Upload
others
View
4
Download
0
Embed Size (px)
Citation preview
PRELIMINARY REPORT on GEOTECHNICAL INVESTIGATION PROPOSED MULTI STOREY BUILDING CORNER MARSDEN AND MACQUARIE STREETS PARRAMATTA Prepared for CROWN LANDMARK PTY LTD Project 71342 Revision 1 March 2010
PRELIMINARY REPORT on GEOTECHNICAL INVESTIGATION PROPOSED MULTI STOREY BUILDING CORNER MARSDEN AND MACQUARIE STREETS PARRAMATTA Prepared for CROWN LANDMARK PTY LTD Project 71342 Revision 1 March 2010
Douglas Partners Pty Ltd ABN 75 053 980 117
96 Hermitage Road West Ryde NSW 2114 Australia
PO Box 472 West Ryde NSW 1685 Phone (02) 9809 0666 Fax (02) 9809 4095 [email protected]
Proposed Multi Storey Building Project 71342 Rev 1 Corner Marsden and Macquarie Streets, Parramatta March 2010
TABLE OF CONTENTS Page 1. INTRODUCTION.......................................................................................................... 1 2. BACKGROUND ........................................................................................................... 2 3. SITE DESCRIPTION.................................................................................................... 4 4. GEOLOGY ................................................................................................................... 5 5. FIELD WORK............................................................................................................... 6
5.1 Field Work Methods ......................................................................................... 6 5.2 Field Work Results ........................................................................................... 6
5.2.1 Soil Stratigraphy ................................................................................... 6 5.2.2 Water Levels......................................................................................... 7 5.2.3 Strata Permeability ............................................................................... 8
6. LABORATORY TESTING ............................................................................................ 8 7. PROPOSED DEVELOPMENT................................................................................... 10 8. COMMENTS .............................................................................................................. 10
8.1 Geotechnical Model........................................................................................ 10 8.2 Excavation Conditions.................................................................................... 11 8.3 Vibration ......................................................................................................... 12 8.4 Excavation Support ........................................................................................ 12
8.4.1 Diaphragm Wall .................................................................................. 13 8.4.2 Secant Pile Wall.................................................................................. 14 8.4.3 Soldier Piles and Jet Grouting ............................................................ 14 8.4.4 Design Parameters ............................................................................. 14
8.5 Ground Anchors ............................................................................................. 15 8.6 Foundations.................................................................................................... 16 8.7 Groundwater Control ...................................................................................... 16 8.8 Acid Sulphate Soils ........................................................................................ 17 8.9 Further Work .................................................................................................. 18
APPENDIX A: Plans and Sections APPENDIX B: Borehole Results and Notes Relating to this Report APPENDIX C: Results of SPOCAS Testing APPENDIX D: Results of In Situ Permeability Tests
Page 1 of 18
Proposed Multi Storey Building Project 71342 Rev 1 Corner Marsden and Macquarie Streets, Parramatta March 2010
BOK:jlb Project 71342 Rev 1
10 March 2010
PRELIMINARY REPORT ON GEOTECHNICAL INVESTIGATION
PROPOSED MULTI STOREY BUILDING CORNER MARSDEN AND MACQUARIE STREETS
PARRAMATTA
1. INTRODUCTION
This preliminary report presents the results of a geotechnical investigation carried out by
Douglas Partners Pty Ltd (DP) for a proposed multi-storey building at the corner of Marsden and
Macquarie Streets, Parramatta. The work was commissioned by Mr Russel Strahle of Crown
Landmark Pty Ltd, developers for the project.
It is understood that the proposed development will now involve six levels of basement parking
over about two thirds of the site, a podium of three levels of commercial and retail outlets and a
twenty two level residential tower above the podium. The investigation was required to provide
information on subsurface conditions for the design of foundations and excavations, and to
assess groundwater levels and possible methods of designing a structure to accommodate
groundwater inflows. Some preliminary information on Acid Sulphate Soils (ASS) is also
provided in this report
The investigation comprised:
• Four additional boreholes to 16 boreholes drilled previously by Douglas Partners on the site;
• In situ testing to assess the engineering properties of the strata, to obtain samples for
identification purposes, and to enable laboratory testing to assess acid sulphate soil
conditions;
Page 2 of 18
Proposed Multi Storey Building Project 71342 Rev 1 Corner Marsden and Macquarie Streets, Parramatta March 2010
• Installation of standpipe piezometers for groundwater level measurements and for short
duration pump tests to assess the hydraulic characteristics of the local soils;
• Engineering evaluation and reporting.
Details of the fieldwork and laboratory testing are given in this report, together with some
preliminary comments relating to possible design and construction issues.
The investigation was limited to assessing the local soil and rock conditions on the site and the
geotechnical constraints imposed to the proposed development. The Douglas Partners
investigation did not include the assessment of contamination of soils and groundwater. The
investigation was carried out in accordance with DP’s proposal dated 27 July 2009.
A previous report for this project dated January 2010 was prepared on the understanding that
the development would comprise five basement levels to RL -5.3 m AHD. The increased depth
of excavation now proposed means that twelve of the eighteen bores completed during the
current and 1988 investigations have not penetrated below the proposed excavation level.
Moreover, the other six bores have finished only 0.6 – 1.6 m below excavation level. Therefore,
further testing will be needed during construction to confirm foundation conditions for pad
footings.
This report supercedes in every respect the preliminary report dated January 2010.
2. BACKGROUND
Douglas Partners has previously undertaken investigations on this site in 1962, 1980 and 1988.
These investigations comprised augered and cored boreholes to depths of up to 20 m below
ground surface level and in-situ testing to determine the engineering properties of the soils.
The two previous investigations carried out by DP on the current site in 1980 and 1988 (Project
Nos. 6746 and 11581) comprised a total of 16 boreholes (Bores 1 – 16) located at the positions
as shown in Drawing 1. The boreholes were drilled using auger/rotary rigs employing
Page 3 of 18
Proposed Multi Storey Building Project 71342 Rev 1 Corner Marsden and Macquarie Streets, Parramatta March 2010
continuous spiral flight auger and rotary methods in the upper clays and sands, with NMLC core
drilling used to penetrate the underlying rock, recovering 50 mm diameter continuous core
samples.
The detailed results of Bores 1 – 16 are given in Appendix B, together with accompanying notes
defining classification methods and descriptive terms. It is noted that the strength descriptions
for rock used in these borehole logs have been changed to be consistent with the current
Australian Standard for site investigation. Table 1 shows the relationship between terms in the
old discontinued classification system and the current one.
