Drilling and Sampling of Soil and Rock

8/10/2019 Drilling and Sampling of Soil and Rock

1/45

CIVL576 1

Unit 2: Drilling and sampling of soil and rock

Exploration in soil Soil drilling

Soil samples Soil samplers

Sampling interval

Sample identification and tests

Exploration in rock Rock drilling and sampling

Non-core drilling

Core drilling

Observation during core drilling

Geologic mapping


2/45

CIVL576 2

References

GEO. 1987. Geoguide 2-Guide to site investigation.Geotechnical Engineering Office, Hong Kong SAR.

Mayne, P.W., Christopher, B.R., and DeJong, J. 2001.Manual on Subsurface Investigations. National HighwayInstitute Publication No. FHWA NHI-01-031, Federal

Highway Administration, Washington, DC. (Chapter 3)


3/45

CIVL576 3

Existing guidance

Key guidance on site investigations is contained in GEOs Guide toSite Investigation (Geoguide 2). Other relevant documents

include: AGS-HKs Ground Investigation Guidelines. GEO (2001). Geospec 3, Model Specification for Soil Testing.

BS5930 (BSI, 1999) gives international guidance. International Society for Rock Mechanics and American Society

for Testing and Materials standards for rock testing.

IMMM-HK (2003). Ground Investigation Working Party Final

Report. GEO (2005). Site Investigation for Tunnel Works, Technical

Guidance Note No. 24 (TGN 24).


4/45

CIVL576 4

Soil drilling

A wide variety of equipment is available for performingborings and obtaining soil samples. The method used to

advance the boring should be compatible with the soiland groundwater conditions to assure that soil samplesof suitable quality are obtained.

Solid stem continuous flight augers

Hollow stem continuous flight augers

Rotary wash borings

Bucket auger borings

Exploration pit excavation


5/45

CIVL576 5

Solid stem continuous flight augers

Solid Stem Continuous Flight Auger Drilling System: (a) In use on drill rig, (b) Finger and

fishtail bits, (c) Sizes of solid stem auger flights, (d) Different assemblies of bits and augerflights. (All pictures in the above format are courtesy of DeJong and Boulanger, 2000)

(b)

(c) (d)

Limited to stiff

cohesive soils

where the boring

walls are stable forthe entire depth of

boring.


6/45

CIVL576 6

Hollow stemcontinuous flightaugers

Hollow Stem Continuous Flight

Auger Drilling Systems: (a)Comparison with solid stemauger; (b) Typical drillingconfiguration; (c) Sizes of hollowstem auger flights; (d) Stepwisecenter bit; (e) Outer bits; (f)Outer and inner assembly.


7/45

CIVL576 7


Dimensions of common hollow-stem augers

(1 8.500)470(17.500)446(12.250)311

(14.750)375(14.000)356(10.250)260

(13.000)330(12.250)311(8.250)210

(12.000)318(11.250)295(7.250)184

(10.250)260(9.625)244(6.250)159

(8.250)210(7.625)194(4.250)108(7.750)197(7.125)181(3.750)95

(7.250)184(6.625)168(3.250)83

(6.750)171(6.125)156(2.750)70

(6.250)159(5.625)143(2.250)57

Cutting Diameter ofAuger Head

mm (in)

Outside Diameter ofFlighting

mm (in)

Inside Diameter ofHollow Stem

mm (in)

Note: Adapted after Central Mine Equipment Company. For updates, see: http://www.cmeco.com/


8/45

CIVL576 8


Hollow-stem augering methods are commonly used in claysoils or in granular soils above the groundwater level,

where the boring walls may be unstable. The augers form a temporary casing to allow sampling of

the "undisturbed soil" below the bit. The cuttings

produced from this drilling method are mixed as theymove up the auger flights and therefore are of limited usefor visual observation purposes.

At greater depths there may be considerable differencesbetween the soil being augered at the bottom of theboring and the cuttings appearing at the ground surface.The field supervisor must be aware of these limitations inidentification of soil conditions between sample locations.


