report to metro housing on a … n7297 prepared by c. j. ross date november 2007 report to metro...

Reference

N7297

Prepared By

C. J. Ross

Date

November 2007

REPORT TO METRO

HOUSING ON A

GEOTECHNICAL INVESTIGATION

FOR THE PROPOSED

KWA NGQATHU (NTSHONGWENI

PHASE 2) HOUSING PROJECT,

KWAZULU-NATAL

TABLE OF CONTENTS

1. Terms of Reference 1

2. Scope of Report 1

3. Information Supplied 2

4. Site Description 2

5. Fieldwork 3

6. Geology & Subsoils 4

6.1 Overview

6.1.1 Natal Group Sandstone Bedrock

6.1.2 Soil Cover

6.1.3 Characteristics of the Soil Cover

6.1.4 Irregularities in Bedrock Surface

6.2 Geotechnical Zonation

6.2.1 Geotechnical Zone 1




7. Groundwater 11

8. Laboratory Testing 11

9. Stability Assessment 13

9.1 Potentially Unstable Areas

9.2 Former Borrow Areas

10. Excavatability 16

11. Earthworks 17

12. Road Subgrade Assessment 19

13. Potential Borrow Areas 20

14. Subsoil Drainage 21

15. Founding Assessment 21

16. Sizing of Erf 23

17. Wastewater Disposal 23

18. Stormwater Management 25

TABLE OF CONTENTS (Cont./….)

APPENDICES

Appendix 1 Soil Profiles

Appendix 2 Dynamic Cone Penetrometer (DCP) Test Results

Appendix 3 Photographs

DRAWINGS

Dwg No. N7297/01 Geotechnical Site Plan

Dwg. No. N7297/02 Geotechnical Site Plan

REPORT TO METRO HOUSING ON A GEOTECHNICAL INVESTIGATION FOR

THE PROPOSED KWA NGQATHU (NTSHONGWENI PHASE 2) HOUSING

PROJECT, KWAZULU-NATAL

November 2007 Davies Lynn & Partners (Pty) Ltd Page 1

Ref. N7297

1. TERMS OF REFERENCE

In reply to a request dated 10th July 2007, Davies Lynn & Partners (Pty) Ltd

[DLP] submitted to Metro Housing a quotation to undertake geotechnical

investigations for the proposed Kwa Ngqathu (Ntshongweni Phase 2)

Housing Projects on the 16th July 2007. DLP were subsequently appointed

to carry out the above investigations.

2. SCOPE OF REPORT

This report documents the findings of the geotechnical investigation carried

out for the proposed Kwa Ngqathu Housing Project. The scope of this report

is as follows:

!" To describe and present the fieldwork and laboratory testing carried out

during the investigation;

!" To assess the site geology and geotechnical characteristics of the subsoil

materials with respect to suitability for the proposed development and

engineering services; and

!" To recommend sound and economical development practices and initial

founding guidelines to ensure long-term stability of the development

based on the geotechnical conditions encountered.





Ref. N7297

3. INFORMATION SUPPLIED

For the purpose of this investigation, DLP have made use of the following

information:

!" Orthophoto imagery and cadastral information from the eThekwini

Municipality GIS database;

!" Plans showing the proposed layout of erven and roads prepared by

Future Works;

!" Site survey, aerial photography and contour information provided by

MPL Land Survey;

!" 1:50 000 topographical map 2930; and

!" 1:250 000 Geological Series 2930 DURBAN.

4. SITE DESCRIPTION

The proposed development area is situated on elevated plateau land above

the western flank of the Sterkspruit River and a few kilometres upstream of

the Shongweni Dam. The Ntshonweni Township borders the site along the

southwestern side. Elevations across the proposed development area range

from approximately 640m to 500m MSL.

The topography of the site is dominated by a central and elevated spur

which grades in a southeasterly direction with several smaller spurs radiating

outwards interspersed with moderately sloping valley lines. A very steep

escarpment occurs along the northern and eastern boundaries of the

proposed development area.

The western part of the site is semi-formally developed on moderately to

steeply sloping easterly facing Hillside.





Ref. N7297

5. FIELDWORK

The fieldwork for this investigation comprised the following activities:

!" An evaluation of the area at desktop level, during which existing

geological and topographical maps were sourced and assessed;

!" A subsurface geotechnical investigation comprising excavation, profiling

and backfilling of inspection pits and auger borings across the proposed

development area in order to establish the subsoil geology and shallow

groundwater conditions;

!" A terrain reconnaissance of the site to map the geomorphology and

profile existing cuttings or exposures to supplement the subsurface

geotechnical investigation. Soil profiles were logged and they are

included in Appendix 1 of this report;

!" Performance of Dynamic Cone Penetrometer (DCP) tests in order to

assess the relative densities and approximate CBR of the insitu subsoils.

The DCP tests results are included in Appendix 2 of this report;

!" Performance of percolation tests in accordance with SABS 0400

requirements (refer to Section 16 of this report for results and

recommendations);

!" Sampling of the various subsoils encountered for laboratory testing. A

number of bulk disturbed samples were retrieved from selected

inspection pits within the proposed Kwa Nqathu Housing Project areas

and submitted to a commercial soils testing laboratory. The laboratory





Ref. N7297

testing and results thereof are discussed in more detail in Section 8 of

this report.

The positions of the above field tests, recorded with a hand-held GPS, are

shown on the accompanying Geotechnical Site Plans (Drawing Number

N7297/01 and N7297/02). Selected photographs of inspection pits and the

site development area showing subsoil and topographical conditions

respectively are attached to this report in Appendix 3.

6. GEOLOGY & SUBSOILS

6.1 Overview

The proposed development area is underlain by bedrock of and subsoils

derived from the Natal Group Sandstone. The Natal Group Sandstone

beneath the study area varies from highly weathered feldspathic soft rock to

hard rock quartzite outcrop. The quartzite horizons are resistant to

weathering and form the prominent cliff faces that occur above the

Sterkspruit River.

The soils overlying the sandstone bedrock are very sandy in nature and are

highly susceptible to erosion by channelled water flow.

In the western sector of the study area the colluvial sandy soils contain

numerous sandstone boulders scattered throughout the profile.





Ref. N7297

The soils overlying the spur crests are typically very thin (<0,3m). Subsoil

profiles vary considerably across the site, typically related to

geomorphological and historic weathering conditions. In terms of

engineering characteristics, four (4No) geotechnical zones have been

identified in the area where similar subsoil conditions exist. These

geotechnical zones are discussed in more detail in Section 6.2 of this report

below, and illustrated on the attached Geotechnical Site Plan (Drawing

Number N7297/01 and N7297/02).

