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
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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
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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.
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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).
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Figure 2: View of the embankment from the east
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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.
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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.
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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)
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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.
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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.
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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
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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.
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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
LD TP03 99807 2894935 2.3 Target depth reached;
located at the
embankment toe; very
slow seepage at 1.2m
LD TP04 99774 2894944 2.2 Target depth reached;
test pit located on the
crest; very slow seepage
at the base
LD TP05 99743 2894949 2.1 Target depth reached;
test pit located at edge of
embankment
LD TP06 99724 2894925 1.3 Terminated due to
seepage; test pit located
along discharge chute
LD TP07 99738 2894962 0.6 Terminated due to
seepage; test pit located
along spillway channel
LD TP08 99757 2894978 1.5 Target depth reached;
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.
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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.
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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
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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
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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
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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
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TP
No
Depth
(m)
Material
type
Particle Size % Atterberg Limits
%
GM AASHTO/
USCS
classification;
expansion
potential
Clay Silt Sand Gravel LL PI LS
LD TP03 0.2-0.5 Embankment
fill material
20 21 50 9 27 13 50.0 1.01 A-7-6(7) / SC;
Low
LD TP04 0.5-1.2 Embankment
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)
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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
LD TP03 SC Clayey sand,
many fines
20.5 (± 2.0) 28 (± 4) 5 (± 5.0)
LD TP04 SC Clayey sand,
many fines
20.5 (± 2.0) 28 (± 4) 5 (± 5.0)
LD TP05 SC Clayey sand,
many fines
20.5 (± 2.0) 28 (± 4) 5 (± 5.0)
Alluvium
LD TP03 SC Clayey sand,
many fines
20.5 (± 2.0) 28 (± 4) 5 (± 5.0)
LD TP06 SC Clayey sand,
many fines
20.5 (± 2.0) 28 (± 4) 5 (± 5.0)
LD TP07 SC Clayey sand,
many fines
20.5 (± 2.0) 28 (± 4) 5 (± 5.0)
LD TP08 SC Clayey sand,
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 TP03 Embankment fill material 0.20-0.50 1806 13.4
LD TP04 Embankment fill material 0.50-1.20 1738 18.5
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.
Project number 504630-G2-00 File 504630-G2-00 Geotechnical report_JvR lower dam FINAL.docx, 30 July 2019 Revision 0 21
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
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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.
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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.
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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.
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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
ort I
D:
_ZA
TR
AIL
PIT
LO
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Pro
ject
: JV
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AR
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ER
DA
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PJ
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y: G
INT
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D A
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4_0
_SA
.GLB
|| D
ate:
Jul
y 26
, 201
9
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
Johannesburg Roads Agency
HOLE No: LDTP02
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: 2894948
5/30/2019
5/30/2019DATE DRILLED:
DIAM:
INCLINATION:
Y COORD: 99838
Rep
ort I
D:
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PIT
LO
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Pro
ject
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AR
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|| Li
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y: G
INT
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D A
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4_0
_SA
.GLB
|| D
ate:
Jul
y 26
, 201
9
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
Johannesburg Roads Agency
HOLE No: LDTP03
Geotechnical Investigation for Janvan Riebeek Park (Top dams)
Lower Dam
CONTRACTOR:
MACHINE: New Holland 890B
PROFILED BY: A. Nxumalo & T. Mofokeng
TYPE SET BY:
JVR PARK LOWER DAM.GPJ
DATE PROFILED:
ELEVATION:
X COORD: 2894935
5/31/2019
5/31/2019DATE DRILLED:
DIAM:
INCLINATION:
Y COORD: 99807
Rep
ort I
D:
_ZA
TR
AIL
PIT
LO
G ||
Pro
ject
: JV
R P
AR
K L
OW
ER
DA
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PJ
|| Li
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y: G
INT
ST
D A
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4_0
_SA
.GLB
|| D
ate:
Jul
y 26
, 201
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
Johannesburg Roads Agency
HOLE No: LDTP04
Geotechnical Investigation for Janvan Riebeek Park (Top dams)
Lower Dam
CONTRACTOR:
MACHINE: New Holland 890B
PROFILED BY: A. Nxumalo & T. Mofokeng
TYPE SET BY:
JVR PARK LOWER DAM.GPJ
DATE PROFILED:
ELEVATION:
X COORD: 2894944
5/30/2019
5/30/2019DATE DRILLED:
DIAM:
INCLINATION:
Y COORD: 99774
Rep
ort I
D:
_ZA
TR
AIL
PIT
LO
G ||
Pro
ject
: JV
R P
AR
K L
OW
ER
DA
M.G
PJ
|| Li
brar
y: G
INT
ST
D A
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4_0
_SA
.GLB
|| D
ate:
Jul
y 26
, 201
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
Johannesburg Roads Agency
HOLE No: LDTP05
Geotechnical Investigation for Janvan Riebeek Park (Top dams)
Lower Dam
CONTRACTOR:
MACHINE: New Holland 890B
PROFILED BY: A. Nxumalo & T. Mofokeng
TYPE SET BY:
JVR PARK LOWER DAM.GPJ
DATE PROFILED:
ELEVATION:
X COORD: 2894950
5/31/2019
5/31/2019DATE DRILLED:
DIAM:
INCLINATION:
Y COORD: 99743
Rep
ort I
D:
_ZA
TR
AIL
PIT
LO
G ||
Pro
ject
: JV
R P
AR
K L
OW
ER
DA
M.G
PJ
|| Li
brar
y: G
INT
ST
D A
GS
4_0
_SA
.GLB
|| D
ate:
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
Johannesburg Roads Agency
HOLE No: LDTP06
Geotechnical Investigation for Janvan Riebeek Park (Top dams)
Lower Dam
CONTRACTOR:
MACHINE: Hand dug
PROFILED BY: A. Nxumalo & T. Mofokeng
TYPE SET BY:
JVR PARK LOWER DAM.GPJ
DATE PROFILED:
ELEVATION:
X COORD: 2894925
5/31/2019
5/31/2019DATE DRILLED:
DIAM:
INCLINATION:
Y COORD: 99724
Rep
ort I
D:
_ZA
TR
AIL
PIT
LO
G ||
Pro
ject
: JV
R P
AR
K L
OW
ER
DA
M.G
PJ
|| Li
brar
y: G
INT
ST
D A
GS
4_0
_SA
.GLB
|| D
ate:
Jul
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)
Johannesburg Roads Agency
HOLE No: LDTP07
Geotechnical Investigation for Janvan Riebeek Park (Top dams)
Lower Dam
CONTRACTOR:
MACHINE: Hand dug
PROFILED BY: A. Nxumalo & T. Mofokeng
TYPE SET BY:
JVR PARK LOWER DAM.GPJ
DATE PROFILED:
ELEVATION:
X COORD: 2894962
5/31/2019
5/31/2019DATE DRILLED:
DIAM:
INCLINATION:
Y COORD: 99738
Rep
ort I
D:
_ZA
TR
AIL
PIT
LO
G ||
Pro
ject
: JV
R P
AR
K L
OW
ER
DA
M.G
PJ
|| Li
brar
y: G
INT
ST
D A
GS
4_0
_SA
.GLB
|| D
ate:
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
Johannesburg Roads Agency
HOLE No: LDTP08
Geotechnical Investigation for Janvan Riebeek Park (Top dams)
Lower Dam
CONTRACTOR:
MACHINE: Hand dug
PROFILED BY: A. Nxumalo & T. Mofokeng
TYPE SET BY:
JVR PARK LOWER DAM.GPJ
DATE PROFILED:
ELEVATION:
X COORD: 2894978
5/31/2019
5/31/2018DATE DRILLED:
DIAM:
INCLINATION:
Y COORD: 99757
Rep
ort I
D:
_ZA
TR
AIL
PIT
LO
G ||
Pro
ject
: JV
R P
AR
K L
OW
ER
DA
M.G
PJ
|| Li
brar
y: G
INT
ST
D A
GS
4_0
_SA
.GLB
|| D
ate:
Jul
y 26
, 201
9
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 TextLDTP2
AutoCAD SHX TextLDTP3
AutoCAD SHX TextLDTP4
AutoCAD SHX TextLDTP5
AutoCAD SHX TextLDTP7
AutoCAD SHX TextLDTP8
AutoCAD SHX TextLDTP6
AutoCAD SHX TextX = 2 894 800
AutoCAD SHX TextX = 2 894 900
AutoCAD SHX TextY = 99 900
AutoCAD SHX TextY = 99 800
AutoCAD SHX TextY = 99 700
AutoCAD SHX TextX = 2 894 800
AutoCAD SHX TextX = 2 894 900
AutoCAD SHX TextX = 2 895 000
AutoCAD SHX TextX = 2 895 100
AutoCAD SHX TextX = 2 895 100
AutoCAD SHX TextY = 99 800
AutoCAD SHX TextY = 99 700
AutoCAD SHX TextY = 99 900
AutoCAD SHX TextX = 2 895 000
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 :
Project :Project No : 3 of 15
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
0.060 mm 38 380.040 mm 36 36 Atterberg Limits -425µ
0.020 mm 33 34 Liquid Limit %0.006 mm 30 29 Plasticity Index %0.002 mm 27 27 Linear Shrinkage %
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. :
Sieve Analysis (Wet Prep) SANS 3001 GR1
Perc
enta
ge P
assin
g
Grading Modulus
FOUNDATION INDICATOR
CIVILAB (PTY) LTD - CENTURION Date Received: 06/06/2019