9/45

CIVL576 9

Rotary wash borings

The most appropriate method for

use in soil formations below the

groundwater level. In rotary wash

borings, the sides of the boreholeare supported either with casing or

with the use of a drilling fluid.

Where drill casing is used, the

boring is advanced sequentially by:

driving the casing to thedesired sample depth,

cleaning out the hole to the

bottom of the casing, and

inserting the sampling deviceand obtaining the sample from

below the bottom of the casing.


10/45

CIVL576 10

(a) Typical drilling configuration;

(b) Casing and driving shoe;

(c) Diamond, drag, and roller bits;

(d) Drill f luid discharge;

(e) Fluid cuttings catch screen;

(f) Settling basin (mud tank).


11/45

CIVL576 11

Dimensions of common drill rods, Http://www.boartlongyear.com/

34.9 (1.375)57.2 (2.250)66.7 (2.625)NW

19.0 (0.750)44.5 (1.750)54.0 (2.125)BW

15.9 (0.625)31.0 (1.250)44.4 (1.750)AW

12.7 (0.500)22.2 (0.875)34.9 (1.375)EW10.3 (0.405)18.3 (0.720)27.8 (1.095)RW

Inside Diameter ofCoupling mm (in)

Inside Diameter ofRod

mm (in)

Outside Diameter ofRod

mm (in)

Size

Dimensions of common f lush-joint casings, http://www.boartlongyear.com/

(3.000)76.2(3.500)88.9NW

(2.375)60.3(2.875)73.0BW

(1.906)48.4(2.250)57.1AW

(1.500)38.1(1.811)46.0EW

(1.185)30.1(1.437)36.5RW

mm (in)

Inside Diameter of CasingOutside Diameter of Casingmm (in)

Size


12/45

CIVL576 12

Bucket auger boring

Used where it is desirable toremove and/or obtain large

volumes of disturbed soilsamples;

Bucket diameter: 0.6-1.2 m

Cylinder height: 0.6-0.9 m Good for most soils,particularly gravel andcobble soils.

Setup of Bucket Auger & Rig (from ASTM D 4700)


13/45

CIVL576 13

Exploration pit

Exploration pits and trenches permit detailed examination of the soiland rock conditions at shallow depths and relatively low cost.

Depth: 2-3 m depending on requirements Sequence:

Logging vertical profile The contacts between geologic units should be identified and drawn

Characteristics and types of soil or lithologic contacts should be

noted Variations within the geologic units must be described and indicated

on the pit log wherever the variations occur.

Sample locations should be shown in the exploration pit log and theirlocations written on a sample tag showing the station location andelevation.

Groundwater should also be noted on the exploration pit log.

Photography and video logging

Backfilling


14/45

CIVL576 14

Soil samples

Disturbed samplesDisturbed samples are those obtained using equipment that destroy themacro structure of the soil but do not alter its mineralogical composition.

Specimens from these samples can be used for determining the generallithology of soil deposits, for identification of soil components and generalclassification purposes, for determining grain size, Atterberg limits, andcompaction characteristics of soils.

Undisturbed samplesUndisturbed samples are obtained in clay soil strata for use in laboratorytesting to determine the engineering properties of those soils. It should benoted that the term undisturbed soil sample refers to the relative degree of

disturbance to the soils in-situ properties. Undisturbed samples are obtainedwith specialized equipment designed to minimize the disturbance to the in-situ structure and moisture content of the soils. Specimens obtained byundisturbed sampling methods are used to determine the strength,stratification, permeability, density, consolidation, dynamic properties, and

other engineering characteristics of soils.


15/45

CIVL576 15

Common sampling methods


16/45

CIVL576 16

Soil samplers

Split barrel sampler Both granular and cohesive soils

Thin wall sampler Cohesive soils

Piston sampler

Soft soils Pitcher tube sampler:

Both hard and soft soils

Other samplers


17/45

CIVL576 17

Split barrel sampler

The split-barrel (or split spoon)sampler is used to obtaindisturbed samples in all types of

soils. The split spoon sampler istypically used in conjunction withthe Standard Penetration Test(SPT).