6.1.1 Natal Group Sandstone Bedrock

The Natal Group Sandstone generally comprises a pinkish brown, fine to

medium grained sandstone with intercalated maroonish pink, micaceous

arkosic horizons and minor maroon siltstone horizons. The sandstone is

well bedded with bedding thickness generally in the range 200mm to

1000mm. Jointing in the sandstone is well developed and continuous,

normally medium spaced except in the vicinity of fault and shear zones,

where closely spaced jointing occurs. In its unweathered state the

sandstone is a medium hard to very hard rock becoming a soft, friable rock

with increased weathering. In particular the micaceous arkosic sandstone

on weathering forms an expansive sandy clay residuum. In general, due to

the regional geological structure of tilted fault bounded blocks, the

sandstone bedding dips in a south easterly or easterly direction at angles of

about 5 to 15 degrees.





Ref. N7297

6.1.2 Soil Cover

Soils developed on the Natal Group Sandstone are characteristically sandy.

On hilltops and hillsides, the soil cover is generally shallow (0,2m to 1,0m

thick), the sandy topsoil resting directly on the underlying weathered

sandstone, from which it has been derived mainly by physical

disintegration. On lower slopes and in valley bottoms soil thickness

increases to between about 2,0 and 4,0m in which a residual sandy clay

horizon is generally developed between the sandy topsoil and the

underlying bedrock. Furthermore, in poorly drained areas a subhorizon of

the sandy topsoil has been formed by the continuous ground water flow

along the topsoil/bedrock interface. This horizon is called the “E horizon”

(Elluvial) and is often termed “running sand”. This horizon will be shown

to be extremely important in later discussions of ground water movement

and slope failures.

Sandy Topsoil Horizon – is generally a light grey, loose, silty, fine SAND

exhibiting a high collapse potential. The permeability of the topsoil is

moderate to high (Coefficient of permeability K typically in the range 1 x

10-2 to 10-3mm/s).

“E” Horizon – Running Sand is typically a clean, almost white, loose, fine

to medium sand, normally saturated throughout the year and exhibiting

high permeabilities in the range K = 1 x 10-1 to 1 x 10-2mm/s.

Residual Sandy Clay – is typically a yellowish orange mottled grey, stiff,

fissured and micro-fissured, sandy, silty clay of low permeabilities in the

range K = 10-4 to 10-6mm/s.





Ref. N7297

6.1.3 Characteristics of the Soil Cover

The overriding characteristics of the SANDS encountered in the sandy soils

derived from the Natal Group Sandstone which are important in slope

stability considerations may be summarised as :

1. Uniform rounded fine grained sand with slight silt content.

2. Very loose to loose, voided structure exhibiting a high collapse

potential with typical in-situ densities 1500-1600 kg/m3.

3. Non-cohesive, exhibiting an angle of internal friction 0 of between

about 28 and 30o and an effective cohesion of zero.

4. Moderate to high permeability.

5. Highly erodable.

6.1.4 Irregularities in Bedrock Surface

The sandstone bedrock surface generally runs parallel to the natural ground

surface. However, due to variations in weathering and rock hardness, the

Sandstone bedrock surface is irregular giving rise to variations in soil

thickness. Thicker soil cover occurs generally over softer bands of

sandstone and over more weathered zones. Conversely, soil cover is

shallower over harder resistant bands. In places the hard sandstone

outcrops on surface. Within shear zones gulleys may also develop along

the bedrock surface which become buried channels down which ground

water gravitates.





Ref. N7297

6.2 Geotechnical Zonation


Geotechnical Zone 1 is characterised by weathered sandstone outcrop. This

zone is typically located around the northern fringe above the steeply

sloping hillside and in the area where quarrying has been undertaken in the

past as indicated on the Geotechnical Site Plan attached.

The topsoil in Geotechnical Zone 1 varied from 0,0m to 0,2m in thickness

and was typically described as dry to slightly moist, dark brown, very loose

to loose, fissured, trace fine gravelly, Sand.

Beneath the topsoil weathered Sandstone was encountered. The weathered

Sandstone was described as (W4/3) light maroon blotched pale orange,

highly to slightly weathered soft to medium hard rock SANDSTONE.


Geotechnical Zone 2 is characterised by a thin (0,2 – 0,5m) thick sandy

colluvium overlying highly weathered, medium grained, medium bedded,

extremely soft to soft rock SANDSTONE.

In this zone the weathered sandstone is typically pickable to depths of

approximately 1,2m below N.G.L.





Ref. N7297


Geotechnical Zone 3 is characterised by loose sandy soils overlying residual

sandstone and/or weathered Sandstone bedrock. This zone dominates the

site as indicated on the Geotechnical Site Plan attached.

The topsoil in Geotechnical Zone 3 varied from 0,1m to 0,3m in thickness

and was typically described as dry to slightly moist, light brown to brown to

brownish grey, very loose, slightly silty to SILTY SAND.

Immediately beneath the topsoil, loose sands typically described as very

slightly to slightly moist, greyish brown to light brown to pale orange brown

to very light grey, very loose to loose, silty to slightly silty SAND. These

loose sands were observed to extend to depths of between 0,5m and 1,5m

(with a thickness ranging between 0,3m and 2,0m). These loose sands are

typically low in strength, highly erodible and potentially unstable in terms of

trench excavations, however they are good road subgrade and select

materials (subject to compaction).

Underlying the loose sands, laterite and/or residual sandstone generally

occurs. The laterite is typically described as very slightly to slightly moist,

orange brown to reddish orange blotched brown, brownish grey and

reddish, medium dense (dense in places), medium to fine ferruginised

gravelly to GRAVELLY, slightly to moderately clayey SAND and varies

between 0,2m and greater than 0,5m in thickness.

The residual sandstone is typically described as dry to slightly moist, pinkish

brown to brownish grey to pale reddish brown blotched orange, red and/or

brown, loose to medium dense to dense, silty, locally slightly clayey SAND

to stiff, SANDY CLAY with minor to abundant Sandstone gravel and small





Ref. N7297

boulders in places. firm to stiff, sandy to SANDY CLAY and ranges from

approximately 0,5m to 1,4m in thickness.


Underlying the topsoil as very slightly moist, brown, medium dense to

dense, silty, sandy to SANDY GRAVEL or very slightly moist, greyish brown

to dark orange brown, loose to medium dense, silty to slightly clayey SAND

with minor to abundant Sandstone gravels and hard rock boulders was

typically encountered to between 1,5m and 2,5m depth.

Weathered Sandstone bedrock described as (W4/3) pale pink to pink to pale

orange or yellow brown, highly to medium weathered, medium hard to hard

rock SANDSTONE was recorded at depths between 1,5m and 2,5m within

Geotechnical Zone 4. A bedding orientation dipping less than 10o towards

the southeast was recorded in this area.

Valley Head Areas

Within the valley head areas saturated e-horizon type sands (running sands)

typical occur beneath a shallow topsoil layer. With increasing depth these

sands grade into residual clayey soils and/or completely weathered soft rock

sandstone.

