REPORT TO JOHN R BROGAN AND ASSOCIATES PTY LTD ON ...

JK Geotechnics GEOTECHNICAL & ENVIRONMENTAL ENGINEERS

PO Box 976, North Ryde BC NSW 1670 Tel: 02 9888 5000 Fax: 02 9888 5001 www.jkgeotechnics.com.au

Jeffery & Katauskas Pty Ltd, trading as JK Geotechnics ABN 17 003 550 801

REPORT

TO

JOHN R BROGAN AND ASSOCIATES PTY LTD

ON

PRELIMINARY GEOTECHNICAL INVESTIGATION

FOR

DUE DILIGENCE

OF PROPOSED WAREHOUSE DEVELOPMENT

AT

750 PRINCES HIGHWAY (CORNER SMITH STREET)

TEMPE, NSW

2 December 2014

Ref: 27926Vrpt-Tempe

27926Vrpt-Tempe Page ii

Date: 2 December 2014 Report No: 27926Vrpt-Tempe Revision No: 1

For and on behalf of

JK GEOTECHNICS

PO Box 976

NORTH RYDE BC NSW 1670

Document Copyright of JK Geotechnics.

This Report (which includes all attachments and annexures) has been prepared by JK Geotechnics (JK) for its Client, and is intended for the use only by that Client. This Report has been prepared pursuant to a contract between JK and its Client and is therefore subject to:

a) JK’s proposal in respect of the work covered by the Report;

b) the limitations defined in the Client’s brief to JK;

c) the terms of contract between JK and the Client, including terms limiting the liability of JK.

If the Client, or any person, provides a copy of this Report to any third party, such third party must not rely on this Report, except with the express written consent of JK which, if given, will be deemed to be upon the same terms, conditions, restrictions and limitations as apply by virtue of (a), (b), and (c) above. Any third party who seeks to rely on this Report without the express written consent of JK does so entirely at their own risk and to the fullest extent permitted by law, JK accepts no liability whatsoever, in respect of any loss or damage suffered by any such third party.

27926Vrpt-Tempe Page iii

TABLE OF CONTENTS

1 INTRODUCTION 1

2 INVESTIGATION PROCEDURE 2

3 RESULTS OF INVESTIGATION 3

3.2 Site Description 3

3.3 Geology and Subsurface Conditions 4

3.4 Laboratory Test Results 5

4 COMMENTS AND PRELIMINARY RECOMMENDATIONS 6

4.1 Summary of Principal Geotechnical Findings and Issues and Further Work 6

4.1.1 Further Geotechnical Work 8

4.2 Dilapidation Surveys and Neighbouring Structures 9

4.3 Excavation Methodology and Vibration Monitoring 9

4.4 Groundwater Considerations and Drainage 11

4.5 Retention and Batter Slopes 12

4.5.1 Lateral Pressures 14

4.6 Foundation Strata 15

4.7 Other Earthworks 17

4.7.1 Engineered Fill Specifications 18

4.8 Pavement Design 19

5 GENERAL COMMENTS 20

STS TABLE A: MOISTURE CONTENT, ATTERBERG LIMITS & LINEAR SHRINKAGE TEST REPORT

STS TABLE B: FOUR DAY SOAKED CALIFORNIA BEARING RATIO TEST REPORT

BOREHOLE LOGS BH1 TO BH13 INCLUSIVE

DYNAMIC CONE PENETRATION TEST RESULTS (DCP8 AND DCP13)

FIGURE 1: BOREHOLE LOCATION PLAN

FIGURE 2: GRAPHICAL BOREHOLE SUMMARY

VIBRATION EMISSION DESIGN GOALS SHEET

REPORT EXPLANATION NOTES

27926Vrpt-Tempe Page 1

1 INTRODUCTION

JK GEOTECHNICS have been commissioned by John R Brogan and Associates Pty Ltd to carry

out a preliminary geotechnical investigation to assist with the Due Diligence process for a

proposed warehouse development at 750 Princes Highway (corner Smith Street), Tempe, NSW.

The commission was by Official Order Ref.: RCO: am: 39134, which was extended by email on 7

November 2014.

A summary of the principal geotechnical issues, based on the findings of this

investigation, is provided on Section 4.1.

This report presents the investigation procedures and findings and goes on to make comments

and preliminary recommendations on the principal geotechnical aspects of the proposed

development to assist the architects and structural engineers with the Due Diligence process,

preliminary planning and design, based on the results of thirteen test boreholes. The report

provides information and preliminary recommendations on:

Detailed logs of the boreholes with penetration test results and groundwater observations;

Interpretation of Subsurface Profile including bedrock depth and quality;

AS2870 site classification;

Main Geotechnical Issues of this site for the development;

Earthworks including excavation issues;

Retention;

Groundwater Issues;

Lateral Parameters for Retention Design;

Suitable Footings Systems and Options;

Foundation strata and depth;

Allowable Bearing Pressures;

Allowable Shaft Adhesions;

External Pavements including CBR value.

We also provide requirements for a detailed geotechnical subsurface investigation of the site. The

recommendations provided herein are preliminary and must be reviewed once further

geotechnical work has been completed, after demolition and at DA and CC stages, and after the

development details such as layout drawings, floor levels, footing system and structural loads are

decided upon and determined.


A preliminary environmental site assessment, including soil and groundwater contamination

screen and acid sulphate assessment, was carried out in conjunction with the geotechnical

investigation and the results are presented in a separate report Ref. E27926KGrpt, which has

been prepared by our specialist division Environmental Investigation Services (EIS).

1.1 Prospective Development

The prospective development was at Due Diligence stage. From the basic concept layout plans,

we understand that the development may comprise a large warehouse (5720m2) over a two level

car park basement. The warehouse would be located in the southern portion of the site towards

the Smith Street end of the site. The basement carpark will extend from south to north close to

the western part of the site, next to the existing building façade facing Princes Highway, which is

proposed to be retained.

Adjoining the warehouse to the north will be a timber sales yard (1945 m2), building materials and

a landscape yard (1075 m2). Ramps down to the carpark and driveways are proposed to be

located along the eastern part of the site. There is will a portion of surplus land (about 1146 m2)

on the ‘L’ shape part of the site to the east.

At this concept stage, other details of the development such as floor, pavement and earthwork

levels and structural loads had not been determined or supplied. Structural loads had not been

determined at this DD stage, but we have assumed moderate to high loads may apply.

The above information has been gleaned from the following supplied concept drawings by John R

Brogan and Associates:

Concept A: Project No. 1381 Drawing Nos: K100, K101 and K103 dated October 2013.

2 INVESTIGATION PROCEDURE

The following general procedures were adopted:

1. Prior to drilling, all boreholes were checked for buried services by a specialist contractor,

using radio-detection equipment with reference to “Dial Before You Dig” plans;

2. On the 13, 14 and 17 November 2014, twelve geotechnical boreholes (BHs 1 to 12) were

drilled to a maximum depth of 7.5m using our track mounted JK300 drilling rig.

3. An additional borehole (BH13) was drilled using hand operated equipment due to access

constraints, down to a depth of 0.8m and supplemented by a Dynamic Cone Penetration

(DCP) test down to a depth of 2.55m.


4. The approximate borehole locations, as shown on Figure 1 were approximately set out by

taped measurements and measuring wheel from existing surface features and inferred site

boundaries. Location of the boreholes was partly dictated by access constraints imposed by

existing development.

5. The apparent compaction of the fill and strengths of the residual clay profile were by and large

assessed by Standard Penetration Test (SPT) 'N' values, which were augmented, where

possible, by hand penetrometer tests on cohesive samples recovered in the SPT split tube.

6. The strength of the bedrock was assessed by observation of the auger penetration resistance

using a tungsten carbide ‘TC’ drill bit, together with examination of the recovered rock

cuttings. It should be noted that strengths assessed in this way are approximate and

variances of one strength order should not be unexpected.