Standard lengths of 457 mm (18

in) and 610 mm (24 in) withinside diameters ranging from38.1 mm (1.5 in) to 114.3 mm(4.5 in) in 12.7 mm (0.5 in)increments. The 38.1 mm (1.5 in)inside diameter sampler is

popular because correlations havebeen developed between thenumber of blows required forpenetration and a few selectedsoil properties.

Split-Barrel Samplers:

(a) Lengths of 457 mm (18 in) and 610 mm (24 in);

(b) Inside diameters from 38.1 mm (1.5 in) to 89 mm

(3.5 in).


18/45

CIVL576 18

(a) Open sampler with soil sample and cutting shoe; (b) Sample jar, split-spoon, Shelby tube, and storage box

for transport of jar samples.

(a) Stainless steel and brass retainer rings (b) Sample catchers.


19/45

CIVL576 19

Thin wall sampler

The thin-wall tube (Shelby)

sampler is commonly used to

obtain relatively undisturbed

samples of cohesive soils forstrength and consolidation testing.

The sampler commonly used has

a 76 mm outside diameter and a

73 mm inside diameter, resulting

in an area ratio of 9 percent.

Thin wall samplers vary in outside

diameter between 51 mm and 76

mm and typically come in lengthsfrom 700 mm to 900 mm. The test

method for thin-walled tube

sampling is described in ASTM D

1587.


20/45

CIVL576 20

(a) (b)

The sample in Shelby Tube should be sealed with (a) 25 mm thickMicrocrystalline wax, or (b) O-ring packer.


21/45

CIVL576 21

Piston sampler

Piston Sampler. (a) Picture with thin-walled tube cut-out toshow piston, (b) Schematic (After ASTM D 4700)

(a)

The piston sampler is

basically a thin-wall tube

sampler with a piston, rod,

and a modified samplerhead. This sampler, also

known as an Osterberg or

Hvorslev sampler, is

particularly useful for

sampling soft soils where

sample recovery is often

difficult.

The quality of sampleobtained is excellent.


22/45

CIVL576 22

Pitcher tube sampler

The pitcher tube sampler isused in stiff to hard clays andsoft rocks, and is well adaptedto sampling deposits consistingof alternately hard and softlayers. This


23/45

CIVL576 23

Pitcher Sampler. (a) Sampler Being Lowered into Drill Hole; (b) Sampler During Sampling of Soft Soils, (c)

Sampler During Sampling of Stiff or Dense Soils. (Courtesy of Mobile Drilling, Inc.)


24/45

CIVL576 24

Bulk and block samples

Bulk samples are suitable for soil classification, index testing, compaction,California Bearing Ratio (CBR), and tests used to quantify the properties ofcompacted geomaterials. The bulk samples may be obtained using hand tools

without any precautions to minimize sample disturbance. The sample may betaken from the base or walls of a test pit or a trench, from drill cuttings, froma hole dug with a shovel and other hand tools, by backhoe, or from astockpile.

For projects where the determination of the undisturbed properties is verycritical, and where the soil layers of interest are accessible, undisturbed blocksamples can be of great value. Undisturbed block sampling is limited tocohesive soils and rocks. The procedures used for obtaining undisturbedsamples vary from cutting large blocks of soil using a combination of shovels,hand tools and wire saws, to using small knives and spatulas to obtain smallblocks. For cohesive soils, the Sherbrooke sampler has been developed and isable to obtain samples 250 mm diameter and 350 mm height (Lefebvre andPoulin 1979). In-situ freezing methods for saturated granular soils and resinimpregnation methods have been implemented to lock the soil in the in-situcondition prior to sampling.


25/45

CIVL576 25

Taking block rectangular sample(ASTMD7015-04)


26/45

CIVL576 26

Taking cylindrical sample(ASTMD7015-04)


27/45

CIVL576 27

Sampling interval

The sampling interval will vary between individual projects andbetween regions.

A common practice is to obtain split barrel samples at 0.75 mintervals in the upper 3 m and at 1.5 m intervals below 3 m.

In some instances, a greater sample interval, often 3 m, is allowedbelow depths of 30 m. In other cases, continuous samples may berequired for some portion of the boring.