Due to the permeable nature of the e-horizon sands, soaking rains easily

infiltrate the subsoils and migrate downslope along the bedrock surface.

Over prolonged periods of rainfall the entire subsoil profile becomes

saturated to ground level with the potential for liquefaction of the soils and

the potential for mudflows and/or landslides.





Ref. N7297

7. GROUNDWATER

Shallow groundwater seepage activity was not recorded in any of the

inspection pits excavated during the field investigation. However, it should

be noted that the field investigation was after a fairly dry winter season.

It is therefore considered that intermittent seepage activity could develop

along the interface between relatively more permeable sandy soils and the

less permeable residual subsoils or weathered bedrock, particularly after

prolonged or intensive rainfall periods.

Areas where shallow groundwater seepage activity may develop seasonally

or intermittently are indicated on the attached Geotechnical Site Plans.

8. LABORATORY TESTING

In order to assist with classifying the major subsoil materials across the site,

and to assess their suitability for use in earthworks and road construction,

laboratory testing has been undertaken on bulk disturbed samples retrieved

from inspection pits during the field investigation.

The results of the laboratory testing are summarized in the Table 1 overleaf.

The implications of these results in terms of material assessment and

classification applicable to the proposed development are briefly discussed

below and in more detail subsequently in the relevant sections of this report.





Ref. N7297

Table 1: Summary of Laboratory Test results

Sample No. 1 2 3

Inspection

Pit No.

Sample

Depth (m) 0,5m 0,6m 0,6m – 1,1m

Material Description Brown, silty SAND

Light maroon blotched pale

orange, completely weathered

extremely soft to very soft rock

SANDSTONE

Orange brown, moderately

clayey SAND

Origin Loose Sands Natal Group Residual Sandstone

% Gravel 0,4 0,3 0,1

% Sand 82,6 83,7 56,8

% Silt 11,2 14,4 23,3

Soil

Mort

ar

% Clay 5,8 1,6 19,8

Liquid Limit 17 16 22

Plasticity Index 0 NP 6

Linear Shrinkage 0 0 3,3

Grading Modulus 1,06 0,82 0,63

Maximum Dry Density

(kg/m3) 2064

Optimum Moisture

Content (%) 9,5

90% 2

95% 5

98% 6

CB

R a

t %

Mod.

AA

SH

TO

100% 11

CBR Swell (%) 0,00

Group Index

Classification A-2-4 (0) A-2-4 A-4

TRH 14 Classification G10

Table 1 above reflects the variety of subsoils across the proposed

development area, and indicates their engineering properties.

Plasticity Indices ranged from Non Plastic for the loose sands, residual

sandstone and weathered Sandstone bedrock to a PI of 6 for the residual

moderately clayey sands. Similarly, linear shrinkages varied from 0,0% for

the loose sands, residual sandstone and weathered Sandstone bedrock to

3,3% for the residual clayey sands.





Ref. N7297

Maximum Dry Densities of the loose sands, residual sandstone, laterite and

weathered Sandstone bedrock tested varied between 1999kg/m3 and

2064kg/m3 while the Optimum Moisture Contents ranged from 5,7% to

11,6% respectively.

Typical (average) TRH 14 classifications for the loose sands, laterite,

residual sandstone and weathered Sandstone of between G8 and G10 are

anticipated based on the results of the laboratory testing undertaken. The

residual clayey sand is expected to exhibit a TRH 14 classification of

approximately G10.

9. STABILITY ASSESSMENT

The findings of this geotechnical investigation indicate that most of the land

on which development is proposed is mostly stable and suitable for

development subject to the following precautions to ensure long-term

stability:

!" Formation of cut and fill embankments in accordance with the

recommendations in Section 11 of this report;

!" Provision of adequate stormwater control facilities such as retention

structures, interceptors, as well as midblock drainage and similar such

measures to reduce concentrated overland flows;

!" Establishment of erosion protection measures at all stormwater outlets or

headwalls, particularly in areas where the highly erodible, loose sands

prevail; and





Ref. N7297

!" Adherence to the foundation and wastewater disposal recommendations

in Sections 15 and 16 of this report respectively.

9.1 Potentially Unstable Areas

The characteristics of the Natal Group Sandstone soils which give rise to

potential unstable slope conditions comprise :

1. The sandy soils are highly permeable, readily permitting infiltration of

large volumes of rain water.

2. The sandy soils are generally thin, 1,0 to 2,0m thick, and therefore

soon become saturated during periods of prolonged rain. On sloping

ground this causes, firstly, high seepage pressures as the ground water

flows downslope giving rise to instability, and secondly results in

surface flow over the highly erodable, saturated soils.

3. The sandy soils exhibit a very loose, voided and open structure of

typical in-situ densities 1500-1600kg/m3, and exhibit high potentials

for collapse when saturated under load.

4. The sandy soils are non-cohesive and silty, and the individual grains

are subangular to rounded, resulting in low angles of internal friction

in the range 0 = 28o to 30o. The sandy soils are therefore highly

erodable.

5. The sandy soils are low in humic content (pedologically classified as

Orthic A soils) and thus not particularly nutrient rich and do not





Ref. N7297

support good grass growth. This adds to the erodability risk due to

patchy grass growth.

6. The development of the ‘E’ horizon “running sand” results in artesian

conditions of excess groundwater pressure on the lower slopes and in

the valley head areas.

It is evident that any slopes steeper than 14o – 16o (batter greater than

1:4) will be unstable if the slope should become fully saturated. In the

elevated terrain of portions of Kwa Ngqathu, many slopes exceed

14o-16o and where the landform and geological conditions are

conducive to saturation of the soil mantle (for example, steep slopes

and Valley Heads) potentially unstable slope conditions exist.

Accordingly in these areas viz slopes steeper than 1:4 (14 degrees)

and within the valley head areas as shown on Dwg. No. N7297/02

the potential for instability exists and as such these areas should be

excluded from development.

9.2 Former Borrow Areas

This area demarcated in the southeastern sector of the Geotechnical Site

Plan drawing N7297/1 has been subjected to erosion by channelled water

flow with evidence of liquification scars and erosion to bedrock level in

numerous areas.

This area will require remedial earthworks prior to development with

provision of erosion protection measure, drainage control measures and

with the founding of all structures i.e. house foundations, manhole culverts

etc keyed into the sandstone bedrock below the sandy colluvium.





Ref. N7297

10. EXCAVATABILITY

The final depths to which the inspection pits were excavated during the field

investigation give a good indication of the depths to which excavations with

a TLB (backacter) or similar plant can be achieved with relative ease. Based

on this, as well as engineering experience with subsoils of similar nature, the

classes of excavation which should be expected and catered for during

excavations into the various materials is outlined overleaf.