Table 1 – Strength Description and Terms for Shale / Siltstone
Previous Term Is50 (MPa) Current Term
Extremely weak < 0.03 Extremely low strength
Very weak 0.03 – 0.1 Very low strength
Weak 0.1 – 0.3 Low strength
Medium strong 0.3 – 1 Medium strength
Strong 1 – 3 High strength
Is(50) is Point Load Strength Index
Levels shown on borehole logs were determined using the current survey drawings, assuming
that the existing site levels are the same as or similar to the levels at which the boreholes were
drilled during the previous investigations. This is probably correct because the boreholes drilled
in 1988 (BH9 – 16) and three unlisted boreholes drilled in 1962 were levelled relative to
temporary benchmarks which were assigned levels of RL 100.0 ft (1962) and RL 100.0 m
(1988). These temporary benchmarks were on the kerb of surrounding streets and as the street
levels appear to have not changed and the boreholes were all at about street level it is
considered reasonable to assume that site levels have not changed substantially in the years
since the original investigations.
Page 4 of 18
Proposed Multi Storey Building Project 71342 Rev 1 Corner Marsden and Macquarie Streets, Parramatta March 2010
The principal strata penetrated by the boreholes during the previous investigations comprised:
Filling – Shallow filling at most locations, mainly to depths of 0.2 m – 1.4 m. The filling was
quite variable, but comprised mostly clay or sand soils with varying fractions of gravel, rubble
and topsoil.
Alluvium – Initially very stiff silty and sandy clays, becoming medium dense sands and silty
sands below depths of 5 m – 8 m. Somewhat different conditions were encountered in Bore 15,
near the middle of the site, where mainly sandy soils were encountered for the full depth to rock,
except for a 2 m thick layer of hard sandy clay around a depth of 3 m.
Residual Clay – A thin layer of hard shaly clay, generally less than 1 m thick but not present at
all locations. The shaly clay exhibited the characteristics of weathered shale from which the clay
was derived.
Rock – Shale at first, grading into laminite which, in the deeper boreholes (Bores 1, 8 and 9),
was underlain by fine and medium grained sandstone. The rock was mostly medium strength to
high strength, except for an upper weathered zone and minor defects in the form of seams and
joints as noted in the logs. The rock strength increased progressively with increasing depth, with
the laminite and sandstone beds containing generally high strength rock.
Groundwater was encountered in all of the boreholes at depths of 2.2 m – 6.2 m. Although
monitoring of groundwater in the boreholes did not extend over a sufficiently long period of time
to establish a definitive pattern, the lowest water table levels appear to be associated with the
lower portion of the site.
3. SITE DESCRIPTION
The currently undeveloped site (132 – 142 Marsden Street) is approximately rectangular with an
area of about 4900 m2. It is bounded on three sides by existing streets, having frontage to
Hunter Street (approximately 65 m), Marsden Street (85 m) and Macquarie Street (54 m). The
site is also bounded to the southwest by an existing two storey building and at the northwest by
Page 5 of 18
Proposed Multi Storey Building Project 71342 Rev 1 Corner Marsden and Macquarie Streets, Parramatta March 2010
31 – 39 Macquarie Street, which is a multistorey reinforced concrete building with one level of
basement car parking.
The site has a 2 – 3 m cross-fall in a northerly direction from Hunter Street to Macquarie Street
and has recently been used mainly as an open, generally unpaved car park (but with some
areas of remaining concrete floor slabs and bitumen pavements).
At the time of the current fieldwork, the site was occupied by two large corrugated iron sheds,
which it is understood are being used by archaeologists to study the remains of historical
building(s) that formerly occupied the site. It is further understood that the portion of the site
occupied by these sheds will not form part of the final site development.
A Douglas Partners report of July 2001 (6746A) noted that eight groups of piles had been
installed sometime after the previous investigation had been carried out in 1980. The piles were
intended for support of a then proposed building. These pile groups comprised closely spaced
auger grouted piles, presumably drilled to bedrock. It is assumed that these pile groups are now
buried by the current site filling and the proposed excavation may encounter these piles which
will then have to be removed unless they can be utilised for the current development. However,
for this reuse to be feasible, full details of the pile design and installation would need to be
available.
4. GEOLOGY
Reference to the Sydney 1:100,000 Geological Sheet indicates that the site is underlain by
Quaternary alluvium comprising silty sand, silt and clay, with bedrock in the area mapped as
Ashfield Shale within the Wianamatta Group of the Triassic Age.
It would appear that the site lies within a former channel of the Parramatta River because the
fieldwork has confirmed the presence of sand and clay to considerable depth overlying siltstone
(shale) and then sandstone. Further, at other locations in Parramatta the medium strength rock
is overlain by several metres of weathered rock which is mostly absent on this site, possibly due
to erosion by river flow in the former channel.
Page 6 of 18
Proposed Multi Storey Building Project 71342 Rev 1 Corner Marsden and Macquarie Streets, Parramatta March 2010
5. FIELD WORK
5.1 Field Work Methods
The field work for the current investigation comprised four boreholes (BH101-104) drilled with a
truck-mounted auger/rotary drilling rig to supplement the information already available for the
site. The boreholes were drilled initially through the soils to depths of between 14.5 m and
14.7 m using a 100 mm diameter continuous spiral flight auger and rotary drilling. Standard
penetration tests (SPTs) were carried out at regular depth intervals to assess the soil strength
and to obtain samples. Disturbed auger samples were also retrieved for identification and
laboratory testing purposes. The boreholes were then advanced into the bedrock using NMLC
size (50 mm diameter) diamond core drilling equipment to total depths of between 20.0 m and
20.35 m.
The locations of the previous and current boreholes are shown on Drawing 1 in Appendix A.
The assumed surface levels for boreholes from the previous investigations, used to produce
cross-sections, were taken from current contour/survey plans of the site. It is assumed that the
current levels of the site are the same as or similar to the levels at which the previous
geotechnical testing was carried out.
Following installation of two standpipe piezometers, short term pump tests were conducted to
evaluate the permeability of the alluvial soils. The tests were performed by adding water to
surface level in each of the piezometers and then recording the fall in water level with time.
5.2 Field Work Results
5.2.1 Soil Stratigraphy Details of the conditions encountered in the twenty boreholes drilled on the site are given in
Appendix B, together with notes defining classification methods and descriptive terms. Colour
photographs of the rock core recovered from each borehole are also included.
Page 7 of 18
Proposed Multi Storey Building Project 71342 Rev 1 Corner Marsden and Macquarie Streets, Parramatta March 2010
The recent boreholes encountered the following typical conditions:
FILLING – minor cemented sand / roadbase filling in all boreholes ranging from 0.3 m to 0.5 m
depth, with BH101 encountering a 0.1 m thick layer of concrete at 0.5 m overlying crushed
sandstone filling to 1.4 m depth.
SANDY CLAY/CLAYEY SAND AND CLAY – generally stiff and very stiff with varying
percentages of sand and clay. A very soft, 1.0 m thick layer of sandy clay was encountered in
BH102 at 7.0 m depth.
