inchesmax. part. Size: 3.36mm

Figure 5.3. This graph shows direct shear test results for a dry sample versus a sample with gravimetric moisture content of 12.4%.

In the case of saturated soils, is often further reduced if small amounts of clay are

present in the fines.

Internal friction angles were correlated with weathering, chemistry, and

mineralogical effects. As such, the reader is reminded that these tests were conducted on

disturbed samples. The values determined from these tests should not be used for slope

stability considerations.

5.3. Verification of Direct Shear Test Results

Additional direct shear tests were conducted using a calibrated Ele direct shear

testing apparatus borrowed from Kleinfelder Laboratory in Albuquerque. The proving

ring for this motorized machine is annually calibrated. A 2.5-inch round shear box was

used to test three samples from the GHN rock pile: GHN-KMD-0014, GHN-KMD-0017,

62

and GHN-KMD-0027. The purpose of these tests was to provide validation of the tests

conducted with the manual Soiltest shear box machine in the Mineral Engineering

Department at New Mexico Tech.

The Mohr-Coulomb diagrams for these tests using both machines are shown in

Figures 5.4 through 5.6. The shear test results using the Ele machine fell along the trend

lines defined by data generated with the machine at New Mexico Tech (NMT). The

addition of the corroborating data did not change the values. Therefore, all test results

obtained at New Mexico Tech are considered to be representative and reproducible.

R2 = 1.00

R2 = 0.92

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800Norma stress (kPa)

Sh

ear

str

en

gth

(k

Pa

)

Friction angle-NMT Residual Friciton angle- NMT

Kleinfelder Lab. Kleinfelder Lab.

Sample ID. GHN-KMD-0014

Figure 5.4. This graph shows the Mohr-Coulomb diagram for sample GHN-KMD-0014. Data points generated by both the automatic Ele and the manual NMT shear box machines are included.

63

R2 = 0.96

R2 = 0.97

0

100

200

300

400

500

600

0 100 200 300 400 500 600

Normal load (kPa)

Sh

ear

Str

eng

th (

kPa)

Friction angle- NMT Residual friction angle - NMT

Kleinfelder Lab Kleinfelder Lab

Sample ID. GHN-KMD-0017

Figure 5.5. This graph shows the Mohr-Coulomb diagram for sample GHN-KMD-0017.

Data points generated by both the automatic Ele and the manual NMT shear box

machines are included.

R2 = 0.97

0

100

200

300

400

500

600

0 100 200 300 400 500 600

Normal Load (kPa)

Sh

ea

r s

tre

ng

th (

kP

a)

Friction angle - NMT Kleinfelder Lab

Sample ID. GHN-KMD-0027

64

Figure 5.6. This graph shows the Mohr-Coulomb diagram for sample GHN-KMD-0027. Data points generated by both the automatic Ele and the manual NMT shear box machines are included.

5.4.Correlations of Direct Shear Results with Geological and Geotechnical Parameters

The influence of geological and geotechnical parameters on internal friction angle

() were evaluated and correlated. Correlations were made with respect to geologic units.

An example of these units is given in Figure 5.7 for bench 9 from Trench LFG-006.

Similar stratigraphic positions of the units were evident at other elevations where samples

were collected. The geological and geotechnical parameters examined included texture

(lithology and alteration), modal mineralogy, chemistry, % fines, and Atterberg limit

(liquid limit and plasticity index). The geological and geotechnical data used in this

section are summarized in tables in Appendix E.

Correlations are presented in Figures 5.8 through 5.22. In these plots, the samples

are presented according to geologic unit. For all the plots in this section, the outer zone

(oxidized zone) of the pile included unit I, the intermediate zone included units N and J,

and the internal zone (unoxidized zone) included units O, K, M, S, P, R, U, and V.

Graphs on the left represent correlations for bench 9 and graphs to the right

represent all samples tested in this study, including bench 9.

65

Figure 5.7. This diagram shows the stratigraphic positions of the geologic units for bench 9 (Trench LFG-006).

40

41

42

43

44

45

46

47

48

0 1 2 3 4 5 6 7 8 9 10

Paste pH

Inte

rna

l fri

cti

on

an

gle

(d

eg

ree

s)

I J-N O K M-S-P R-U-V

40

41

42

43

44

45

46

47

48

0 1 2 3 4 5 6 7 8 9 10

Paste pH

Inte

rnal

fri

cti

on

an

gle

(d

eg

rees

)

I J-N O K M-S-P R-U-V

Figure 5.8. These graphs show cross plots of internal friction angle versus paste pH. Plot on the left side includes samples only from bench 9. Plot on the right side includes all GHN samples tested in this study.

40

41

42

43

44

45

46

47

48

0 1 2 3 4 5 6 7 8 9 10

NAGpH

Inte

rna

l fri

ctio

n a

ng

le (

deg

ree

s)

I J-N O K M-S-P R-U-V

40

41

42

43

44

45

46

47

48

0 1 2 3 4 5 6 7 8 9 10

NAGpH

Inte

rna

l fr

icti

on

an

gle

(d

eg

ree

s)

I J-N O K M-S-P R-U-V

Figure 5.9. These graphs show cross plots of internal friction angle versus NAGpH. Plot on the left side includes samples only from bench 9. Plot on the right side includes all GHN samples tested in this study.

66

40

41

42

43

44

45

46

47

48

0 2 4 6 8 10 12 14 16 18 20 22

%Fines

Inte

rna

l fri

cti

on

an

gle

(d

eg

rees

)

I J-N O K M-S-P R-U-V

40

41

42

43

44

45

46

47

48

0 2 4 6 8 10 12 14 16 18 20 22

%FinesIn

tern

al f

rict

ion

an

gle

(d

egre

es)

I J-N O K M-S-P R-U-V

Figure 5.10. These graphs show cross plots of internal friction angle versus percentage of fines. Plot on the left side includes samples only from bench 9. Plot on the right side includes all GHN samples tested in this study.

40

41

42

43

44

45

46

47

48

0 2 4 6 8 10 12 14 16 18 20

Plasticity index

Inte

rna

l fr

icti

on

an

gle

(d

eg

ree

s)

I J-N O K M-S-P R-U-V

40

41

42

43

44

45

46

47

48

0 2 4 6 8 10 12 14 16 18 20

Plasticity index

Inte

rna

l fri

cti

on

an

gle

(d

eg

rees

)

I J-N O K M-S-P R-U-V

Figure 5.11. These graphs show cross plots of internal friction angle versus plasticity index. Plot on the left side includes samples only from bench 9. Plot on the right side includes all GHN samples tested in this study.

67

40

41

42

43

44

45

46

47

48

20 22 24 26 28 30 32 34 36 38 40 42

Liquid limit

Inte

rna

l fr

icti

on

an

gle

(d

eg

ree

s)

I J-N O K M-S-P R-U-V

40

41

42

43

44

45

46

47

48

20 22 24 26 28 30 32 34 36 38 40 42

Liquid limitIn

tern

al f

ric

tio

n a

ng

le (

deg

rees

)

I J-N O K M-S-P R-U-V

Figure 5.12. These graphs show cross plots of internal friction angle versus liquid limit. Plot on the left side includes samples only from bench 9. Plot on the right side includes all GHN samples tested in this study.

40

41

42

43

44

45

46

47

48

0 20 40 60 80 100

%Amalia Tuff

Inte

rna

l fri

ctio

n a

ng

le (

deg

ree

s)

I J-N O K M-S-P R-U-V

40

41

42

43

44

45

46

47

48

0 20 40 60 80 100

%Amalia Tuff

Inte

rna

l fr

icti

on

an

gle

(d

eg

ree

s)

I J-N O K M-S-P R-U-V

Figure 5.13. These graphs show cross plots of internal friction angle versus percentage of Amalia Tuff. Plot on the left side includes samples only from bench 9. Plot on the right side includes all GHN samples tested in this study.

68

40

41

42

43

44

45

46

47

48

0 20 40 60 80 100

%Andesite

Inte

rna

l fri

cti

on

an

gle

(d

egre

es)

I J-N O K M-S-P R-U-V

40

41

42

43

44

45

46

47

48

0 20 40 60 80 100

%AndesiteIn

tern

al

fric

tio

n a

ng

le (

de

gre

es

)

I J-N O K M-S-P R-U-V

Figure 5.14. These graphs show cross plots of internal friction angle versus percentage of Andesite. Plot on the left side includes samples only from bench 9. Plot on the right side includes all GHN samples tested in this study.

40

41

42

43

44

45

46

47

48

0 10 20 30 40 50 60 70 80 90 100

%QSP alteration

Inte

rna

l fri

cti

on

an

gle

(d

eg

rees

)

I J-N O K M-S-P R-U-V

40

41

42

43

44

45

46

47

48

0 10 20 30 40 50 60 70 80 90 100

%QSP alteration

Inte

rnal

fri

ctio

n a

ng

le (

deg

rees

)

I J-N O K M-S-P R-U-V

69

Figure 5.15. These graphs show cross plots of internal friction angle versus quartz-sericite-pyrite (QSP) alteration. Plot on the left side includes samples only from bench 9. Plot on the right side includes all GHN samples tested in this study.

40

41

42

43

44

45

46

47

48

0 10 20 30 40 50 60 70 80 90 100

%Propylitic alteration

Inte

rna

l fri

cti

on

an

gle

(d

eg

ree

s)

I J-N O K M-S-P R-U-V

40

41

42

43

44

45

46

47

48

0 10 20 30 40 50 60 70 80 90 100

%Propylitic alteration

Inte

rna

l fri

cti

on

an

gle

(d

eg

ree

s)

I J-N O K M-S-P R-U-V

Figure 5.16. These graphs show cross plots of internal friction angle versus propyllitic alteration. Plot on the left side includes samples only from bench 9. Plot on the right side includes all GHN samples tested in this study.

40

41

42

43

44

45

46

47

48

0 1 2 3 4 5 6 7 8

LOI

Inte

rna

l fri

cti

on

an

gle

(d

egre

es

)

I J-N O K M-S-P R-U-V

40

41

42

43

44

45

46

47

48

0 1 2 3 4 5 6 7 8

LOI

Inte

rnal

fri

cti

on

an

gle

(d

egre

es)

I J-N O K M-S-P R-U-V

70

Figure 5.17. These graphs show cross plots of internal friction angle versus LOI (lost of ignition). Plot on the left side includes samples only from bench 9. Plot on the right side includes all GHN samples tested in this study.

40

41

42

43

44

45

46

47

48

0 2 4 6 8 10 12 14 16 18 20

%Epidote

Inte

rnal

fri

cti

on

an

gle

(d

eg

rees

)

I J-N O K M-S-P R-U-V

40

41

42

43

44

45

46

47

48

0 2 4 6 8 10 12 14 16 18 20

%Epidote

Inte

rna

l fri

ctio

n a

ng

le (

de

gre

es)

I J-N O K M-S-P R-U-V

Figure 5.18. These graphs show cross plots of internal friction angle versus percentage of epidote. Plot on the left side includes samples only from bench 9. Plot on the right side includes all GHN samples tested in this study.