Rehabilitation of Braamfontein West Water Management Unit Date Reported: 04/07/2019
Aditional InformationJVR Lower
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
Weston Swell @ 1 kPa
HRB (AASHTO) A-7-6(7) A-6(4)Unified (ASTM D2487) SC SC
Hydrometer Analysis SANS 3001 GR3
Perc
enta
ge
Passin
g
Laboratory Number 4 6SANS 3001 GR10
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
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
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
Fine Medium Fine Medium Coarse Fine Medium Coarse
Client :
Project :Project No : 4 of 15
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
0.060 mm 26 510.040 mm 25 47 Atterberg Limits -425µ
0.020 mm 24 40 Liquid Limit %0.006 mm 20 27 Plasticity Index %0.002 mm 18 17 Linear Shrinkage %
Gravel % 21 13 Overall PI %Sand % 53 36Silt % 8 34Clay % 18 17Note: An assumed S.G. may be used in Hydrometer Analysis calculations
Sieve Analysis (Wet Prep) SANS 3001 GR1
Perc
enta
ge P
assin
g
Grading Modulus
2019-B-840 Page No. :
FOUNDATION INDICATOR
CIVILAB (PTY) LTD - CENTURION Date Received: 06/06/2019
Rehabilitation of Braamfontein West Water Management Unit Date Reported: 04/07/2019
Aditional InformationJVR Lower
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
Hydrometer Analysis SANS 3001 GR3
Perc
enta
ge
Passin
g
Laboratory Number 7 5SANS 3001 GR10
36 3519 209.5 8.010 14
Classifications
Weston Swell @ 1 kPa
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
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
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
Fine Medium Fine Medium Coarse Fine Medium Coarse
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
10% 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)
Moisture Content (%)
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)
Moisture Content (%)
Client : Date Received:
Project : Date Reported:
Project No: Page No. : 6 of 15
X
Y
Dry Density kg/m³
Moisture Content %
Dry Density
0% Air-Voids at SG= 2.65
10% Air-Voids at SG= 2.65
9.5 11.5 13.5 15.5 17.5 #N/A
Max. Dry Density kg/m³ 1806
Optimum Moisture % 13.4
Maximum Dry Density & Optimum Moisture Content - ASTM D698
Compactive Effort: Standard Proctor
1748 1782 1806 1777 1751 #N/A
Description
Additional Information JVR Lower Dam
Calcrete / Crushed
Stabilizing Agent
CIVILAB (PTY) LTD - CENTURION 06/06/2019
Rehabilitation of Braamfontein West Water Management Unit 04/07/2019
2019-B-840
MOISTURE DENSITY RELATIONSHIPLaboratory Number 3
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)
Moisture Content (%)
Client : Date Received:
Project : Date Reported:
Project No: Page No. : 7 of 15
X
Y
Dry Density kg/m³
Moisture Content %
Dry Density
0% Air-Voids at SG= 2.65
10% Air-Voids at SG= 2.65
14.5 16.5 18.5 20.5 22.5 #N/A
Max. Dry Density kg/m³ 1738
Optimum Moisture % 18.5
Maximum Dry Density & Optimum Moisture Content - ASTM D698
Compactive Effort: Modified AASHTO
1672 1712 1738 1713 1687 #N/A
Description
Additional Information JVR Lower Dam
Calcrete / Crushed
Stabilizing Agent
CIVILAB (PTY) LTD - CENTURION 06/06/2019
Rehabilitation of Braamfontein West Water Management Unit 04/07/2019
2019-B-840
MOISTURE DENSITY RELATIONSHIPLaboratory Number 5
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)
Moisture Content (%)
Client : Date Received:
Project : Date Reported:
Project No: Page No. : 8 of 15
X
Y
Dry Density kg/m³
Moisture Content %
Dry Density
0% Air-Voids at SG= 2.65
10% Air-Voids at SG= 2.65
10.7 12.7 14.7 16.7 18.7 #N/A
Max. Dry Density kg/m³ 1860
Optimum Moisture % 14.5
Maximum Dry Density & Optimum Moisture Content - ASTM D698
Compactive Effort: Standard Proctor
1787 1831 1860 1822 1790 #N/A
Description
Additional Information JVR Lower Dam
Calcrete / Crushed
Stabilizing Agent
CIVILAB (PTY) LTD - CENTURION 06/06/2019
Rehabilitation of Braamfontein West Water Management Unit 04/07/2019
2019-B-840
MOISTURE DENSITY RELATIONSHIPLaboratory Number 6
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)
Moisture Content (%)
Client : Date Received:
Project : Date Reported:
Project No: Page No. : 9 of 15
X
Y
Dry Density kg/m³
Moisture Content %
Dry Density
0% Air-Voids at SG= 2.65
10% Air-Voids at SG= 2.65
13.8 15.8 17.8 19.8 21.8 #N/A
Max. Dry Density kg/m³ 1633
Optimum Moisture % 17.7
Maximum Dry Density & Optimum Moisture Content - ASTM D698
Compactive Effort: Standard Proctor
1567 1609 1633 1604 1577 #N/A
Description
Additional Information JVR Lower Dam
Calcrete / Crushed
Stabilizing Agent
CIVILAB (PTY) LTD - CENTURION 06/06/2019
Rehabilitation of Braamfontein West Water Management Unit 04/07/2019
2019-B-840
MOISTURE DENSITY RELATIONSHIPLaboratory Number 7
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)
Moisture Content (%)
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
Final #REF! 11.6 #REF! #REF! #REF!
Initial 18.20 2851.04 12.2 1.66 0.718 48.3
Final #REF! 92.3 #REF! #REF! #REF!
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