SAND - generally medium dense with a loose layer in BH103 at 8.0 – 10.0 m and a dense layer
in BH104 between depths of 8.0 m and 11.5 m.
CLAYEY SAND – encountered in BH102 only, medium dense to 14.0 m depth.
SHALE / SILTSTONE –variably weathered, initially extremely to very low strength grading to
medium and high strength, with some very high strength rock in BH101.
SANDSTONE – fresh, high strength with a very high strength layer in BH103.
Cross sections summarising the subsurface conditions at the boreholes completed during the
previous and current investigations are presented in Drawings 2, 3 and 4 in Appendix A.
5.2.2 Water Levels No free groundwater was observed in the boreholes during augering. The use of water for
flushing the boreholes during rotary and core drilling precluded groundwater observations below
about 2–3 m depth.
Groundwater level monitoring wells were installed at boreholes BH101 and BH104 to allow long
term monitoring of groundwater levels. A measurement was made of groundwater levels in the
standpipes piezometers on 21 October 2009. Table 2 presents a summary of the observed
groundwater levels.
Page 8 of 18
Proposed Multi Storey Building Project 71342 Rev 1 Corner Marsden and Macquarie Streets, Parramatta March 2010
Table 2 – Summary of Observed Groundwater Levels
Borehole Date Depth to
Groundwater (m)
Reduced Level (AHD) of
Groundwater
101 21-10-2009 4.55 5.95
104 21-10-2009 4.65 5.55
5.2.3 Strata Permeability The results of the short term permeability tests (SLUG Tests) are provided in Appendix D and
are summarised in Table 3 below.
Table 3 – Results of Permeability Tests
Borehole Estimated Hydraulic Conductivity (m/sec)
BH101 3.5 x 10-5
BH104 2.2 x 10-6
6. LABORATORY TESTING
Selected samples of rock core from the boreholes were tested for point load strength index
values (Is(50)). The results are presented on the borehole logs at the appropriate depths. The
tests gave (Is(50)) values mostly in the range of 0.6 MPa to 2.9 MPa indicating medium to high
strength rock, but with some (Is(50)) values of between 3.9 MPa to 5.0 MPa indicating very high
strength bands in BH101 and BH103. Inferred unconfined compressive strengths (UCS) range
from about 12 MPa to as high as 100 MPa (based upon an assumed UCS: (Is(50)) ratio of 20).
Soil samples, selected from three borehole locations, were tested to assess whether Potential
Acid Sulphate Soils (PASS) are present on the site. These tests included pH screening of 12
soil samples from the three boreholes and then detailed SPOCAS testing on four samples which
gave screening results indicative of PASS. Tables 4 and 5 present a summary of the laboratory
results. The detailed laboratory test result sheets are included in Appendix C.
Page 9 of 18
Proposed Multi Storey Building Project 71342 Rev 1 Corner Marsden and Macquarie Streets, Parramatta March 2010
Table 4 – Results of DP Laboratory pH Screening Bore No.
Depth (m) pHF pHFOX Strength of
reaction* Soil Description
101 10.0-10.45 7.98 6.10 1 Grey brown sand
101 13.0-13.45 7.78 1.90 1 Dark grey sand with some wood fragments
102 1.0-1.45 7.01 6.41 1 Grey and red brown clay 102 4.0-4.45 6.84 6.09 1 Light grey and brown sandy clay
102 7.0-7.45
7.83 7.50 1 Light grey and orange brown
clayey sand 102 8.5-8.95 7.67 7.07 1 Grey clayey sand 102 10.0-10.45 7.55 4.33 1 Dark grey clayey sand 104 8.5-8.95 8.47 7.22 1 Light brown sand 104 10.0-10.3 8.23 6.75 1 Light brown sand 104 10.3-10.4 8.17 5.93 1 Grey slightly silty sand 104 11.5-11.95 7.65 5.93 1 Light brown and grey sand 104 13.0-13.45 7.45 2.86 1 Grey sand
Notes: * Strength of reaction key: F after reaction number indicates a bubbly/frothy reaction 1 Denotes no or slight effervescence BOLD Selected for SPOCAS testing 2 Denotes moderate effervescence pHF pH in distilled water 3 Denotes vigorous effervescence pHFOX pH when oxidised in H2O2 4 Denotes very vigorous effervescence,
gas evolution and heat
Table 5 - Results of Laboratory Analysis for SPOCAS
Sample location and
depth SPOS (%)
SKCL
SP pHKCl pHox TPA
(Mol H+/ tonne)
TSA (Mol H+/ tonne)
101/13-13.45 0.66 0.021 0.68 5.7 2.4 280 278 102/8.5-8.95 <0.005 <0.005 <0.005 6.8 4.7 <5 <5
102/10.0-10.45 <0.005 <0.005 <0.005 6.7 4.9 <5 <5 104/13.0-13.45 0.030 0.007 0.037 6.2 3.9 <5 <5 Action Criteria*
(more than 1000 tonnes disturbed)
0.03 - - 4 3.5 18 18
Action Criteria* (less than 1000
tonnes disturbed)
0.06 - - 4 3.5 36 36
Notes: SCR Chromium Reducible Sulphur TAA Total Actual Acidity TPA Total Potential Acidity TSA Total Sulphidic Acidity (TPA-TAA) * Action Criteria based on ‘Medium Texture’, sandy loams to light clays Results in bold exceed the ASSMAC action criteria (Ref 1).
Page 10 of 18
Proposed Multi Storey Building Project 71342 Rev 1 Corner Marsden and Macquarie Streets, Parramatta March 2010
One sample tested (BH 101, 13.0 m to 13.45 m) exceeded the ‘Sulphur Trail’ and the ‘Acid Trail’
action criteria, indicating the presence of a minor amount of PASS beneath the site.
7. PROPOSED DEVELOPMENT
It is understood that the proposed development will comprise a multistorey residential and
commercial building with a six level basement. The supplied drawings by Bates Smart show
that the building is generally rectangular with the basement covering approximately two thirds of
the site.
The proposed basement level of the development is at approximately RL -8.3 AHD, with
excavations required to depths of approximately 18 m across the basement area.
No information has been provided to Douglas Partners on the likely foundation loads but given
the scope of the proposed development it is probable that the building will impose loads of about
15,000 – 20,000 kN on the building footings based upon an average building column spacing of
7.5 – 8.0 m.
8. COMMENTS
8.1 Geotechnical Model
The investigation indicates that the site is underlain by a relatively uniform strata sequence
comprising minor surface filling over saturated alluvial soils to depths of about 13 – 15 m,
overlying bedrock. The upper 6 – 8 m of alluvial profile includes sand, sandy clay and clayey
sand whereas the lower proportion of the alluvium is predominantly loose or medium dense
sand with some dense layers. Bedrock is at a depth of 13 – 15 m below the site and apart from
a 1 – 2 m extremely low or very low strength weathered zone, the material is generally medium
or high strength siltstone and sandstone.