40

41

42

43

44

45

46

47

48

0 2 4 6 8 10 12 14 16 18 20

%Illite

Inte

rnal

fri

cti

on

an

gle

(d

eg

rees

)

I J-N O K M-S-P R-U-V

40

41

42

43

44

45

46

47

48

0 2 4 6 8 10 12 14 16 18 20

%Illite

Inte

rnal

fri

ctio

n a

ng

le (

de

gre

es)

I J-N O K M-S-P R-U-V

71

Figure 5.19. These graphs show cross plots of internal friction angle versus percentage of illite. Plot on the left side includes samples only from bench 9. Plot on the right side includes all GHN samples tested in this study.

40

41

42

43

44

45

46

47

48

0 0.5 1 1.5 2 2.5 3 3.5

%MgO

Inte

rnal

fri

cti

on

an

gle

(d

eg

rees

)

I J-N O K M-S-P R-U-V

40

41

42

43

44

45

46

47

48

0 1 2 3 4%MgO

Inte

rna

l fri

ctio

n a

ng

le (

de

gre

es)

I J-N O K M-S-P R-U-V

Figure 5.20. These graphs show cross plots of internal friction angle versus percentage of MgO. Plot on the left side includes samples only from bench 9. Plot on the right side includes all GHN samples tested in this study.

40

41

42

43

44

45

46

47

48

0 0.5 1 1.5 2 2.5 3 3.5

%CaO

Inte

rna

l fri

cti

on

an

gle

(d

egre

es)

I J-N O K M-S-P R-U-V

40

41

42

43

44

45

46

47

48

0 1 2 3 4 5

%CaO

Inte

rna

l fri

cti

on

an

gle

(d

egre

es)

I J-N O K M-S-P R-U-V

72

Figure 5.21. These graphs show cross plots of internal friction angle versus percentage of CaO. Plot on the left side includes samples only from bench 9. Plot on the right side includes all GHN samples tested in this study.

40

41

42

43

44

45

46

47

48

12 12.5 13 13.5 14 14.5 15 15.5 16

%Al2O3

Inte

rna

l fri

ctio

n a

ng

le (

deg

ree

s)

I J-N O K M-S-P R-U-V

40

41

42

43

44

45

46

47

48

12 12.5 13 13.5 14 14.5 15 15.5 16

%Al2O3

Inte

rna

l fri

ctio

n a

ng

le (

deg

rees

)

I J-N O K M-S-P R-U-V

Figure 5.22. These graphs show cross plots of internal friction angle versus percentage of Al2O3. Plot on the left side includes samples only from bench 9. Plot on the right side includes all GHN samples tested in this study.

Variations in values with paste pH and NAGpH are shown in Figures 5.8 and

5.9. A positive correlation of paste pH and NAGpH with is apparent only for bench 9

data. In Figures 5.10 through 5.12 correlations with geotechnical properties show a

decrease in as PI, LL, and percent fines increase. These correlations are expected and

documented in the literature (Das, 1983; Holtz and Kovacs, 2003). The increase of fines

reduces the contacts between coarse grains, thereby reducing the interlocking contacts

that results in a decrease in . Although test results are for dry samples, the effects of

73

fines with atmospheric moisture (1-3% in the laboratory) are apparent. If tests had been

conducted at field moisture contents, these correlations would be far stronger.

Correlations of with lithology (andesite and Amalia Tuff), shown in Figure 5.13

and 5.14, are not apparent. Alteration of these rock types is given in Figures 5.15 and

5.16. QSP alteration shows a weak negative trend with . The negative trend is probably

caused by the presence of the clay mineral sericite.

The negative correlation of with LOI (Figure 5.17) may be explained by the

presence of clay minerals. An increasing in LOI can be translated in an increasing in clay

minerals. Figures 5.18 and 5.19 show that there are weak trends to no correlations of

with mineralogy. The same is true with MgO, CaO, and Al2O3 chemistry data (Figures

5.20 through 5.22). When each of these elements is plot separately correlations are week

to absent.

In summary, correlations of with geological parameters are weak or non-

existent. The weak correlations might be due to the small range in values obtained.

Results from direct shear tests showed that varies from 42 to 47 degrees, with an

average of 44 degrees, as summarized in Table 5.4. Considering a maximum error of ±2

degrees in friction angle (W. Wilson, personal communication, 2005), there is only a

small statistical variation in friction angle within the rock pile.

5.5. Correlations of Direct Shear Test Results with Weathering Indexes

A weathering index is a measure of how much the sample has weathered.

Numerous weathering indexes have been proposed and used over the years, but most of

74

them are based only on geochemical parameters, which restricts their application to the

type of environment for which they were developed. Therefore, there is a need to develop

a weathering index for the rock piles at the Questa mine. For the purpose of identifying

relative intensity of weathering of samples collected in the project, McLemore (2005)

described a simple, descriptive weathering index (SWI) that is based upon field

observations (color, grain size, mineral texture, and presence or absence of certain

minerals indicative of weathering).

Together with SWI, other published chemical weathering indexes are being

evaluated as well.

WPI – Weathering Potential Index (Reiche, 1943, Infran, 1996, 1999) WPI = 100*(K2O+Na2O+CaO+MgO-H2O) / (SiO2 +Al2O3 +Fe2O3+ FeO + TiO2+CaO+MgO +Na2O+K2O)

MI – Miura Index (Miura, 1973) MI = (MnO +FeO+CaO +MgO+Na2O+K2O) / (Fe2O3+Al2O3+3H2O)

The Weathering Potential Index, WPI (Reiche, 1943, Infran, 1996, 1999) and the

Miura index, MI (Miura, 1973) had shown to be applicable in this study. These

weathering indexes show a trend similar to paste pH (Figures 5.23 and 5.24). The paste

pH and the weathering indexes show a trend of increasing weathering from the inner

portion (less oxidized) to the outer portion (oxidixed egde). These weathering indexes are

calculated based on chemical data reflecting changes in mineralogy (i.e. feldspar to clay,

calcite-pyrite to gypsum-jarosite). The data and graphs in Figure 5.23 and 5.24 were

generated by geoscientists at the New Mexico Bureau of Geology and Mineral

Resources.

75

11- bedrock12- rubble zone13- shear zone14- R,U,V and W15- M,S,P16- K17- O18- N19- J20- C and I

Figure 5.23. This figure shows plots of the WPI and MI weathering indexes with distance across bench 9, trench LFG-006. The outer oxidized edge is at Hfrom=0 and the inner zone of the bench is at Hfrom=105. Weathering increases towards the left.

2 3 4 5 6 7 8 9 100.1

0.2

0.3

0.4

0.5

0.6

0.7

pastepH

MI

2 3 4 5 6 7 8 9 10-20

-10

0

10

20

pastepH

WP

I

0 100 2000.2

0.3

0.4

0.5

0.6

0.7

Hfrom

MI

0 100 2000

10

20

Hfrom

WP

I

76

Figure 5.24. This figure shows plots of WPI and MI vs. paste pH for all GHN samples. WPI and MI are explained in Figure 5.23.

Figure 5.25 through 5.27 are plots of weathering indexes (SWI, WPI and MI)

versus internal friction angle for samples from bench 9, trench LFG-006. A general trend

of decreasing friction angle with increasing degree of weathering is apparent for all of

these weathering indexes. A similar trend was observed in friction angle and weathering

by Ifran (1996, 1999). The effects of weathering are not linear because weathering is so

complex and dependent upon, lithology, composition of original rock, composition of

fluids interacting with the rock pile material.

40

41

42

43

44

45

46

47

48

012345

SWI

Inte

rnal

fri

ctio

n a

ng

le (

deg

rees

)

I J-N O K M-S-P R-U-V

Figure 5.25. This figure shows a cross plot of Friction angle versus simple weathering index (SWI) for bench 9 samples, trench LFG-006. Weathering intensity increases towards the left.

77

40

41

42

43

44

45

46

47

48

0 2 4 6 8 10 12 14

WPI

Inte

rnal

fri

ctio

n a

ng

le (

deg

rees

)

I J-N O K M-S-P R-U-V

Figure 5.26. This figure shows a cross plot of Friction angle versus weathering potential index (WPI) for samples from bench 9, trench LFG-006. The weathering intensity increases towards the left.

40

41

42

43

44

45

46

47

48

0 0.2 0.4 0.6 0.8

MI

Inte

rnal

fri

ctio

n a

ng

le (

deg

rees

)

I J-N O K M-S-P R-U-V

Figure 5.27. This figure shows a cross plot of Friction angle versus Miura Index (MI) for samples from bench 9, trench LFG-006. The weathering intensity increases towards the left.

78

79

6. CONCLUSIONS AND RECOMENDATIONS

This study presents an investigation of the influence of physical, geological,

mineralogical, and chemical properties on shear strength properties of the GHN rock pile

at Questa molybdenum mine, New Mexico. Representative samples were collected based

upon visible changes in the weathering characteristics and were not collected for the

purpose of slope stability analysis. Shear strength was analyzed using dry samples to

eliminate the effects of cohesion. The influences of the physical, geological,

mineralogical, and chemical properties of rock pile samples on friction angle were

studied. The synthesis of these analyses leads to the following conclusions:

The majority of samples from the GHN rock pile are classified as poorly

to well graded gravels with fines and sand.

Most of the fines (silt &clay) are classified as inorganic clay with low

swell potential.

The peak internal friction angle ranged from 40º to 47º and residual

friction angle varied between 37º and 41º. These high values of peak

internal and residual friction angle are attributed to grain shape

(subangular to very angular) and relative density of the test specimens.

The lowest were for materials near the face of the pile.

Correlations of from GHN samples with chemistry, and mineralogy are

shown to be weak or absent.

80

Negative correlations were observed for %Fines, LL, PI, LOI. The

decreased as these parameters increased.

Correlation of with lithology was not observed.

The internal friction angle for samples from bench 9, trench LFG-006

showed some trends with three different weathering indexes. Friction

angle decreased as degree of weathering increased.

Recommendations for future work include:

Determine the effects of cementation on friction angle. (Based on

laboratory observations it may be possible to test the cementation by

allowing the sample to air dry in the shear box. After the test is performed

the sample would be broken down and tested again. The difference

between the two friction angles is an estimation of the effect of

cementation on friction angle.)

Determine the effects of cohesion on the strength of the mine rock.

Examine the mineralogy and chemistry on the same size fraction

that is used in the direct shear test (i.e. test the assumption that the

analyses on the entire sample reflect the particle size fraction used in the

shear tests).

81

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ASTM, 1998. Standard Test Method for Direct Shear Test of Soils Under Consolidated Drained Conditions (D3080), Annual Book of ASTM Standards. American Society for Testing and Materials (ASTM), West Conshohocken, PA.

ASTM, 2001a. Standard Laboratory Determination of Water (moisture) Content of Soil, Rock, and Soil-Aggregate Mixtures (D2216). Annual Book of ASTM Standards. American Society for Testing and Materials (ASTM), West Conshohocken, PA.

ASTM, 2001b. Standard Test Method for Liquid Limit, Plastic Limit, and Plasticity Index of Soils (D4318). Annual Book of ASTM Standards. American Society for Testing and Materials (ASTM), West Conshohocken, PA.

