Geotechnical investigation for the rehabilitation of Jan van ......engineering team conducted geotechnical investigations for the dams; this report presents the findings of the investigations

Geotechnical investigation for the rehabilitation of Jan van Riebeek Park (Top dams) Lower Dam – Braamfontein West Water Management Unit

Reference: 504630-G2-00

Report No: 12240

Revision: 00

30 July 2019

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Report title Geotechnical investigation for the rehabilitation of Jan van Riebeek Park (Top dams) Lower Dam – Braamfontein West Water Management Unit

Document ID 12240 Project number 504630-G2-00

File path P:\Projects\504630 JRA Dams\5 DEL DES\505 Field Investigations\Geotech\JvR lower dam

Client Johannesburg Roads Agency (JRA)

Client contact Salona Moodley Client reference JRA – 18 - 107

Rev Date Revision details/status Author Reviewer Verifier (if required)

Approver

00 30 July 2019 A Nxumalo G Davis M Wainstein G Davis

Current revision 00

Coordinates Latitude: 26° 9'35.80"S Longitude: 28° 0'5.30"E

Keywords Geotechnical investigation, Jan van Riebeek park, dam, fill material, alluvium, test pits, permeability, direct shear test, embankment, Johannesburg Dome, granite

Approval

Author signature

Approver signature

Name A Nxumalo Pr Sci Nat Name G Davis Pr Sci.Nat

Title Engineering geologist Title Technical Director

Executive Summary The Johannesburg Roads Agency (JRA) was appointed by The Environment and Infrastructure Services

Department (EISD), the implementing agent for the Water and Biodiversity Project, for rehabilitation of a

number of dams within the Braamfontein West Water Management Unit in the City of Johannesburg. As part

of this appointment JRA appointed Aurecon for the design of the remedial works. The Aurecon ground

engineering team conducted geotechnical investigations for the dams; this report presents the findings of the

investigations of the Jan van Riebeek Park (Top dams) Lower Dam.

The site investigation was conducted on the 31st of May 2019 and comprised the mechanical excavation of

eight (8 No.) test pits across the site. A general appraisal of the geotechnical conditions was also carried out.

Representative samples were taken from selected horizons and submitted to SANAS accredited laboratory,

Civilab, to determine the material properties. The laboratory test results are summarised and discussed within

this report and detailed results sheets attached to Appendix D.

The objectives of the geotechnical investigation were:

• To characterise the materials in the embankment and immediate environs, with a view to

assessing their use in the embankment,

• To provide such inputs to the dam design team,

• To appraise geotechnical factors that might influence the dam condition, as well as re-design and

construction, and

• To provide generic geotechnical related considerations and recommendations.

According to the geological map of the area (East Rand 2628, 1:250 000 Geological Series), the site is

underlain by basement rocks of the Johannesburg Dome, formerly known as Halfway House granite. A fault

system trending NE – SW occurs approximately 1 km southeast of the site.

The embankment at the site appears stable, i.e. no signs of instability were noted. The natural slopes defining

the dam basin are considered stable. Furthermore, laboratory test results indicate high shear strength

parameters of the embankment fill material.

Seepages were encountered in most test pits. These test pits are located on the crest and at the toe of the

embankment as well as along the spillway channel. It noted that very wet conditions and surface water flow

occur on the right embankment and the immediate vicinity.

Significant seepage was observed beneath the spillway sill points due to the presence of a permeable horizon.

This may either be a stratum within the embankment fill or even the underlying alluvium, or even at the

interface. Further downstream, water overflows the channel which has implications for erosion of the

downstream areas.

The horizons encountered in the test pits comprised embankment fill material and alluvium. The fill material is

typically characterised by dense clayey sand and occasionally firm to stiff, sandy clay with scattered fine to

medium angular gravel. The alluvial soils are described as very soft to soft, sandy clay containing gravel in

places.

Falling head permeability tests conducted on certain horizons of fill embankment and alluvium indicate

practically impervious materials on site. According to the Unified Soil Classification System the bulk of the

materials encountered on site classify as SC type, i.e. clayey sand with many fines.

Although results show materials on site to be suitable embankment material, quantities will depend on how

much can be extracted from excavations. It is not anticipated that materials can be sourced at the park due to

nature of the facility, therefore commercial sourcing will have to be considered. This is more likely for rip-rap

material as no rock was encountered.

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Contents 1 Introduction .......................................................................................................................................... 3

2 Available information .......................................................................................................................... 3

3 Site location and description.............................................................................................................. 3

4 Geology ................................................................................................................................................. 9

5 Climate ................................................................................................................................................ 10

6 Seismicity ........................................................................................................................................... 11

7 Site investigation rationale and methodology ................................................................................ 11

8 Investigation results .......................................................................................................................... 13

8.1 Site walk-over observations ................................................................................................... 13

8.2 Soil profile ............................................................................................................................... 14

8.2.1 Embankment fill material ......................................................................................... 15

8.2.2 Alluvium ................................................................................................................... 15

8.3 Groundwater / seepage .......................................................................................................... 15

8.4 Dynamic Cone Penetrometer (DCP) test results ................................................................... 16

9 Laboratory test results ...................................................................................................................... 18

9.1 Foundation indicator test results ............................................................................................ 18

9.2 Compaction test results .......................................................................................................... 20

9.3 Shearbox test results .............................................................................................................. 21

9.4 Falling head permeability test results ..................................................................................... 21

10 Geotechnical considerations............................................................................................................ 22

10.1 Foundation permeability ......................................................................................................... 22

10.2 Erodibility of downstream areas ............................................................................................. 22

10.3 Construction materials ............................................................................................................ 22

10.4 Stability of slopes .................................................................................................................... 22

10.5 Excavatability .......................................................................................................................... 23

10.6 Groundwater conditions / seepages ....................................................................................... 23

10.7 Stability of excavations ........................................................................................................... 23

10.8 Compressible / collapsible soils ............................................................................................. 23

11 Closing remarks ................................................................................................................................. 23

12 Limitations of report .......................................................................................................................... 24

13 References.......................................................................................................................................... 25

Figures

Figure 1: Location of the site .............................................................................................................................. 4 Figure 2: View of the embankment from the east............................................................................................... 5 Figure 3: Spillway channel on the right bank ...................................................................................................... 6 Figure 4: Erosion of the upstream face of the embankment (photo is taken in the vicinity of LD TP2 looking west) ................................................................................................................................................................... 7 Figure 5: Saturated / very wet area on the right bank extending at least 50m in the easterly direction (the walkway is seen at the far end of the photo) ...................................................................................................... 8 Figure 6: Surface water flow from the dam noted at least 50m upstream of the dam ....................................... 9 Figure 7: Regional geological setting of the site (from published 1:250 000 geological map; Sheet 2628 East Rand, Council for Geoscience, 1986) .............................................................................................................. 10 Figure 8: Seismic hazard map showing peak ground acceleration (g) with 10% probability of being exceeded in a 50 year period (after SANS 10160-4:2011). .............................................................................................. 11 Figure 10: Spillway chute at the embankment ................................................................................................. 14

Project number 504630-G2-00 File 504630-G2-00 Geotechnical report_JvR lower dam FINAL.docx, 30 July 2019 Revision 0 ii

Figure 11: DCP results for LD TP07 - conducted at 240mm from surface ...................................................... 16 Figure 12: DCP results for LD TP07 - conducted from 600mm ....................................................................... 17 Figure 13: DCP results for LD TP08 - conducted at 10mm from surface ........................................................ 17 Figure 14: DCP results for LD TP08 - conducted from 1.5m ........................................................................... 18

Tables

Table 1: Summary of test pit positions ............................................................................................................. 13 Table 2: Summary of the ground profiles present in the test pits ..................................................................... 15 Table 3: Summary of test pit seepages encountered ....................................................................................... 15 Table 4: Summary of indicator test results ....................................................................................................... 18 Table 5: Parameters related to USCS groups .................................................................................................. 19 Table 6: Summary of compaction test results .................................................................................................. 20 Table 7: Summary of shearbox test results ...................................................................................................... 21 Table 8: Summary of permeability test results ................................................................................................. 21

Appendices

Appendix A: Soil and rock profile description terminology Appendix B: Test pit profiles Appendix C: Drawing (504630-0000-DRG-G2-0001 - Plan of Jan van Riebeek Lower Dam with test pit positions) Appendix D: Laboratory test results Appendix E: Dynamic Cone Penetrometer (DCP) test results

Project number 504630-G2-00 File 504630-G2-00 Geotechnical report_JvR lower dam FINAL.docx, 30 July 2019 Revision 0 3

1 Introduction

The Johannesburg Roads Agency (JRA) was appointed by the Environment and Infrastructure Services

Department (EISD), the implementing agent for the Water and Biodiversity Project, for rehabilitation of a

number of dams within the Braamfontein West Water Management Unit in the City of Johannesburg. As part

of this appointment JRA appointed Aurecon for the design of the remedial works. The Aurecon ground

engineering team conducted geotechnical investigations for the dams, this report presents the findings from

the Jan van Riebeek Park (Top Dams) Lower Dam, that will feed into the design of the remedial works.