Page 11 of 18
Proposed Multi Storey Building Project 71342 Rev 1 Corner Marsden and Macquarie Streets, Parramatta March 2010
Summary interpreted geological sections are given on Drawings 2 – 5 in Appendix A.
8.2 Excavation Conditions
The field investigation indicates that excavation to depths of about 13 m below existing surface
level should be relatively straightforward as the majority of the excavation will be through filling,
clay, shaly clay sand and extremely low to very low strength siltstone. All of these materials
should be easily removed using conventional earthmoving equipment although much of the
material will be saturated because it will be excavated from below the standing water table.
Further comments on dewatering and retention systems that are suitable for the site conditions
are given below.
Excavation below 13 – 15 m depth will take place through medium or high strength bedrock and
this will require heavy ripping with a dozer of at least D10 capacity and possibly with the
assistance from hydraulic rock breakers. The production rate for excavation of medium and high
strength bedrock may not be economical by ripping alone and therefore the use of hydraulic
rock breakers to split the rock may be necessary. In addition, the use of hydraulic rock
breakers, rock headers or rock saws may be required to remove material in the corners of
excavation and for trimming the face of the rock excavation.
The excavation rate that can be achieved in Ashfield Shale varies considerably and is
dependent upon the degree of jointing in the rock, the overall rock strengths, the type of
machinery being used and the skill of the operator. Some of these factors vary between
individual contractors and it is therefore recommended that a single unit rate be used for
excavation and that bulk excavation tenderers be required to make their own assessment of the
equipment required to carry out the work. This can be achieved by utilising the borehole
information provided and the core photographs, but it is recommended that contractors be
invited to inspect the cores before submitting their final price.
The investigation indicates that high and very high strength rock is generally at or slightly above
the base of the excavation. It is, however, possible that these units could be encountered in the
lower 2 – 4 m of the proposed bulk excavation, thus requiring heavy ripping.
Page 12 of 18
Proposed Multi Storey Building Project 71342 Rev 1 Corner Marsden and Macquarie Streets, Parramatta March 2010
8.3 Vibration
Vibration and noise associated with rock excavation, particularly the use of rock hammers may
result in some vibration and possibly complaints from occupants from neighbouring buildings
that are founded on piles to rock. However, it is unlikely that vibration will be a significant
problem for this site because excavation of rock will take place at a depth of about 15 m below
existing surface levels and presumably in excess of 10 m below basement levels of adjoining
structures. It is therefore likely that any vibration which is transmitted to pile foundations of
adjoining buildings will be dampened significantly before reaching areas where it could be felt by
people occupying these buildings.
The recommended maximum peak particle velocity from AS 2187 Explosives Code for various
structures subject to vibration is 10 mm/sec for houses and low rise residential buildings and
25 mm/sec for commercial and industrial buildings or structures of reinforced concrete or steel
construction. However, these values of peak particle velocity are meant to limit damage to
structures and do not take into consideration personal comfort. For this reason it is
recommended that the lower vibration level of 10 mm/sec be set for this particular site. This
takes into consideration that the excavation of rock using rock hammers or heavy ripping
equipment will be located well below street level and therefore there will be significant
dampening of any vibration due to excavation on the site.
8.4 Excavation Support
In order to be able to carry out the excavation to depths of about 18 m below existing site level a
permanent retaining wall system will be required to support the surrounding ground in both the
short term while excavation is being undertaken and also in the long term when the building
structure is competed. These retaining walls will also be required to fully seal the perimeter of
the site to prevent groundwater inflow as significant flows are likely through the sand strata
between depths of 6 m to 15 m below current site level. Further comments are given on
potential groundwater flow and dewatering in Section 8.7 below.
Three different types of retaining structures could be utilised for this site with each requiring
temporary anchors for support until the permanent structure is completed. Alternatively, top-
Page 13 of 18
Proposed Multi Storey Building Project 71342 Rev 1 Corner Marsden and Macquarie Streets, Parramatta March 2010
down construction techniques could be used such that the permanent support structure is
installed progressively as the excavation is deepened.
The three types of retaining structures that would be suitable for this site are:
• A diaphragm wall;
• A secant pile wall;
• A close spaced soldier pile wall with jet grouting.
8.4.1 Diaphragm Wall Given the conditions on this site it is suggested that a diaphragm system wall be adopted as this
will provide a permanent seal for the site and a low risk option that will prevent substantial
groundwater inflow in the short and long term. Secant pile walls can sometimes achieve an
acceptable seal to groundwater inflow but when installed to depths of 18 m or more some
misalignment of the piles could occur, thus resulting in substantial groundwater inflows into the
site. Close spaced soldier piles with jet grouting have been used previously on sites close to
Sydney Harbour but control of the jet grouting is often difficult and it can result in areas that are
not properly sealed. The lack of a complete seal can only be identified when excavation takes
place and at this stage secondary grouting is required to provide a complete seal.
Diaphragm walls are the most expensive type of structure but provide a clean finish to the inside
wall and would completely seal the site from all but minor groundwater seepage which may
occur as upflow through the siltstone and sandstone bedrock. The installation, however, does
require a considerable amount of plant because temporary support of the alluvial soils is
achieved by using bentonite. A de-sanding unit is required to clean the recycled bentonite and
grout pumps are necessary because of the very high volumes of concrete that must be used to
form the diaphragm wall. In addition, cranes will require access to the site for lifting
reinforcement cages and for inserting blockouts between each wall panel.
Diaphragm walls are constructed using a large grab which excavates the soil in panels with each
panel then cast using concrete tremmied into the bentonite supported excavation. The joints
between the panels are sealed with a waterstop so that a complete water tight wall is achieved.
The construction, however, is relatively slow but when diaphragm walls are socketed into
bedrock they provide a significant load capacity for the structure.
Page 14 of 18
Proposed Multi Storey Building Project 71342 Rev 1 Corner Marsden and Macquarie Streets, Parramatta March 2010
8.4.2 Secant Pile Wall Secant pile walls are formed by drilling alternate soft concrete piles and then installing
intermediate hard concrete piles by cutting into the previously drilled soft piles. This overlap
ensures that piles are sealed but even at relatively shallow depths some misalignment can occur
so that minor gaps appear in the wall. Secant pile walls are normally drilled through a top
template so it is necessary to excavate on adjoining sites to position the template so that the
outside of the secant pile wall will be directly along the boundary. Alternatively, the template can
be set-up entirely within the subject property but this means that the basement area is slightly
smaller than the overall site dimensions.