ASTM, 2002a. Standard Test Method for Particle-Size Analysis of Soils (D422), Annual Book of ASTM Standards. American Society for Testing and Materials (ASTM), West Conshohocken, PA.

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86

APPENDIX A – SAMPLE LOCATION

87

Sample UnitsUTM east (meters)

UTM north (meters)

Elevation (ft)

GHN-KMD-0013 O 453696 4062143 9731GHN-KMD-0014 K 453677 4062146 9691GHN-KMD-0015 R 453723 4062142 9736GHN-KMD-0016 S 453698 4062143 9731GHN-KMD-0017 I 453772 4062140 9688GHN-KMD-0018 J 453685 4062146 9694GHN-KMD-0019 O 453708 4062147 9738GHN-KMD-0026 M 453682 4062140 9689GHN-KMD-0027 N 453708 4062148 9739GHN-KMD-0051 O 453711 4062142 9734GHN-KMD-0052 K 453727 4062144 9739GHN-KMD-0053 contact between Unit N 453695 4062145 9698GHN-KMD-0055 I 453696 4062139 9694GHN-KMD-0056 V 453705 4062140 9697GHN-KMD-0057 O 453657 4062127 9635GHN-KMD-0062 N 453734 4062140 9755GHN-KMD-0063 J 453647 4062115 9600GHN-KMD-0065 V 453643 4062115 9599GHN-KMD-0071 Unit U, V contact 453648 4062115 9601GHN-KMD-0072 coarse zone in Unit O 453667 4062137 9644GHN-KMD-0073 O (coarse sand) 453667 4062137 9644GHN-KMD-0074 U 453671 4062137 9646GHN-KMD-0078 U 453672 4062134 9644GHN-KMD-0079 U 453718 4062144 9737GHN-KMD-0081 R 453676 4062138 9650GHN-KMD-0082 O 453731 4062143 9760GHN-KMD-0088 O 453657 4062127 9635GHN-KMD-0092 O1 453729 4062141 9736GHN-LFG-0085 K 453740 4062141 9758GHN-LFG-0088 O 453734 4062141 9736GHN-LFG-0090 P 453740 4062142 9758GHN-VTM-0450 O (coarse layer) 453723 4062141 9736GHN-VTM-0453 O (clay rich) 453676 4062137 9650GHN-VTM-0454 O 453680 4062137 9650

88

APPENDIX B – GRAIN SIZE DISTRIBUTION CURVES AND SUMMARY

TABLE

89

D1

0D

30D

60G

rave

lS

and

Fin

esS

iltC

lay

(mm

)(m

m)

(mm

)(%

)(%

)(%

)(%

)(%

)

CG

HN

KM

D00

950.

054

1.05

5.1

944.

041

.83

46.9

511

.22

5.51

5.71

CL

SP

-SC

Poo

rly g

rade

d

HG

HN

LFG

0037

0.05

0.73

6.3

125

1.7

45.9

840

.313

.72

10.3

73.

34n.

d.n.

d.W

ell g

rade

d

IG

HN

KM

D00

170.

013

0.22

4.0

308

0.9

37.2

143

.66

19.1

314

.57

4.56

ML

SM

Wel

l gra

ded

IG

HN

KM

D00

550.

055

1.8

10.3

187

5.7

55.6

932

.32

11.9

910

.87

1.12

ML

GP

-GM

Poo

rly g

rade

d

JG

HN

JRM

0029

0.25

3.5

10.2

414.

863

.429

.36

7.24

6.67

0.57

CL

GP

-GC

Poo

rly g

rade

d

JG

HN

KM

D00

180.

473.

310

.322

2.3

61.7

133

.59

4.7

4.42

0.28

n.d.

GW

Wel

l gra

ded

JG

HN

KM

D00

630.

091.

49

100

2.4

49.8

441

.01

9.15

8.34

0.82

CL

SW

-SC

Wel

l gra

ded

JG

HN

KM

D00

960.

064

1.6

694

6.7

50.1

339

.17

10.7

6.74

3.97

CL

GP

-GC

Poo

rly g

rade

d

KG

HN

JRM

0028

0.05

41.

66

111

7.9

45.0

644

.210

.74

7.97

2.77

n.d.

n.d.

Poo

rly g

rade

d

KG

HN

KM

D00

140.

354.

710

.731

5.9

69.6

224

.97

5.41

3.12

2.28

CL

GP

-GC

Poo

rly g

rade

d

KG

HN

KM

D00

520.

041.

157

175

4.7

47.9

739

.49

12.5

46.

835.

71C

LS

CP

oorly

gra

ded

KG

HN

LFG

0085

0.06

72.

112

.518

75.

356

.95

32.3

210

.74

6.73

4C

LG

P-G

CP

oorly

gra

ded

MG

HN

KM

D00

260.

075

2.55

19.2

256

4.5

61.1

828

.83

9.99

5.58

4.41

CL

GP

-GC

Poo

rly g

rade

d

NG

HN

KM

D00

270.

075

2.45

10.3

137

7.8

57.5

732

.89.

368.

181.

45M

LG

W-G

MP

oorly

gra

ded

NG

HN

KM

D00

280.

030.

232.

997

0.6

51.5

338

.95

9.53

8.07

1.46

n.d.

n.d.

Wel

l gra

ded

N-J

con

tant

GH

NK

MD

0053

0.14

2.6

1913

62.

558

.77

33.3

47.

895.

062.

83C

LG

W-G

CW

ell g

rade

d

OG

HN

JRM

0030

0.08

28

100

6.3

51.4

838

.110

.42

7.88

2.54

n.d.

n.d.

Poo

rly g

rade

d

OG

HN

JRM

0031

0.15

2.5

1067

4.2

56.9

435

8.06

5.84

2.22

n.d.

n.d.

Poo

rly g

rade

d

OG

HN

KM

D00

190.

12.

410

.210

25.

653

.25

37.8

28.

935.

823.

11M

LG

P-G

MP

oorly

gra

ded

OG

HN

KM

D00

510.

061.

48

133

4.1

49.8

139

.48

10.7

16.

544.

17C

LS

P-S

CP

oorly

gra

ded

OG

HN

KM

D00

570.

115

2.55

11.6

101

4.9

59.5

631

.69

8.75

5.31

3.44

CL

GP

-GC

Poo

rly g

rade

d

OG

HN

LFG

0088

0.16

2.9

1594

3.5

62.5

329

.42

8.05

5.92

2.13

CL

GP

-GC

Poo

rly g

rade

d

OG

HN

KM

D00

720.

0395

0.99

7.9

200

3.1

48.5

138

.85

12.6

47.

754.

89C

LS

P-S

CP

oorly

gra

ded

O (

clay

ric

h)G

HN

VT

M04

530.

070.

835.

173

1.9

41.5

647

.93

10.5

18.

22.

3C

LS

W-S

CW

ell g

rade

d

O (

coar

se s

and)

GH

NK

MD

0073

0.07

92.

3512

152

5.8

58.3

931

.97

9.64

6.09

3.55

n.d.

n.d.

Poo

rly g

rade

d

O (

coar

se)

GH

NV

TM

0450

0.55

4.9

10.7

204.

170

.45

24.2

15.

343.

232.

1n.

d.n.

d.P

oorly

gra

ded

RG

HN

KM

D00

150.

173

11.6

684.

663

.12

29.0

77.

826.

051.

77n.

d.n.

d.P

oorly

gra

ded

RG

HN

KM

D00

810.

049

0.97

6.7

137

2.9

45.9

41.1

212

.98

8.78

4.2

CL

SC

Wel

l gra

ded

SG

HN

KM

D00

800.

056

1.65

1323

23.

754

.98

33.6

811

.34

7.04

4.31

n.d.

n.d.

Poo

rly g

rade

d

SG

HN

KM

D00

160.

425

7.2

4711

12.

674

.83

19.5

95.

584.

70.

88C

LG

W-G

CW

ell g

rade

d

UG

HN

KM

D00

740.

192.

7515

792.

760

.06

32.3

37.

614.

573.

04n.

d.n.

d.W

ell g

rade

d

UG

HN

KM

D00

782.

8527

320

112

0.8

87.3

99.

662.

951.

71.

25C

LG

PW

ell g

rade

d

UG

HN

KM

D00

790.

112.

819

.517

73.

761

.03

30.3

18.

665.

053.

61C

LG

P-G

CP

oorly

gra

ded

U-

V c

onta

ctG

HN

KM

D00

710.

12.

814

.814

85.

360

.45

30.6

58.

95.

313.

58M

LG

P-G

MP

oorly

gra

ded

VG

HN

KM

D00

560.

263.

317

652.

565

.12

28.1

16.

774.

572.

2M

LG

W-G

MW

ell g

rade

d

VG

HN

KM

D00

650.

162.

620

125

2.1

58.7

533

.31

7.94

5.03

2.91

CL

GW

-GC

Wel

l gra

ded

Cla

ssifi

catio

n fr

om p

last

icity

ch

art

US

CS

C

lass

ifica

tion

Com

men

tsG

eolo

gic

Uni

tsF

ield

_id

Cu

Cc

90

Par

tic

le S

ize

Dis

trib

uti

on

- G

HN

-JR

M-0

037

0102030405060708090100

0.00

100.

0100

0.10

001.

0000

10.0

000

100.

0000

1000

.000

0

GR

AIN

SIZ

E M

ILL

IME

TE

RS

PER CENT FINER BY WEIGHT

CO

BB

LE

S

GR

AV

EL

S

AN

D

S

ILT

C

LA

YB

OU

LD

ER

S

Coa

rse

Fin

eC

oars

eM

ediu

mF

ine

HY

DR

OM

ET

ER

3/8

34

1-1/

21

103/

416

3040

5060

200

100

U.S

. ST

AN

DA

RD

SIE

VE

NU

MB

ER

S2

91

Pa

rtic

le S

ize

Dis

trib

uti

on

- G

HN

-KM

D-0

014

0102030405060708090100

0.00

100.

0100

0.10

001.

0000

10.0

000

100.

0000

1000

.000

0

GR

AIN

SIZ

E M

ILL

IME

TE

RS

PER CENT FINER BY WEIGHT

CO

BB

LE

S

GR

AV

EL

S

AN

D

S

ILT

C

LA

YB

OU

LD

ER

S

Coa

rse

Fin

eC

oars

eM

ediu

mF

ine

HY

DR

OM

ET

ER

3/8

34

1-1/

21

103/

416

3040

5060

200

100

U.S

. ST

AN

DA

RD

SIE

VE

NU

MB

ER

S2

92

Pa

rtic

le S

ize

Dis

trib

uti

on

- G

HN

-KM

D-0

015

0102030405060708090100

0.00

100.

0100

0.10

001.

0000

10.0

000

100.