The field investigations were conducted on the 31st of May 2019 comprising test pitting and sampling. The Jan

van Riebeek Park (Top Dams) are located within the Johannesburg Botanical Gardens in the suburb of

Emmarentia.

The objectives of the geotechnical investigation were:

• To characterise the materials in the embankment and immediate environs, with a view to assessing

their use in the embankment,

• To provide such inputs to the dam design team,

• To appraise geotechnical factors that might influence the dam condition, as well as re-design and

construction, and

• To provide generic geotechnical related considerations and recommendations.

The following works are planned as part of the rehabilitation:

• Raising of the embankment by 500mm,

• Rip-rap for upstream slope protection,

• Desilting of basin,

• Excavation of an emergency spillway channel at left bank and lining with Armorflex, and

• Repair of spillway channel at right bank.

This report deals with the findings of the investigation conducted for Jan van Riebeek Lower Dam. Findings

relating to the investigations conducted for Jan van Riebeek Upper Dam are covered in a separate report;

504630-G1-00.

2 Available information

The available information comprised:

• The 1:250 000 scale geological map (Sheet 2628 East Rand, Council for Geoscience, 1986).

• An electronic file (KMZ) showing the site location.

It is noted that no reports of previous geotechnical investigations were available during the time of the

investigation. It is considered unlikely that any such investigations have been conducted. The desk study

comprised a review of geological maps.

3 Site location and description

The Jan van Riebeek Park (Top dams) lower dam is located in the Johannesburg Botanical Gardens in the

suburb of Emmarentia. The site is accessible through Thomas Bowler street off Beyers Naude Drive. The site

location is shown in Figure 1 below.


The park, which includes the dam, is a recreational facility open to the public and is predominantly used as a

dog park.

Figure 1: Location of the site

The dam wall is an earth embankment approximately 4m high, and just over 150m in length. The slope angle

is 12 degrees. Scattered patches of grass occur on the crest of the embankment while the slope is covered

with thick lawn (Figure 2). A concrete-lined spillway channel is noted on the right bank (Figure 3).


Figure 2: View of the embankment from the east


Figure 3: Spillway channel on the right bank

At the time of the investigation the reservoir level was below crest level.

Some erosion of the upstream side of the embankment was noted (Figure 4) in the form of over-steepening

likely resulting a combination of wave action and human activity. Scattered trees are noted on the embankment.


Figure 4: Erosion of the upstream face of the embankment (photo is taken in the vicinity of LD TP2 looking west)

The right bank is defined by wet conditions extending at least 50m east (Figure 5) and significant visible surface

flow emanating from the reservoir, a significant point of surface seepage, is noted (Figure 6). The extent of

these conditions is indicated on the drawing.


Figure 5: Saturated / very wet area on the right bank extending at least 50m in the easterly direction (the

walkway is seen at the far end of the photo)


Figure 6: Surface water flow from the dam noted at least 50m upstream of the dam

4 Geology

According to the 1:250 000 geological map of the area (Sheet 2628 East Rand, Council for Geoscience, 1986),

the site is underlain by basement rocks of the Johannesburg Dome, formerly known as Halfway House granite.

The specific lithologies comprise ultramafic rocks, granites, dioritic gneiss, hornblende gneiss, biotite gneiss

and hybrid mafic rocks. The geological setting of the site is shown in Figure 7 below. A fault system trending

NE – SW occurs approximately 1 km SE of the site.


Figure 7: Regional geological setting of the site (from published 1:250 000 geological map; Sheet 2628 East

Rand, Council for Geoscience, 1986)

5 Climate

The site is in an area with a Weinert N-value (Weinert, 1980) of about 3.3, which indicates a humid climate.

These conditions indicate that chemical decomposition of the underlying bedrock is the main mode of

weathering and generally thick residual soil sequences tend to develop.


Where in-situ soils were encountered these comprised alluvial deposits accumulating along the banks of

Braamfontein Spruit (stream). The occurrence of occasional ferricrete concretions (LD TP06) within the

alluvium is noted.

6 Seismicity

The greater Johannesburg area is affected by natural and mining induced seismic activities. The Jan van

Riebeek Lower Dam is located in this area characterised by the seismic hazard considered moderate to high.

A Peak Ground Acceleration (PGA) close to 0.2g (SANS 10160-4:2011) can be associated with the area with

a probability of being exceeded in a 50-year period. The seismic map below, from the published SANS 10160-

4:2011 document, shows the relative position of the site to the defined seismic zones.

Figure 8: Seismic hazard map showing peak ground acceleration (g) with 10% probability of being exceeded in a

50 year period (after SANS 10160-4:2011).

7 Site investigation rationale and methodology

These investigations are considered high level investigations aimed at providing geotechnical information for the design of the remedial works. Shallow test pitting only, supplemented by sampling and laboratory testing was undertaken. No deep investigations, i.e. drilling of boreholes were included. Dynamic Cone Penetrometer (DCP) tests were conducted at LD TP07 and LD TP08. The investigation methodology is expanded below.

The site investigation commenced with a review of all available information of the area such as geological maps, relevant literature etc. The desktop study was followed by field investigations.

A health and safety file was compiled as part of compliance to the South African Occupational Health and Safety Act, OHS (Act 85 of 1993) to ensure a safe working environment for Aurecon staff on site and the sub-

SITE


contractors. Part of the documents contained in the file is the safe working procedures document which covers the assessment of test pits by an appointed excavation competent person prior to entry into the test pit. An inspection checklist cited in this document was used to assess the safety of the test pit excavations before entry.

A site walk-over and the test pitting were conducted on the 31st of May 2019. Mechanical (using a New Holland

B90B Tractor Loaded Backhoe) and hand excavated test pits were located on site. Very wet conditions, which

were ultimately observed to be soft areas, on the right bank would have presented a challenge to entry of the

TLB, i.e. damage of the lawn and possibly sinking, therefore hand excavated test pits were located in this area.

A total of eight (8 No.) test pits were excavated at predetermined locations. The test pits were terminated at

depths ranging between 0.6 and 2.3m from surface. Test pits LD TP02, LD TP06 and LD TP07 were terminated

at depths less than 1.5 to 2m due to seepage and the resulting. unsafe working conditions. The locations of

the test pits are indicated on Drawing 504630-0000-DRG-G2-0001. The test pit positions were recorded on site

using a hand-held GPS.

The test pits were profiled by engineering geologists in accordance with South African best practice, after Jennings, Brink and Williams (1973). A summary of the test pit data is given in Table 1 and detailed ground profile descriptions are attached in Appendix B of this report.

Test pits were backfilled immediately after profiling and sampling, and not excavations were left open unattended, or overnight. Controlled compaction of test pits on the embankment was carried by Civilab personnel.

Representative samples were taken from the test pits and submitted to SANAS-accredited laboratory, Civilab (Pty) Ltd, for classification and geotechnical testing. Tests conducted include:

• Foundation indicator tests (comprising of grading and hydrometer analyses, Atterberg limits and Linear Shrinkage);

• Proctor compaction; Maximum Dry Density (MDD) and Optimum Moisture Content (OMC);

• Quick direct shear tests; and

• Falling head permeability tests.

Laboratory test results are summarised in Section 9 and detailed test results sheets attached to Appendix D.