7. Groundwater observations were recorded during drilling and soon after completion of the field

work.

8. Three slotted PVC standpipe wells were installed into BHs 1, 4 and 9 to allow for longer term

monitoring of groundwater levels and for water sample to be taken for the purposes of the

environmental assessment by EIS.

9. Two gas monitoring standpipes were also installed into BHs 4 and 9 for the purposes of the

environmental assessment by EIS

10. Environmental samples of the soils were recovered from select boreholes by EIS.

11. Selected samples were returned to Soil Test Services (STS), a NATA registered laboratory,

for testing that included moisture content, Atterberg Limits and Linear Shrinkage; these results

are summarised in Table A.

12. In addition, one bulk sample of the clay subgrade was tested to determine its standard

compaction properties and four day soaked CBR value; the result is summarised in Table B.

All fieldwork was carried out by our geotechnical engineer, Miss Rachael Price, and engineering

geologist, Mr Ian Squibbs, in full time attendance, to direct the sampling and testing and compile

logs of the subsurface strata encountered. The borehole logs, which include field test results and

groundwater observations, are attached to this report, together with a set of report explanation

notes.

3 RESULTS OF INVESTIGATION

3.2 Site Description

The site location is shown on the attached Figure 1. The site is identified as Lot 2 in DP803493

or 750 Princes Highway,Tempe. The site is rectangular in shape and covers an area


approximately 155m in length by 120m wide, with an additional 30m by 70m rectangular area on

its north eastern side. The site has a north-western frontage onto the Princes Highway and south-

western frontage onto Smith Street. The site is situated towards the upper reaches of a gentle hill

that slopes down at between 3° and 4° towards the Alexander Canal located about 500m-600m to

the south-east.

At the time of investigation, the majority of the site was occupied by a one and two storey brick

and concrete office and warehouse building. The main office/factory building had a brick façade

with a ‘sawtooth’ design roof with the concrete warehouse attached on the southern side. The

site sloped down to the southeast at approximately 4° so to create a levelled warehouse floor the

south-western side has been built up by up to 2.3m. Between the building and the highway was a

grassed garden area that sloped down at between 4° and 10° towards the office building. A

concrete covered service yard was on the eastern side of the site with a rectangular gravel car

parking area extending from the main site down the north-eastern side and sloping at around 4°.

To the north of the site was an IKEA superstore with its access road extending along the adjacent

boundary. The IKEA site lies partly on disturbed terrain of the former Tempe Landfill, which

included deep fill with demolition rubble, household and industrial wastes. The road sloped down

from the Princes Highway and was retained in parts by up to 1m on its western side and was

suspended on concrete piers on the eastern side to create a level loading dock. To the southeast

of the site were several two and three storey factory and warehouse units of brick and concrete

construction that abutted the site. All structures on and surrounding the site appeared in relatively

good condition when given a cursory inspection from within the subject site.

3.3 Geology and Subsurface Conditions

The 1:100,000 Sydney Geological Series Sheet indicates that the site is underlain by Ashfield

Shale and is close to the boundary with the underlying Hawkesbury Sandstone which is shown to

underlie just to the west of the site. However, this geological profile does not take into account

the residual soils derived from in-situ weathering of the bedrock or earthworks (fill) that may have

previously been undertaken at the site.

The boreholes exposed a variable subsurface profile of fill covering residual clay that grades into

shale bedrock. A graphical summary of borehole information is presented in attached Figure 2.

Reference must be made to the attached borehole logs for details at each specific location;

however, a general discussion of the encountered subsurface conditions, including groundwater,

is presented below.


Fill was encountered in all of the boreholes down to depths of between 0.3m and 2.3m, with the

deepest fill present under the existing warehouse slab. Underneath the warehouse slab the fill

generally comprised a gravelly sand that was assessed to be well compacted. Elsewhere around

the site the fill comprised silty sand and sandy clay. The fill was generally assessed to be variably

compacted (in the poorly and moderately compacted range).

Residual Silty Clay was only encountered in five of the boreholes (BHs 1, 3, 7, 9 & 10) and had

a maximum thickness of 0.8m in BH1. The clay was assessed to be of medium plasticity and

very stiff to hard in strength.

Shale Bedrock was encountered in all of the deep boreholes at depths ranging from 0.3m (BH4)

down to 2.3m (BH8). The approximate reduced level of the shale surface drops across the site

from about RL16.1m-RL18.1m in the south-western portion down to RL10.7m-RL14.9m in the

north-eastern portion of the site. The shale was quite variable in strength and weathering and

generally was assessed to be in the low (L) to medium (M) strength range with weaker strength

(EL-VL) layers and higher (H) strength layers interspersed throughout the profile. A layer of

siltstone was found in BH 2 covering the shale.

Groundwater was encountered in BHs 1 and 3 at a depth of 7.4m whilst all of the other

boreholes were dry during and shortly upon completion of drilling. BH7 was dry on completion

but recorded a groundwater level of 6.9m after 30 minutes. Monitoring standpipe wells were

installed in BH1, BH4 and BH9 and recorded highest groundwater levels at 3.76m (or about

RL13.9m), 3.9m (or about RL12.8m) and 4.6m (or about RL7.9m), respectively. We note that

seepage was relatively slow given that it took three days for the water level in BH 1 standpipe to

rise 1.7m, i.e. from RL12.2m to RL13.9m.

3.4 Laboratory Test Results

The results of the moisture content tests (Table A) generally correlate well with the field logging

assessments of rock strength.

The results of the Atterberg Limits and Linear Shrinkage test (refer to Table A) on sample of the

residual clay confirmed the clay to be of medium plasticity and indicated the clay to have a

moderate potential for shrink/swell movements with changes in moisture content.


A bulk sample of the residual clay from BH1 was tested for compaction and four day soaked CBR,

producing value of 3.5% at a density of 98% of Standard Maximum Dry Density (refer to Table

B).

4 COMMENTS AND PRELIMINARY RECOMMENDATIONS

4.1 Summary of Principal Geotechnical Findings and Issues and Further Work

As discussed in more detail in Section 3.2, the test boreholes penetrated a cover of fill over

residual clays grading into weathered shale bedrock at depths ranging from 0.3m (BH4) down to

2.3m (BH8). The approximate reduced level of the shale surface drops across the site from about

RL16.1m-RL18.1m in the south-western portion down to RL10.7m-RL14.9m in the north-eastern

portion of the site. The quality of the shale was quite variable in strength and weathering and

generally was assessed to be in the low (L) to medium (M) strength range with weaker strength

(EL-VL) layers and higher (H) strength layers interspersed throughout the profile. Monitoring

standpipe wells were installed in BH1, BH4 and BH9 and recorded highest groundwater levels at

3.76m (or about RL13.9m), 3.9m (or about RL12.8m) and 4.6m (or about RL7.9m), respectively.

Based on the results of the test boreholes and our understanding of the proposed development

(refer to Section 1.1), we have summarised the principal geotechnical findings, issues and

recommendations to be considered in the DA planning, design and construction of the

development:

1. Prior to demolition or excavation commencing, dilapidation reports should be compiled on

any adjoining structure that falls in the area of influence of the excavation.

2. Although final lowest floor levels had not been advised or determined at this Due Diligence

stage, assuming car park basement excavation to depths of less than 6m then most of it

will be through shale bedrock profile of variable strength, but for the most part of low to

medium strengths. The shale will require the use of rock excavation equipment for

effective excavation, which may transmit vibrations through the rock mass that could affect

adjoining buildings. Vibration effects (associated with general excavation but more

critically rock excavation) on adjoining structures must be considered.