0000

1000

.000

0

GR

AIN

SIZ

E M

ILL

IME

TE

RS

PER CENT FINER BY WEIGHT

CO

BB

LE

S

GR

AV

EL

S

AN

D

S

ILT

C

LA

YB

OU

LD

ER

S

Coa

rse

Fin

eC

oars

eM

ediu

mF

ine

HY

DR

OM

ET

ER

3/8

34

1-1/

21

103/

416

3040

5060

200

100

U.S

. ST

AN

DA

RD

SIE

VE

NU

MB

ER

S2

93

Pa

rtic

le S

ize

Dis

trib

uti

on

- G

HN

-KM

D-0

016

0102030405060708090100

0.00

100.

0100

0.10

001.

0000

10.0

000

100.

0000

1000

.000

0

GR

AIN

SIZ

E M

ILL

IME

TE

RS

PER CENT FINER BY WEIGHT

CO

BB

LE

S

GR

AV

EL

S

AN

D

S

ILT

C

LA

YB

OU

LD

ER

S

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ediu

mF

ine

HY

DR

OM

ET

ER

3/8

34

1-1/

21

103/

416

3040

5060

200

100

U.S

. ST

AN

DA

RD

SIE

VE

NU

MB

ER

S2

94

Pa

rtic

le S

ize

Dis

trib

uti

on

- G

HN

-KM

D-0

017

0102030405060708090100

0.00

100.

0100

0.10

001.

0000

10.0

000

100.

0000

1000

.000

0

GR

AIN

SIZ

E M

ILL

IME

TE

RS

PER CENT FINER BY WEIGHT

CO

BB

LE

S

GR

AV

EL

S

AN

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LA

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OU

LD

ER

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ine

HY

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3/8

34

1-1/

21

103/

416

3040

5060

200

100

U.S

. ST

AN

DA

RD

SIE

VE

NU

MB

ER

S2

95

Pa

rtic

le S

ize

Dis

trib

uti

on

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HN

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D-0

018

0102030405060708090100

0.00

100.

0100

0.10

001.

0000

10.0

000

100.

0000

1000

.000

0

GR

AIN

SIZ

E M

ILL

IME

TE

RS

PER CENT FINER BY WEIGHT

CO

BB

LE

S

GR

AV

EL

S

AN

D

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LA

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ediu

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ine

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DR

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ET

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3/8

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103/

416

3040

5060

200

100

U.S

. ST

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118

APPENDIX C – DIRECT SHEAR STRESS DIAGRAMS

119

Shear strain (H)

Shear strain is obtained considering the following equation:

H = (Horizontal deformation/ Sample length)*100

Horizontal deformation (in. 10-3) Sample length, Lo (in)

Date 12/9/2005

Visual Description

notes

2 Loads no. Mass(Kg) check mark25.81 Frame+Hanger 9.96 1

1 2 8.46 00.02 3 8.12 0

20 4 8.13 0116.27 5 8.14 0

2.54 6 8.15 0dry 7 16 1

1.77 8 16 1 9 16 0

41.96 10 16 0

159.46 11 14.33 0

159.155.00 primary 132.79

-1.01 secondary none

Elapsed Time

Horizontal deformation

Vertical deformation

Load Dial Gage

Shear Strain H

Vertical Strain V

Shear Load P

Shear Stress P(98.07)/Ao

(sec) LC-8 (in.10-3) (in.) LC-2 (in.10-4) (kg) (kPa)

0 0 0.2932 0 0 0 0 015 5 0.2953 117 0.250 -0.2100 16.33 62.0730 10 0.297 145 0.500 -0.3800 20.24 76.9245 15 0.2983 171 0.750 -0.5100 23.87 90.7260 20 0.2994 195 1.000 -0.6200 27.22 103.4575 25 0.3001 215 1.250 -0.6900 30.01 114.0690 30 0.3009 231 1.500 -0.7700 32.25 122.55

105 35 0.3025 244 1.750 -0.9300 34.06 129.44120 40 0.3041 258 2.000 -1.0900 36.02 136.87135 45 0.305 268 2.250 -1.1800 37.41 142.18150 50 0.3058 274 2.500 -1.2600 38.25 145.36165 55 0.306 280 2.750 -1.2800 39.09 148.54180 60 0.306 286 3.000 -1.2800 39.93 151.73195 65 0.306 288 3.250 -1.2800 40.20 152.79210 70 0.306 290 3.500 -1.2800 40.48 153.85225 75 0.306 293 3.750 -1.2800 40.90 155.44240 80 0.3057 295 4.000 -1.2500 41.18 156.50

Residual shear strength (kPa)

Shear stain at failure, H (%)

GHN-EHP-0002_1d_2_152

Sample height (cm)Mass of sample(g)

Sample area, Ao (cm2)

Strain rate,L/Lo (100)/min (%/min)Deformation rate, L/min (in/min) (Lo x strain rate)

Direct Shear Test Data Sheet

Vertical stain at failure, V (%)

SpecimenNo.

Dry density (Mg/m3)Moist/saturated density (Mg/m3)

Shear stress at failure,(kPa)

Normal load (kg)Normal stress, n (kPa)

Moisture content (%)

Sample Length, Lo (in)

LC-8 dial gage divisions per min.

Molycorp

sample sieved with No. 6

Name

Project

120

GHN-KMD-0013

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 637kPa

Normal stress = 457kPa

Normal stress = 303kPa

Normal stress = 159kPa

GHN-KMD-0013

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ver

tic

al

stra

in (

%)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPaNormal stress = 637kPa

121

GHN-KMD-0014

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)Normal stress = 637kPa

Normal stress = 457kPa

Normal stress = 303kPa

Normal stress = 159kPa

GHN-KMD-0014

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ver

tic

al

stra

in (

%)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPaNormal stress = 637kPa

122

GHN-KMD-0015

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 754kPa

Normal stress = 562kPa

Normal stress = 356kPa

Normal stress = 159kPa

GHN-KMD-0015

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ver

tic

al

stra

in (

%)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPaNormal stress = 754kPa

123

GHN-KMD-0016

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 453kPa

Normal stress = 368kPa

Normal stress = 243kPa

Normal stress = 152kPa

GHN-KMD-0016

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ve

rtic

al

sra

in (

%)

Normal stress = 152kPa

Normal stress = 243kPa

Normal stress = 368kPaNormal stress = 453kPa

124

GHN-KMD-0017

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ea

r s

tre

ss (

kPa

)

Normal stress = 460kPa

Normal stress = 368kPa

Normal stress = 243kPa

Normal stress = 122kPa

GHN-KMD-0017

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ve

rtic

al

str

ain

(%

)

Normal stress = 122kPa

Normal stress = 243kPa

Normal stress = 368kPa

Normal stress = 460kPa

125

GHN-KMD-0018

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 453kPaNormal stress = 368kPaNormal stree = 243kPaNormal stress = 152kPa

GHN-KMD-0018

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ver

tic

al

stra

in(%

)

Normal stress = 152kPa

Normal stree = 243kPa

Normal stress = 368kPa

Normal stress = 453kPa

126

GHN-KMD-0019

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ea

r st

res

s (

kP

a)

Normal stress = 754kPa

Normal stress = 562kPa

Normal stress = 356kPa

Normal stress = 159kPa

GHN-KMD-0019

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ve

rtic

al

str

ain

(%

)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPaNormal stress = 754kPa

127

GHN-KMD-0026

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 427kPa

Normal stress = 368kPa

Normal stress = 243kPa

Normal stress = 152kPa

GHN-KMD-0026

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ve

rtic

al

str

ain

(%

)

Normal stress = 152kPa

Normal stress = 243kPa

Normal stress = 368kPa

Normal stress = 427kPa

128

GHN-KMD-0027

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ea

r s

tre

ss (

kPa

)

Normal stress = 453kPa

Normal stress = 368kPa

Normal stress = 243kPa

Normal stress = 122kPa

GHN-KMD-0027

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ve

rtic

al

str

ain

(%

)

Normal stress = 122kPa

Normal stress = 243kPa

Normal stress = 368kPa

Normal stress = 453kPa

129

GHN-KMD-0051

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 637kPa

Normal stress = 457kPa

Normal stress = 303kPa

Normal stress = 159kPa

GHN-KMD-0051

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ver

tic

al

stra

in (

%)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPaNormal stress = 637kPa

130

GHN-KMD-0052

0

100

200

300

400

500

600

700

800

900

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ea

r s

tre

ss

(k

Pa

)

Normal stress = 637kPa

Normal stress = 457kPa

Normal stress = 303kPa

Normal stress = 159kPa

GHN-KMD-0052

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ver

tic

al

Str

ain

(%

)

Normal stress = 159kPaNormal stress = 303kPaNormal stress = 457kPaNormal stress = 637kPa

131

GHN-KMD-0053

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 637kPa

Normal stress = 457kPa

Normal stress = 303kPa

Normal stress = 159kPa

GHN-KMD-0053

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ver

tic

al

stra

in (

%)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPaNormal stress = 637kPa

132

GHN-KMD-0053_DUPLICATE

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 637kPa

Normal stress = 303kPa

Normal stress = 159kPa

GHN-KMD-0053- DUPLICATE

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 637kPa

133

GHN-KMD-0055

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 754kPa

Normal stress = 562kPa

Normal stress = 356kPa

Normal stress = 159kPa

GHN-KMD-0055

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ver

tic

al

stra

in (

%)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPaNormal stress = 754kPa

134

GHN-KMD-0056

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ea

r s

tre

ss

(kP

a)

Normal stress = 504kPa

Normal stress = 368kPa

Normal stress = 274kPa

Normal stress = 152kPa

GHN-KMD-0056

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ve

rtic

al s

tra

in (

%)

Normal stress = 152kPa

Normal stress = 274kPa

Normal stress = 368kPa

Normal stress = 504kPa

135

GHN-KMD-0057

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 637kPa

Normal stress = 457kPa

Normal stress = 303kPa

Normal stress = 159kPa

GHN-KMD-0057

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ver

tic

al

stra

in (

%)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPaNormal stress = 637kPa

136

GHN-KMD-0057-DUPLICATE

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ea

r s

tre

ss

(kP

a)

Normal stress = 637kPa

Normal stress = 457kPa

Normal stress = 303kPa

Normal stress = 159kPa

GHN-KMD-0057-DUPLICATE

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ve

rtic

al

Str

ain

(%

)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPaNormal stress = 637kPa

137

GHN-KMD-0062

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 637kPa

Normal stress = 457kPa

Normal stress = 303kPa

Normal stress = 159kPa

GHN-KMD-0062

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ver

tic

al

stra

in (

%)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPaNormal stress = 637kPa

138

GHN-KMD-0063

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 637kPa

Normal stress = 457kPa

Normal stress = 303kPa

Normal stress = 159kPa

GHN-KMD-0063

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ver

tic

al

stra

in (

%)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPaNormal stress = 637kPa

139

GHN-KMD-0071

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 754kPa

Normal stress = 562kPa

Normal stress = 356kPa

Normal stress = 159kPa

GHN-KMD-0071

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ve

rtic

al s

tre

ss

(%

)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPaNormal stress = 754kPa

140

GHN-KMD-0072

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 754kPa

Normal stress = 562kPa

Normal stress = 356kPa

Normal stress = 159kPa

GHN-KMD-0072

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ver

tic

al

stra

in (

%)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPaNormal stress = 754kPa

141

GHN-KMD-0073

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ea

r st

res

s (

kP

a)

