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Appendix D Geotech Site stability · MCU18/0013
Attached to the e-mail Detached House - MCU18/0013.
Soil Surveys Engineering Pty Limited Directors
Specialists in Applied Geotechnics
A.B.N. 70 054 043 631 PJ Dixon BE(Hons) RPEQ
PR Cosh BE(Civil) CPEng MIE Aust RPEQ
www.soilsurveys.com.au NT Perkins BAppSC(AppGeol) BEng(Hons1)
MV Geale BEng(Civil) MBA CPEng MIE Aust RPEQ
GEJ Gray
P Elkington BE(Civil)
Associates
AM Rutten BE(Hons1) MEngSc LGE CPEng
MIE Aust RPEQ
SL Gamble BE(Geol) CPEng MIE Aust RPEQ
Sunshine Coast Office
Our Ref: 3-2014 LT sg 2006-04-24
Author: Stephen Gamble
24th April, 2006
Gabriel & Elizabeth Poole Design Company
PO Box 1158
NOOSAVILLE DC QLD 4566
ATTENTION: MR DAN SPARKS
Dear Sir,
RE: KRIMMER RESIDENCE - 26 ARAKOON CRESCENT, SUNSHINE BEACH
GEOTECHNICAL ENGINEERING - SLOPE STABILITY
We refer to your request for our review of the proposed retaining wall design, and its effect
on the stability conditions of the above site, and we understand that this is to be submitted to
Noosa Council, in support of the MCU/DA submission.
Our review refers to the following documentation:
y Geotechnical Report Ref 304-2014 dated November 2004 by Soil Surveys Engineering
Pty Limited (SSE).
y Letter report by SSE, Ref 304-2014 dated 2nd December 2004, containing a review and
preliminary analysis of the then proposed contiguous pile retaining wall.
y Sheet Piling Gen. Arrangement Plan and Section 1, as well as Structural Drawings by
Bligh Tanner Pty Ltd (BT) - Drg. No's. 2004.052/W01/A, W02/A, S00/B, S01/C, S02/B,
S10/C, S11/B and S12/B.
The SSE report determined that this site is located on a sand dune. The soil profile
encountered by the drilling was entirely fine to medium grained sand, and typically the
density was seen to be loose for the upper 0.5 metres, and medium dense from below that
depth. The deeper boreholes encountered indurated sand ("coffee rock") at 3.5 - 3.8m
depth.
Shortly after the site investigation was completed, SSE carried out an analysis and
preliminary design of a contiguous pile retaining wall, which was at that time proposed for
the building development. However, it is understood that access constraints prevent the
construction of this pile wall for the site retention, and consequently an alternative wall and
building configuration has been proposed. The revised retaining wall is based on the use of
temporary steel sheetpiles, followed by construction of a reinforced concrete permanent
wall.
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Job No. 304-2014
The Bligh Tanner drawings referenced above, show that the site formation for the revised
building platform will require the construction of anchored, steel sheetpile retaining walls for
the temporary works. These temporary walls would then be followed by the construction of
reinforced concrete walls on the inside of the sheetpiles, and propped by the floor slabs.
In order to maintain the site stability, both the temporary and permanent retaining walls must
be designed to properly cater for the loads that could be applied to the wall. These include
appropriately selected soil lateral load (i.e. taking full account of the soil properties and
backslope angle), correct live load above the wall, as well as possible transient earthquake
and groundwater loads. It is considered that the surcharge loads shown in the notes to Drg.
No. 2004.052/A - item SP6, would adequately allow for these.
We are satisfied that if these retaining walls are designed, with these loads properly defined
and considered, detailed and constructed with appropriate good building practices, and the
site properly managed in the long-term, then current stability can be maintained, if not
improved.
That opinion notwithstanding, the certification of the ongoing stability of this site during and
after construction of this development is wholly dependent on the proper design of the
temporary and permanent retaining walls proposed for the site formation. Therefore such
certification must rest with the designers of these elements, who should be RPEQ with
appropriate experience in the design of retaining walls for sand excavations. We also note
that the final retaining wall design is to be subject to review by Soil Surveys Engineering Pty
Limited.
∗ ∗ ∗
We trust this information is satisfactory for your current needs, however, should you require
additional details or discussion, please do not hesitate to contact the undersigned at our
Sunshine Coast Office.
Yours faithfully,
STEPHEN GAMBLE (RPEQ 6644)
for and on behalf of
SOIL SURVEYS ENGINEERING PTY LIMITED
SOIL SURVEYS ENGINEERING PTY LIMITED
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