3. Groundwater seepage into the excavation is unlikely to be a significant issue for the

proposed basement, since seepage appears to be slow through mostly very low

permeability materials (clay and shale); and water levels were quite deep in standpipe

BH4 (RL12.8m) and BH9 (RL7.9m); only standpipe BH1 had a shallower water level at

RL13.9m. The base of the excavation will be well above the groundwater level measured.


4. Given the low to medium or lesser strength of the shale, the excavation sides should be

fully supported by appropriate shoring/retention systems.

5. The building should be supported on footings uniformly founded into the shale bedrock.

Supporting structures on hybrid foundations (e.g. partly on engineered fill/residual clay and

partly on rock) must be avoided and is not recommended. Additional test boreholes using

rock coring methods are recommended for the detailed geotechnical investigation of the

site, after demolition has been completed and access is possible to the entire site area.

6. We are unaware of records that document the manner of placement, compaction

specification and control of the fill present beneath the site. Most of this fill is expected to

be removed by the basement excavation or other earthworks. Notwithstanding, we

consider this existing material to be ‘uncontrolled’ fill. Because of this fill, the site as seen

is considered to be Class P (‘problem’) in accordance with AS2870-2011. The residual

silty clays have a moderate to high potential for shrink/swell with changes in moisture

content: estimated as Class H1 in terms of AS2870-2011. We advise that in the strict

sense AS2870-2011 site classification does not apply to this development but it is a useful

guide in estimating foundation as well as shrink/swell movements that have the potential

to occur at this site.

7. It is also important to note that the fill is a variable material from unknown origins that may

contain large inclusions and obstacles, which may not have been picked by our small

diameter boreholes (100mm) and which could affect future construction. Variations in fill

quality/nature should be anticipated. There is a possibility that some of the fill may contain

contaminants and reference to the EIS report is recommended. Reference should be

made to the EIS report in regards to material classifications to be excavated for waste

disposal purposes.

8. The fill is deemed unsuitable as a bearing stratum for footings and slabs and is considered

a ‘moderate to high risk’ (of poor performance) as a supporting subgrade under external

pavements.

9. The residual clays beneath the fill at the site were also determined to have low four

soaked CBR (3.5%) and hence, this clay subgrade is considered to be “poor” subgrade for

the pavements and slabs. The use of thick pavements and/or treating of the subgrade with

lime would be required.

Further comments on these issues and geotechnical design parameters are provided in the

subsequent sections of this report. The preliminary recommendations provided in this report may

be used for preliminary design and construction planning purposes only; they would need to be

confirmed by further geotechnical borehole investigation as discussed further below.


4.1.1 Further Geotechnical Work

At the time of our investigation, details of the development such as floor and pavement levels and

structural loads were unknown or not determined at the time of this Due Diligence investigation.

The subsequent earthworks and footing recommendations are, therefore, provided in general and

preliminary terms only, which will require revision once exact development details, such as

earthwork levels, final floor levels, structural loads etc. are determined.

Given the variability in subsurface conditions, we consider that the number of boreholes and tests

employed in this investigation provides only a broad general coverage of the site. We recommend

that further eight boreholes be drilled to test the soils and sample the bedrock using diamond

coring methods to assess for higher bearing values. A meeting of the design team, once the

design has been further advanced, would be of benefit to discuss the geotechnical issues in more

detailed and determine the scope of the further detailed investigations.

Furthermore, it will be essential during earthworks and construction that regular geotechnical

inspections and testing be commissioned to check initial assumptions about earthworks and

foundation conditions and likely variations that may occur between borehole/test locations and to

provide further relevant geotechnical advice. Irregular or ‘milestone’ inspections by a

geotechnical engineer are often not adequate for such variations in subsurface conditions and for

excavation and foundation works. It is recommended that the Client be made aware of the need

to commission a geotechnical engineer for regular frequent inspections.

The preliminary recommendations provided in this report should be reviewed following the

additional geotechnical investigation as well as after these inspections. Furthermore, the

recommendations provided herein should also be reviewed once exact development details, such

structural layout, earthwork levels, floor levels, structural loads etc., are determined.

It is likely that further advice/input will be required during the structural design to address issues

that may not have been addressed in this report. To some degree, this is an “iterative” process

between evaluation of the geotechnical site conditions and the structural design. For the

earthworks, piling and other foundation works, we strongly recommend that only competent

contractors be considered, and that they are provided with a full copy of this report.


4.2 Dilapidation Surveys and Neighbouring Structures

Dilapidation surveys of adjoining buildings and other structures that fall in the area of influence of

the excavation are a necessary part of the process of claim protection, i.e. avoiding spurious

claim of damage where, in fact, the damage existed prior to demolition or excavation

commencing.

Prior to demolition or excavation commencing, detailed dilapidation reports should be compiled

on neighbouring buildings or other structures that fall within the zone of influence of the

excavation, which is defined by a distance back from the excavation perimeter of twice the depth

of the excavation. The respective owners should be asked to confirm that the dilapidation reports

represent a fair record of actual conditions. These reports should be carefully reviewed prior to

excavation commencing to ensure that appropriate equipment is used.

Excavations and retention systems will need to be carefully planned and scheduled so as not to

have any adverse effects on the buildings and other structures adjoining or above the excavation.

4.3 Excavation Methodology and Vibration Monitoring

The basement is expected to be taken down to a maximum depth approximately equivalent to two

levels, i.e. assumed 6m depth maximum (to be confirmed once the final basement floor levels

have been finalised). Therefore, the excavation will be taken through the soils and for the most

part, through the variable shale profile. Prior to any excavation commencing we recommend that

reference be made to ‘Excavation Work – Code of Practice’ by Safe Work Australia (July 2012).

An assessment of the excavation characteristics of the various strata is presented below. The

excavatability of the shale and the selection of appropriate excavation equipment have been

assessed on the basis of augered borehole logs (attached). It should be noted that rock strengths

assessed in this way are approximate and variances of one strength order should not be

unexpected. Assessment of excavation characteristics and productivity is not an exact science

and contractors must make their own evaluation based on experience with specific equipment,

and their own study of the borehole information; they might also request for further cored

boreholes to be completed at the site (note: we recommend the completion of further cored

boreholes-Refer to Section 4.1.1). The ease with which excavation of rock is achieved depends

upon the equipment used, the skill, and experience of the operator and the characteristics of the

rock. The contractor must make his own judgement on all of these factors.


For the earthworks, shoring, piling and other foundation works, we strongly recommend that only

competent contractors be considered that they are provided with a full copy of this report.

The materials to be excavated will comprise fill, residual silty clay, and for the most part, the

underlying shale bedrock. The soils can be readily excavated by buckets of a large hydraulic

excavator.

Excavation in extremely low to very low strength shale can be achieved using a Caterpillar D9

tractor or equivalent, probably with some light to medium ripping. Some of this material can

probably also be excavated with a large excavator bucket. Localised stronger bands/zones may

require heavy ripping or the use hydraulic rock hammers.

The shale of low or greater strengths will present hard or heavy ripping or “hard rock” excavation

conditions, and may require a higher capacity and heavier bulldozer for effective production.

Alternatively, hydraulic rock breakers could be used, although if large areas are to be excavated,

productivity is expected to be lower. This equipment would also be required for detailed

excavations such as footings or services in the rock.

The use of excavators with hydraulic impact hammer attachments, albeit small and lightweight, for

any shale excavation should be approached with considerable caution, as there will likely be

direct transmission of ground vibrations to nearby structures and buildings. Guideline levels of

vibration velocity for evaluating the effects of vibration in structures are given in the attached

Vibration Emission Design Goals sheet. We recommend that the acceptable limit for transmitted

vibrations be set at quite a low peak particle velocity of 5mm/s for frequencies of less than 10Hz

at foundation level. If it is found that transmitted vibrations are unacceptable, then it may then be

necessary to change to a smaller excavator with a smaller rock hammer, or to a rotary rock

grinder, rock saws, or jackhammers.