Normal stress = 754kPa

Normal stress = 562kPa

Normal stress = 356kPa

Normal stress = 159kPa

GHN-KMD-0073

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ver

tic

al

stra

in (

%)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPa

Normal stress = 754kPa

142

GHN-KMD-0074

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 754kPa

Normal stress = 562kPa

Normal stress = 356kPa

Normal stress = 159kPa

GHN-KMD-0074

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ver

tic

al

stra

in (

%)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPa

Normal stress = 754kPa

143

GHN-KMD-0078

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 637kPa

Normal stress = 457kPa

Normal stress = 303kPa

Normal stress = 159kPa

GHN-KMD-0078

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ve

rtic

al

str

ain

(%

)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPa

Normal stress = 637kPa

144

GHN-KMD-0079

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ea

r st

res

s (

kP

a)

Normal stress = 754kPa

Normal stress = 562kPa

Normal stress = 356kPa

Normal stress = 159kPa

GHN-KMD-0079

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ver

tic

al

stra

in (

%)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPa

Normal stress = 754kPa

145

GHN-KMD-0079-DUPLICATE

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20 22 24 26

Shear strain (%)

Sh

ea

r s

tre

ss

(kP

a)

Normal stress = 754kPa

Normal stress = 562kPa

Normal stress = 356kPa

Normal stress = 159kPa

GHN-KMD-0079-DUPLICATE

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20 22 24 26

Shear strain (%)

Ver

tic

al

stra

in (

%)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPaNormal stress = 754kPa

146

GHN-KMD-0081

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 430kPa

Normal stress = 368kPa

Normal stress = 274kPa

Normal stress = 152kPa

GHN-KMD-0081

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ve

rtic

al s

tra

in (

%)

Normal stress = 152kPa

Normal stress = 274kPa

Normal stress = 368kPa

Normal stress = 430kPa

147

GHN-KMD-0081-DUPLICATE

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20 22 24

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 637kPa

Normal stress = 457kPa

Normal stress = 303kPa

Normal stress = 159kPa

GHN-KMD-0081-DUPLICATE

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20 22 24

Shear strain (%)

Ver

tic

al

stra

in (

%)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPa

Normal stress = 637kPa

148

GHN-KMD-0088

0

100

200

300

400

500

600

700

800

900

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ea

r s

tre

ss

(k

Pa

)

Normal stress = 637kPa

Normal stress = 457kPa

Normal stress = 303kPa

Normal stress = 159kPa

GHN-KMD-0088

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ve

rtic

al

str

ain

(%

)

Normal stress = 159kPaNormal stress = 303kPaNormal stress = 457kPaNormal stress = 637kPa

149

GHN-LFG-0037

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20 22 24

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 637kPa

Normal stress = 457kPa

Normal stress = 303kPa

Normal stress = 159kPa

GHN-LFG-0037

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20 22 24

Shear strain (%)

Ver

tic

al

stra

in (

%)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPaNormal stress = 637kPa

150

GHN-LFG-0085

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 637kPa

Normal stress = 457kPa

Normal stress = 303kPa

Normal stress = 159kPa

GHN-LFG-0085

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ver

tic

al

stra

in (

%)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPa

Normal stress = 637kPa

151

GHN-LFG-0088

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 637kPa

Normal stress = 457kPa

Normal stress = 303kPa

Normal stress = 159kPa

GHN-LFG-0088

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ver

tic

al

stra

in (

%)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPaNormal stress = 637kPa

152

GHN-LFG-0090

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 637kPa

Normal stress = 457kPa

Normal stress = 303kPa

Normal stress = 159kPa

GHN-LFG-0090

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ver

tic

al

stra

in (

%)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPa

Normal stress = 637kPa

153

GHN-VTM-0450

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 754kPa

Normal stress = 562kPa

Normal stress = 356kPa

Normal stress = 159kPa

GHN-VTM-0450

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ea

r st

res

s (

kP

a)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPaNormal stress = 754kPa

154

GHN-VTM-0453

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ear

str

es

s (

kP

a)

Normal stress = 754kPa

Normal stress = 562kPa

Normal stress = 356kPa

Normal stress = 159kPa

GHN-VTM-0453

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ver

tic

al

stra

in (

%)

Normal stress = 159kPa

Normal stress = 303kPa

Normal stress = 457kPaNormal stress = 754kPa

155

GHN-VTM-0454

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Sh

ea

r s

tre

ss

(kP

a)

Normal stress = 637kPa

Normal stress = 457kPa

Normal stress = 303kPa

Normal stress = 159kPa

GHN-VTM-0454

-4

-3

-2

-1

0

1

2

3

4

0 2 4 6 8 10 12 14 16 18 20

Shear strain (%)

Ve

rtic

al

str

ain

(%

)

Normal stress = 159kPaNormal stress = 303kPaNormal stress = 457kPaNormal stress = 637kPa

156

APPENDIX D – MOHR COULOMB DIAGRAMS

157

Minimum Maximum

(mm) (g/cm3) (g/cm3)

GHN-KMD-0056No. 6 sieve (3.36mm)

1.42 1.85

GHN-LFG-0003No. 6 sieve (3.36mm)

1.38 1.76

GHN-KMD-0071No. 6 sieve (3.36mm)

1.43 1.84

1.41 1.82

Dry DensityMaximum Particle SizeSample ID

Average

(1) Test density for one sample is an average of the achieved density from 4 specimens.

Geologic Units Sample IDPeak Friction

Angle (degrees)

Residual Friction Angle

(degrees)

Test Density (g/cm3)

Relative Density

(%)

H GHN-LFG-0037 41 38 1.75 96I GHN-KMD-0017 42 38 1.72 95I GHN-KMD-0055 43 38 1.78 98

J GHN-KMD-0018 44 39 1.48 81J GHN-KMD-0063 45 39 1.61 88

contact between Unit N-J GHN-KMD-0053 43 38 1.59 87N GHN-KMD-0027 44 37 1.62 89N GHN-KMD-0062 44 39 1.76 97

O GHN-KMD-0013 43 38 1.62 89O GHN-KMD-0019 45 39 1.77 97O GHN-KMD-0051 43 38 1.63 90O GHN-KMD-0057 43 40 1.61 88O GHN-KMD-0082 44 37 1.75 96O GHN-KMD-0088 45 38 1.74 96O GHN-LFG-0088 42 39 1.78 98O GHN-VTM-0454 43 35 1.77 97O GHN-VTM-0453 44 38 1.79 98O GHN-VTM-0450 44 41 1.71 94O GHN-KMD-0073 43 39 1.8 99O GHN-KMD-0092 44 39 1.77 97O GHN-KMD-0072 43 38 1.78 98

K GHN-KMD-0014 47 39 1.73 95K GHN-KMD-0052 43 37 1.73 95K GHN-LFG-0085 42 39 1.74 96

M GHN-KMD-0026 44 41 1.64 90P GHN-LFG-0090 46 37 1.68 92S GHN-KMD-0016 45 39 1.68 92

R GHN-KMD-0015 45 40 1.76 97R GHN-KMD-0081 43 39 1.79 98U GHN-KMD-0074 44 39 1.79 98U GHN-KMD-0078 46 38 1.78 98U GHN-KMD-0079 43 38 1.75 96

Unit U, V contact GHN-KMD-0071 43 37 1.79 98V GHN-KMD-0056 47 40 1.82 100V GHN-KMD-0065 44 39 1.77 97

44 38 1.72 95

47 41 1.82 100

41 35 1.48 81

Average

Maximum

Minimum

(1)

158

GHN-KMD-0013

R2 = 0.99

peak =42.6o

R2 = 0.99

residual =38o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residuall friciton angle

GHN-KMD-0014

R2 = 1.00

peak =47.3o

R2 = 0.92

residual =40.1o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ear

stre

ss (

kPa)

Peak internal friction angle Residual friciton angle

159

GHN-KMD-0015

R2 = 0.99

peak =45.3o

R2 = 0.99

residual =39.8o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

GHN-KMD-0016

R2 = 1.00

peak =44.9o

R2 = 0.99

residual =39.1o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

160

GHN-KMD-0017

R2 = 0.96

peak =42.1o

R2 = 0.97

residual =37.9o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

GHN-KMD-0018

R2 = 0.99

peak =44.4o

R2 = 0.98

residual =38.7o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

161

GHN-KMD-0019

R2 = 0.95

peak =45.2o

R2 = 0.81

residual =38o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

GHN-KMD-0026

R2 = 0.99

peak =44o

R2 = 0.97

residual =40.7o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

162

GHN-KMD-0027

R2 = 0.97

peak =44.4o

R2 = 0.99

residual =37.2o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

GHN-KMD-0051

R2 = 0.98

peak =42.7o

R2 = 0.99

residual =37.9o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

163

GHN-KMD-0052

R2 = 0.99

peak =42.3o

R2 = 0.99

residual =36.9o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

GHN-KMD-0053

R2 = 0.99

peak =43.3o

R2 = 0.99

residual =38o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

164

GHN-KMD-0053-DUPLICATE

R2 = 0.99

peak =42.8o

R2 = 0.99

residual =37.7o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

GHN-KMD-0055

R2 = 0.99

peak =43.2o

R2 = 0.99

residual =37.7o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

165

GHN-KMD-0056

R2 = 1.00

peak = 47o

R2 = 0.99

residual = 40o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

GHN-KMD-0057

R2 = 1.00

peak =43.1o

R2 = 0.98

residual =38.5o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

166

GHN-KMD-0057-DUPLICATE

R2 = 1.00

peak =43.7o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle

GHN-KMD-0062

R2 = 0.99

peak =43.9o

R2 = 0.97

residual =38.9o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

167

GHN-KMD-0063

R2 = 1.00

peak =44.9o

R2 = 0.99

residual =38.9o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

GHN-KMD-0071

R2 = 1.00

peak =43.2o

R2 = 0.99

residual =36.9o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

168

GHN-KMD-0072

R2 = 0.99

peak =42.5o

R2 = 1.00

residual =37.6o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

GHN-KMD-0073

R2 = 1.00

peak =43o

R2 = 0.98

residual =39o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

169

GHN-KMD-0074

R2 = 0.98

peak =43.6o

R2 = 0.96

residual =38.8o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

GHN-KMD-0078

R2 = 0.99

peak =46o

R2 = 0.99

residual =37.9o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

170

GHN-KMD-0079

R2 = 1.00

peak =42.7o

R2 = 0.99

residual =37.6o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

GHN-KMD-0079-DUPLICATE

R2 = 1.00

peak =42.8o

R2 = 1.00

residual =39.8o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

171

GHN-KMD-0081

R2 = 0.99

peak =44.1o

R2 = 0.97

residual =39.2o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

GHN-KMD-0081-DUPLICATE

R2 = 0.99

peak =41.7o

R2 = 0.99

residual =37.1o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

172

GHN-KMD-0088

R2 = 0.99

peak =42.1o

R2 = 0.95

residual =38.7o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

GHN-LFG-0037

R2 = 0.98

peak =40.8o

R2 = 0.99

residual =37.9o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

173

GHN-LFG-0085

R2 = 0.99

peak =42.4o

R2 = 0.99

residual =39o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

GHN-LFG-0088

R2 = 0.99

peak =42.1o

R2 = 0.95

residual =38.7o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

174

GHN-LFG-0090

R2 = 0.98

peak = 45.7o

R2 = 1.00

residual =37o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

GHN-VTM-0450

R2 = 1.00

peak = 44o

R2 = 0.99

residual =40.6o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

175

GHN-VTM-0453

R2 = 1.00

peak =44.1o

R2 = 1.00

residual =38.3o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

GHN-VTM-0454

R2 = 0.99

peak = 43o

R2 = 0.99

residual =35.2o

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

Normal stress (kPa)

Sh

ea

r s

tre

ss

(k

Pa

)

Peak internal friction angle Residual friciton angle

176

APPENDIX E – DESCRIPTION OF GEOLOGIC UNITS, SUMMARY OF

GEOLOGICAL AND GEOTECHNICAL DATA USED FOR CORRELATIONS

177

Descriptions of geologic units at GHN. No relative age relationships can be determined between surface units A-H. (McLemore et al. 2005) Geologic Unit in this report

Description Structure Lithology Location

A Light brown unit with approximately 60% covered by cobbles or larger sized rocks with vegetation growing upon the surface.