Table 1: Summary of test pit positions

Test Pit No. SA Lo 29 WGS84 Depth (m) Remarks

Latitude Longitude

LD TP01 99881 2894889 2.0 Target depth reached;

test pit located on the

crest

LD TP02 99838 2894938 1.6 Terminated due to

seepage – excavation

unsafe; test pit located on

the crest


located at the

embankment toe; very

slow seepage at 1.2m


test pit located on the

crest; very slow seepage

at the base


test pit located at edge of

embankment


seepage; test pit located

along discharge chute


seepage; test pit located

along spillway channel


test pit located on right

bank

8 Investigation results

8.1 Site walk-over observations

The dam on the upslope has been eroded likely as a combined result of wave action against the unprotected

face and human activities. The extent of the erosion is shown in Figure 4 above and runs almost the entire

length of the embankment.


Figure 9: Spillway chute at the embankment

The existing spillway chute is shown in Figure 3 and Figure 9. The spillway and chute indicate a significant

seepage problem; no water is observed to flow over the spillway sill, yet significant water flow was noted to

exit from beneath the concrete slabs. Erosion of the channel sidewalls was also noted.

The downstream areas are vegetated with trees and tall grass. Trees were also noted scattered on the

embankment.

8.2 Soil profile

Embankment fill material and alluvium (occasionally ferruginised) were encountered in the test pits. The details of the horizons in each test pit are summarised in the table below.


Table 2: Summary of the ground profiles present in the test pits

Test Pit No. Fill (m) Alluvium (m)

LD TP01 0.0 - 2.0+ -

LD TP02 0.0 - 1.6+ -

LD TP03 0.0 – 0.5 0.5 – 2.3+

LD TP04 0.0 – 2.2+ -

LD TP05 0.0 - 1.3 1.3 – 2.1+

LD TP06 - 0.0 – 1.3+

LD TP07 - 0.0 – 0.6+

LD TP08 - 0.0 – 1.5+

8.2.1 Embankment fill material

The embankment fill material at the Lower Dam is typically characterised by dense, clayey sand and

occasionally firm to stiff, sandy clay with scattered, predominantly fine to medium, angular gravel. The moisture

conditions are generally slightly moist becoming moist with depth and wet to very wet below depths at which

seepage was encountered. At the embankment toe (test pit LD TP03) the embankment fill is described as

moist, very soft to soft, sandy clay.

8.2.2 Alluvium

Alluvial soils occur at the toe of the embankment, the right bank and along the spillway channel. Alluvial soils

at the toe are described as soft, silty clay while at the right bank and along the spillway channel the alluvium

comprises very soft to firm sandy clay with fine to medium, angular to sub-rounded quartz gravel.

Of interest is the very low rate of seepage at the boundary of the silty clayey alluvium horizons at LD TP03.

Here seepage was noted but only limited seepage after the short time the pit was open suggesting low

permeability material.

8.3 Groundwater / seepage

A summary of test pits at which seepages were encountered are given in the table below and also shown on

the drawing.

Table 3: Summary of test pit seepages encountered

Test Pit No. Depth (m) Location of test pit

LD TP02 1.5 Crest of embankment

LD TP03 1.2 Toe of embankment

LD TP04 2.0 Crest of embankment


Test Pit No. Depth (m) Location of test pit

LD TP06 1.0 Along discharge chute

LD TP07 0.6 Spillway channel

8.4 Dynamic Cone Penetrometer (DCP) test results

Dynamic Cone Penetrometer (DCP) tests were conducted at LD TP07 and LD TP08, i.e. adjacent to and at

the base of each test pit. DCPs were incorporated into the field investigation programme to determine useful

parameters i.e. stiffness, particularly in test pits which would likely have shallow seepage therefore be profiled

from surface spoil. Such conditions were suspected at the right bank due to wet conditions apparent on the

surface. LD TP07 had seepage and the DCP at LD TP08 was conducted to correlate the results as these test

pits are defined by a similar profile. The results are presented in Figure 13 to Figure 16 below showing mm /

blow with depth and associated consistencies stipulated in Byrne et al., (1995).

Figure 10: DCP results for LD TP07 - conducted at 240mm from surface

The above DCP was conducted from 240mm below surface to a depth of just over 1000m below surface. The profile in this area comprises fine grained soils. The results indicate a range of 35 to 52mm/blow from surface to 0.5m indicative of firm to soft soils Below this depth to 1000mm, the values range between 18 and 25mm/blow indicative of stiff soils.

0

100

200

300

400

500

600

700

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Dep

th (

mm

)

mm / blow

DCP Test Results


Figure 11: DCP results for LD TP07 - conducted from 600mm

The DCP conducted at the base of the LD TP07. i.e. at 600mm show variable consistency ranging from very soft to stiff. Below this depth the consistency varies from firm to stiff.

Figure 12: DCP results for LD TP08 - conducted at 10mm from surface

The DCP test results indicate that the top 300mm of the ground profile is predominantly very soft with a maximum value of 65mm/blow recorded. Below this depth the values decrease pointing to firm to stiff soils. It is noted that the profile below 0.7m contains scattered gravel which tends to influence DCP readings.

0

100

200

300

400

500

600

700

0 10 20 30 40 50 60 70

Dep

th (

mm

)mm / blow

DCP Test Results

0

100

200

300

400

500

600

700

0 10 20 30 40 50 60 70

Dep

th (

mm

)

mm / blow

DCP Test Results


Figure 13: DCP results for LD TP08 - conducted from 1.5m

The top 0.35m shows values that range between 30 and 45mm/blow. A pocket of very soft / very loose material occurs at the top 100mm (60mm/blow). The values tend to improve below these depths ranging between 5 and 20mm/blow. These values are indicative of stiff to very stiff or medium dense to dense soils.

9 Laboratory test results

The laboratory test results are summarised and discussed below, and the detailed test results are attached

in Appendix D.

9.1 Foundation indicator test results

Disturbed soil samples of representative horizons were taken for laboratory testing to confirm the compositions

of the materials. The results are summarised in the table below.

Table 4: Summary of indicator test results

TP

No

Depth

(m)

Material

type

Particle Size % Atterberg Limits

%

GM AASHTO/

USCS

classification;

expansion

potential

Clay Silt Sand Gravel LL PI LS

Embankment Fill Material

LD TP01 1.3- 2.0 Embankment

fill material

7 34 54 5 23 11 4.5 0.71 A-6 (2) / SC;

Medium

LD TP02 0.7-1.5 Embankment

fill material

9 9 45 37 51 20 7.5 1.85 A-2-7(2) / SM;

Low

0

100

200

300

400

500

600

700

800

900

1000

0 10 20 30 40 50 60 70

Dep

th (

mm

)mm / blow

DCP Test Results


TP

No

Depth

(m)

Material

type

Particle Size % Atterberg Limits

%

GM AASHTO/

USCS

classification;

expansion

potential

Clay Silt Sand Gravel LL PI LS


fill material

20 21 50 9 27 13 50.0 1.01 A-7-6(7) / SC;

Low


fill material

17 34 36 13 35 20 8.0 0.91 A-6(4) / SC;

Medium

LD TP05 0.55- 0.9 Embankment

fill material

21 23 54 2 27 12 6.0 0.75 A-6 (2) / SC;

Low

Alluvium

LD TP03 0.50-1.20 Alluvium 27 11 62 - 50 29 13.5 0.97 A-7-6 (7) / SC;

Medium

LD TP06 0.90-1.30 Alluvium 27 11 57 5 35 20 8.0 0.94 A-6 (4) / SC;

Medium

LD TP07 0.4-0.6 Alluvium 2 21 67 10 25 8 3.5 1.2 A-2-4 (0) / SC,

Low

LD TP08 0.00-0.60 Alluvium 18 8 53 21 25 8 3.5 1.20 A-2-4 (0) / SC;

Low

AASHTO – American Association of State Highway and Transport Officials USCS – Unified Soil Classification System LL – Liquid Limit PI – Plasticity Index LS – Linear Shrinkage GM – Grading Modulus SC – Clayey Sand, sandy-clay mixtures SM– Silty sands, sand-silt mixtures

Based on the table above, the results show the following:

• The results show that the alluvial soils contain percentages of silt ranging between 8 and 21% and

sand ranging between 53 and 67%. Maximum clay percentage recorded is 27% and a lowest value of

2%. Gravel percentage ranges between 5 and 21%. According to the Unified Soil Classification

System (USCS) the material classified as SC. In accordance to the method proposed by Van der

Merwe (1973) this material has low and medium potential for expansion.