With reference to Section 6.2 of this report above, excavations within the

topsoil, loose sands, residual laterite, laterite, residual sandstone and

completely weathered Sandstone are considered to classify as soft

excavation in terms of SABS 1200 DA criteria. In this regard, excavations to

at least 1,0m within Geotechnical Zones 2, 3 and 4 should classify as soft

excavation. Excavation within Geotechnical Zone 1 and 2 below a level of

1,0m depth below N.G.L. to approximately 2,0m depth below N.G.L. will

classify as intermediate and/or boulder Class B.

Sidewalls of excavations within the loose sands (typical of Geotechnical

Zone 3 and 4) are prone to caving in. Therefore care should be taken to

ensure safety of workers in trenches greater than 1,0m depth within these

subsoils. For example, battering of side slopes to minimum 1:1,5 or use of

temporary shoring measures.

Excavations within openly jointed Sandstone and highly to medium

weathered Sandstone bedrock (ie. typically within Geotechnical Zones 1

and 2) are expected to classify as boulder class B and intermediate to hard

rock excavation respectively in terms of SABS 1200 DA criteria. In this

regard, allowances for limited heavy ripping and/or blasting are

recommended in these areas.





Ref. N7297

11. EARTHWORKS

Considering the undulating topography of the area, it is expected that much

of the road construction will adopt a cut-to-fill methodology, while cut-to-fill

platforms are anticipated on the majority of sites to facilitate construction. All

cut and fill earthworks / embankment construction should be carried out in

accordance with the current SANS/SABS 1200 series.

Generally, road embankments and housing platforms may be constructed

with the in-situ subsoils. Materials to be avoided in embankment

construction however include the topsoil and residual laterite clays.

The following measures are recommended :

!" Site earthworks of road cuts and embankments should be carefully

planned together with house site earthworks.

!" Bank batters should be kept to a maximum of 1 : 2 (26o). All banks

should be properly grassed.

!" Ensure that house platforms are graded to discharge along contour and

not downslope.

!" Driveways should be hardened. Driveways on properties below road

level should be graded to discharge into the house stormwater

reticulation system and should be graded such that overflow of surface

runoff discharges out along contour and not downslope.





Ref. N7297

!" All structures, ie. houses, manholes, culverts, should be founded

through the sandy topsoil onto the sandstone bedrock wherever

possible.

!" Ensure that the home owners in potential problem areas are aware of

the situation and therefore care for their homes in a responsible

manner.

Where ground slopes exceed 1:6, benching into the insitu materials should

be carried out prior to placement and compaction of fills. Fill for road

embankments should be placed in layers not exceeding 300mm and

compacted to minimum 93% Mod AASHTO maximum dry density.

Boulders greater than 200mm must be removed from the fill material to

enhance compaction and reduce the risk of piping. Fill for housing platforms

should be placed in layers not exceeding 200mm and compacted to

minimum 90% Mod AASHTO maximum dry density. Regular compaction

density control tests should be performed during the development of fill

embankments as specified in SANS/SABS 1200 DA.

The following batters are recommended:

!" 1:1+ (45o or greater) for cuts within medium to slightly weathered

Sandstone bedrock, depending on joint / bedding orientation and

condition;

!" 1:1,5 (34o) for cuts within completely to highly weathered Sandstone

bedrock, depending on joint / bedding orientation and condition;

!" 1:2 (26o) for cuts within all other subsoils subject to a maximum height

of 1,5m; and

!" 1:2 (26o) for fill embankments subject to a maximum height of 1,5m.





Ref. N7297

The cut batters recommended above for bedrock are subject to the rock

being intact and not showing adverse bedding / joint orientations or clay

gouge. It is recommended that a geotechnical consultant inspects and

approves these slopes immediately after construction.

Materials meeting the requirements for “Bedding Sands” as described in

SANS/SABS 1200 LB definitions were not encountered on site during the

field investigation. Accordingly, allowance for importing suitable sands for

support and covering of pipes in service trenches should be made.

12. ROAD SUBGRADE ASSESSMENT

With reference to Sections 6 and 8 of this report, the anticipated TRH 14

classifications for the various subsoils on the site as well as the geotechnical

zone in which they could occur at road subgrade level are summarised in

Table 2 below.

Table 2: Summary of Road Subgrade Assessment

Material Brief Description

Geotechnical Zone in

which material could occur

at road subgrade level

TRH 14

Residual Laterite Reddish, sandy to SANDY CLAY Geotechnical Zone 3 <G10

Loose Sands Brown, silty SAND Geotechnical Zone 3 G8

Residual

Sandstone

Brown to orange to pinkish to

yellow, sandy CLAY to moderately

clayey SAND with weathered

Sandstone inclusions

Geotechnical Zones 3 and 4 <G10-G5

(W5) Sandstone Light maroon to pale orange to

pinkish, extremely soft to very soft

rock SANDSTONE Geotechnical Zones 1, 2 and 3 G7

(W3) Sandstone Pale pink to pale orange to yellow

brown, medium hard to hard rock

SANDSTONE Geotechnical Zone 4 G6-G5





Ref. N7297

In terms of Table 2 above, where encountered at road subgrade level, it is

generally recommended that the in-situ materials be ripped to a minimum

depth of 400mm and recompacted to 93% Mod AASHTO Maximum Dry

Density at Optimum Moisture Content. Where topsoil, residual laterite clays

or clayey residual sandstone is encountered however, these materials should

be undercut by 400mm, removed to spoil and replaced with selected

material classifying as G7 or better in terms of TRH14 criteria compacted to

93% Mod AASHTO Maximum Dry Density at Optimum Moisture Content.

The above recommendations are based on a limited number of tests and

should suffice for initial planning and costing purposes. More regular and

detailed laboratory testing and classification of in-situ road subgrade

materials is recommended (and will be required) during construction, as

specified by SANS/SABS 1200.

13. POTENTIAL BORROW AREAS

The loose sands in Geotechnical Zone 3 and weathered Sandstone bedrock

in Geotechnical Zone 1 and 2 are considered to be suitable sources of

shallow borrow material. In terms of TRH 14 criteria, these subsoils typically

classify as G7 to G5. However given the restrictions with regard to housing

densities, steep slopes and erosion susceptibility it is not recommended that

materials be borrowed in this area other than that removed in cut for

roadworks.





Ref. N7297

14. SUBSOIL DRAINAGE

It is considered that some form of subsoil drainage will be required within

any poorly drained slopes affected by perennial and/or seasonal shallow

groundwater seepage activity. It is provisionally anticipated that subsoil

drainage measures will be required where services / development traverses

areas of potential groundwater seepage demarcated on the attached

Geotechnical Site Plan. (Valley Head Areas)

The requirement for and details of any subsoil drainage measures along

proposed cut embankments and as a protection for the road prism from

groundwater ingress should however be confirmed on site during

construction.