Layered in some of the rills near the base.

mixed volcanic rocks

Southern-most surface unit of the stable part

B Massive, light brown to gray to yellow brown unit containing crusts of soluble acid salts. Approximately 65% is covered by cobbles or larger sized rocks. Consists of clayey sand with gravel and cobbles and is locally cohesive.

Shallow rills (0.2-1 m deep) of finer grained material are cut into the surface.

quartz-sericite-pyrite (QSP) altered Amalia Tuff (70%) and andesite (30%).

Surface unit of stable portion of the GHN rock pile

C Grayish brown to yellowish gray unit consisting of fine-grained materials (sand with cobbles and gravel) and approximately 15% boulders. Locally is cohesive and well cemented by clays and soluble minerals.

Massive alternating zones, up to 10 ft thick.

Amalia Tuff (70%) and andesite (30%)

Surface unit of stable portion of the GHN rock pile

D Yellow-brown gravely sand unit that differs from Unit C by a marked increase in cobbles and boulders (approximately 30-40%).

Massive Amalia Tuff (80%) and andesite (20%).

Surface unit of unstable portion of the GHN rock pile

E Orange brown unit with patches of gray sandy clay with approximately 15% cobbles and boulders.

Massive 70 % moderate to strong QSP altered Amalia Tuff and 30% weakly altered Amalia Tuff

Surface unit of unstable portion of the GHN rock pile

F Similar to Unit A, consists of dark brown, silty sand with some gravel.

Massive andesite Surface unit of unstable portion of the GHN rock pile

G Orange brown to yellow brown sandy gravel with some cobbles, includes colluvium material.

Massive andesite Surface unit of unstable portion of the GHN rock pile

H Dark gray to red-brown V-shaped unit with oxidized orange zones and consists of poorly sorted, well graded, weakly cemented, gravel sand with some fine sand to fine sand with clay, approximately 80% cobbles or boulders.

Massive andesite Surface unit at the top of stable portion of the GHN rock pile

I Light-gray, poorly sorted, well graded clayey to sandy gravel, medium hard with weak cementation, and no plasticity. The matrix is locally sandy clay with medium to high plasticity. The unit is less cemented and finer grained than the overlying unit C.

Overlain by Unit C, up to 10 ft thick

Andesite and Amalia Tuff

Subsurface oxidized unit of stable portion of the GHN rock pile

178

Geologic Unit in this report

Description Structure Lithology Location

J Dark orange-brown, poorly sorted, well graded, coarse gravel with clay matrix and weak cementation. The top of the unit locally is a bright orange oxidized layer, 2-4 inches thick.

Overlain by unit I, 3-12 ft thick

Primarily andesite Subsurface oxidized unit of stable portion of the GHN rock pile

N Light to dark brown moderately sorted, uniformly graded, moderately hard sandy clay with cobbles, with moderate to high plasticity and well cemented by clay, zones of bright orange to punky yellow oxidized sandy clay.

Heterogeneous with numerous coarse and fine layers, 5-10 ft thick

andesite and Amalia Tuff

Subsurface intermediate unit of stable portion of the GHN rock pile

K Distinctive purplish-brown gravelly sand with cobbles and is weakly cemented and very coarse, almost no clay. Cobble layer is locally overlain and underlain by finer gravelly sand layers and contacts are gradational.

grades into Unit O, 0-4 ft thick

Primarily andesite Subsurface unoxidized unit of stable portion of the GHN rock pile

L Brown gray, poorly sorted, well graded gravelly sand with cobbles.

Grades into Unit O

andesite Subsurface unoxidized unit of stable portion of the GHN rock pile

O Brown, poorly sorted, sandy gravel matrix in coarse gravel and cobbles. Numerous coarse and fine layers at varying dips and thicknesses appear in the mass of the unit. The unit has cobbles and clay layers. Heterogeneous, deformed layer with numerous S-shaped clay lenses and coarse layers.

Variable dip of individual beds

Primarily andesite Subsurface unoxidized unit of stable portion of the GHN rock pile

M Orange brown to brown, poorly sorted, well graded sandy gravel with boulders (up to 1 m diameter). Sandy gravel forms a matrix between boulders and cobbles. The fines are generally gritty.

Unit locally flattens with 20 degree dip

andesite and Amalia Tuff

Subsurface unoxidized unit of stable portion of the GHN rock pile

P dark brown, poorly sorted, well graded, sandy gravel with medium hardness and no to weak cementation

Pinches out, 0-3 ft thick

andesite Subsurface unoxidized unit of stable portion of the GHN rock pile

Q Dark brown, poorly sorted, well graded, sandy gravel with cobbles with medium hardness and no to low cementation.

Steeply dipping andesite Subsurface unoxidized unit of stable portion of the GHN rock pile

R Orange gray, poorly sorted, well graded sandy gravel to gravel with cobbles with medium to weak cementation by clay.

Pinches out, 0-3 ft thick

Primarily andesite Subsurface unoxidized unit of stable portion of the GHN rock pile

179

Geologic Unit in this report

Description Structure Lithology Location

S Dark gray, poorly sorted, well graded sandy silt with no cementation or plasticity.

Pinches out, 0-4 ft thick

Primarily andesite Subsurface unoxidized unit of stable portion of the GHN rock pile

T Dark gray, poorly sorted, well graded sandy gravel.

andesite Subsurface unoxidized unit of stable portion of the GHN rock pile

U Brown, poorly sorted well graded, sandy gravel with cobbles.

Pinches out, 0-2 ft thick

andesite Subsurface unoxidized unit of stable portion of the GHN rock pile

V Gray to brown gray poorly sorted, sandy gravel.

Pinches out, 0-10 ft thick

andesite Subsurface unoxidized unit of stable portion of the GHN rock pile

W Olive gray clay zone, similar and possibly correlated to Unit S.

andesite Subsurface unoxidized unit of stable portion of the GHN rock pile

180

Sample Units FrictAngle ResidFrictAngle LL PI NAGpH pastepHGHN-KMD-0013 O 43 38 37.81 14.31 6.06 2.49GHN-KMD-0014 K 47 39 26.51 8.47 8.55 3.19GHN-KMD-0015 R 45 40 n.d n.d 6.78 4.92GHN-KMD-0016 S 45 39 28.11 7.17 8.36 5.74GHN-KMD-0017 I 42 38 35.28 17.91 2.43 2.19GHN-KMD-0018 J 44 39 28.73 9.26 3.88 3.5GHN-KMD-0019 O 45 39 29.55 6.69 n.d 5.84GHN-KMD-0026 M 44 41 30.03 11.01 n.d 3.8GHN-KMD-0027 N 44 37 33.88 14.29 n.d 2.49GHN-KMD-0051 O 43 38 31.67 14.29 8.51 7.19GHN-KMD-0052 K 43 37 n.d n.d n.d 5.08GHN-KMD-0053 contact between Unit 43 38 35.2 17.24 6.26 4.32GHN-KMD-0055 I 43 38 29.95 5.28 n.d 4.27GHN-KMD-0056 V 47 40 29.54 3.9 7.05 4.85GHN-KMD-0057 O 43 40 32.75 14.69 n.d 7.96GHN-KMD-0062 N 44 39 35.58 15.14 n.d 4.43GHN-KMD-0063 J 45 39 38.44 16.36 n.d 3.95GHN-KMD-0065 V 44 39 35.34 16.98 n.d 5.77GHN-KMD-0071 Unit U, V contact 43 37 34.52 8.07 2.53 4.35GHN-KMD-0072 coarse zone in Unit O 43 38 32.99 16.44 n.d 7.15GHN-KMD-0073 O (coarse sand) 43 39 n.d n.d 8.62 6.55GHN-KMD-0074 U 44 39 n.d n.d 6.59 3.36GHN-KMD-0078 U 46 38 n.d n.d n.d 3.26GHN-KMD-0079 U 43 38 32.71 14.38 6.4 3.07GHN-KMD-0081 R 43 39 35.51 18.76 3.15 3.29GHN-KMD-0082 O 44 37 n.d n.d n.d 3.3GHN-KMD-0088 O 45 38 n.d n.d n.d 2.63GHN-KMD-0092 O1 44 39 n.d n.d n.d 3.72GHN-LFG-0085 K 42 39 34.68 15.13 4.2 2.98GHN-LFG-0088 O 42 39 36.06 17.82 8.99 5.43GHN-LFG-0090 P 46 37 n.d n.d 8.43 6.71GHN-VTM-0450 O (coarse layer) 44 41 n.d n.d 7.18 6.7GHN-VTM-0453 O (clay rich) 44 38 31.63 9.15 8.49 4.55GHN-VTM-0454 O 43 35 n.d n.d 3.33 3.56 n.d. = not determined, LL= Liquid limit, PI= Plastic index