The potential for misalignment on deep secant pile walls is very high but if the secant pile wall
can be installed with only slight misalignment at the bottom of the wall a secant pile wall can
form a relatively water tight structure with only minor seepage. It may, however, be necessary to
also undertake jet grouting if misalignment does occur because the very high groundwater
pressures near the base of the excavation will probably mean that it is not feasible to patch any
minor gaps in the secant pile wall should they occur.
8.4.3 Soldier Piles and Jet Grouting A close spaced soldier pile wall with jet grouting is the third possible alternative which could be
considered for temporary retaining structures on this site. Essentially the piles would be drilled
at spacings of approximately 2 pile diameters and then the intermediate area jet grouted to
provide a complete seal. Jet grouting is quite effective in sandy or gravelly soils but sometimes
difficulties occur in clayey soils in achieving sufficient penetration to arch between the soldier
piles and to form a complete seal. It may therefore be necessary to undertake secondary
grouting as the excavation proceeds to ensure a completely watertight site.
8.4.4 Design Parameters Regardless of which wall type is chosen, temporary anchors will need to be installed to provide
support until the permanent structure is erected unless ‘top-down’ construction techniques are
adopted. Further advice on the design of ground anchors is given below.
In carrying out the design of a propped or anchored temporary and permanent retaining walls it
is suggested that a rectangular pressure distribution be assumed over the central 80% of the
Page 15 of 18
Proposed Multi Storey Building Project 71342 Rev 1 Corner Marsden and Macquarie Streets, Parramatta March 2010
wall height, tapering to zero at the top and bottom of the excavation. A design horizontal active
pressure of 7H (where H is the height of the excavation) could be adopted.
In order to ensure that an effective groundwater cut off is provided, it is suggested that the
retaining walls be taken to a depth of at least 1 m below the bulk excavation level. This will also
be required to ensure that sufficient toeing of the retaining wall is achieved to prevent substantial
horizontal movement of the toe of the wall when excavation is completed.
8.5 Ground Anchors
In order to provide temporary support for the retaining wall it will be necessary to install ground
anchors around the perimeter of the building. The only other alternative that is considered
feasible would be to adopt ‘top-down’ construction whereby the ground-floor slab is cast
immediately after the perimeter walls are installed to prop the excavation. Earthworks could
then be commenced and each successive floor slab installed as excavation continues
downwards. Top-down construction is normally much more expensive than conventional
techniques but avoids the need to install ground anchors under adjoining buildings or roadways.
In addition, very long anchors will be needed due to the very high loads and the low soil-grout
adhesion values that can be adopted for design.
The ground anchors should be drilled at approximately 30˚ below the horizontal and preferably
taken down to bedrock to obtain relatively high load capacity. However, for the upper row of
anchors it is unlikely that anchoring into bedrock would be feasible because the length of the
anchors will probably be in excess of 30 m and for the conditions encountered on this site it will
be extremely difficult for these anchors to be successfully installed through water charged
alluvial soils using normal construction techniques. For design purposes however, it is
suggested that a grout-soil adhesion value of 30 kPa be used with a grout-rock adhesion value
of 800 kPa for anchors drilled into medium high strength siltstone and sandstone.
In deciding whether temporary ground anchors are feasible it will be necessary to take into
consideration the likelihood that they will need to be installed between pile foundations of
adjoining buildings. If ground anchors are not feasible then ‘top-down’ construction is the only
Page 16 of 18
Proposed Multi Storey Building Project 71342 Rev 1 Corner Marsden and Macquarie Streets, Parramatta March 2010
alternative because it will not be possible to install a fully cantilevered retaining system that will
support the soil until the final structure is erected.
8.6 Foundations
At this stage, it would appear that the excavation to 18 m below existing surface level will mean
that medium or medium to high strength rock will be exposed in the base of the excavation. On
this basis, it is suggested that an allowable bearing pressure of 6000 kPa be used for footings
supported by medium / high strength rock. This bearing pressure is based upon limiting
settlement to less than 1% of the least footing dimensions but if higher settlements will not
severely affect the structure, increased bearing pressures could be adopted.
In order to verify the foundation design bearing pressure and to be able to provide an opinion on
the adequacy of the founding materials prior to pouring of concrete it will be necessary to carry
out detailed spoon testing of at least 50% of the footings immediately after excavation to check
that there are no soft seams below founding level. This is especially important as many of the
bores were discontinued above the now proposed bulk excavation level.
8.7 Groundwater Control
The investigation indicates that the groundwater level is approximately 4 m below current
surface levels and that the alluvial soils are saturated. It will therefore be necessary to design a
retention system which cuts off any groundwater inflow. It will also be necessary to
depressurise the bedrock during construction to prevent significant upflows through the bedrock
strata until after the building is erected. Likewise, it will be necessary to provide an under
drainage system beneath the lower basement floor slab to prevent uplift pressures on the floor
slab once construction is completed.
The investigation did not include hydraulic conductivity testing of the bedrock strata but testing
of the Ashfield Shale and other similar formations containing medium and high strength
sandstone lenses indicates permeability values of less than about 10-7 m/sec. Adopting this
value as the upper limit it is calculated that the upflow beneath a diaphragm or secant pile wall
Page 17 of 18
Proposed Multi Storey Building Project 71342 Rev 1 Corner Marsden and Macquarie Streets, Parramatta March 2010
installed to a 1.0 m depth below excavation level would be of the order of 0.2 m3 / day per m2 of
excavation floor area. It must be noted, however, this is based upon a hydraulic conductivity of
the bedrock strata of 10-7 m/sec and it may well be one or two orders of magnitude lower. If the
flow rates calculated on the basis of this hydraulic conductivity are much higher than can be
economically handled by an underfloor drainage and pump out system it would be necessary to
fully tank the basement to prevent any inflow of groundwater. Alternatively, it may be worthwhile
performing in-situ permeability testing on the bedrock to refine the estimate of potential upflow of
groundwater beneath the floor slab. A secondary consideration when deciding whether to tank
the basement or design a depressurised basement would be the quality of the groundwater.
Groundwater from within the Ashfield Shale is known to contain relatively high totally dissolved
solids and it may therefore be necessary to treat the groundwater before disposal to the
stormwater drainage system.
On the understanding that the perimeter walls will be effectively sealed into the bedrock there
will be a need to lower the groundwater levels within the site before excavation commences.
This could be achieved by large diameter bores sunk into the alluvial soils or by spear points.
On the basis of a drainable porosity of 0.20 (20%) for the alluvial soils it is estimated that
approximately 9000 m3 of water would need to be pumped from the site before the excavation
reached the full depth of approximately 18 m below current site level.
8.8 Acid Sulphate Soils
Testing indicates that some of the sandy soil at depths of about 8 – 13 m below the current
surface level is potential acid sulphate soil and will therefore require treatment before disposal.
However, only one of the 4 samples tested displayed characteristics of PASS with Total
Potential Acidity (TPA) and Total Sulphur Activity (TSA) above the guideline values. Therefore
only some of the soil will require treatment, on the basis of current testing, but it is not possible
at this stage to distinguish between soils requiring treatment and that which does not.