15. FOUNDING ASSESSMENT

The preliminary geotechnical investigation has identified several factors that

impact on the founding conditions across the proposed residential

development. These are:

#"Variation in natural depths to competent founding materials

With reference to Section 6 of this report, the depth to suitable founding

materials (below any low strength sands and/or expansive clays) varies

considerably within the proposed development area.

#"Differential conditions resulting from cut-to-fill earthworks

Across sloping portions of the development area, cut-to-fill earthworks

are likely to result in shallow founding over the cut layout with deeper

founding over the fill portions. In terms of the above, siting of proposed





Ref. N7297

houses on cut terraces would maximise opportunities for shallower

founding.

In terms of the above, various founding options are presented and discussed

below.

Option 1 : Conventional, shallow strip foundations

The economic use of conventional, shallow strip foundations is considered

feasible across much of the proposed development area. Areas within which

these foundations are likely to be feasible include Geotechnical Zones 1 and

2 where shallow bedrock occurs. These foundations are also likely to be

feasible in portions of Geotechnical Zone 3, particularly along cut portions

of platforms where approved founding materials may be encountered at less

than 1,0m depth.

Option 2 : Reinforced strip foundations on mass concrete pads

Where approved founding materials typically exceed 1,0m depth but are

within approximately 2,0m of platform level, mass concrete pads founded

into the Sandstone bedrock may be constructed with reinforced strip

foundations spanning between the pads. These foundations should prove

feasible within Geotechnical Zone 1, as well as beneath fill portions of

platforms within Geotechnical Zone 2 and portions of Geotechnical Zone 3.

Option 3 : Raft foundations

Given the highly erodable nature of the sandy subsoils and the potential for

collapse type settlement it is recommended that consideration be given to

founding of the structures on raft foundations. The design of rafts should





Ref. N7297

take into account potential differential settlements across cut-to-fill lines as

well as potential collapse settlement in the sandy subsoils. Geotechnical

Zones 3 and 4 would require the use of raft foundations with pier supports

through any fill portions.

16. SIZING OF ERF

Minimum plot sizes is mainly dependant on slope and socio-economic

requirements. Geotechnical considerations include susceptibility of the soils

to movement, slope stability and the proposed sanitation methods.

It is recommended that a minimum plot size of 500m2 be considered for

development of the southeasterly facing spur area and immediate surrounds

(Geotechnical Plan N7297/1 refers).

In the western sector where steeper slopes prevail it is recommended that

plots sizes of 1000m2 be considered. (Refer Geotechnical Plan N7297/2)

It is recommended that provisions be made for the creation of open

areas/green belts in the areas of potential instability. Similarly it is

recommended that planning development across the valley head areas as

identified in the Geotechnical Plan N7297/2 be avoided.

17. WASTEWATER DISPOSAL

Percolation testing in accordance with SABS 0400 criteria has been

undertaken as part of this geotechnical investigation. Percolation tests were

carried out at locations indicated on the attached Geotechnical Site Plan.





Ref. N7297

The tests were carried out within the various subsoils encountered to

determine their percolation characteristics.

Percolation rates of between 180mm/hr and 480mm/hr were recorded,

indicating that the requirement for a minimum 25mm fall in 30 minutes was

typically met in some areas.

However it is considered that disposal of wastewater by subsoil percolation

not be considered for the Kwa Ngqathu Phase 2 Housing Development due

to the very shallow soil cover and potential for slope instability associated

with saturation of the cohesionless soils above bedrock.

Accordingly in areas with soil cover exceeding 1,0m depth VIPs with urine

diversion could successfully be employed. However due to the cohesionless

nature of the subsoils pit lining support will be required.

Generally the construction of the VIPs with urine diversion should be

located downslope of the dwelling and below fill embankments.

In areas of shallower soil cover overlying highly weathered sandstone

bedrock a combination of excavation into the bedrock and/or the

construction of raised, lined and sealed latrines would be required.

In areas of hard rock exposure difficulties associated with excavations of the

pits is to be expected and may require pneumatic tools to construct the pit.

Raised lined and sealed pit latrines will be required.





Ref. N7297

18. STORMWATER MANAGEMENT

Within the proposed development area it is important to control and

dispose of stormwater effectively as uncontrolled runoff will cause damage

to property and may erode and destabilise large areas of this site as much of

the site is covered with highly erodible subsoils. The objectives of a

stormwater management system should thus be as follows:

$" To adequately dispose of runoff from developed areas without

causing soil saturation or erosion. This is particularly important on

steep slopes and where erodible subsoils exist;

$" To provide overland or piped flow routes to cater for major storms

and thereby minimising any risk of damage to property;

$" Stormwater systems should be designed to function adequately with

low maintenance in the long terms, and should cater for silting.

$" Installation of Midblock Stormwater Reticulation is Recommended

- Avoid use of stormwater soakpits or uncontrolled discharge

on surface.

- Avoid at all costs soakpits located in fill embankments near to

houses.

$" Soakpits – if soakpits are used they should be properly designed

with large retention chambers and adequate dormant open space for

infiltration. The plot sizes should be increased accordingly.





Ref. N7297

$" Roads – should cross fall into the slope wherever possible in order to

serve as cut-off channels should mud rushes occur upslope thereof.

$" Stormwater Pipes – keep pipe grades steep to avoid clogging, design

for silting where reductions in grade occur (eg. oversize pipes, drop

manholes). Oversize critical stormwater lines and especially inlets.

$" Plan for runoff and groundwater seepage from outside and upslope

of the development.

$" Plan for long term maintenance, eg. low level bridge/valley head

crossings which can withstand over-topping during heavy rains, eg.

open greenbelts vs. culverts subject to blockages.

$" Plan for overland flow and provide erosion protection along such

routes.

Stormwater from roads should be attenuated in temporary detention

facilities with subsequent slow rate of discharge into valley bottoms or

drainage courses provided that adequate erosion protection measures are

provided.

-------oo0oo-------

APPENDIX 1

Logs of Soil Profiles

Dwg. N7297/01 – SP1 to SP21

Dwg. N7297/02 – SP1 to SP15

DRAWING N7297/01

(SP1 TO SP21)

PROJECT: KWA NGQATHU HOUSING PROJECT –PHASE 2

DATE: 05 / 11 / 2007 SOIL PROFILE NO.

SP 1 LOCATION: NTSHONGWENI LOGGED BY: M. DANIEL

DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Slightly moist, greyish brown, very loose, trace gravelly, slightly silty medium to fine SAND. [Topsoil/Colluvium]

W4/3, pinkish grey / greyish brown, highly to medium weathered, medium to fine grained, medium to thickly bedded, medium to widely jointed, joints slightly rough and stained orange, soft rock – SANDSTONE. [Natal Group]

Note

Bedding orientation of Sandstone 258o / 10

o SW

0.15m

2.50m

WATER TABLE : Not encountered

CLIENT : METRO HOUSING REF. NO.