181

Sample WPI MI SWI GravMoist Amalia Andesite IntrusiveGHN-KMD-0013 4.18 0.39 3 13.67 25 75 0GHN-KMD-0014 12.01 0.7 2 8.34 10 90 0GHN-KMD-0015 6.65 0.49 2 9.91 0 100 0GHN-KMD-0016 9.34 0.58 2 9.18 0 100 0GHN-KMD-0017 1.37 0.31 4 14.97 80 20 0GHN-KMD-0018 4.13 0.37 3 7.27 35 65 0GHN-KMD-0019 9.2 0.54 2 10.05 0 100 0GHN-KMD-0026 4.82 0.41 2 12.7 60 40 0GHN-KMD-0027 3.53 0.37 3 17.25 50 50 0GHN-KMD-0051 8.36 0.55 2 7.86 60 40 0GHN-KMD-0052 6.47 0.46 2 9.81 n.d. n.d. n.d.GHN-KMD-0053 4.31 0.39 3 9.35 50 50 0GHN-KMD-0055 0.65 0.26 4 10.72 n.d. n.d. n.d.GHN-KMD-0056 6.93 0.48 2 8.59 70 30 0GHN-KMD-0057 n.d n.d 2 7.89 n.d. n.d. n.d.GHN-KMD-0062 n.d n.d 3 13.54 n.d. n.d. n.d.GHN-KMD-0063 n.d n.d 3 10.3 n.d. n.d. n.d.GHN-KMD-0065 6.45 0.5 2 9.49 60 40 0GHN-KMD-0071 6.36 0.43 2 9.6 40 30 30GHN-KMD-0072 7.82 0.52 2 7.35 n.d. n.d. n.d.GHN-KMD-0073 8.95 0.57 2 11.39 10 90 0GHN-KMD-0074 7.33 0.52 2 20 80 0GHN-KMD-0078 n.d n.d 2 n.d. n.d. n.d.GHN-KMD-0079 6.4 0.46 2 20 80 0GHN-KMD-0081 6.29 0.44 2 50 50 0GHN-KMD-0082 7.98 0.51 2 11.05 95 5 0GHN-KMD-0088 4.56 0.37 2 11.76 n.d. n.d. n.d.GHN-KMD-0092 n.d n.d 2 9.75 n.d. n.d. n.d.GHN-LFG-0085 6.11 0.45 2 90 10 0GHN-LFG-0088 6.83 0.45 2 0 100 0GHN-LFG-0090 7.89 0.53 2 0 100 0GHN-VTM-0450 7.97 0.55 2 10 80 10GHN-VTM-0453 6.34 0.46 2 0 75 25GHN-VTM-0454 4.81 0.37 2 35 60 5

182

Sample_id Sphericity Roundness

GHNKMD0013 subprismoidal subangular GHNKMD0014 subprismoidal very angularGHNKMD0015 subdiscoidal angularGHNKMD0016 subprismoidal subangular GHNKMD0017 spherical subangular GHNKMD0018 spherical subangularGHNKMD0019 subprismoidal subangular GHNKMD0026 spherical angular GHNKMD0027 subdiscoidal subangular GHNKMD0051 subprismoidal subroundedGHNKMD0053 subdiscoidal angular GHNKMD0056 spherical subangularGHNKMD0071 spherical angular GHNKMD0073 subdiscoidal subangular GHNKMD0074 subdiscoidal subangularGHNKMD0079 subdiscoidal subrounded GHNKMD0081 subdiscoidal subangular GHNVTM0450 subprismoidal subangular GHNVTM0453 subprismoidal subangular

Field_idSpecific_Gravity

(g/cm3)

GHNKMD0014 2.68

GHNKMD0015 2.66

GHNKMD0017 2.65

GHNKMD0018 2.65

GHNKMD0019 2.75

GHNKMD0026 2.67

GHNKMD0027 2.66

GHNKMD0071 2.62

183

Percent of Hydrothermal Alteration. QSP = quartz-sericite-pyrite

Sample QSP Propylitic ArgilicGHN-KMD-0017 50 2 20GHN-KMD-0013 30 5 3GHN-KMD-0014 25 20 0GHN-KMD-0015 25 12 3GHN-KMD-0016 25 20 0GHN-KMD-0018 20 8 0GHN-KMD-0019 10 25 0GHN-KMD-0026 40 1 0GHN-KMD-0027 30 7 0GHN-KMD-0051 25 15 3GHN-KMD-0052 n.d n.d n.dGHN-KMD-0053 30 5 0GHN-KMD-0055 n.d n.d n.dGHN-KMD-0056 30 7 2GHN-KMD-0057 n.d n.d n.dGHN-KMD-0062 n.d n.d n.dGHN-KMD-0063 n.d n.d n.dGHN-KMD-0065 20 5 0GHN-KMD-0071 25 10 0GHN-KMD-0072 n.d n.d n.dGHN-KMD-0073 25 12 2GHN-KMD-0074 35 10 0GHN-KMD-0078 n.d n.d n.dGHN-KMD-0079 50 7 3GHN-KMD-0081 55 10 3GHN-KMD-0082 30 15 0GHN-KMD-0088 n.d n.d n.dGHN-KMD-0092 n.d n.d n.dGHN-LFG-0085 25 2 4GHN-LFG-0088 25 12 3GHN-LFG-0090 25 8 3GHN-VTM-0450 15 8 5GHN-VTM-0453 55 15 4GHN-VTM-0454 40 6 3

184

Sam

ple

SiO

2T

iO2

Al2

O3

Fe2

O3T

FeO

TF

eOF

e2O

3M

nO

Mg

OC

aON

a2O

K2O

P2O

5S

FC

O2

LO

IG

HN

-KM

D-0

013

63.6

80.

614

.59

6.23

n.d

3.48

2.4

0.07

1.46

1.17

2.42

3.68

0.23

0.24

0.01

120

4.81

GH

N-K

MD

-001

461

.05

0.82

14.7

95.

1n.

d2.

722.

110.

222.

743.

123.

314.

650.

290.

080.

0081

02.

34G

HN

-KM

D-0

015

63.8

30.

714

.36

5.72

n.d

3.15

2.25

0.37

2.05

1.38

2.49

4.07

0.25

0.18

0.01

380

3.7

GH

N-K

MD

-001

661

.88

0.79

14.4

45.

51n.

d3

2.21

0.31

2.83

2.97

3.36

3.12

0.29

0.13

0.00

990

3.42

GH

N-K

MD

-001

761

.34

0.61

14.3

76.

03n.

d3.

352.

350.

081.

511.

152.

53.

490.

233.

060.

0151

07.

4G

HN

-KM

D-0

018

70.4

50.

3612

.95

3.48

n.d

1.73

1.58

0.22

1.23

0.81

1.29

4.81

0.08

0.8

0.01

220

4.2

GH

N-K

MD

-001

961

.78

0.81

14.9

45.

35n.

d2.

882.

180.

323.

143.

593.

482.

920.

260

0.01

030

4.3

GH

N-K

MD

-002

669

.83

0.32

12.8

13.

863.

521.

981.

680.

150.

760.

52.

594.

260.

130.

170.

0075

03.

53G

HN

-KM

D-0

027

68.0

30.

4312

.93

4.57

4.15

2.45

1.88

0.21

1.05

0.56

2.03

4.15

0.19

00

04.

48G

HN

-KM

D-0

051

67.8

30.

5914

.44

4.32

n.d

2.22

1.88

0.29

1.8

1.94

3.22

3.96

0.16

00.

0071

02.

72G

HN

-KM

D-0

052

61.8

20.

614

.16

5.34

4.85

2.9

2.15

0.37

2.23

2.32

2.48

3.44

0.27

00

04.

49G

HN

-KM

D-0

053

70.6

20.

3312

.82

3.73

n.d

1.9

1.64

0.3

0.91

0.53

1.78

4.54

0.06

00.

0096

03.

65G

HN

-KM

D-0

055

71.8

60.

2712

.19

3.49

3.17

1.77

1.54

0.06

0.63

0.76

0.38

3.88

0.1

00

05.

04G

HN

-KM

D-0

056

68.3

40.

5914

.53

4.31

n.d

2.2

1.89

0.22

1.64

1.21

3.21

3.8

0.16

00.

0088

03.

09G

HN

-KM

D-0

057

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

GH

N-K

MD

-006

2n.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dG

HN

-KM

D-0

063

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

GH

N-K

MD

-006

566

.82

0.66

14.6

96.

12n.

d3.

42.

380.

522.

151.

292.

763.

730.

20.

110.

0121

03.

59G

HN

-KM

D-0

071

67.8

10.

4914

.77

3.85

n.d

1.89

1.77

0.13

1.35

1.28

3.1

3.75

0.13

0.29

0.01

270

3.35

GH

N-K

MD

-007

263

.63

0.65

14.2

65.

254.

772.

842.

130.

42.

252.

13.

093.

570.

290

00

3.6

GH

N-K

MD

-007

362

.63

0.72

14.3

85.

14n.

d2.

762.

10.

342.

652.

283.

333.

370.

260.

040.

0093

03.

17G

HN

-KM

D-0

074

65.1

60.

7114

.68

5.7

n.d

3.12

2.27

0.33

2.26

1.66

2.86

3.53

0.22

0.16

0.00

910

3.23

GH

N-K

MD

-007

8n.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dG

HN

-KM

D-0

079

67.5

80.

5514

.22

4.56

n.d

2.38

1.94

0.23

1.49

1.26

2.8

3.82

0.16

0.12

0.01

130

3.21

GH

N-K

MD

-008

166

.80.

4314

.17

3.82

3.47

1.9

1.73

0.13

1.32

1.11

2.79

3.87

0.19

0.13

0.00

870

3.16

GH

N-K

MD

-008

260

.30.

7414

.32

5.31

4.83

2.88

2.14

0.64

2.74

2.74

3.46

3.05

0.34

00

04.

6G

HN

-KM

D-0

088

64.3

50.

4914

.19

4.19

3.81

2.14

1.84

0.16

1.51

1.13

2.92

3.8

0.21

00

05.

14G

HN

-KM

D-0

092

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

GH

N-L

FG

-008

562

.66

0.69

14.6

86.

13n.

d3.

412.

380.

282.

482.

082.

623.

560.

240.

370.

0109

04.

94G

HN

-LF

G-0

088

61.2

50.

7714

.44

5.04

n.d

2.69

2.08

0.3

2.77

2.96

3.31

3.41

0.27

0.14

0.00

840

6.03

GH

N-L

FG

-009

060

.36

0.77

14.7

6.52

n.d

3.66

2.49

0.46

2.55

2.3

3.32

3.37

0.29

0.55

0.01

030

4.13

GH

N-V

TM

-045

063

.45

0.77

14.6

26.

38n.

d3.

572.

450.

362.

61.

683.

273.

30.

250.

190.

0091

03.

19G

HN

-VT

M-0

453

59.8

0.71

14.4

96.

185.

473.

452.

380.

462.

572.

262.

613.

530.

291.

460.

0134

05.

13G

HN

-VT

M-0

454

64.8

70.

4815

.32

4.11

n.d

2.04

1.87

0.19

1.61

1.46

2.68

3.68

0.13

0.96

0.09

530

4.9

185

Sam

ple

Qu

artz

k-fe

ldsp

arP

lag

iocl

ase

epid

ote

calc

ite

pyr

ite

FeM

nO

xid

eg

oet

hit

eh

emat

ite

chlo

rite

Au

thG

ypD

etri

tGyp

To

talC

lay

GH

N-K

MD

-001

346

740

00

2.87

00.

010.

040

0.00

18

32G

HN

-KM

D-0

014

0G

HN

-KM

D-0

015

GH

N-K

MD

-001

641

1813

70

0.25

40.

120.

083

11

13G

HN

-KM

D-0

017

GH

N-K

MD

-001

847

1712

50.

001

03

20.

92.

111

GH

N-K

MD

-001

943

1611

51

04

31

1G

HN

-KM

D-0

026

GH

N-K

MD

-002

7G

HN

-KM

D-0

051

4034

114

00.