Consequently, it is recommended that further testing be undertaken when excavation is
underway to determine the extent of treatment. In the meantime, it would be prudent to assume
that 25% of the soils will need to be treated and disposed of as general solid waste (non
putrescible).
APPENDIX A Plans and Sections
SOIL CONSISTENCYvs - very softs - softf - firmst - stiffvst - very stiffh - hard
2
1
CORE LOSS
Clay
Cnr Macquarie & Marsden Streets, Parramatta
10101 103
A A'
Concrete
Sandstone coarse grained
Sandstone fine grained
SandN - Standard penetration test value
- Water levelSubsurface profile is accurate at borelocations only and may vary away frominvestigation locations
vl - very loosel - loosemd - medium densed - densevd - very dense
SITE MAPLEGEND DISTANCE ALONG PROFILE (m)
ELE
VATI
ON
(AH
D)
Proposed Multi Storey Building71342
Sandy Clay
Shale
Siltstone
Silty Clay
ROCK STRENGTHEL - Extremely LowVL - Very LowL - LowM - MediumH - HighVH - Very High
Clayey Sand
Filling
1: 250 (H)
Crown International Holding Group CROSS SECTION A-A'DRAWING No:
PROJECT No:
REVISION:10.3.2010
CLIENT:
DRAWN BY:
APPROVED BY:
SCALE:
DATE:
OFFICE:
TITLE:
LD
-20
-15
-10
-5
0
5
10
15
20
0 10 20 30 40 50 60 70 80
-20
-15
-10
-5
0
5
10
15
20
st
md
vst
EL
M
H
N = 7
N = 20
N = 14
10
vst
st-vst
md
md
d
VL-L
M
H
H-VH
H
refusal
N = 19
N = 13
N = 16
N = 12
N = 21
N = 12
N = 32
N = 34
refusal
101
st
st
md
vst
M
H,M-H
H
VH
H
N = 14
N = 18
N = 13
N = 13
N = 24
N = 5
N = 37
N = 22
TESTS / OTHER
N = 29
refusal
103
md
NOTE
SOIL CONSISTENCYvs - very softs - softf - firmst - stiffvst - very stiffh - hard
3
1
TESTS / OTHERN - Standard penetration test value
- Water level
Filling
Topsoil
Cnr Macquarie & Marsden Streets, Parramatta
11216
B B'
Sandy Clay
Clayey Sand
Silty Sand
Sandvl - very loosel - loosemd - medium densed - densevd - very dense
SITE MAPLEGEND DISTANCE ALONG PROFILE (m)
ELE
VATI
ON
(AH
D)
Proposed Multi Storey Building71342
Shale
Sandstone fine grained
Shaly Clay
ROCK STRENGTHEL - Extremely LowVL - Very LowL - LowM - MediumH - HighVH - Very High
Clay
Silty Clay
1: 250 (H)
Crown International Holding Group CROSS SECTION B-B'DRAWING No:
PROJECT No:
REVISION:10.3.2010
CLIENT:
DRAWN BY:
APPROVED BY:
SCALE:
DATE:
OFFICE:
TITLE:
LD
-20
-15
-10
-5
0
5
10
15
20
0 10 20 30 40 50 60 70 80
-20
-15
-10
-5
0
5
10
15
20
h
vst
st
st
d
md
md
VL-L
M
M
HH
N=14
N=13
N=10
N=7
N=30
N=35/150mm
N=13
N=23
N=30/50mm
1
vst-h
st
vst
M
H
N = 17
N = 13
12
h
md-d
md
EL-VL
M
H
N = 14
N = 30
refusal
N = 23
16
h
Subsurface profile is accurate at borelocations only and may vary away frominvestigation locations
NOTE
-20
-15
-10
-5
0
5
10
15
20
0 10 20 30 40 50 60 70 80
-20
-15
-10
-5
0
5
10
15
20
vst
vst
L-M
H
N = 9
N = 20
13
h
h
md-d
md
EL-VL
M
H
N = 14
N = 30
refusal
N = 23
16
vst
st-vst
md
md
d
VL-L
M
H
H-VH
H
refusal
N = 19
N = 13
N = 16
N = 12
N = 21
N = 12
N = 32
N = 34
refusal
101
l
st
vst
md
vs
d
md
md-d
EL-VL
M
H
N = 9
N = 10
N = 17
N = 16
N = 1
N = 38
N = 17
N = 13
N = 29
refusal
102
SOIL CONSISTENCYvs - very softs - softf - firmst - stiffvst - very stiffh - hard
4
1
TESTS / OTHERN - Standard penetration test value
- Water level
CORE LOSS
Clay
Cnr Macquarie & Marsden Streets, Parramatta
13
16
101
102
C C'
Concrete
Sandstone coarse grained
Sandy Clay
Sandvl - very loosel - loosemd - medium densed - densevd - very dense
SITE MAPLEGEND DISTANCE ALONG PROFILE (m)
ELE
VATI
ON
(AH
D)
Proposed Multi Storey Building71342
Shale
Shaly Clay
Siltstone
Silty Sand
ROCK STRENGTHEL - Extremely LowVL - Very LowL - LowM - MediumH - HighVH - Very High
Clayey Sand
Filling
1: 250 (H)
Crown International Holding Group CROSS SECTION C-C'DRAWING No:
PROJECT No:
REVISION:10.3.2010
CLIENT:
DRAWN BY:
APPROVED BY:
SCALE:
DATE:
OFFICE:
TITLE:
LD
Subsurface profile is accurate at borelocations only and may vary away frominvestigation locations
NOTE
SOIL CONSISTENCYvs - very softs - softf - firmst - stiffvst - very stiffh - hard
5
1
N - Standard penetration test value- Water level
Filling
Topsoil
Cnr Macquarie & Marsden Streets, Parramatta
15
9
103
104
D D'
Sandy Clay
Clayey Sand
Silty Sand
Sandvl - very loosel - loosemd - medium densed - densevd - very dense
SITE MAPLEGEND DISTANCE ALONG PROFILE (m)
ELE
VATI
ON
(AH
D)
Proposed Multi Storey Building71342
Shale
Sandstone fine grained
Shaly Clay
Laminite
Siltstone
Sandstone coarse grained
ROCK STRENGTHEL - Extremely LowVL - Very LowL - LowM - MediumH - HighVH - Very High
Clay
Silty Clay
1: 250 (H)
Crown International Holding Group CROSS SECTION D-D'DRAWING No:
PROJECT No:
REVISION:10.3.2010
CLIENT:
DRAWN BY:
APPROVED BY:
SCALE:
DATE:
OFFICE:
TITLE:
LD
-20
-15
-10
-5
0
5
10
15
20
0 10 20 30 40 50 60 70 80
-20
-15
-10
-5
0
5
10
15
20
h
vst
st
st
d
md
md
VL-L
M
M
HH
N=14
N=13
N=10
N=7
N=30
N=35/150mm
N=13
N=23
N=30/50mm
1
md
hEL-VL
L
M
MH
5
st-vst
md
vstEL-VL
M-H
H
H
N = 20
N = 17
9
st
st
md
vst
l-md
M
H,M-H
H
VH
H
N = 14
N = 18
N = 13
N = 13
N = 24
N = 5
N = 37
N = 22
N = 29
refusal
103
st
st
md
d
md
EL-VL
M-H
H
H
N = 15
N = 10
N = 15
N = 13
N = 14
N = 39
refusal
N = 24
N = 18
104
Subsurface profile is accurate at borelocations only and may vary away frominvestigation locations
TESTS / OTHER NOTE
APPENDIX B Borehole Results
Notes Relating to this Report
NOTES RELATING TO THIS REPORT Introduction
These notes have been provided to amplify the geotechnical report in regard to classification methods, specialist field procedures and certain matters relating to the Discussion and Comments section. Not all, of course, are necessarily relevant to all reports.
