1-22276-01 site plan

Project No. 1-22276                                                                                                                  Page | 16
February, 2020
Ref: 1-22276, 2020-02-28, BR VER 2
Wessel Petroleum Pty Ltd – GEOTECHNICAL INVESTIGATION - Proposed Service Station Reconstruction, 52-54 Mary Street and Weyba Road,
Noosaville




Strong consideration should be given to trenches deeper than 1.0m to 1.5m being supported to
prevent sidewall collapse. Support may be provided by hydraulic shutters or alternatively,
trenches may be benched or battered back to a stable angle, as per Tables 2A and 2B.

Excavations in the insitu soils should be within the capabilities of light plant, small dozer (Cat
D4C or similar) in bulk cuts and a medium sized backhoe (Case 580 or similar) or small
excavator (12t – 15t) in trenching, based on the investigation findings.

Use of larger equipment would be recommended to expedite construction particularly in the
deeper excavations that extend into and through the indurated sand layers.

           6.2.5       Site Preparation Procedures

Earthworks preparation procedures should include:-

Fill and loose sandy material was encountered across the site to depths between 0.3m and
2.4m.

The presence of this fill and loose natural sandy material will impact on the proposed foundation
system, pavements and earthworks operations.

Considering that proposed earthworks operations, the following is recommended:-

          Treatment of existing fill and loose natural sands to create a controlled fill platform i.e.
           compaction of existing fill insitu where possible along with partial or complete removal as
           required.
          Placement of imported fill in a controlled manner.
          Provided existing fill is adequately treated and imported fill is of low plasticity and
           placed/compacted under controlled conditions and is appropriately certified by a
           Registered Engineer, a conventional high level foundation system could be adopted.
Partial Subgrade Replacement

Partial subgrade replacement of the existing fill is recommended prior to construction of the
pavement areas in the area where fill stratum exceeds, say 0.5m. This option involves
excavation and replacement of the top, say 500mm below box level, with a good quality
(granular) compacted fill, with the objective being to provide a ‘bridging layer’. However, this
option is not “risk free”; the Owner would still need to accept some risk that settlement of the fill
stratum may occur - the possibility exists that the partial subgrade replacement works may not
detect all weak areas and that these undetected weak zones may lead to unacceptable
differential settlement.

Partial subgrade replacement procedures should include the following:-

          Excavate existing fill to a level of approximately 500mm below box level or shallower
           where competent natural soils are encountered.
          The subgrade should be proof rolled (where appropriate) under the supervision of Soil
           Surveys Engineering using a vehicle with a tare of at least 5 tonnes and be compacted
           to the required degree. Areas demonstrating excessive movement should be treated.
           Treatment should be determined on site conditions by Soil Surveys Engineering in
           conjunction with other relevant parties, as relevant.



                                                                                                            SOIL SURVEYS