678

0.17

0.3

42

313

GH

N-K

MD

-005

226

1513

162

03

122

1G

HN

-KM

D-0

053

3914

109

20

56

0.00

13

11G

HN

-KM

D-0

055

GH

N-K

MD

-005

637

1311

120

07

81.

291.

71G

HN

-KM

D-0

057

0G

HN

-KM

D-0

062

3314

1111

30.

001

40

08

1.95

1.05

14G

HN

-KM

D-0

063

4513

106

10.

001

30

03

31

15G

HN

-KM

D-0

065

436

510

42

10

08

11

19G

HN

-KM

D-0

071

3318

149

20

50

05

0.2

0.8

12G

HN

-KM

D-0

072

3614

1210

20.

001

30

08

2.04

0.96

13G

HN

-KM

D-0

073

GH

N-K

MD

-007

40

GH

N-K

MD

-007

8G

HN

-KM

D-0

079

3413

1112

00.

953

00.

756

22

14G

HN

-KM

D-0

081

0G

HN

-KM

D-0

082

4920

121

0.00

10.

001

20

02

11

6G

HN

-KM

D-0

088

GH

N-K

MD

-009

250

1611

21

02

02

2G

HN

-LF

G-0

085

3515

139

10.

001

60

06

1.95

1.05

14G

HN

-LF

G-0

088

3212

1114

10.

914

0.04

0.35

101

113

GH

N-L

FG

-009

0G

HN

-VT

M-0

450

3313

1111

00.

656

0.16

0.06

80.

92.

114

GH

N-V

TM

-045

347

86

80

0.00

13

00

53.

782.

2218

GH

N-V

TM

-045

440

1310

80

05

82

211

186

APPENDIX F – STANDARD OPERATING PROCEDURES FOR

PETROGRAPHIC ANALYSES

187

STANDARD OPERATING PROCEDURE NO. 24

PETROGRAPHIC ANALYSES

REVISION LOG

Revision Number Description Date

24.0 Original SOP

24.1 Revisions by PJP 1/14/04

24.2 Revisions by PJP 5/19/2004

1.0 PURPOSE AND SCOPE

This Standard Operating Procedure describes the method for petrographic analyses involving optical examinations and mineral identification, which are the basis for all geologic models and characterization, specifically in differentiating various rock units, determining rank and intensity of alteration, determining chemistry of alternating fluids, describing cementation, and determination of paragenesis of mineralization, alteration, and cementation. Mineralogical data is required in selecting samples for weathering cells (Lapakko), and for developing geotechnical models (Wilson), weathering models (Trujillo), and geologic (mineralogy, stratigraphy, internal structure) models of the rock piles. Alteration rank is based upon the mineral assemblages, which infers temperature, pressure, and permeability conditions at the time of formation. Forms are in Appendix 1. Digital photographs will be taken (SOP 4).

2.0 RESPONSIBILITIES AND QUALIFICATIONS

The Team Leader and Characterization Team will have the overall responsibility for implementing this SOP. They will be responsible for assigning appropriate staff to implement this SOP and for ensuring that the procedures are followed. All personnel performing these procedures are required to have the appropriate health and safety training. In addition, all personnel are required to have a complete understanding

188

of the procedures described within this SOP, and receive specific training regarding these procedures, if necessary. All environmental staff and assay laboratory staff are responsible for reporting deviations from this SOP to the Team Leader.

3.0 DATA QUALITY OBJECTIVES

This SOP address objectives 2-7 and 9 in the data quality objectives outline by Virginia McLemore for the "Geological and Hydrological Characterization at the Molycorp Questa Mine, Taos County, New Mexico”. Determine how mineralogy, stratigraphy, and internal structure of the rock piles

contribute to weathering and stability. Determine if the sequence of host rock hypogene and supergene alteration and

weathering provides a basis to predict the effects weathering can have on mine rock material.

Determine how weathering of the rock pile affects the geotechnical properties of the rock pile material.

Determine if cementation forms in the rock piles and the effect of such cementation on the stability of the rock piles.

Determine the concentrations of pyrite and carbonate minerals so that a representative sample goes into the weathering cells.

Determine how the concentration and location of pyrite and its weathering products in the waste rock piles affect the weathering process.

Determine if the geotechnical and geochemical characteristics of the bedrock (foundation) underlying the rock piles influences the rock pile stability.

4.0 RELATED STANDARD OPERATING PROCEDURES

The procedures set forth in this SOP are intended for use with the following SOPs: SOP 1 Data management (including verification and validation) SOP 2 Sample management (chain of custody) SOP 4 Taking photographs SOP 5 Sampling outcrops, rock piles, and drill core (solid) SOP 6 Drilling, logging, and sampling of subsurface materials (solid) SOP 8 Sample preparation (solids) SOP 9 Test pit excavation, logging, and sampling (solid)

5.0 EQUIPMENT LIST

The following materials are required for petrographic analyses: Petrographic microscope

Camera

Forms

189

6.0 PROCEDURES

Petrography will be performed using standard petrographic and reflected ore microscopy techniques. Mineral concentrations will be estimated using standard charts and data are summarized. Estimates of both primary and alteration minerals will be determined, cementation described, diagenesis described, porosity estimated, and the alteration intensity will be determined from the concentration of alteration minerals. Any special features will be noted on the forms (Appendix 1). Photographs will be taken and the thin section photograph subform will be filled out. Description of alteration

Alteration is a general term describing the mineralogic, textural, and chemical changes of a rock as a result of a change in the physical, thermal, and chemical environment in the presence of water, steam, or gas (Bates and Jackson, 1980; Henley and Ellis, 1983). The nature of the alteration depends upon (a) temperature and pressure at the alteration site, (b) composition of the parent rock, (c) composition of the alteration (invading) fluids, (d) permeability of the parent rock, and (e) duration of the alteration process. Recognition and genesis of alteration are important in mineral exploration and understanding the formation of ore deposits, because specific alteration types are associated with specific ore deposits. Furthermore, alteration halos surrounding ore deposits are typically more widespread and easier to recognize than some of the orebodies themselves (Guilbert and Park, 1986).

Intensity of alteration is a measure of how much alteration has occurred and can

be estimated by determining the percentage of newly formed secondary minerals by visual estimation (P. R. L. Browne, unpubl. report, Spring 1992). For example, a parent rock that has not been affected by any alteration would have zero intensity of alteration, whereas a parent rock in which all primary minerals have been replaced by secondary minerals would have an alteration intensity of 100%.

Alteration rank is based upon the identification of new secondary minerals and their significance in terms of alteration conditions such as temperature, pressure, and permeability. The intensity of alteration is independent of rank of alteration (Browne, 1978; Simmons et al., 1992). It is possible to have rocks with a high rank but low intensity (hot, impermeable zones) or other rocks of low rank, but high intensity (cooler, permeable zones; P. R. L. Browne, unpubl. report, Spring 1992).

Alteration of parent rock occurs by several processes: (1) direct deposition, (2) replacement, (3) leaching, and (4) ejecta (Browne, 1978). All four processes are found in the Questa district. Direct deposition occurs by precipitation of new minerals in open spaces, such as vugs or fractures. Replacement occurs when one mineral is converted to a new mineral by fluids entering the rock. These two processes are common and depend upon permeability and duration of the process. Complete fluid/mineral equilibrium is rarely achieved because of these factors. Leaching and supergene enrichment occurs locally where steam condensate reacts to form acidic solutions by the oxidation of H2S or CO2 which then attacks the parent rock and dissolves primary or secondary minerals.

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Silica residue is a common result of leaching and is a spongy or vuggy altered rock consisting of predominantly quartz, iron and titanium oxides. Direct deposition or replacement may occur after leaching, thereby producing overlapping alteration types. Ejecta, hydrothermal brecciation, and hydrofracturing are another form of alteration, where hot water and/or steam physically breaks the parent or even altered rock apart. If this forceful ejection of fluids occurs at or near the surface, hydrothermal eruptions of water, steam, and rock can occur. Silicification following the brecciation is common.

The term mineral assemblage implies mutual equilibrium growth of mineral

phases, whereas mineral association implies that the mineral phases are only in physical contact. A number of terms are applied to various alteration assemblages. Deuteric alteration refers to the interaction between volcanic or magmatic rocks and magmatic-hydrothermal fluids during the cooling of the igneous rocks. A variety of alteration minerals may be produced. Propylitic alteration is the mineral assemblage consisting of epidote, chlorite, pyrite, quartz and carbonate minerals. Sericitic alteration is defined by the dominance of illite, sericite, and/or muscovite. The major difference between these three K-micas is size: illite is a clay-size K-mica, whereas muscovite is larger. Sericite is of intermediate size. Some minor compositional differences also occur between the three minerals. Argillic alteration consists of kaolinite, smectite (montmorillonite clays), chlorite, and sericite. Advanced argillic alteration consists of kaolinite, quartz, alunite, pyrophyllite, and other aluminosilicate minerals. Silicic alteration is produced by the addition of silica, predominantly as quartz. Then the rock and minerals are subjected to supergene alteration and finally weathering, which continues today. It may be difficult to distinguish between supergene alteration and modern weathering.

Description of pyrite and carbonate minerals Pyrite and carbonate minerals are described in detail because of their importance in generating or preventing acid drainage. The abundance, texture, grain size, contact relationships, shape, integrity, paragenesis, composition, surface area, and occurrence or association are described in detail in the petrographic form. Specific carbonate minerals are identified.

7.0 COLLECTION OF SAMPLES

Samples are collected according to the sample plan and SOP 5, 6, and 9 and prepared according to SOP 8. Thin sections are preferred, but grain mounts can be used for unconsolidated material.

8.0 QUALITY ASSURANCE/QUALITY CONTROL PROCEDURES AND SAMPLES

9.0 SAMPLE HANDLING

Thin sections, grain mounts and other samples are archived after petrographic description.

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APPENDIX F – TERMINOLOGY

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Terminology Definition Liquid Limit The liquid limit is the dividing line

between the liquid and plastic states. The liquid limit is reported in terms of the water content at which a soil changes from the liquid to the plastic state (Liu and Evett, 2003).

NAG pH(Net Acid Generation) The NAG pH measures the net acid remaining, if any, after complete oxidation of the material with hydrogen peroxide and allowing complete reaction of the acid formed with the neutralizing components of the materials (Lewis et al., 1997). After neutralization is complete, the remaining H2SO4, if any, is titrated with NaOH. The amount of NaOH needed is expressed as kg of CaCO3

equivalents per ton of material and is equal to the NAG of the material.

Paste pH Paste pH is the pH measured on a mixture of soil and deionized water which forms a slurry or paste.

Plasticity Index The plasticity index is the difference between the liquid and the plastic limits (Liu and Evett, 2003).

Plastic Limit Plastic limit is the dividing line between the plastic and semisolid states. It is quantified for a given soil as a water content at which the will begin to crumble when rolled into small threads (Liu and Evett, 2003).

Specific gravity The term specific gravity is defined as the ratio of the mass of a given volume of material to the mass of an equal volume of water. Equation: Gs = (Ms/Vs)/w, where Ms is the mass of solids, Vs is the volume of solids, and w is the density of water (Liu and Evett, 2003).

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