Geotechnical reports are based on information gained from limited subsurface test boring and sampling, supplemented by knowledge of local geology and experience. For this reason, they must be regarded as interpretive rather than factual documents, limited to some extent by the scope of information on which they rely.
Description and Classification Methods The methods of description and classification of soils
and rocks used in this report are based on Australian Standard 1726, Geotechnical Site Investigations Code. In general, descriptions cover the following properties - strength or density, colour, structure, soil or rock type and inclusions.
Soil types are described according to the predominating particle size, qualified by the grading of other particles present (eg. sandy clay) on the following bases:
Soil Classification Particle Size
Clay less than 0.002 mm Silt 0.002 to 0.06 mm Sand 0.06 to 2.00 mm Gravel 2.00 to 60.00 mm
Cohesive soils are classified on the basis of strength
either by laboratory testing or engineering examination. The strength terms are defined as follows.
Classification Undrained
Shear Strength kPa Very soft less than 12 Soft 12—25 Firm 25—50 Stiff 50—100 Very stiff 100—200 Hard Greater than 200
Non-cohesive soils are classified on the basis of
relative density, generally from the results of standard penetration tests (SPT) or Dutch cone penetrometer tests (CPT) as below:
Relative Density SPT “N” Value (blows/300 mm)
CPT Cone Value (qc — MPa)
Very loose less than 5 less than 2 Loose 5—10 2—5 Medium dense 10—30 5—15 Dense 30—50 15—25
Very dense greater than 50 greater than 25 Rock types are classified by their geological names.
Where relevant, further information regarding rock classification is given on the following sheet.
Sampling Sampling is carried out during drilling to allow
engineering examination (and laboratory testing where required) of the soil or rock.
Disturbed samples taken during drilling provide information on colour, type, inclusions and, depending upon the degree of disturbance, some information on strength and structure.
Undisturbed samples are taken by pushing a thin-walled sample tube into the soil and withdrawing with a sample of the soil in a relatively undisturbed state. Such samples yield information on structure and strength, and are necessary for laboratory determination of shear strength and compressibility. Undisturbed sampling is generally effective only in cohesive soils.
Details of the type and method of sampling are given in the report.
Drilling Methods. The following is a brief summary of drilling methods
currently adopted by the Company and some comments on their use and application.
Test Pits — these are excavated with a backhoe or a tracked excavator, allowing close examination of the in-situ soils if it is safe to descent into the pit. The depth of penetration is limited to about 3 m for a backhoe and up to 6 m for an excavator. A potential disadvantage is the disturbance caused by the excavation.
Large Diameter Auger (eg. Pengo) — the hole is advanced by a rotating plate or short spiral auger, generally 300 mm or larger in diameter. The cuttings are returned to the surface at intervals (generally of not more than 0.5 m) and are disturbed but usually unchanged in moisture content. Identification of soil strata is generally much more reliable than with continuous spiral flight augers, and is usually supplemented by occasional undisturbed tube sampling.
Continuous Sample Drilling — the hole is advanced by pushing a 100 mm diameter socket into the ground and withdrawing it at intervals to extrude the sample. This is the most reliable method of drilling in soils, since moisture content is unchanged and soil structure, strength, etc. is only marginally affected.
Continuous Spiral Flight Augers — the hole is advanced using 90—115 mm diameter continuous spiral flight augers which are withdrawn at intervals to allow
Issued: October 1998 Page 1 of 4
sampling or in-situ testing. This is a relatively economical means of drilling in clays and in sands above the water table. Samples are returned to the surface, or may be collected after withdrawal of the auger flights, but they are very disturbed and may be contaminated. Information from the drilling (as distinct from specific sampling by SPTs or undisturbed samples) is of relatively lower reliability, due to remoulding, contamination or softening of samples by ground water. Non-core Rotary Drilling — the hole is advanced by a rotary bit, with water being pumped down the drill rods and returned up the annulus, carrying the drill cuttings. Only major changes in stratification can be determined from the cuttings, together with some information from ‘feel’ and rate of penetration. Rotary Mud Drilling — similar to rotary drilling, but using drilling mud as a circulating fluid. The mud tends to mask the cuttings and reliable identification is again only possible from separate intact sampling (eg. from SPT). Continuous Core Drilling — a continuous core sample is obtained using a diamond-tipped core barrel, usually 50 mm internal diameter. Provided full core recovery is achieved (which is not always possible in very weak rocks and granular soils), this technique provides a very reliable (but relatively expensive) method of investigation. Standard Penetration Tests
Standard penetration tests (abbreviated as SPT) are used mainly in non-cohesive soils, but occasionally also in cohesive soils as a means of determining density or strength and also of obtaining a relatively undisturbed sample. The test procedure is described in Australian Standard 1289, “Methods of Testing Soils for Engineering Purposes” — Test 6.3.1.
The test is carried out in a borehole by driving a 50 mm diameter split sample tube under the impact of a 63 kg hammer with a free fall of 760 mm. It is normal for the tube to be driven in three successive 150 mm increments and the ‘N’ value is taken as the number of blows for the last 300 mm. In dense sands, very hard clays or weak rock, the full 450 mm penetration may not be practicable and the test is discontinued.
The test results are reported in the following form. • In the case where full penetration is obtained with
successive blow counts for each 150 mm of say 4, 6 and 7 as 4, 6, 7 N = 13
• In the case where the test is discontinued short of full penetration, say after 15 blows for the first 150 mm and 30 blows for the next 40 mm as 15, 30/40 mm. The results of the tests can be related empirically to the
engineering properties of the soil. Occasionally, the test method is used to obtain
samples in 50 mm diameter thin walled sample tubes in clays. In such circumstances, the test results are shown on the borelogs in brackets.