In cohesive soils, at least one undisturbed soil sample should beobtained from each different stratum encountered. If a uniform cohesive soil deposit extends for a considerable depth,

additional undisturbed samples are commonly obtained at 3 m to 6 mintervals.

Where borings are widely spaced, it may be appropriate to obtainundisturbed samples in each boring; however, for closely spacedborings, or in deposits which are generally uniform in lateral extent,undisturbed samples are commonly obtained only in selected borings.


28/45

CIVL576 28

Unit 2: Drilling and sampling of soil and rock

Exploration in soil Soil drilling

Soil samples Soil samplers

Sampling interval

Sample identification and tests

Exploration in rock Rock drilling and sampling

Non-core drilling

Core drilling Observation during core drilling

Geologic mapping


29/45

CIVL576 29

Exploration in rock

Drilling Non-core drilling

Core drilling

Exploration pits (test pits) Observation during core drilling

Geologic mapping Geophysical methods: seismic refraction and ground

penetrating radar (Unit 8)


30/45

CIVL576 30

Soil or rock?

Defining the top of rockfrom drilling operations can be difficult,especially where large boulders exist, below irregular residual soilprofiles, and in karst terrain.

As per ASTM D 2113, core drilling procedures are used whenformations are encountered that are too hard to be sampled by soilsampling methods.

A penetration of 25 mm or less by a 51 mm diameter split-barrelsampler following 50 blows using standard penetration energy orother criteria established by the geologist or engineer should indicatethat soil sampling methods are not applicable and rock drilling orcoring is required.

In many instances, geophysical methods, such as seismic refraction,can be used to assist in evaluating the top of rock elevations in anexpedient and economical manner.


31/45


32/45

CIVL576 32

Core drilling

(b) Single Tube Core Barrel; (a) Rigid Type Double Tube Core Barrel; (c) Swivel Type Double

Tube Core Barrel, Series M with Ball Bearings. (Courtesy of Sprague & Henwood, Inc.)

(c)


33/45

CIVL576 33

Double tube core barrel

(a) Outer barrel assembly (b) Inner barrel assembly. The double-tube core

barrel offers better recovery by isolating the rock core from the drilling fluidstream and consists of an inner and outer core barrel.


34/45

CIVL576 34

Dimensions of core sizes

(after Christensen Dia-Min Tools, Inc.)

(4.827)122.6(3.346)85.0CP, PQ Wireline

(3.791)96.3(2.500)63.5HQ Wireline

(3.650)92.7(2.406)61.1HWD4,HXB Wireline, HWD3

(2.980)75.7(1.874)47.6NQ Wireline, NV

(2.980)75.7(1.874)47.6NXB Wireline, NWC3

(2.980)75.7(2.059)52.3NWD4,NWD3

(2.980)75.7(2.154)54.7NX

(2.358)59.9(1.433)36.4BQ Wireline, BV

(2.358)59.9(1.433)36.4BXB Wireline, BWC3

(2.358)59.9(1.614)41.0BWD4, BWD3

(2.358)59.9(1.654)42.0BX

(1.890)48.0(1.067)27.1AQ Wireline, AV

(1.890)48.0(1.185)30.1AWM

(1.890)48.0(1.138)28.9AWD4, AWD3

(1.890)48.0(1.185)30.1AX

(1.484)37.7(0.835)21.2EWD3

(1.484)37.7(0.846)21.5EX,EXM

Diameter of Boreholemm (in)

Diameter of Coremm (in)

Size


35/45

CIVL576 35

Coring bits

Coring bits. From left to right:

Diamond from soft to extremely hard rock

Carbide soft to medium hard rock

Sawtooth overburden and very soft rock

The coring bit is the bottommost

component of the core barrel

assembly. It is the grinding action

of this component that cuts thecore from the rock mass. Three

basic categories of bits are in use:

diamond, carbide insert, and

sawtooth. Coring bits are generally

selected by the driller and are

often approved by the

geotechnical engineer. Bit

selection should be based on

general knowledge of drill bitperformance for the expected

formations and the proposed

drilling fluid.