N7297

FIG. NO.

PROJECT: KWA NGQATHU HOUSING PROJECT – PHASE 2



DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Moist, greyish brown, very loose to loose, trace gravelly, slightly silty medium to fine SAND. [Topsoil/Colluvium]

(W4) moderate brown, highly weathered, medium to fine grained with coarse zones, medium bedded, medium jointed to openly jointed in places, very soft rock – SANDSTONE. [Natal Group]

(W4/3) pinkish grey, highly to medium weathered, medium to fine grained, medium bedded, medium jointed, soft rock – SANDSTONE. [Natal Group]

2.00m

2.50m

2.70m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

(W2) pale pinkish grey / grey, slightly weathered, medium to fine grained thickly bedded, widely jointed, medium hard rock – Sandstone. [Natal Group]

- Thinly bedded very soft rock horizons [0,5m to 1.0m thick] located upslope of this profile

1.10m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

(W4/3) Pinkish grey, highly to medium weathered, medium grained, thickly bedded, widely jointed, soft rock – SANDSTONE. [Natal Group]

(W4) Orange / pinkish grey, highly weathered, medium to fine grained, thickly bedded, widely jointed, very soft rock – Sandstone. [Natal Group]

1.10m

1.80m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0


(W4) Orange brown, highly weathered, medium grained, openly jointed, extremely soft rock to very soft rock – SANDSTONE. [NatalGroup]

1.00m

1.40m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Slightly moist to moist, greyish brown, very loose to loose, trace gravelly, slightly silty medium to fine SAND. [Topsoil / Colluvium]

(W4) Orange brown, highly weathered, medium to coarse grained, openly jointed, extremely soft rock – Sandstone. [Natal Group]

0.80m

1.30m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Moist to wet, greyish brown, very loose to loose, trace gravelly, medium to fine SAND. [Topsoil/Colluvium]

(W4) Dark orange brown to dark yellowish orange, highly weathered, openly jointed, very soft rock to soft rock – Sandstone.

Note : Advanced weathering of joints with black/reddish iron coating on joint surfaces.

Note

Lower half of profile poorly exposed

1.50m

2.10m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0


(W4) Orange brown, highly weathered, medium to coarse grained, medium bedded, openly jointed, extremely soft rock to very soft rock – SANDSTONE. [Natal Group]

0.80m

1.00m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Slightly moist to moist, greyish brown, very loose to loose, slightly silty medium to fine SAND. [Topsoil/Colluvium]

0.90m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

(W4) Orange grey, highly weathered, medium grained, medium bedded, openly jointed, extremely soft rock – SANDSTONE. [Natal Group]

(W4) Pinkish grey to brownish grey, highly weathered, medium grained, medium bedded, medium jointed, extremely soft rock to very soft rock – SANDSTONE. [Natal Group]

0.30m

0.90m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Moist, greyish brown, very loose to loose, trace to minor gravelly, slightly silty medium to fine SAND. [Topsoil / Colluvium]

(W4) Yellowish grey, highly weathered, coarse grained, medium bedded, openly jointed, extremely soft rock to very soft rock – SANDSTONE. [Natal Group]

0.50m

0.80m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Slightly moist to moist, moderate orange brown, loose, fine to medium slightly to moderately clayey SAND. [Colluvium]

2.00m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Moist, moderate brown, very loose to loose, trace gravelly, slightly silty medium to fine SAND. [Topsoil / Colluvium]

(W4) Pinkish / orange / yellowish grey to micaceous purple grey, highly to medium weathered, medium to fine grained, thickly bedded, medium to widely jointed, soft rock – Sandstone. [Natal Group]

Note

Bedding dipping at 120o / 16

o SE

0.70m

3.70m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Slightly moist to moist, moderate orange brown, very loose to loose, trace gravelly, slightly to moderately clayey fine to medium SAND. [Colluvium]

- Contains minor ferricrete nodules at base.

(W4) Orangish / pinkish grey, highly weathered, medium to fine grained, medium bedded, medium to openly jointed, soft rock – Sandstone. [Natal Group]

2.70m

3.20m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0


Pale pinkish grey, highly weathered, fine to medium grained, medium to thickly bedded, widely to openly jointed, extremely soft rock to very soft rock – Sandstone. [Natal Group]

- Inferred medium hard rock at 2.30m

1.60

1.90m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Moist, greyish brown, very loose, trace gravelly, slightly silty medium to fine SAND. [Topsoil/Colluvium]

(W4/3) Orange / pink / purple grey, highly weathered to medium weathered, fine to medium grained, thickly to medium bedded, medium to widely jointed, soft rock to medium hard rock – Sandstone. [Natal Group]

Bedding orientation – 210o / 10

o SW

1.50m

3.10m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Moist, greyish brown, very loose to loose, trace gravelly slightly silty medium to fine SAND. [Topsoil/Colluvium]

(W4) Pinkish / orange grey, highly weathered, medium grained, medium to thickly bedded, medium to openly jointed, extremely soft rock to very soft rock – Sandstone. [Natal Group]

0.50m

0.80m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Moist, pinkish grey, very loose to loose, slightly silty medium to fine SAND. [Topsoil / Colluvium]

1.50m



N7297

FIG. NO.

PROJECT: KWA NGQATHU HOUSING PROJECT DATE: 05 / 11 / 2007 SOIL PROFILE NO.


DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0


Moist, moderate orange brown, loose, trace to minor gravelly, slightly clayey fine to medium SAND. [Colluvium]

Reddish / orange grey, medium bedded, openly jointed, extremely soft rock Sandstone present at bottom of profile.

0.70m

1.50m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Slightly moist, greyish brown, medium dense to loose, slightly silty medium to fine SAND. [Topsoil/Colluvium]

1.50m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Slightly moist to moist, greyish brown, trace gravelly, loose, slightly silty, fine to medium SAND. [Topsoil/Colluvium]

1.50m



N7297

FIG. NO.

DRAWING N7297/02

(SP1 TO SP15)




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Moist, moderate brown to pinkish brown, loose, trace fine gravelly, medium to fine SAND. [Colluvium]

End of Profile

1.50m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Slightly moist, greyish brown, loose, trace fine gravelly with scattered gravel to boulder sized sandstone fragments, medium to fine SAND. [Colluvium]

Moist, moderate brown, loose, moderate fine gravelly medium to fine SAND with moderate to abundant extremely soft rock sandstone boulders and coarse gravel. [Colluvium]

(W4) pinkish / orange grey, highly weathered, medium to coarse grained, thickly to medium bedded, medium to widely jointed (openly jointed at top of unit), very soft rock to soft rock – SANDSTONE.