• The embankment fill material is classified as SC and SM according to the Unified Soil Classification

System (USCS). The material consists of gravel ranging between 2 and 37%. Silt ranges between 9

to 34% and clay ranges between 7 to 21%. In accordance to the method proposed by Van der Merwe

(1973) this material has low and medium potential for expansion.

The USCS grouping of soils can be used to provide friction angles and other parameters of the materials, in

the absence of other test data. These parameters are presented below for the materials encountered on site,

but other test results have also subsequently been provided.

Table 5: Parameters related to USCS groups

Test Pit No. USCS group Classification Unit weight

(kN/m3)

Friction angle

(º)

Cohesion

(kPa)

Embankment fill material

LD TP01 SC Clayey sand,

many fines

20.5 (± 2.0) 28 (± 4) 5 (± 5.0)


Test Pit No. USCS group Classification Unit weight

(kN/m3)

Friction angle

(º)

Cohesion

(kPa)

Embankment fill material

LD TP02 SM Silty sand; little

fines

20 (± 2.5) 34 (± 3) 0


many fines

20.5 (± 2.0) 28 (± 4) 5 (± 5.0)


many fines

20.5 (± 2.0) 28 (± 4) 5 (± 5.0)


many fines

20.5 (± 2.0) 28 (± 4) 5 (± 5.0)

Alluvium


many fines

20.5 (± 2.0) 28 (± 4) 5 (± 5.0)


many fines

20.5 (± 2.0) 28 (± 4) 5 (± 5.0)


many fines

20.5 (± 2.0) 28 (± 4) 5 (± 5.0)


many fines

20.5 (± 2.0) 28 (± 4) 5 (± 5.0)

Note: The soil classes and estimated properties have been adapted from Krahenbuhl and Wagner (1983).

The lower bound value for cohesion (5±5kPa) should be considered representative of the alluvial profile

encountered in the area of the embankment i.e.: UD TP04.

9.2 Compaction test results

Compaction tests were also conducted on selected samples to determine the compaction properties of the

materials and the results are summarised in the table below.

Table 6: Summary of compaction test results

TP No. Material type Depth (m) Standard Proctor

MDD (kgm3) OMC %

LD TP02 Embankment fill material 0.70-1.50 1864 12.6



LD TP06 Alluvium 0.90-1.30 1860 14.5

LD TP08 Alluvium 0.0-0.60 1633 17.7

MDD – Maximum Dry Density OMC – Optimum Moisture Content

According to the table above, embankment fill materials have a Maximum Dry Density (MDD) ranging between

1738 to 1864 kg/m3. The Optimum Moisture Content (OMC) ranges between 12.6 and 18.5%. These

parameters would be consistent with required material properties for a homogeneous embankment.


The alluvial soils yielded MDD ranging between 1633 to 1860 kg/m3 and an OMC of 14.5 to 17.7%. The

alluvium’s compaction characteristics are therefore compatible with the materials in the embankment.

9.3 Shearbox test results

Quick undrained shear tests were conducted on remoulded disturbed samples of embankment fill material and

alluvium to determine the strength parameters of these materials. The test was conducted on samples

remoulded to 90% standard Proctor compaction. The results are of significance for the stability of the

embankment and are summarised as follows:

Table 7: Summary of shearbox test results

TP No. Material type Depth (m) Shear strength parameters

Cu (kPa) Nu (deg)

LD TP02 Embankment fill material 0.7 - 1.5 53.5 47.6

LD TP03 Embankment fill material 0.2 - 0.5 44.6 45.0

LD TP03 Alluvium 0.5 - 1.2 18.1 27.5

LD TP06 Alluvium 0.9 - 1.3 55.7 35.9

LD TP08 Alluvium 0.0-0.6 85 27.6

Cu = Cohesion intercept Nu = Angle of shearing resistance

These shear strength parameters for both the embankment materials as well as the alluvium would fall in the

range that might be expected for a homogeneous embankment. Note that it is assumed the current

embankment is homogeneous, and not a zoned embankment.

9.4 Falling head permeability test results

Falling permeability tests were conducted on disturbed soil samples of embankment fill material and alluvium

remoulded to 90% standard proctor compaction. The samples were saturated and tested under a load of

100kPa. Densities are reported under this load.

Table 8: Summary of permeability test results

TP No. Material type Depth (m) Dry density

(kg/m3)

Coefficient of Permeability (m/s)

Minimum Maximum Average

LD TP02 Embankment fill material 0.7 - 1.5 1731 1.5 E-07 2.0 E-07 1.7 E-07

LD TP03 Embankment fill material 0.2 - 0.5 1679 1.5 E-09 2.2 E-09 1.8 E-09

LD TP03 Alluvium 0.5 - 1.2 1265 1.4 E-10 2.4 E-10 1.9 E-10

LD TP08 Alluvium 0.0 – 0.6 1531 1.7 E-10 4.8 E-10 2.7 E-10


An average coefficient of permeability value ranging between 1.7 E-07 and 1.8 E-09 m/s was recorded from

embankment fill material samples. Average values ranging between 1.9 E-10 and 2.7 m/s were recorded for

the alluvium. It is of interest that the alluvium is less permeable than the embankment materials. The results

of the permeability testing indicate both the embankment materials as well as the alluvium comply with typical

permeability criteria for a homogeneous embankment – or for that matter impervious core material.

10 Geotechnical considerations

10.1 Foundation permeability

Seepage at the contact of the alluvium horizons at LD TP3 (toe of embankment) was noted but the flow could

be seen after a prolonged period with the test pit being open. Such was the slow rate of seepage that it is

indicative of low permeability material. Results of the falling head permeability test support this observation;

average coefficient of permeability values ranging between 1.9 E-10 and 2.7 E10 m/s were recorded indicative

of an impervious material.

The embankment fill material also recorded values consistent with impervious material therefore it is concluded

that materials encountered on site have low permeability characteristics. The seepages noted in the test pits

then would have occurred at or towards the contact of successive horizons.

Though the permeabilities as described and measured are therefore very low, the observation of the significant

seepage beneath the spillway sill points to the presence of a permeable horizon. This may either be a stratum

within the embankment fill or even the underlying alluvium, or even at the interface. Importantly, at the time of

this visit the seepage water flowed clear and there was no sediment load that might point to internal erosion.

10.2 Erodibility of downstream areas

A walk-over did not yield evidence of any erosion of the downstream areas, apart from the above-mentioned

erosion along the spillway chute. Nevertheless, the fact that this is an earth embankment implies that material

will be erodible in the event of any sustained overtopping (of significant magnitude). The embankment is

however well grassed and low flow overtopping is not expected to result in erosion. Establishing grass cover

on any new raised embankment would be important.

10.3 Construction materials

The laboratory test results show that materials encountered on site including the existing embankment as well

as the underlying alluvium would be suitable for the raising of the embankment. It is assumed that the materials

within the basin would have the same properties as the alluvium recovered from the current test pits.

Material for rip-rap will have to be sourced commercially.

10.4 Stability of slopes

No major signs of instability, e.g. excessively steep slopes or surface cracking for example, were noted on the

fill embankment. Similarly, no such indications were noted on the natural slopes defining the dam basin at the

time of the investigation. The slopes are in any event generally flat.


10.5 Excavatability

The excavation conditions as encountered within the shallow test pits across the site, i.e. within a depth of 2m,

can be described as “Soft Excavation” according to SABS 1200 DA-1998 specification.

10.6 Groundwater conditions / seepages

Seepages were encountered in five of the test pits excavated during the investigation. These test pits are

located on the crest and at the toe of the embankment, on the right bank and along the spillway channel. Very

wet conditions and surface flow were noted on the right bank. This aspect of foundation permeability is also

discussed more fully above (Section10.1).