If rock hammers are to be used, we recommend that the initial excavation in rock should

preferably be commenced away from likely critical areas and instrument vibration monitoring

undertaken. The monitoring program should be confirmed when details of the contractor’s

excavation methods and sequence are known. By monitoring vibrations in this way, it will allow

some freedom to the excavation contractor in the equipment he adopts, so that a balance can be

made between productivity and vibration reduction.


Vibrations induced by excavations can be reduced by alternative methods such as the following:

Start the rock excavation away from likely critical areas.

Maintain rock hammer orientation into the face and enlarge excavation by breaking small

wedges off faces.

Operate hammers in short bursts only, to prevent amplification of vibrations.

Use smaller equipment (offset by a loss in productivity and economy and greater duration of

the nuisance).

Use line sawing, especially along boundaries, to aid breaking and trimming.

In addition, we recommend that only excavation contractors with appropriate insurances and

experience on similar projects be used. The contractor should also be provided with a copy of

this report to make his own judgement on the most appropriate excavation equipment.

4.4 Groundwater Considerations and Drainage

The groundwater levels vary significantly at the site. Most boreholes did not encounter

groundwater seepage during and on completion of drilling. The seepage appears to be slow,

which is not surprising in view of the very low permeability clays and shale, since it took some

time to materialize into a water level in the boreholes that had standpipe wells installed (BHs 1, 4

and 9). Furthermore, it is known from measurements in BH1 standpipe that the water level took 3

days to rise over a height of 1.7m.

Hence, we assess that groundwater seepage into the excavation is unlikely to be a significant

issue for the proposed basement, since seepage appears to be slow and water levels were quite

deep in standpipe BH4 (RL12.8m) and BH9 (RL7.9m); only standpipe BH1 had a shallower water

level at RL13.9m. We suspect that the water levels recorded in the borehole standpipes do not

represent a ‘true’ groundwater table, but rather indicate that seepage occurs through defects in

the rock mass and probably along the soil bedrock interface, and these seepage flows collect in

the borehole standpipes to the levels indicated. This should be confirmed by completing pump out

tests that show diminution of seepage rate with time.

In general terms, any retaining structures around the perimeter of the basement must incorporate

permanent drainage provisions and perimeter spoon drains around the basement will be required

to collect seepage flows and direct them to appropriate pumping sumps. Such water could be

used for irrigation around the site depending on the results of the groundwater assessment by

EIS: refer to their report. Some drainage will be required below the basement floor slabs and this

may take the form of discrete drains on a grid pattern or a drainage blanket of single sized 'blue


metal' gravel. A fail safe automatic pump-out system may have to be adopted to reduce the

likelihood of flooding of the basement. However, based on the low permeability subsurface

profile, we are of the opinion that seepage volumes into the basement would be of a relatively low

order. We recommend that under-floor drainage or uplift resistance requirements be reviewed

following pump out testing in existing wells and inspection of the completed excavation when

such issues can be more readily considered.

We do not anticipate that drainage of such flows would have a significant effect on properties in

the surrounding area and that the volumes which would be pumped from the basement are

assumed at this preliminary stage to be quite minor. The completed excavation should be

inspected by the geotechnical and hydraulic engineers shortly after completion, in order to

confirm that these assumed groundwater conditions are realistic and to identify any particular

seepage flows, which require drainage measures.

4.5 Retention and Batter Slopes

The basement excavation will require full support by shoring pile walls, which is our preferred

method of support, due to the low or lesser strengths layers in the shale profile encountered in a

number of boreholes; this can be reviewed once we have completed more detailed investigation

using rock cored boreholes (refer to Section 4.1.1). Properly designed in situ shoring pile systems

may be incorporated into the permanent basement retention system. We recommend that the

support system either be anchored or propped.

An anchored contiguous pile will be required to limit wall movement along critical or movement

sensitive sides of the excavation. An anchored soldier pile wall with shotcrete infill panels should

generally be suitable along boundaries given where there are no buildings within close proximity

of the excavation and assuming some wall movement is acceptable.

Temporary anchors to support shoring piles should be bonded into shale of at least low to

medium strength. Where anchors extend beyond the property boundaries, it will be necessary to

obtain permission from the owners of the adjacent properties prior to their installation. Careful

checks must be made of any adjoining buildings, which might have basement structures that may

interfere with anchor installations.

Bored pier or CFA (augered grout injected) piles may be used for the shoring walls. Piles should

be socketed for an appropriate design depth to maintain wall stability, preferably below the base

of the excavation, including below local footing and service excavations. We recommend large


and high capacity drilling rigs with rock drilling equipment be used to drill the piles. The proposed

piling contractor must, therefore, be given a copy of the final detailed geotechnical investigation

report to ensure that appropriate equipment with sufficient power is brought to site. Piles should

be poured immediately or at the very latest, on the same day, as drilling, cleaning and inspection.

Special tools should be used to roughen the sides of load bearing pile sockets in the shale.

Water should be removed from the base of bored piles prior to concreting or the concrete placed

using tremie methods.

Another support alternative is to cut the excavation sides at stable shallow angle batter slopes, if

there is room or space within the site to accommodate these slopes. Our recommended

temporary batters would be no steeper than 1 Horizontal (H) to 1 Vertical (V) in soils and shale of

low or lesser strengths.

However, surcharge loadings (footings, vehicles, etc) should not be within the zone of influence of

the excavation. As a guide, surcharge loadings should be no closer than 2H from the top of any

batter or the face of any excavation (including footing excavations), where H is the vertical height

of the batter or depth of the excavation. Flatter batters may be required where groundwater

seepage is encountered. The stability of the batters in the shale must be subject to confirmation

by an inspection by a geotechnical engineer as the excavation progresses and the batters are

formed say in intervals of 1.5m depth.

During construction, the excavation should be inspected by a geotechnical engineer at vertical

intervals not exceeding 1.5m in order that any inclined defects (e.g. very steep joints) or other

adverse conditions can be identified and, if necessary, stabilisation measures implemented. The

most likely stabilisation measures which may be required would involve rock bolting with bolt

lengths ranging from 3m to 5m being most probable. A provision for rock bolting and shotcrete

and mesh should be included in the Contract Documents for works nominated following the

geotechnical inspections. If extensive weathered seams are found, it may be necessary to

provide temporary as well as permanent support in order to maintain safe working conditions; the

use of shotcrete together with mesh and rock dowels are the most common means of providing

this type of support. In the long term, some treatment of seams or fractured zones may also be

necessary and such support may be provided either by means of retaining walls propped from the

permanent structure or, in this case, by means of permanent rock bolts which can be

accommodated within the site boundaries. Of course permanent rock bolts would require

appropriate detailing for long term corrosion protection. Design lateral pressures for support of


weathered and fractured zones by structural means would be determined once the problems

could be assessed in the excavation.

During the excavation, every care should be taken to not undermine or render unstable the

footings of any adjoining structure. The effect of ground movements on any buildings and

services that lie within the influence zone of the excavation must also be taken into account. No

matter what method of excavation and support system is used, some ground displacement will

occur both within and immediately surrounding the bulk excavation. The final deformations of the

excavation support systems, which are recommended in this report, are highly dependent on the

construction sequence and detailing. The magnitude of lateral movement is also directly related to

the stiffness of the retaining system. The risks of architectural and/or structural damage to the

neighbouring buildings will depend on their sensitivity to horizontal and vertical deformations

(induced by the proposed excavation), structural loading, type and founding levels of footings and

foundation conditions. All these factors must be carefully investigated and evaluated prior to

excavation commencing.