End of Profile

Note

Bedding of Sandstone dipping at 20o towards 124 SE.

0.50m

0.80m

1.50m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Moist, greyish brown, loose, trace fine gravelly, medium to fine SAND. [Colluvium]

(W4) Purple / orange grey, highly weathered, medium to coarse grained, medium bedded, medium to widely jointed (openly jointed at top), extremely soft rock with very soft rock zones – SANDSTONE.

End of Profile

0.60m

1.20m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Slightly moist, greyish brown, loose, trace fine gravelly, medium to fine SAND. [Colluvium]

(W4) Orange brown, highly weathered, medium grained, medium bedded, openly jointed to closely jointed, extremely soft rock – Sandstone.

(W4) Purple grey, highly weathered, medium to coarse grained, medium to thickly bedded, widely jointed, very soft rock to soft rock – SANDSTONE.

End of Profile

0.90m

1.40m

1.70m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Moist, greyish brown, loose, trace fine gravelly, medium to fine SAND. [Colluvium]

Moist, moderate brown, loose to medium dense, moderate fine gravelly medium to fine SAND with scattered inclusions of extremely soft rock – SANDSTONE. [Colluvium]

End of Profile EXTREMELY SOFT ROCK AT BASE OF PROFILE

0.40m

0.70m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Slightly moist, greyish brown, loose, medium to fine SAND with moderate to abundant inclusions of coarse gravel to boulder sized SANDSTONE. [Collluvium]

(W4) Orange brown to pinkish brown, highly weathered with minor completely weathered zones, medium grained with scattered medium to coarse and fine to medium zones, medium bedded, closely jointed to medium jointed below 1,30m, extremely soft rock – SANDSTONE.

End of Profile

0.70m

2.20m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Very slightly moist, greyish brown, loose, trace fine gravelly, medium to fine SAND. [Colluvium]

Very slightly moist, greyish brown, loose, fine gravelly medium to fine SAND with abundant boulder sized inclusions of orange grey extremely soft rock medium to coarse SANDSTONE. [Colluvium]

(W4) Purple / orange grey, highly weathered, medium grained, thickly bedded, widely jointed, extremely soft rock – SANDSTONE.

End of Profile

0.20m

0.80m

1.30m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Slightly moist to moist, moderate brown, loose, trace fine gravelly, medium to fine SAND. [Collluvium]

End of Profile

1.30m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Slightly moist, greyish brown, loose, trace fine gravelly, medium to fine SAND with scattered coarse gravel to boulder sized fragments of medium grained extremely soft rock SANDSTONE. [Colluvium]

Moist, greyish brown, loose to medium dense, moderate to abundant fine gravelly medium to fine SAND with abundant coarse gravel to boulder sized fragments of extremely soft rock to very soft rock SANDSTONE. [Colluvium]

End of Profile

ORANGE / PURPLE GREY, MEDIUM GRAINED, VERY SOFT ROCK SANDSTONE AT BASE OF PROFILE

0.50m

0.80m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

(W4) Pale pinkish / orange grey, highly weathered, micaceous, medium grained, thinly to medium bedded, openly to very closely jointed, extremely soft rock – SANDSTONE.

(W4) Pale pinkish grey, highly weathered, micaceous, medium grained, thinly bedded, medium jointed, extremely soft rock to very soft rock – SANDSTONE.

End of Profile

0.50m

0.70m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Slightly moist to moist, greyish brown, loose, trace fine gravelly, medium to fine SAND. [Colluvium]

End of Profile

0.80m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Very slightly moist to slightly moist (becoming moist to very moist below 0,80m), greyish brown, loose, trace fine gravelly, medium to fine SAND. [Colluvium]

End of Profile

1.10m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Very slightly moist to slightly moist, greyish brown, loose to medium dense (partially cemented through termite activity), trace fine gravelly medium to fine SAND with moderate to abundant coarse gravel sized SANDSTONE fragments below 1.10m.

End of Profile

1.30m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Slightly moist, greyish brown, loose, trace fine gravelly, medium to fine SAND becoming gravelly at base. [Colluvium]

(W4) Orange brown to pinkish brown, highly weathered, medium grained with medium to coarse grained zones, medium to thickly bedded, medium jointed (openly jointed at top of unit), extremely soft rock – Sandstone.

- Open joint at 1,10m infilled with very moist colluvium indicating possible seepage level.

End of Profile

0.80m

1.70m



N7297

FIG. NO.




DEPTH(M)

DESCRIPTION

.........

.........

.........

.........

0,5

.........

.........

.........

.........

1,0

.........

.........

.........

.........1,5

.........

.........

.........

.........2.0

.........

.........

.........

.........2,5

.........

.........

.........

.........3,0

.........

.........

.........

.........3,5

.........

.........

.........

.........4,0

.........

.........

.........

.........4,5

.........

.........

.........

.........5,0

Slightly moist, greyish brown, loose to medium dense, moderate gravelly medium to fine SAND. [Collluvium]

(W4) Pinkish grey, highly weathered, medium grained, micaceous, medium bedded, openly to very closely jointed, extremely soft rock – SANDSTONE.

(W4) Pinkish grey, highly weathered, medium to coarse grained, micaceous, thickly to medium bedded, medium to widely jointed, very soft rock – SANDSTONE.

End of Profile

1.00m

1.30m

2.10m



N7297

FIG. NO.

APPENDIX 2

Dynamic Cone Penetrometer (DCP) Test Results

Dwg. N7297/01 – DCP1 to DCP16

Dwg. N7297/02 – DCP1 to DCP15

DRAWING N7297/01

(DCP1 TO DCP16)

PROJECT: KWA NGQATHU HOUSING PROJECT - PHASE 2 DATE: 08/11/2007

LOCATION: NTSHONGWENI LOGGED BY: M. DANIEL

DEPTH DCP 1 EQV. DCP 2 EQV. DCP 3 EQV. DCP 4 EQV. DCP 5 EQV.

(m) Blows/100mm CBR. Blows/100mm CBR. Blows/100mm CBR. Blows/100mm CBR. Blows/100mm CBR.

2 4 2 4 1 1 R 1 1

1 1 1 1 2 4 1 1

2 4 1 1 0 <1 1 1

1 1 1 1 1 1 1 1

0.5 1 1 1 1 1 1 1 1

1 1 2 4 1 1 2 4

1 1 1 1 1 1 1 1

2 4 1 1 0 <1 2 4

1 1 2 4 1 1 2 4

1.0 1 1 2 4 1 1 2 4

2 4 2 4 1 1 3 6

2 4 2 4 5 10 3 6

3 6 2 4 4 8 3 6

3 6 2 4 5 10 3 6

1.5 4 8 2 4 3 6 3 6

3 6 3 6 4 8 2 4

4 8 3 6 7 15 2 4

3 6 3 6 7 15 2 4

10 22 4 8 17 41 7 15

2.0 14 32 4 8 25 50 8 17

9 20 15 36 24 50 R

10 22 R 30 50

20 50 14 32

21 50 11 25

2.5 20 50 5 10

10 22 24 50

5 10 R

25 50

>30

3.0

3.5

4.0

4.5

5.0

FROM 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10

TO 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 +

NOTE: The equivalent CBR values above are provided as an indication only. R - Refusal

REF.No.