10.7 Stability of excavations

Test pit sidewalls were stable in all test pits excavated on site and the high friction angle values is also indicative

of materials that can retain stability of a period of time. Even with such appraisal, as part of safe practice during

the construction phase, assessment of the slope stability would be required for deep excavations, those left

open for longer periods and those where seepage is encountered. This must be conducted by an appointed

geotechnically-competent person.

10.8 Compressible / collapsible soils

The very soft to soft alluvial soils encountered on site are considered compressible.

11 Closing remarks

This report presents the results of the geotechnical investigation conducted for the remedial works at Jan van

Riebeek Park Lower Dam. The observations and parameters provided are considered adequate to address

the proposed re-design works.

The issue of embankment fill material for use in raising of the embankment will need to be considered with

regards to quantities of suitable materials that can be extracted from the site itself. It is not anticipated that

material can be sourced from the immediate surrounds as the site is located within a park, i.e. a public space.

Construction materials will therefore need to be sourced possibly from within the basin itself. Rip-rap material

requirements would have to be met by commercial sources.

Although excavations are said to be stable care will still need to be taken particularly with deep excavations,

those left open for long periods and where seepage occurs.

Scattered trees were noted on the embankment, and it is assumed that these will be removed during the

rehabilitation.


12 Limitations of report

1. Aurecon Tshwane Ground Engineering has prepared this report for the use of our Client,

Johannesburg Roads Agency (JRA) and to support the Aurecon dam design team. The report has not

been prepared for use by parties other than the Client, and the Client’s respective consulting advisors.

2. This report has been written with the express intent of providing enough information for the design of

the remedial works. The investigation has been conducted in accordance with generally accepted

engineering practice, and the opinions and conclusions expressed in the report are made in good faith

based on the information available to Aurecon Ground Engineering at the time of preparing this report.

3. There are always some variations in subsurface conditions across a site due to geological conditions

that cannot be defined fully even by exhaustive investigation. Hence, it is possible that the

measurements and values obtained from sampling and testing during the investigation may not

represent the extremes of conditions which exist within the site. The precision with which subsurface

conditions are identified depends on the method of excavation, the frequency and recovery of samples,

the method of sampling, and the uniformity of the subsurface conditions. Subsurface conditions at

other than the test pit positions may vary from the conditions encountered in the test pit locations.

4. Further, subsurface conditions, including groundwater levels can change over time. The groundwater

conditions described in this report refer only to those observed at the place and time of observation

noted in the report. These conditions may vary seasonally or as a consequence of construction

activities in the area. This should be borne in mind, particularly if the report is used after a protracted

delay or a period of protracted climatic conditions.

5. Should conditions exposed at the site during subsequent investigation or construction works vary

significantly from those provided in this report, we request that Aurecon Ground Engineering be

informed and have the opportunity to review any of the findings or conclusions of this report. It is highly

recommended that during construction the site conditions be inspected by a representative of Aurecon

Ground Engineering to confirm the geotechnical interpretations in this report.

6. Unless otherwise stated, this report does not address potential environmental hazards, or groundwater

contamination that may be present. In addition to soil variability, fill material of variable physical and

chemical composition can be present over portions of the site or on adjacent properties

7. The test pit logs represent the subsurface conditions at the specific test location only. Boundaries

between zones on the logs are not often distinct, but rather are transitional and have been interpreted.

The soil descriptions in this report are based on commonly accepted methods of classification and

identification employed in geotechnical practice, as stated in this report. Classification and

identification of soil involves judgement, and Aurecon Ground Engineering infers accuracy in the

classification and identification methods to the extent that is common in current geotechnical practice,

and within the limitations of the ground investigation that was performed.

8. It is recommended that further geotechnical input from Aurecon Ground Engineering should be sought

as the project moves into the next phase to confirm that the geotechnical assumptions made in this

report are compatible with the structural performance requirements and are being applied

appropriately.


13 References

• Byrne, G. Everett, J. P and Schwartz, K (1995). A Guide to Practical Geotechnical Engineering in Southern

Africa. 3rd edition. Franki.

• Jennings, J. E. B, Brink, A.B.A and Williams, A. A. B, (1993). Revised Guide to Soil Profiling for Civil

Engineering Purposes in Southern Africa. The Civil Engineer in SA, p 3-12. January 1973.

• Krahenbuhl, J and Wagner, A (1983). Survey, design, and construction of trial suspension bridges for

remote areas, SKAT Center for Appropriate Technology in St Gallen, Switzerland.

• SABS 1200D: 1988 Standardised specification for civil engineering construction. D: Earthworks, South

African Bureau of Standards, Pretoria.

• SANS 10160-4:2009 (2011). South African National Standard: Basis of structural design and actions for

buildings and industrial structures. Part 4: Seismic actions and general requirements for buildings. ISBN

978-0-626.

• Weinert (1980). The natural road construction materials of southern Africa. National Institute for Transport

and Road Research Pretoria.

Appendix A:

Soil and rock profile description terminology

STANDARD DESCRIPTIONS USED IN SOIL PROFILING

1. MOISTURE CONDITION 2. COLOUR

Term Description

The Predominant colours or colour combinations

are described including secondary coloration

described as banded, streaked, blotched,

mottled, speckled or stained.

Dry

Slightly moist

Requires addition of water to reach optimum moisture content for compaction

Moist Near optimum content

Very Moist Requires drying to attain optimum content

Wet Fully saturated and generally below water table

3. CONSISTENCY

3.1 Non-Cohesive Soils 3.2 Cohesive Soils

Term Description Term Description

Very Loose

Crumbles very easily when scraped with geological pick

Very soft Easily penetrated by thumb. Sharp end of pick can be pushed in 30 - 40mm. Easily moulded by fingers.

Loose Small resistance to penetration by sharp end of geological pick

Soft Pick head can easily be pushed into the shaft of handle. Moulded by fingers with some pressure.

Medium Dense

Considerable resistance to penetration by sharp end of geological pick

Firm Indented by thumb with effort. Sharp end of pick can be pushed in up to 10mm. Can just be penetrated with an ordinary spade.

Dense

Very high resistance to penetration to sharp end of geological pick. Requires many blows of hand pick for excavation.

Stiff Penetrated by thumbnail. Slight indentation produced by pushing pick point into soil. Cannot be moulded by fingers. Requires hand pick for excavation.

Very Dense

High resistance to repeated blows of geological pick. Requires power tools for excavation

Very Stiff Indented by thumbnail. Slight indentation produced by blow of pick point. Requires power tools for excavation.

4. STRUCTURE 5. SOIL TYPE

5.1 Particle Size

Term Description Term Size ( mm )

Intact Absence of fissures or joints Boulder >200

Fissured Presence of closed joints Pebbles 60 – 200

Shattered Presence of closely spaced air filled joints giving cubical fragments

Gravel 60 – 2

Micro-shattered

Small scale shattering with shattered fragments the size of sand grains

Sand 2 – 0,06

Slickensided Polished planar surfaces representing shear movement in soil

Silt 0,06 – 0,002

Bedded Foliated

Many residual soils show structures of parent rock.

Clay

SUMMARY OF DESCRIPTIONS USED IN ROCK CORE LOGGING

1. WEATHERING

Term Symbol Diagnostic Features

Residual Soil W5 Rock is discoloured and completely changed to a soil in which original rock fabric is completely destroyed. There is a large change in volume.

Completely Weathered

W5 Rock is discoloured and changed to a soil but original fabric is mainly preserved. There may be occasional small corestones.

Highly Weathered

W4 Rock is discoloured, discontinuities may be open and have discoloured surfaces, and the original fabric of the rock near the discontinuities may be altered; alternation penetrates deeply inwards, but corestones are still present.

Moderately Weathered

W3 Rock is discoloured, discontinuities may be open and will have discoloured surfaces with alteration starting to penetrate inwards, intact rock is noticeably weaker than the fresh rock.

Slightly Weathered

W2 Rock may be slightly discoloured, particularly adjacent to discontinuities, which may be open and will have slightly discoloured surfaces, the intact rock is not noticeably weaker than the fresh rock.

Unweathered W1 Parent rock showing no discolouration, loss of strength or any other weathering effects.

2. HARDNESS 3. COLOUR

Classification Field Test Compressive Strength Range

MPa

The predominant colours or colour combination

are described including secondary colouration

described as banded, streaked, blotched,

mottled, speckled or stained.