4.5.1 Lateral Pressures

For design of anchored or propped walls, we recommend the use of a trapezoidal lateral pressure

distribution with at least magnitude of 4H kPa (where H is the total depth in metres of the residual

clay and upper extremely low (EL) to low (L) strength shale, which may be reduced down to 2H

over the shale of at least low (L) to medium (M) strength or greater strengths. The full lateral

pressure is applicable over the central 50% of the trapezoidal pressure distribution. For areas that

are highly sensitive to lateral movement, consideration should be given to using a trapezoidal

lateral pressure distribution of magnitude 8H kPa and 4H kPa, over the aforementioned materials

respectively, or greater, to limit deflections.

All appropriate hydrostatic pressures and surcharge loads should be incorporated in the design of

the retaining walls. Design surcharge loads on the shoring should take account of existing façade

loads, any traffic loads, heavy crane loads, hoarding loads and vehicle impact on hoarding

structure. We recommend that only the services of a proven and competent earthworks and

shoring contractor be considered. The above lateral pressures and coefficients assume horizontal

backfill surfaces and where inclined backfill is proposed the pressures or coefficients would need

to be increased or the inclined backfill taken as a surcharge load.


For the design of walls socketed into the shale of at least low to medium strength, it is

recommended that a maximum allowable toe resistance of 250kPa may be used below the base

of the excavation, including footing and service excavations, to resist the lateral pressure.

Anchors should have their anchor bond length within shale of at least low strength. For the

design of anchors bonded into such strength rock an allowable bond stress of 200kPa is

recommended subject to the following conditions:

Anchor bond length of at least 3m behind the ‘active’ zone of the excavation.

Overall stability, including anchor group interaction, is satisfied.

All anchors are respectively proof loaded to at least 1.3 times the design working load before

locking off at working load.

Higher bond stresses may be justified if the results from a testing program on prototype anchors

indicate this to be appropriate.

4.6 Foundation Strata

Following bulk excavations, shale is expected to be exposed over the lowest basement level or to

be close to the finished floor level, depending on the final basement levels adopted. It is

recommended that all footings for the building and retaining walls be founded within the shale of

relatively similar competency to provide uniform support and reduce the potential for differential

footing settlements.

The footing systems will require careful consideration due to the variable shale conditions. A

mixture of footing types is expected to be required to reach the desired shale strength. Pad or

strip or piled footings may be designed using the following maximum allowable bearing pressure

(ABP); higher bearing pressures (e.g. 3500kPa) might be probable subject to proving and

confirmation by the additional deep cored boreholes:

1. Shale of Extremely Low (EL) Strength: ABP of 700kPa;

2. Shale of Very Low (VL) Strengths: ABP of 1000kPa;

3. Shale of Low (L) or greater Strengths: ABP of 1500kPa;

During construction inspections the geotechnical engineer should nominate any additional testing

if necessary. The presence of significant defects or lower strength bedrock would require a

reduction in allowable bearing capacity or an increase in footing depth.


An allowable shaft adhesion (ASA) of equivalent to 10% of the above ABP values may be

adopted for design of pile sockets in compression through the shale. For uplift or tension, the

ASA value should be halved. We expect that deep or long sockets into shale of medium or

greater strength would be slow and difficult to drill and it would be advisable to avoid these

wherever possible.

All footing excavations should be free from all loose or softened materials prior to placement of

concrete. We recommend that footing excavations be checked and approved prior to concrete

being poured. The initial stages of footing excavation should be inspected by a geotechnical

engineer to ascertain that the recommended foundation has been reached and to check initial

assumptions about foundation conditions and possible variations that may occur between

borehole locations. The need for further inspections can be assessed following the initial visit.

We can assist with future geotechnical inspections if you wish to commission us at the

appropriate time.

During installation of piles it is recommended that the initial piles be installed as close as practical

to our borehole locations to calibrate the equipment and operator to the subsurface conditions by

direction comparison of the installation performance and readings to the borehole results. These

initial readings can then be used to assist with installation of piles away from the borehole

locations to assess that the appropriate foundation material has been reached. Bored or CFA

(augered grout injected) piles may be used. We recommend large capacity drilling rigs with rock

drilling equipment be used to drill the piles. The proposed piling contractor must, therefore, be

given a copy of the final detailed geotechnical investigation report to ensure that appropriate

equipment with sufficient power is brought to site. Piles should be poured immediately or at the

very latest, on the same day, as drilling, cleaning and inspection. Special tools should be used to

roughen the sides of load bearing pile sockets in the shale. Water should be removed from the

base of bored piles prior to concreting or the concrete placed using tremie methods.

The site has been altered by fill and hence, is classified as Class 'P' in accordance with AS2870-

2011. We note that the underlying residual clays are considered to be moderately reactive

equivalent to Class M. Although the behaviour of reactive clays and its effects on a building or

other movement sensitive structures is very complex, the prediction of ground movements may be

undertaken in accordance with the method suggested in AS2870-2011 “Residential Slabs and

Footings – Construction”. We advice that in the strict sense AS2870 site classification does not


apply to this size structure but it is a useful guide in highlighting the potential foundation problems

of the soils of this site.

4.7 Other Earthworks

The main geotechnical issues with other earthworks, including subgrade preparation, under floor

slab (and external pavement areas) are to do with any existing fill that may remain after

excavation for the proposed car parking basement levels. The existing fill appears to be variably

compacted. The fill is deemed unsuitable as a bearing stratum for warehouse footings and floor

slabs. In the building and slab footprint areas most of the fill is expected to be removed by the

proposed graded excavations. However, where it is seen to be remaining then it should be

excavated and replaced with engineered fill that can then support the slab on grade; all footings

must be founded on the shale bedrock. The fill is also considered a ‘moderate to high risk’ (of

poor performance) as a supporting subgrade under external pavements. Again, we prefer that the

fill be removed and replaced with engineered fill.

Earthworks recommendations provided in this report should be complemented by reference to

AS3798. In summary, we recommend that:

1. After reaching the bulk excavation level for the basement car parking levels (unknown at the

time of this Due Diligence investigation), excavate further any remaining fill down to surface of

the residual clay. The backfilling should then proceed with engineered, controlled fill. The

replacement should extend to at least 2m beyond the boundaries of the floor/pavement area.

Such an excavation if deeper than 1.2m would have to be completed with battered sides of

not steeper than 1 Vertical to 1.5 Horizontal. The earthworks contractor must ensure that

during the backfilling earthworks that the engineered fill is well ‘keyed’ into the side batters of

the excavation.

2. The exposed subgrade at the base of the excavation should be proof rolled with at least 8

passes of a heavy (not less than 12 tonne) smooth drum vibratory roller. The purpose of the

proof rolling is to detect any soft or heaving areas. Caution is required when proof rolling near

any neighbouring improvements and buried services.

3. The final pass should be undertaken in the presence of a geotechnician or geotechnical

engineer, to detect any unstable or soft subgrade areas, and to allow for some further

improvement in strength/compaction.

4. If dry conditions prevail at the time of construction then any exposed residual clay subgrade

may become desiccated or have shrinkage cracks prior to pouring any concrete slabs. If this

occurs then the subgrade must be watered and rolled until the cracks disappear.


5. Unstable subgrade detected during proof rolling should be locally excavated down to a stiff or

sound base and replaced with engineered fill or further advice should be sought. Allowance

should be made for either, tyning, aerating and drying the subgrade, or removal and

replacement with a select imported fill, or lime/cement stabilisation.

6. It is important to provide good and effective site drainage both during construction and for

long-term site maintenance. The principle aim of the drainage is to promote run-off and

reduce ponding. A poorly drained clay subgrade may become untraffickable when wet. The

earthworks should be carefully planned and scheduled to maintain good cross-falls during

construction.