N7297

FIG.No.

DYNAMIC CONE PENETRATION TESTS

CLIENT : METRO HOUSING





1 1 1 1 2 4 1 1 1 1

2 4 2 4 1 1 1 1 11 25

0 <1 1 1 2 4 6 12 20 50

1 1 2 4 2 4 15 36 13 30

0.5 1 1 1 1 1 1 13 30 12 27

0 <1 2 4 1 1 R 26 50

1 1 2 4 2 4 R

1 1 1 1 2 4

3 6 2 4 1 1

1.0 4 8 2 4 2 4

7 15 1 1 2 4

3 6 2 4 2 4

2 4 2 4

2 4 3 6

1.5 15 36 2 4

R 2 4

2 4

12 27

17 41

2.0 R

2.5

3.0

3.5

4.0

4.5

5.0

FROM 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10

TO 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 +


REF.No.

N7297

FIG.No.







2 4 0 <1 1 1 R 10 22

1 1 0 <1 1 1 16 39

1 1 1 1 2 4 13 30

1 1 0 <1 2 4 11 25

0.5 2 4 0 <1 5 10 9 20

1 1 1 1 15 36 12 27

2 4 1 1 22 50 12 27

2 4 1 1 25 50 6 12

2 4 1 1 19 47 7 15

1.0 2 4 1 1 18 44 6 12

2 4 1 1 21 50 R

1 1 1 1 12 27

3 6 2 4 R

4 8 21 50

1.5 5 10 R

6 12

21 50

35 50

40 50

2.0 R

2.5

3.0

3.5

4.0

4.5

5.0

FROM 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10

TO 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 +


REF.No.

N7297

FIG.No.





DEPTH DCP 16 EQV. DCP EQV. DCP EQV. DCP EQV. DCP EQV.


2 4

3 6

12 27

11 25

0.5 4 8

1 1

2 4

1 1

2 4

1.0 9 20

12 27

18 44

12 27

11 25

1.5 8 17

5 10

7 15

8 17

7 15

2.0 6 12

5 10

R

2.5

3.0

3.5

4.0

4.5

5.0

FROM 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10

TO 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 +


REF.No.

N7297

FIG.No.



DRAWING N7297/02

(DCP1 TO DCP15)





5 10 2 1 1 4 8 2 4

7 15 4 2 4 1 1 1 1

6 12 3 6 1 1 1 1 1 1

4 8 2 4 2 4 1 1 2 4

0.5 4 8 2 4 1 1 1 1 9 20

2 4 1 1 2 4 3 6 7 15

4 8 4 8 2 4 12 27 6 12

3 6 6 12 2 4 9 20 2 4

2 4 7 15 2 4 7 15 2 4

1.0 4 8 4 8 4 8 11 25 3 6

12 27 4 8 8 17 15 36 29 50

11 25 7 15 12 27 R 37 50

14 32 5 10 6 12 29 50

35 50 5 10 18 44 8 17

1.5 R 4 8 25 50 21 50

8 17 11 25 28 50

3 6 35 50 R

7 15 R

18 44

2.0 16 39

4 8

7 15

8 17

7 15

2.5 8 17

10 22

8 17

13 30

R

3.0

3.5

4.0

4.5

5.0

FROM 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10

TO 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 +


REF.No.

N7297

FIG.No.







2 4 2 2 4 2 4 1 1

2 4 1 1 1 1 1 4 8

1 1 2 4 1 1 1 1 2 4

26 50 5 10 1 1 2 4 7 15

0.5 19 47 7 15 1 1 2 4 7 15

28 50 4 8 2 4 2 4 9 20

R 25 50 2 4 3 6 15 36

5 10 1 1 20 50 20 50

7 15 3 6 25 50 10 22

1.0 7 15 4 8 R R

27 50 1 1

31 50 1 1

19 47 2 4

23 50 5 10

1.5 R 9 20

R

2.0

2.5

3.0

3.5

4.0

4.5

5.0

FROM 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10

TO 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 +


REF.No.

N7297

FIG.No.







2 4 2 3 6 2 4 2 4

1 1 1 2 4 2 4 2 4

2 4 1 1 1 1 2 4 1 1

9 20 1 1 1 1 1 1 1 1

0.5 11 25 1 1 1 1 1 1 3 6

32 50 1 1 3 6 2 4 2 4

R 1 1 4 8 1 1 5 10

R 7 15 1 1 11 25

12 27 1 1 14 32

1.0 5 10 1 1 7 15

3 6 2 4 36 50

12 27 2 4 32 50

11 25 2 4 R

15 36 2 4

1.5 26 50 4 8

21 50 2 4

29 50 3 6

20 50 4 8

18 44 3 6

2.0 17 41 10 22

7 15 R

15 36

20 50

26 50

2.5 12 27

R

3.0

3.5

4.0

4.5

5.0

FROM 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10

TO 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 + 2 4 6 8 10 +


REF.No.

N7297

FIG.No.



APPENDIX 3

Photographs

Plates 1 through 14

PLATE 1

View of Hard Sandstone Outcrop

PLATE 2

View of Southeasterly Sloping Spur

PLATE 3

View of Thin Sandy Colluvium Cover Overlying Completely Weathered Sandstone

Bedrock Exposed in Inspection Pit

PLATE 4

Rock Outcrop

PLATE 5

Subsoil Exposure

PLATE 6

Former Borrow Area Showing Erosional Scars

PLATE 7

Profile of Erodable Sandy Soils

PLATE 8

Landform Showing Evidence of Erosion from Channelled Water Flow

PLATE 9

View of Valley Head Area Susceptible to Landslide – No Development Recommended in

this Area

PLATE 10

Shallow Colluvial Soils Overlying Sandstone Bedrock

PLATE 11

Cut Embankment into Sandstone Bedrock Behind Existing Dwelling

PLATE 12

Unsupported Cut Embankment Showing Colluvial Soils Overlying Closely Jointed

Sandstone

PLATE 13

VALLEYARE HEAD A

VALLEY HEADAREAD

View of Steep Slopes within Upper Sectors of Valley Head – Potentially Unstable

PLATE 14

View of Unvegetated Sandy Soils with Erosion

DRAWINGS

Geotechnical Site Plans

Dwg No’s N7297/01 & N7297/02

report to metro housing on a … n7297 prepared by c. j. ross date november 2007 report to metro...

Documents