Very Soft Rock

Can be peeled with a knife. Material crumbles under firm blows with the sharp end of a geological pick.

1 to 3

Soft Rock Can be scraped with a knife, indentation of 2 to 4 mm with firm blows of the pick point.

3 to 10

Medium Hard Rock

Cannot be scraped or peeled with a knife. Hand held specimen breaks with firm blows of the pick.

10 to 25

Hard Rock Point load tests must be carried out in order to distinguish between these classifications

25 - 70

Very Hard Rock

These results may be verified by uniaxial compressive strength tests on selected samples.

70 - 200

Extremely Hard Rock

>200

4. FABRIC

4.1 Grain Size 4.2 Discontinuity Spacing

Term Size (mm) Description for: Bedding, foliation, laminations

Spacing (mm) Descriptions for joints, faults, etc.

Very Coarse >2,0 Very Thickly Bedded > 2000 Very Widely

Coarse 0,6 – 2,0 Thickly Bedded 600 – 2000 Widely

Medium 0,2 – 0,6 Medium Bedded 200 – 600 Medium

Fine 0,06 – 0,2 Thinly Bedded 20 – 200 Closely

Very Fine < 0,06 Laminated 6 – 20 Very closely

Thinly Laminated

Appendix B:

Test pit profiles

Scale1:20

0.00 Slightly moist, dark yellow to orange brown, DENSE,intact, clayey SAND with scattered angular androunded predominantly quartzite gravel. Fill.

Slightly moist, dark red, DENSE, intact, clayey SANDwith scattered fine sub-rounded gravel, Fill. Quartziteboulder at bottom of layer.

Slightly moist, light orange mottled dark yellow,MEDIUM DENSE, intact, clayey SAND with scatteredangular medium ferruginised gravel. Fill.

NOTES:

Final depth at 2.0m on fill materialNo refusalNo groundwater or seepage encounteredSidewalls stableFI sample taken at 1.3-2.0m

Johannesburg Roads Agency

HOLE No: LDTP01

Geotechnical Investigation for Janvan Riebeek Park (Top dams)

Lower Dam

CONTRACTOR:

MACHINE: New Holland 890B

PROFILED BY: A. Nxumalo & P van Helsdingen

TYPE SET BY:

JVR PARK LOWER DAM.GPJ

DATE PROFILED:

ELEVATION:

X COORD: 2894889

5/30/2019

5/30/2019DATE DRILLED:

DIAM:

INCLINATION:

Y COORD: 99881

Rep

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JOB NUMBER: 504630

Sheet 1 of 1

HOLE No: LDTP01

0.00

0.70

1.30

2.00

Disturbedsample

Scale1:20

0.00 Slightly moist, light orange, DENSE, intact, clayeySAND with scattered fine angular quartzite gravel. Fill.

Moist to very wet, dark grey mottled dark yellow,intact, sandy CLAY with abundant rubble (bricks). Fill.

NOTES:

Terminated at 1.6m due to seepageNo refusalSeepage encountered at 1.5mSidewalls stableFI, proctor, shearbox and permeability samples takenat 0.7-1.6mConsistency could not be determined at the depth>1.5m due to seepage


HOLE No: LDTP02


Lower Dam

CONTRACTOR:


PROFILED BY: A. Nxumalo & P van Helsdingen

TYPE SET BY:


DATE PROFILED:

ELEVATION:

X COORD: 2894948

5/30/2019


DIAM:

INCLINATION:

Y COORD: 99838

Rep

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y 26

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JOB NUMBER: 504630

Sheet 1 of 1

HOLE No: LDTP02

0.00

0.70

1.60

Disturbedsample

Scale1:20

0.00 Moist, dark yellow, VERY SOFT, sandy CLAY withoccasional sub-rounded medium gravel and abundantroots. Fill.

Moist, light yellow, SOFT, intact, sandy CLAY.Alluvium.

Moist, dark grey, SOFT, intact, silty CLAY. Alluvium.

Moist becoming wet with depth, dark yellow and lightgrey, SOFT, intact, silty CLAY. Alluvium.

NOTES:

Final depth at 2.3m on alluviumNo refusalVery slow seepage encountered at 1.2mSidewalls stableFI, shear box, permeability and compaction samplestaken at 0.2-0.5mFI, shear box and permeability samples taken at0.5-1.2m


HOLE No: LDTP03


Lower Dam

CONTRACTOR:


PROFILED BY: A. Nxumalo & T. Mofokeng

TYPE SET BY:


DATE PROFILED:

ELEVATION:

X COORD: 2894935

5/31/2019


DIAM:

INCLINATION:

Y COORD: 99807

Rep

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Pro

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9

JOB NUMBER: 504630

Sheet 1 of 1

HOLE No: LDTP03

0.00

0.20

0.50

1.20

2.30

Disturbedsamples

Undisturbedsamples

Scale1:20

0.00 Slightly moist, yellow brown, DENSE/STIFF, intact,clayey SAND/sandy CLAY. Fill.

Slightly moist to moist, purple brown, FIRM, intact,sandy CLAY with abundant fine to mediumpredominantly quartzite gravel. Fill.

Slightly moist to moist, dark grey, MEDIUM DENSE,clayey SAND with scattered medium angularpredominantly quartzite gravel. Fill.

NOTES:

Final depth at 2.2m on fill materialNo refusalVery slow seepage encountered at 2.0mSidewalls stableFI and Proctor samples taken at 0-1.2m


HOLE No: LDTP04


Lower Dam

CONTRACTOR:



TYPE SET BY:


DATE PROFILED:

ELEVATION:

X COORD: 2894944

5/30/2019


DIAM:

INCLINATION:

Y COORD: 99774

Rep

ort I

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Pro

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y 26

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9

JOB NUMBER: 504630

Sheet 1 of 1

HOLE No: LDTP04

0.00

1.20

2.00

2.20

Disturbedsample

Scale1:20

0.00 Slightly moist, dark grey, DENSE, intact, clayey SANDwith occasional sub-rounded predominantly quartzitegravel with abundant roots. Fill.

Slightly moist, dark yellow, DENSE, intact, clayeySAND with scattered sub-angular mediumpredominantly quartzite gravel with abundant roots.Fill.

Dry, dark reddish brown, mottled black, DENSE,intact, clayey SAND with occasional sub-angularquartzite gravel. Fill.

Slightly moist, dark grey, STIFF, intact, sandy CLAY.Alluvium.

NOTES:

Final depth at 2.1m on alluviumNo refusalNo groundwater or seepage encounteredSidewalls stableFI sample taken at 0.55-0.9m


HOLE No: LDTP05


Lower Dam

CONTRACTOR:



TYPE SET BY:


DATE PROFILED:

ELEVATION:

X COORD: 2894950

5/31/2019


DIAM:

INCLINATION:

Y COORD: 99743

Rep

ort I

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Pro

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Jul

y 26

, 201

9

JOB NUMBER: 504630

Sheet 1 of 1

HOLE No: LDTP05

0.00

0.55

0.90

1.30

2.10

Disturbedsample

Scale1:20

0.00 Moist, dark grey, SOFT, intact, sandy CLAY withabundant roots. Alluvium.

Moist, dark olive, SOFT, intact, sandy CLAY withabundant roots. Alluvium.

Moist to wet, dark yellow, mottled light grey, FIRM,intact, sandy CLAY with fine to medium angularquartzite gravel and occasional ferricrete concretions.Alluvium.

NOTES:

Terminated at 1.3m due to seepageNo refusalVery slow seepage encountered at 1.0mSidewalls stableFI and shear box samples taken at 0.9-1.3m


HOLE No: LDTP06


Lower Dam

CONTRACTOR:

MACHINE: Hand dug


TYPE SET BY:


DATE PROFILED:

ELEVATION:

X COORD: 2894925

5/31/2019


DIAM:

INCLINATION:

Y COORD: 99724

Rep

ort I

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Pro

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y 26

, 201

9

JOB NUMBER: 504630

Sheet 1 of 1

HOLE No: LDTP06

0.00

0.25

0.90

1.30

Disturbed&

undisturbedsamples

Scale1:20

0.00 Wet, dark grey, VERY SOFT, intact, sandy CLAY.Alluvium.

Wet, dark yellow, VERY SOFT, intact, sandy CLAY.Alluvium.