Cone Penetrometer Testing and Interpretation Cone penetrometer testing (sometimes referred to as
Dutch cone — abbreviated as CPT) described in this report has been carried out using an electrical friction cone penetrometer. The test is described in Australian Standard 1289, Test 6.4.1.
In the tests, a 35 mm diameter rod with a cone-tipped end is pushed continuously into the soil, the reaction being provided by a specially designed truck or rig which is fitted with an hydraulic ram system. Measurements are made of the end bearing resistance on the cone and the friction resistance on a separate 130 mm long sleeve, immediately behind the cone. Transducers in the tip of the assembly are connected by electrical wires passing through the centre of the push rods to an amplifier and recorder unit mounted on the control truck.
As penetration occurs (at a rate of approximately 20 mm per second) the information is plotted on a computer screen and at the end of the test is stored on the computer for later plotting of the results.
The information provided on the plotted results comprises: — • Cone resistance — the actual end bearing force
divided by the cross sectional area of the cone — expressed in MPa.
• Sleeve friction — the frictional force on the sleeve divided by the surface area — expressed in kPa.
• Friction ratio — the ratio of sleeve friction to cone resistance, expressed in percent. There are two scales available for measurement of
cone resistance. The lower scale (0—5 MPa) is used in very soft soils where increased sensitivity is required and is shown in the graphs as a dotted line. The main scale (0—50 MPa) is less sensitive and is shown as a full line.
The ratios of the sleeve friction to cone resistance will vary with the type of soil encountered, with higher relative friction in clays than in sands. Friction ratios of 1%—2% are commonly encountered in sands and very soft clays rising to 4%—10% in stiff clays.
In sands, the relationship between cone resistance and SPT value is commonly in the range:—
qc (MPa) = (0.4 to 0.6) N (blows per 300 mm) In clays, the relationship between undrained shear
strength and cone resistance is commonly in the range:— qc = (12 to 18) cu
Interpretation of CPT values can also be made to allow estimation of modulus or compressibility values to allow calculation of foundation settlements.
Inferred stratification as shown on the attached reports is assessed from the cone and friction traces and from experience and information from nearby boreholes, etc. This information is presented for general guidance, but must be regarded as being to some extent interpretive. The test method provides a continuous profile of engineering properties, and where precise information on
Issued: October 1998 Page 2 of 4
soil classification is required, direct drilling and sampling may be preferable.
• Water table levels will vary from time to time with seasons or recent weather changes. They may not be the same at the time of construction as are indicated in the report.
Hand Penetrometers
• The use of water or mud as a drilling fluid will mask any ground water inflow. Water has to be blown out of the hole and drilling mud must first be washed out of the hole if water observations are to be made.
Hand penetrometer tests are carried out by driving a rod into the ground with a falling weight hammer and measuring the blows for successive 150 mm increments of penetration. Normally, there is a depth limitation of 1.2 m but this may be extended in certain conditions by the use of extension rods.
More reliable measurements can be made by installing standpipes which are read at intervals over several days, or perhaps weeks for low permeability soils. Piezometers, sealed in a particular stratum, may be advisable in low permeability soils or where there may be interference from a perched water table.
Two relatively similar tests are used. • Perth sand penetrometer — a 16 mm diameter flat-
ended rod is driven with a 9 kg hammer, dropping 600 mm (AS 1289, Test 6.3.3). This test was developed for testing the density of sands (originating in Perth) and is mainly used in granular soils and filling.
Engineering Reports
• Cone penetrometer (sometimes known as the Scala Penetrometer) — a 16 mm rod with a 20 mm diameter cone end is driven with a 9 kg hammer dropping 510 mm (AS 1289, Test 6.3.2). The test was developed initially for pavement subgrade investigations, and published correlations of the test results with California bearing ratio have been published by various Road Authorities.
Engineering reports are prepared by qualified personnel and are based on the information obtained and on current engineering standards of interpretation and analysis. Where the report has been prepared for a specific design proposal (eg. a three storey building), the information and interpretation may not be relevant if the design proposal is changed (eg. to a twenty storey building). If this happens, the Company will be pleased to review the report and the sufficiency of the investigation work.
Laboratory Testing Every care is taken with the report as it relates to interpretation of subsurface condition, discussion of geotechnical aspects and recommendations or suggestions for design and construction. However, the Company cannot always anticipate or assume responsibility for:
Laboratory testing is carried out in accordance with Australian Standard 1289 “Methods of Testing Soil for Engineering Purposes”. Details of the test procedure used are given on the individual report forms.
• unexpected variations in ground conditions — the
potential for this will depend partly on bore spacing and sampling frequency
Bore Logs The bore logs presented herein are an engineering
and/or geological interpretation of the subsurface conditions, and their reliability will depend to some extent on frequency of sampling and the method of drilling. Ideally, continuous undisturbed sampling or core drilling will provide the most reliable assessment, but this is not always practicable, or possible to justify on economic grounds. In any case, the boreholes represent only a very small sample of the total subsurface profile.
• changes in policy or interpretation of policy by statutory authorities
• the actions of contractors responding to commercial pressures. If these occur, the Company will be pleased to assist
with investigation or advice to resolve the matter.
Interpretation of the information and its application to design and construction should therefore take into account the spacing of boreholes, the frequency of sampling and the possibility of other than ‘straight line’ variations between the boreholes.
Site Anomalies In the event that conditions encountered on site during
construction appear to vary from those which were expected from the information contained in the report, the Company requests that it immediately be notified. Most problems are much more readily resolved when conditions are exposed than at some later stage, well after the event.
Ground Water
Where ground water levels are measured in boreholes, there are several potential problems;
Reproduction of Information for Contractual Purposes
• In low permeability soils, ground water although present, may enter the hole slowly or perhaps not at all during the time it is left open. Attention is drawn to the document “Guidelines for the
Provision of Geotechnical Information in Tender Documents”, published by the Institution of Engineers,
• A localised perched water table may lead to an erroneous indication of the true water table.
Issued: October 1998 Page 3 of 4
Issued: October 1998 Page 4 of 4
Australia. Where information obtained from this investigation is provided for tendering purposes, it is recommended that all information, including the written report and discussion, be made available. In circumstances where the discussion or comments section is not relevant to the contractual situation, it may be appropriate to prepare a specially edited document. The Company would be pleased to assist in this regard and/or to make additional report copies available for contract purposes at a nominal charge.
Site Inspection The Company will always be pleased to provide
engineering inspection services for geotechnical aspects of work to which this report is related. This could range from a site visit to confirm that conditions exposed are as expected, to full time engineering presence on site.
Copyright © 1998 Douglas Partners Pty Ltd
APPENDIX C Results of SPOCAS Testing
APPENDIX D Results of In Situ Permeability Tests