4.7.1 Engineered Fill Specifications

Any fill used to backfill unstable subgrade areas, raise surface levels or backfill service trenches

should be engineered fill. Materials preferred for use as engineered fill are well-graded granular

materials, such as ripped or crushed sandstone, free of deleterious substances and having a

maximum particle size not exceeding 75mm. Such fill should be compacted in layers not greater

than 200mm loose thickness, to a minimum density of 98% of Standard Maximum Dry Density

(SMDD).

The existing fill and residual clays at the site are acceptable for re-use on condition that the soils

used are clean (i.e. free of organics and inclusions greater than 75mm size), free of contaminants

(in this respect refer to the EIS report). These clayey soils should be compacted in maximum

200mm loose layers to a density strictly between 98% and 102% of SMDD and at moisture

content within 2% of Standard Optimum. All clay fill should preferably be used in the lower fill

layers. Thus, the use of clay materials for engineered fill will entail more rigorous earthwork

supervision and compaction control, time for drying out the soils and hence, possibly a greater

eventual cost for earthworks.

Density tests should be regularly carried out on the fill to confirm the above specifications are

achieved. The frequency of density testing should be at least one test per layer per 500m2 or

three tests per visit, whichever requires the most tests. We recommend that full time Level 1

control of fill compaction, as defined in AS3798-2007, be adhered to on this site. Preferably, the

geotechnical testing authority (GTA) should be engaged directly on behalf of the client and not by

the earthworks subcontractor.


During construction of the fill platform runoff should be enhanced by providing suitable falls to

reduce ponding of water on the surface of the fill. Ponding of water may lead to softening of the

fill and subsequent delays in the earthworks program.

4.8 Pavement Design

The design of new pavements will depend on subgrade preparation, subgrade drainage, the

nature and composition of fill excavated or imported to the site, as well as vehicle loadings and

use. Refer to Section 4.7 on subgrade preparation and other earthwork procedures including

engineered fill specifications and compaction control.

Various alternative types of construction could be used for the pavements. Concrete construction

would undoubtedly be the best in areas where heavy vehicles manoeuvre such as truck turning

and manoeuvring. Flexible pavements may have a lower initial cost but maintenance will be

higher. These factors should be considered when making the final choice.

The residual clay subgrade has a low soaked CBR value. We recommend that the pavement

thickness design should be based on the CBR of 3%.

Further soaked CBR tests may be carried out on representative samples of the subgrade. If the

existing fill is removed and replaced with imported fill, the CBR of the imported material may be

taken into account. These design values should be confirmed by inspection and DCP testing of

the subgrade following proof rolling.

All upper (base) course are recommended to be crushed rock to RTA QA specification 3051

(1994) unbound base and compacted to at least 100% of Standard Maximum Dry Density. All

lower (sub-base) course are recommended to be crushed rock to RTA QA specification 3051

(1994) unbound base or ripped/crushed sandstone with CBR greater than 40%, maximum particle

size of 60mm, well graded and Plastic Index less than 10. All lower course material should be

compacted to an average of no less than 100% of SMDD, but with a minimum acceptance value

of 98% of SMDD.

Concrete pavements are recommended to have a sub-base layer of at least 100mm thickness of

crushed rock to RTA QA specification 3051 (1994) unbound base material (or equivalent good

quality and durable fine crushed rock) which is compacted to at least 100% SMDD. Concrete

pavements should be designed with an effective shear transmission of all joints by way of either

doweled or keyed joints.


Careful attention to subsurface and surface drainage is required in view of the effect of moisture

on the clay soils. Pavement levels will need to be graded to promote rapid removal of surface

water so ponding does not occur on the surface of pavements.

5 GENERAL COMMENTS

The preliminary recommendations presented in this report include specific issues to be addressed

during the DA, CC and construction phases of the project. In the event that any of the phase

recommendations presented in this report are not implemented, the general recommendations

may become inapplicable and JK Geotechnics accept no responsibility whatsoever for the

performance of the structure where recommendations are not implemented in full and properly

tested, inspected and documented.

The long term successful performance of floor slabs and pavements is dependent on the

satisfactory completion of the earthworks. In order to achieve this, the quality assurance program

should not be limited to routine compaction density testing only. Other critical factors associated

with the earthworks may include subgrade preparation, selection of fill materials, control of

moisture content and drainage, etc. The satisfactory control and assessment of these items may

require judgment from an experienced engineer. Such judgment often cannot be made by a

technician who may not have formal engineering qualifications and experience. In order to

identify potential problems, we recommend that a pre-construction meeting be held so that all

parties involved understand the earthworks requirements and potential difficulties. This meeting

should clearly define the lines of communication and responsibility.

Occasionally, the subsurface conditions between the completed boreholes may be found to be

different (or may be interpreted to be different) from those expected. Variation can also occur

with groundwater conditions, especially after climatic changes. If such differences appear to

exist, we recommend that you immediately contact this office.

This report provides preliminary advice on geotechnical aspects for the proposed civil and

structural design. As part of the documentation stage of this project, Draft Contract Documents

and Specifications may be prepared based on our report. However, there may be design features

we are not aware of or have not commented on for a variety of reasons. The designers should

satisfy themselves that all the necessary advice has been obtained. If required, we could be


commissioned to review the geotechnical aspects of contract documents to confirm the intent of

our recommendations has been correctly implemented.

This report has been prepared for the particular project described and no responsibility is

accepted for the use of any part of this report in any other context or for any other purpose.

If there is any change in the proposed development described in this report then all

recommendations should be reviewed. Copyright in this report is the property of JK Geotechnics.

We have used a degree of care, skill and diligence normally exercised by consulting engineers in

similar circumstances and locality. No other warranty expressed or implied is made or intended.

Subject to payment of all fees due for the investigation, the client alone shall have a licence to

use this report. The report shall not be reproduced except in full.

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JKG Report Explanation Notes Rev2 May 2013 Page 1 of 4

REPORT EXPLANATION NOTES

INTRODUCTION

These notes have been provided to amplify the geotechnicalreport in regard to classification methods, field proceduresand certain matters relating to the Comments andRecommendations section. Not all notes are necessarilyrelevant to all reports.

The ground is a product of continuing natural and man-made processes and therefore exhibits a variety ofcharacteristics and properties which vary from place to placeand can change with time. Geotechnical engineeringinvolves gathering and assimilating limited facts about thesecharacteristics and properties in order to understand orpredict the behaviour of the ground on a particular site undercertain conditions. This report may contain such factsobtained by inspection, excavation, probing, sampling,testing or other means of investigation. If so, they aredirectly relevant only to the ground at the place where andtime when the investigation was carried out.

DESCRIPTION AND CLASSIFICATION METHODS

The methods of description and classification of soils androcks used in this report are based on Australian Standard1726, the SAA Site Investigation Code. In general,descriptions cover the following properties – soil or rock type,colour, structure, strength or density, and inclusions.Identification and classification of soil and rock involvesjudgement and the Company infers accuracy only to theextent that is common in current geotechnical practice.

Soil types are described according to the predominatingparticle size and behaviour as set out in the attached UnifiedSoil Classification Table qualified by the grading of otherparticles present (e.g. sandy clay) as set out below:

Soil Classification Particle Size

Clay

Silt

Sand

Gravel

less than 0.002mm

0.002 to 0.075mm

0.075 to 2mm

2 to 60mm

Non-cohesive soils are classified on the basis of relativedensity, generally from the results of Standard PenetrationTest (SPT) as below:

Relative DensitySPT ‘N’ Value(blows/300mm)

Very loose

Loose

Medium dense

Dense

Very Dense

less than 4

4 – 10

10 – 30

30 – 50

greater than 50

Cohesive soils are classified on the basis of strength(consistency) either by use of hand penetrometer, laboratorytesting or engineering examination. The strength terms aredefined as follows.