NOTES:

Terminated at 0.6m on alluviumNo refusalSeepage encountered at 0.6mSidewalls stableFI sample taken at 0.4-0.6mTest pit is located close to ponding of waterDCP testing was done (inside and outsite the TP)


HOLE No: LDTP07


Lower Dam

CONTRACTOR:

MACHINE: Hand dug


TYPE SET BY:


DATE PROFILED:

ELEVATION:

X COORD: 2894962

5/31/2019


DIAM:

INCLINATION:

Y COORD: 99738

Rep

ort I

D:

_ZA

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PIT

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Pro

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Jul

y 26

, 201

9

JOB NUMBER: 504630

Sheet 1 of 1

HOLE No: LDTP07

0.00

0.40

0.60

Disturbedsample

Scale1:20

0.00 Slightly moist to moist, dark grey, SOFT, slickensided,sandy CLAY. Alluvium.

Slightly moist to moist, dark yellow, mottled light grey,SOFT, slickensided, sandy CLAY with scatteredmedium sub-rounded quartzite gravel. Alluvium.

NOTES:

Final depth at 1.5m on alluviumNo refusalNo groundwater or seepage encounteredSidewalls stableFI, proctor, shear box and permeability samples takenat 0-0.7mDCP testing inside and outside the TP


HOLE No: LDTP08


Lower Dam

CONTRACTOR:

MACHINE: Hand dug


TYPE SET BY:


DATE PROFILED:

ELEVATION:

X COORD: 2894978

5/31/2019


DIAM:

INCLINATION:

Y COORD: 99757

Rep

ort I

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Pro

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JOB NUMBER: 504630

Sheet 1 of 1

HOLE No: LDTP08

0.00

0.70

1.50

Disturbedsample

Appendix C: Drawing (504630-0000-DRG-G2-0001 - Plan of Jan van

Riebeek Lower Dam with test pit positions)

CLIENT

TITLE

REVISION DETAILSDATEREV APPROVED

CHECKED

APPROVED

PROJECT

DRAWN

DESIGNED

PROJECT No.

REV

DISC

NUMBER

DRAWING No.

SCALE SIZE

A1

.

TYPEWBS

REHABILITATION OF JAN VAN RIEBEEK PARK LOWER DAMBRAAMFONTEIN WEST WATER MANAGEMENT UNIT

GEOTECHNICAL INVESTIGATIONLAYOUT OF TEST PITS

-

504630 0000 DRG G2 0001 A

AS SHOWNDESIGN

NOT FOR CONSTRUCTION

S. NKOSI

A. NXUMALO

G. DAVIS

A 07/2019 ISSUE FOR REVIEW

AutoCAD SHX TextLDTP1








AutoCAD SHX TextX = 2 894 800


AutoCAD SHX TextY = 99 900












AutoCAD SHX TextTEST PITS WITHOUT SEEPAGE

AutoCAD SHX TextTEST PITS WITH SEEPAGE

AutoCAD SHX TextWET AREA

AutoCAD SHX TextLEGEND:

AutoCAD SHX TextLAYOUT SCALE 1:500

AutoCAD SHX Text0

AutoCAD SHX Text5

AutoCAD SHX Text10

AutoCAD SHX Text20

AutoCAD SHX Text30

AutoCAD SHX Text40

AutoCAD SHX Text50

AutoCAD SHX TextSCALE 1:1000 (A3) (A3)

AutoCAD SHX TextSCALE 1:500 (A1) (A1)

Appendix D: Laboratory test results

Client :

Address : Client Reference :

: Order No. :

:

Attention : Date Received :

Facsimile : Date Tested :

E-mail : Date Reported :

Project :

Project No. : Report Status :

Page : of

Unless otherwise requested or stated, all samples will be discarded after a period of 3 months.

Deviations in Test Methods: Technical Signatory:

**All results are authorized electronically by approved managers and/or technical signatories.Signature:

Civilab (Proprietary) Limited. Registration No: 1998/019071/07

4.000

5.000

K H Head

BS 1377 Part 5

All interpretations, Interpolations, Opinions and/or Classifications contained in this report falls outside our scope of accreditation.

Relative density of soil (SG)

Atterberg Limits

Client :

Project :Project No : 2 of 15

2 3TP2 TP3 LD LD

0.70-1.50 0.20-0.50

XY

2.845 2.829

100 mm 100 10075 mm 100 10063 mm 100 10050 mm 100 100

37.5 mm 100 10028 mm 100 10020 mm 100 10014 mm 87 1005 mm 71 992 mm 63 911 mm 58 87

0.425 mm 33 680.250 mm 28 540.150 mm 22 450.075 mm 19 40

1.85 1.01

0.060 mm 18 410.040 mm 17 40 Atterberg Limits -425µ

0.020 mm 14 35 Liquid Limit %0.006 mm 11 26 Plasticity Index %0.002 mm 9 20 Linear Shrinkage %

Gravel % 37 9 Overall PI %Sand % 45 50Silt % 9 21Clay % 9 20Note: An assumed S.G. may be used in Hydrometer Analysis calculations

CIVILAB (PTY) LTD - CENTURION Date Received: 06/06/2019

Rehabilitation of Braamfontein West Water Management Unit Date Reported: 04/07/2019Page No. :

FOUNDATION INDICATORLaboratory NumberField NumberClient ReferenceDepth (m)

Position

Coordinates

Description

Aditional InformationJVR Lower

Dam

JVR Lower

Dam

2019-B-840

Sieve Analysis (Wet Prep) SANS 3001 GR1

Perc

enta

ge P

assin

g

Grading Modulus

Calcrete / CrushedStabilizing AgentMoisture Content & Relative Density

Moisture Content (%)Relative Density (S.G.)

137.5 50.09 9

Classifications

Hydrometer Analysis SANS 3001 GR3

Perc

enta

ge

Passin

g

Laboratory Number 2 3SANS 3001 GR10

51 2720

Weston Swell @ 1 kPa

HRB (AASHTO) A-2-7(2) A-7-6(7)Unified (ASTM D2487) SM SC

0

20

40

60

80

100

0.001 0.01 0.1 1 10 100Perc

en

tag

e P

assin

g

2

3

CoarseClay

Silt Sand Gravel

Fine Medium Fine Medium Coarse Fine Medium Coarse

0

10

20

30

40

50

60

0 10 20 30 40 50 60 70 80

Overa

ll P

lasti

cit

y I

nd

ex

Clay Fraction of Whole Sample

POTENTIAL EXPANSIVENESS

LowMedium

High

Very High

0

10

20

30

40

50

60

0 10 20 30 40 50 60 70 80 90 100

Pla

sti

cit

y I

nd

ex

Liquid Limit

USC PLASTICITY CHART

Client :


4 6TP3 TP6 LD LD

0.50-1.20 0.90-1.30

XY

2.687 2.975

100 mm 100 10075 mm 100 10063 mm 100 10050 mm 100 100

37.5 mm 100 10028 mm 100 10020 mm 100 10014 mm 100 1005 mm 100 992 mm 100 951 mm 92 89

0.425 mm 60 700.250 mm 54 550.150 mm 48 470.075 mm 43 41

0.97 0.94



Gravel % 5 Overall PI %Sand % 62 57Silt % 11 11Clay % 27 27Note: An assumed S.G. may be used in Hydrometer Analysis calculations

2019-B-840 Page No. :


Perc

enta

ge P

assin

g

Grading Modulus

FOUNDATION INDICATOR


Rehabilitation of Braamfontein West Water Management Unit Date Reported: 04/07/2019


Dam

JVR Lower

DamCalcrete / CrushedStabilizing AgentMoisture Content & Relative Density

Moisture Content (%)Relative Density (S.G.)