36/45

CIVL576 36

Drilling fluids

In many instances, clear water is used as the drilling fluidin rock coring. If drilling mud is required to stabilize

collapsing holes or to seal zones when there is loss of drillwater, the design engineer, the geologist and thegeotechnical engineer should be notified to confirm thatthe type of drilling mud is acceptable.

Drilling fluid should be contained in a settling basin toremove drill cuttings and to allow recirculation of the fluid.Generally, drilling fluids can be discharged onto the

ground surface. Water flow over the ground surface should be avoided, as

much as possible.


37/45

CIVL576 37

Observation during core drilling

Drilling rate/time Drilling process monitoring devices

Core photographs Rock classification Core recovery

Rock quality designation Drilling fluid recovery


38/45

CIVL576 38

Core recovery

The core recovery is the length of rock core recovered from a corerun (whether solid intact with no full diameter or non-intact), and therecovery ratio is the ratio of the length of core recovered to the total

length of the core drilled on a given run, expressed as either afraction or a percentage.

Core length should be measured along the core centerline. When therecovery is less than the length of the core run, the non-recovered

section should be assumed to be at the end of the run unless there isreason to suspect otherwise (e.g., weathered zone, drop of rods,plugging during drilling, loss of fluid, and rolled or recut pieces ofcore).

Non-recovery should be marked as NCR (no core recovery) on theboring log, and entries should not be made for bedding, fracturing, orweathering in that interval.


39/45

CIVL576 39

Rock QualityDesignation(RQD)

L h f RQD d i i


40/45

CIVL576 40

Length measurement for core RQD determination


41/45

CIVL576 41

Core handling

and labeling

Core Box for Storage of Recovered Rock and Labeling


42/45

CIVL576 42

Boring closure

All borings should be properly closed at the completion of the fieldexploration. This is typically required for safety considerations and toprevent cross contamination of soil strata and groundwater. Boringclosure is particularly important for tunnel projects since an openborehole exposed during tunneling may lead to uncontrolled inflow ofwater or escape of compressed air.

Any time groundwater or contamination is encountered the boreholeshould be grouted using a mixture of powdered bentonite, Portland

cement and potable water. It is good practice to grout all boreholes. Holes in pavements and

slabs should be filled with quick setting concrete, or with asphalticconcrete, as appropriate. Backfilling of boreholes is generallyaccomplished using a grout mixture . The grout mix is normally

pumped though drill rods or other pipes inserted into the borehole. Inboreholes filled with water or other drilling fluids the tremied groutwill displace the drill fluid. Provisions should be made to collect anddispose of all displaced drill fluid and waste grout.


43/45

CIVL576 43

Geologic mapping Geologic mapping is the systematic collection of local, detailed geologic data, and, for engineering

purposes, is used to characterize and document the condition of a rock mass or outcrop. The dataderived from geologic mapping is a portion of the data required for design of a cut slope or forstabilization of an existing slope. Geologic mapping can often provide more extensive and lesscostly information than drilling. The guidelines presented are intended for rock and rock-likematerials.

The first step in geologic mapping is to review and become familiar with the local and regionalgeology from published and non-published reports, maps and investigations. The mapping teamshould be knowledgeable of the rock units and structural and historical geologic aspects of thearea. A team approach (minimum of two people, the buddy system) is recommended formapping as a safety precaution when mapping in isolated areas.

Procedures for mapping are outlined in an FHWA Manual (1989) on rock slope design, excavation

and stabilization and in ASTM D 4879. The first reference describes the parameters to beconsidered when mapping for cut slope design, which include (details in Unit 3): Discontinuity type Discontinuity orientation Discontinuity in filling Surface properties

Discontinuity spacing Persistence Other rock mass parameters

These parameters can be easily recorded on a structural mapping coding form shown in Figure 3-24. ASTM D 4879 also describes similar parameters and presents commonly used geologicsymbols for mapping purposes. It also presents a suggested report outline. Presentation of

discontinuity orientation data can be graphically plotted using stereographic projections.


44/45


45/45

CIVL576 45

Documents

Drilling and Sampling of Soil and Rock