ClassificationUnconfined CompressiveStrength kPa

Very Soft

Soft

Firm

Stiff

Very Stiff

Hard

Friable

less than 25

25 – 50

50 – 100

100 – 200

200 – 400

Greater than 400

Strength not attainable

– soil crumbles

Rock types are classified by their geological names,together with descriptive terms regarding weathering,strength, defects, etc. Where relevant, further informationregarding rock classification is given in the text of the report.In the Sydney Basin, ‘Shale’ is used to describe thinlybedded to laminated siltstone.

SAMPLING

Sampling is carried out during drilling or from otherexcavations to allow engineering examination (andlaboratory testing where required) of the soil or rock.

Disturbed samples taken during drilling provide informationon plasticity, grain size, colour, moisture content, minorconstituents and, depending upon the degree of disturbance,some information on strength and structure. Bulk samplesare similar but of greater volume required for some testprocedures.

Undisturbed samples are taken by pushing a thin-walledsample tube, usually 50mm diameter (known as a U50), intothe soil and withdrawing it with a sample of the soilcontained in a relatively undisturbed state. Such samplesyield information on structure and strength, and arenecessary for laboratory determination of shear strengthand compressibility. Undisturbed sampling is generallyeffective only in cohesive soils.

Details of the type and method of sampling used are givenon the attached logs.

INVESTIGATION METHODS

The following is a brief summary of investigation methodscurrently adopted by the Company and some comments ontheir use and application. All except test pits, hand augerdrilling and portable dynamic cone penetrometers requirethe use of a mechanical drilling rig which is commonlymounted on a truck chassis.

JK GeotechnicsGEOTECHNICAL & ENVIRONMENTAL ENGINEERS


Test Pits: These are normally excavated with a backhoe or

a tracked excavator, allowing close examination of the insitusoils if it is safe to descend into the pit. The depth ofpenetration is limited to about 3m for a backhoe and up to6m for an excavator. Limitations of test pits are the problemsassociated with disturbance and difficulty of reinstatementand the consequent effects on close-by structures. Caremust be taken if construction is to be carried out near test pitlocations to either properly recompact the backfill duringconstruction or to design and construct the structure so asnot to be adversely affected by poorly compacted backfill atthe test pit location.

Hand Auger Drilling: A borehole of 50mm to 100mm

diameter is advanced by manually operated equipment.Premature refusal of the hand augers can occur on a varietyof materials such as hard clay, gravel or ironstone, and doesnot necessarily indicate rock level.

Continuous Spiral Flight Augers: The borehole is

advanced using 75mm to 115mm diameter continuousspiral flight augers, which are withdrawn at intervals to allowsampling and insitu testing. This is a relatively economicalmeans of drilling in clays and in sands above the water table.Samples are returned to the surface by the flights or may becollected after withdrawal of the auger flights, but they canbe very disturbed and layers may become mixed.Information from the auger sampling (as distinct fromspecific sampling by SPTs or undisturbed samples) is ofrelatively lower reliability due to mixing or softening ofsamples by groundwater, or uncertainties as to the originaldepth of the samples. Augering below the groundwatertable is of even lesser reliability than augering above thewater table.

Rock Augering: Use can be made of a Tungsten Carbide

(TC) bit for auger drilling into rock to indicate rock qualityand continuity by variation in drilling resistance and fromexamination of recovered rock fragments. This method ofinvestigation is quick and relatively inexpensive but providesonly an indication of the likely rock strength and predictedvalues may be in error by a strength order. Where rockstrengths may have a significant impact on constructionfeasibility or costs, then further investigation by means ofcored boreholes may be warranted.

Wash Boring: The borehole is usually advanced by a

rotary bit, with water being pumped down the drill rods andreturned up the annulus, carrying the drill cuttings.Only major changes in stratification can be determined fromthe cuttings, together with some information from “feel” andrate of penetration.

Mud Stabilised Drilling: Either Wash Boring or

Continuous Core Drilling can use drilling mud as acirculating fluid to stabilise the borehole. The term ‘mud’encompasses a range of products ranging from bentonite topolymers such as Revert or Biogel. The mud tends to maskthe cuttings and reliable identification is only possible fromintermittent intact sampling (eg from SPT and U50 samples)or from rock coring, etc.

Continuous Core Drilling: A continuous core sample is

obtained using a diamond tipped core barrel. Provided fullcore recovery is achieved (which is not always possible invery low strength rocks and granular soils), this techniqueprovides a very reliable (but relatively expensive) method ofinvestigation. In rocks, an NMLC triple tube core barrel,which gives a core of about 50mm diameter, is usually usedwith water flush. The length of core recovered is comparedto the length drilled and any length not recovered is shownas CORE LOSS. The location of losses are determined onsite by the supervising engineer; where the location isuncertain, the loss is placed at the top end of the drill run.

Standard Penetration Tests: Standard Penetration Tests

(SPT) are used mainly in non-cohesive soils, but can alsobe used in cohesive soils as a means of indicating density orstrength and also of obtaining a relatively undisturbedsample. The test procedure is described in AustralianStandard 1289, “Methods of Testing Soils for EngineeringPurposes” – Test F3.1.

The test is carried out in a borehole by driving a 50mmdiameter split sample tube with a tapered shoe, under theimpact of a 63kg hammer with a free fall of 760mm. It isnormal for the tube to be driven in three successive 150mmincrements and the ‘N’ value is taken as the number ofblows for the last 300mm. In dense sands, very hard claysor weak rock, the full 450mm penetration may not bepracticable and the test is discontinued.

The test results are reported in the following form:

In the case where full penetration is obtained withsuccessive blow counts for each 150mm of, say, 4, 6and 7 blows, as

N = 134, 6, 7

In a case where the test is discontinued short of fullpenetration, say after 15 blows for the first 150mm and30 blows for the next 40mm, as

N>3015, 30/40mm

The results of the test can be related empirically to theengineering properties of the soil.

Occasionally, the drop hammer is used to drive 50mmdiameter thin walled sample tubes (U50) in clays. In suchcircumstances, the test results are shown on the boreholelogs in brackets.

A modification to the SPT test is where the same driving

system is used with a solid 60 tipped steel cone of thesame diameter as the SPT hollow sampler. The solid conecan be continuously driven for some distance in soft clays orloose sands, or may be used where damage wouldotherwise occur to the SPT. The results of this Solid ConePenetration Test (SCPT) are shown as "N c” on the boreholelogs, together with the number of blows per 150mmpenetration.


Static Cone Penetrometer Testing and Interpretation:

Cone penetrometer testing (sometimes referred to as aDutch Cone) described in this report has been carried outusing an Electronic Friction Cone Penetrometer (EFCP).The test is described in Australian Standard 1289, Test F5.1.

In the tests, a 35mm diameter rod with a conical tip ispushed continuously into the soil, the reaction beingprovided by a specially designed truck or rig which is fittedwith an hydraulic ram system. Measurements are made ofthe end bearing resistance on the cone and the frictionalresistance on a separate 134mm long sleeve, immediatelybehind the cone. Transducers in the tip of the assembly areelectrically connected by wires passing through the centre ofthe push rods to an amplifier and recorder unit mounted onthe control truck.

As penetration occurs (at a rate of approximately 20mm persecond) the information is output as incremental digitalrecords every 10mm. The results given in this report havebeen plotted from the digital data.

The information provided on the charts comprise:

Cone resistance – the actual end bearing force dividedby the cross sectional area of the cone – expressed inMPa.

Sleeve friction – the frictional force on the sleeve dividedby the surface area – expressed in kPa.

Friction ratio – the ratio of sleeve friction to coneresistance, expressed as a percentage.

The ratios of the sleeve resistance to cone resistancewill vary with the type of soil encountered, with higherrelative friction in clays than in sands. Friction ratios of1% to 2% are commonly encountered in sands andoccasionally very soft clays, rising to 4% to 10% in stiffclays and peats. Soil descriptions based on coneresistance and friction ratios are only inferred and mustnot be considered as exact.