Laboratory NumberField NumberClient ReferenceDepth (m)

Position

Coordinates

Description

17 14Classifications


HRB (AASHTO) A-7-6(7) A-6(4)Unified (ASTM D2487) SC SC


Perc

enta

ge

Passin

g


50 3529 20

13.5 8.0

0

10

20

30

40

50

60

0 10 20 30 40 50 60 70 80

Overa

ll P

lasti

cit

y I

nd

ex



LowMedium

High

Very High

0

10

20

30

40

50

60

0 10 20 30 40 50 60 70 80 90 100

Pla

sti

cit

y I

nd

ex

Liquid Limit


0

20

40

60

80

100

0.001 0.01 0.1 1 10 100Perc

en

tag

e P

assin

g

4

6

CoarseClay

Silt Sand Gravel


Client :


7 5TP8 TP4 LD LD

0.00-0.60 0.50-1.20

XY

2.747

100 mm 100 10075 mm 100 10063 mm 100 10050 mm 100 100

37.5 mm 100 10028 mm 100 10020 mm 100 10014 mm 99 1005 mm 89 912 mm 79 871 mm 74 82

0.425 mm 53 690.250 mm 41 620.150 mm 32 570.075 mm 27 53

1.41 0.91



Gravel % 21 13 Overall PI %Sand % 53 36Silt % 8 34Clay % 18 17Note: An assumed S.G. may be used in Hydrometer Analysis calculations


Perc

enta

ge P

assin

g

Grading Modulus

2019-B-840 Page No. :

FOUNDATION INDICATOR


Rehabilitation of Braamfontein West Water Management Unit Date Reported: 04/07/2019


Dam

JVR Lower

DamCalcrete / CrushedStabilizing AgentMoisture Content & Relative Density

Moisture Content (%)

SC SC

Relative Density (S.G.)

Laboratory NumberField NumberClient ReferenceDepth (m)

Position

Coordinates

Description


Perc

enta

ge

Passin

g


36 3519 209.5 8.010 14

Classifications


HRB (AASHTO) A-2-6(1) A-6(4)Unified (ASTM D2487)

0

10

20

30

40

50

60

0 10 20 30 40 50 60 70 80

Overa

ll P

lasti

cit

y I

nd

ex



LowMedium

High

Very High

0

10

20

30

40

50

60

0 10 20 30 40 50 60 70 80 90 100

Pla

sti

cit

y I

nd

ex

Liquid Limit


0

20

40

60

80

100

0.001 0.01 0.1 1 10 100Perc

en

tag

e P

assin

g

7

5

CoarseClay

Silt Sand Gravel


Client : Date Received:

Project : Date Reported:

Project No: Page No. : 5 of 15

X

Y

Dry Density kg/m³

Moisture Content %

Dry Density

0% Air-Voids at SG= 2.65


Description

Max. Dry Density kg/m³ 1864

Optimum Moisture % 12.6

JVR Lower Dam 10.7 12.7 14.7 16.7 #N/A

Additional Information JVR Lower Dam

Calcrete / Crushed

1805 #N/A

Stabilizing Agent

Maximum Dry Density & Optimum Moisture Content - ASTM D698

Compactive Effort: Standard Proctor

1800 1836 1864 1833

CIVILAB (PTY) LTD - CENTURION 06/06/2019

Rehabilitation of Braamfontein West Water Management Unit 04/07/2019

2019-B-840

MOISTURE DENSITY RELATIONSHIPLaboratory Number 2

Field Number TP2

Client Reference LD

Depth (m) 0.70-1.50

Position

Coordinates

1833 1864 1836 1805 1800

1790

1800

1810

1820

1830

1840

1850

1860

1870

8 9 10 11 12 13 14 15 16 17 18

Dry

De

nsi

ty (

kg/m

³)


1790

1800

1810

1820

1830

1840

1850

1860

1870

8 9 10 11 12 13 14 15 16 17 18

Dry

De

nsi

ty (

kg/m

³)





X

Y

Dry Density kg/m³

Moisture Content %

Dry Density



9.5 11.5 13.5 15.5 17.5 #N/A





1748 1782 1806 1777 1751 #N/A

Description


Calcrete / Crushed

Stabilizing Agent



2019-B-840


Field Number TP3

Client Reference LD

Depth (m) 0.20-0.50

Position

Coordinates

1777 1806 1782 1748 1751

1740

1750

1760

1770

1780

1790

1800

1810

8 9 10 11 12 13 14 15 16 17 18

Dry

De

nsi

ty (

kg/m

³)





X

Y

Dry Density kg/m³

Moisture Content %

Dry Density



14.5 16.5 18.5 20.5 22.5 #N/A




Compactive Effort: Modified AASHTO

1672 1712 1738 1713 1687 #N/A

Description


Calcrete / Crushed

Stabilizing Agent



2019-B-840


Field Number TP4

Client Reference LD

Depth (m) 0.50-1.20

Position

Coordinates

1713 1687 1738 1712 1672

1670

1680

1690

1700

1710

1720

1730

1740

1750

14 15 16 17 18 19 20 21 22 23 24

Dry

De

nsi

ty (

kg/m

³)





X

Y

Dry Density kg/m³

Moisture Content %

Dry Density



10.7 12.7 14.7 16.7 18.7 #N/A





1787 1831 1860 1822 1790 #N/A

Description


Calcrete / Crushed

Stabilizing Agent



2019-B-840


Field Number TP6

Client Reference LD

Depth (m) 0.90-1.30

Position

Coordinates

1860 1831 1787 1822 1790

1780

1790

1800

1810

1820

1830

1840

1850

1860

1870

10 11 12 13 14 15 16 17 18 19 20

Dry

De

nsi

ty (

kg/m

³)





X

Y

Dry Density kg/m³

Moisture Content %

Dry Density



13.8 15.8 17.8 19.8 21.8 #N/A





1567 1609 1633 1604 1577 #N/A

Description


Calcrete / Crushed

Stabilizing Agent



2019-B-840


Field Number TP8

Client Reference LD

Depth (m) 0.00-0.60

Position

Coordinates

1633 1604 1609 1567 1577

1560

1570

1580

1590

1600

1610

1620

1630

1640

13 14 15 16 17 18 19 20 21 22 23

Dry

De

nsi

ty (

kg/m

³)


36 Fourth Str.,Booysens Reserve,Johannesburg 2091

PO Box 82223,Southdale 2135

Tel:+27 (0)11 835 3117

E-mail: [email protected] Website: www.civilab.co.za

CivilabCivil Engineering Testing Laboratory

Project: Date Tested: 25/6/2019

Batch No.: 2019-B-840 Laboratory Number: 2

Field Sample Number: TP 2 (JVR Lower Dam) Depth (m): 0.7 - 1.5

Remark: A quick undrained test on a sample remoulded to appproximately 90% Proctor.

Height Area Moisture Dry Unit Void Saturation Normal

Content Weight Ratio Stress Stress Displacement

mm mm2

% e % kPa kPa mm

Initial 18.20 2851.04 12.8 1.65 0.727 50.1

Final #REF! 11.7 #REF! #REF! #REF!

Initial 18.20 2851.04 12.4 1.65 0.721 48.8


Initial 18.20 2851.04 12.2 1.66 0.718 48.3


Box Internal Cohesion

Type Test 1 Test 2 Test 3 Test 4 Friction (deg) (kPa)

ROUND 1.1670 1.1769 1.1291 #DIV/0! 47.6 53.52.845

Test 3 140.0 206.5

50.0 108.0

Rate of shear (mm/min) Specific Gravity

9.62

Test 2 105.0 169.5 5.11

Direct Shear Test Results

Peak Shear

Test 1 5.41

REHABILITATION OF BRAAMFONTEIN WEST WATER MANAGEMENT UNIT

0

50

100

150

200

250

0 1 2 3 4 5 6 7 8 9 10 11 12

Sh

ear

Str

ess (

kP

a)

Displacement (mm)

Shear Stress 1 Shear Stress 2 Shear Stress 3

-2

-1.5

-1

-0.5

0

0.5

1

0 1 2 3 4 5 6 7 8 9 10 11 12

Vert

ical D

isp

lacem

en

t (m

m)

Displacement (mm)

Vertical Displacement 1 Vertical Displacement 2 Vertical Displacement 3

0

50

100

150

200

250

0 50 100 150

Sh

ear

Str

ess (

kP

a)

Normal Stress (kPa)

Civilab (Proprietary) Limited. Registration No: 1998/019071/07

36 Fourth

Documents

Geotechnical investigation for the rehabilitation of Jan van ......engineering team conducted geotechnical investigations for the dams; this report presents the findings of the investigations