Correlations between EFCP and SPT values can bedeveloped for both sands and clays but may be site specific.

Interpretation of EFCP values can be made to empiricallyderive modulus or compressibility values to allow calculationof foundation settlements.

Stratification can be inferred from the cone and frictiontraces and from experience and information from nearbyboreholes etc. Where shown, this information is presentedfor general guidance, but must be regarded as interpretive.The test method provides a continuous profile ofengineering properties but, where precise information on soilclassification is required, direct drilling and sampling may bepreferable.

Portable Dynamic Cone Penetrometers: Portable

Dynamic Cone Penetrometer (DCP) tests are carried out bydriving a rod into the ground with a sliding hammer andcounting the blows for successive 100mm increments ofpenetration.

Two relatively similar tests are used:

Cone penetrometer (commonly known as the ScalaPenetrometer) – a 16mm rod with a 20mm diametercone end is driven with a 9kg hammer dropping 510mm(AS1289, Test F3.2). The test was developed initiallyfor pavement subgrade investigations, and correlationsof the test results with California Bearing Ratio havebeen published by various Road Authorities.

Perth sand penetrometer – a 16mm diameter flat endedrod is driven with a 9kg hammer, dropping 600mm(AS1289, Test F3.3). This test was developed fortesting the density of sands (originating in Perth) and ismainly used in granular soils and filling.

LOGS

The borehole or test pit logs presented herein are anengineering and/or geological interpretation of the sub-surface conditions, and their reliability will depend to someextent on the frequency of sampling and the method ofdrilling or excavation. Ideally, continuous undisturbedsampling or core drilling will enable the most reliableassessment, but is not always practicable or possible tojustify on economic grounds. In any case, the boreholes ortest pits represent only a very small sample of the totalsubsurface conditions.

The attached explanatory notes define the terms andsymbols used in preparation of the logs.

Interpretation of the information shown on the logs, and itsapplication to design and construction, should therefore takeinto account the spacing of boreholes or test pits, themethod of drilling or excavation, the frequency of samplingand testing and the possibility of other than “straight line”variations between the boreholes or test pits. Subsurfaceconditions between boreholes or test pits may varysignificantly from conditions encountered at the borehole ortest pit locations.

GROUNDWATER

Where groundwater levels are measured in boreholes, thereare several potential problems:

Although groundwater may be present, in lowpermeability soils it may enter the hole slowly or perhapsnot at all during the time it is left open.

A localised perched water table may lead to anerroneous indication of the true water table.

Water table levels will vary from time to time withseasons or recent weather changes and may not be thesame at the time of construction.

The use of water or mud as a drilling fluid will mask anygroundwater inflow. Water has to be blown out of thehole and drilling mud must be washed out of the hole or‘reverted’ chemically if water observations are to bemade.


More reliable measurements can be made by installingstandpipes which are read after stabilising at intervalsranging from several days to perhaps weeks for lowpermeability soils. Piezometers, sealed in a particularstratum, may be advisable in low permeability soils or wherethere may be interference from perched water tables orsurface water.

FILL

The presence of fill materials can often be determined onlyby the inclusion of foreign objects (eg bricks, steel etc) or bydistinctly unusual colour, texture or fabric. Identification ofthe extent of fill materials will also depend on investigationmethods and frequency. Where natural soils similar tothose at the site are used for fill, it may be difficult withlimited testing and sampling to reliably determine the extentof the fill.

The presence of fill materials is usually regarded withcaution as the possible variation in density, strength andmaterial type is much greater than with natural soil deposits.Consequently, there is an increased risk of adverseengineering characteristics or behaviour. If the volume andquality of fill is of importance to a project, then frequent testpit excavations are preferable to boreholes.

LABORATORY TESTING

Laboratory testing is normally carried out in accordance withAustralian Standard 1289 ‘Methods of Testing Soil forEngineering Purposes’. Details of the test procedure usedare given on the individual report forms.

ENGINEERING REPORTS

Engineering reports are prepared by qualified personnel andare based on the information obtained and on currentengineering standards of interpretation and analysis. Wherethe report has been prepared for a specific design proposal(eg. a three storey building) the information andinterpretation may not be relevant if the design proposal ischanged (eg to a twenty storey building). If this happens,the company will be pleased to review the report and thesufficiency of the investigation work.

Every care is taken with the report as it relates tointerpretation of subsurface conditions, discussion ofgeotechnical aspects and recommendations or suggestionsfor design and construction. However, the Company cannotalways anticipate or assume responsibility for:

Unexpected variations in ground conditions – thepotential for this will be partially dependent on boreholespacing and sampling frequency as well as investigationtechnique.

Changes in policy or interpretation of policy by statutoryauthorities.

The actions of persons or contractors responding tocommercial pressures.

If these occur, the company will be pleased to assist withinvestigation or advice to resolve any problems occurring.

SITE ANOMALIES

In the event that conditions encountered on site duringconstruction appear to vary from those which were expectedfrom the information contained in the report, the companyrequests that it immediately be notified. Most problems aremuch more readily resolved when conditions are exposedthat at some later stage, well after the event.

REPRODUCTION OF INFORMATION FORCONTRACTUAL PURPOSES

Attention is drawn to the document ‘Guidelines for theProvision of Geotechnical Information in Tender Documents’ ,

published by the Institution of Engineers, Australia. Whereinformation obtained from this investigation is provided fortendering purposes, it is recommended that all information,including the written report and discussion, be madeavailable. In circumstances where the discussion orcomments section is not relevant to the contractual situation,it may be appropriate to prepare a specially editeddocument. The company would be pleased to assist in thisregard and/or to make additional report copies available forcontract purposes at a nominal charge.

Copyright in all documents (such as drawings, borehole ortest pit logs, reports and specifications) provided by theCompany shall remain the property of Jeffery andKatauskas Pty Ltd. Subject to the payment of all fees due,the Client alone shall have a licence to use the documentsprovided for the sole purpose of completing the project towhich they relate. License to use the documents may berevoked without notice if the Client is in breach of anyobjection to make a payment to us.

REVIEW OF DESIGN

Where major civil or structural developments are proposedor where only a limited investigation has been completed orwhere the geotechnical conditions/ constraints are quitecomplex, it is prudent to have a joint design review whichinvolves a senior geotechnical engineer.

SITE INSPECTION

The company will always be pleased to provide engineeringinspection services for geotechnical aspects of work towhich this report is related.

Requirements could range from:

i) a site visit to confirm that conditions exposed are noworse than those interpreted, to

ii) a visit to assist the contractor or other site personnel inidentifying various soil/rock types such as appropriatefooting or pier founding depths, or

iii) full time engineering presence on site.

JKG Graph

GEOTEC

hic Log Symbols fo

HNICAL & ENVI

or Soils and Rock

GRAPHI

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s Rev1 July12

IC LOG SY

NGINEERS

MBOLS FOOR SOILS AAND ROCKSKS

Pag

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Note:

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UNIF

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FIED SOIL

ted by combinations olly classified as being

CLASSIFIC

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CATION TA

GW-GC, well graded g

ABLE

gravel-sand mixture wwith clay fines).

JKG Log S

LOG

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ENGINEERS

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ater level. Time d

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ABBRE

ABBR

v1 June12

MATERIAL W

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STRENGTH ngth is defined bThe test proc

Volume 22, No 2,

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ly Low:

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DEFINITION

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FIELD GUIDE

al with soil propert

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dia. core cannot bngs under hamme

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NOT

measured relativetal for vertical ho

cture and substant been significantl

rties, ie it either d

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rength from fresh

substance in theMining, Science

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ties.

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en by hand and eauring handling.

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lt to break with ha

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Page

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rock.

direction normae and Geomec

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to the long core

2 of 2

longer

can be

ally by tion of

al to the chanics.

a

cored

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.

e axis

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