Geotech Report - Initial Findings

Essence of Peregian
215-219 David Low Way, Peregian Beach
Project No. 007-160A,
27 April 2010



       5.3.4     Compaction

       Exposed subgrade should be uniformly compacted (if possible) to the minimum dry density ratio nominated
       in Table 4. If the subgrade is too soft to allow compaction, a granular bridging layer (e.g. crushed concrete)
       and acceptance by engineering inspection under proof-rolling would be required for the bridging layer. Any
       ‘soft spots’ encountered should be either tyned and dried then recompacted, or excavated and replaced with
       compacted granular select fill. In areas of soft/firm clays, or where subgrade level is close to these clays, it
       will not be possible to obtain proper compaction and allowance is suggested for over excavation and
       replacement with a track rolled granular replacement.
       Table 4: Subgrade and Fill Compaction Requirements
                                   Location                                       Minimum Dry Density Ratio
                              Foundation support                                  100% (Standard compaction)*
                           General floor slab support                             100% (Standard compaction)*
                Pavement Subgrade - >500mm below subgrade level                    98% (Standard compaction)
                                  - top 500mm of subgrade                         100% (Standard compaction)
       * ‘Level 1’ supervision


       All fill which is to support building loads and/or movement sensitive features of the development, should be
       ‘controlled’ (i.e. placed in layers having a loose thickness of not more than 250mm and uniformly compacted
       to an appropriate engineering specification). Suggested minimum compaction requirements for fill are given
       in Table 4.

       Reactive materials are not recommended for use as fill. However, if it is not possible to avoid the use of
       reactive material it should be placed and maintained at a moisture content greater than Standard optimum
       moisture content, in order to reduce potential shrink-swell movements. It should be noted that over-
       compacting reactive fill (particularly at a moisture content below optimum) should be avoided as potentially
       significant expansion could occur on ‘wetting up’. Reactive fill/soil moisture should not be allowed to change
       during or following construction.

       To assist with achieving adequate control over fill placement, geotechnical testing as set out in Section 8 of
       AS3798 - 2007 Guidelines on earthworks for commercial and residential developments would be required. It
       is recommended that where fill is to be placed beneath pavements, that ‘Level 2’ geotechnical supervision
       and testing be adopted and the requirement be increased to ‘Level 1’ where fill is to be placed beneath
       buildings or anywhere where future settlement needs to be limited.

       5.3.5     Traffickability

       To assist with traffickability, consideration should be given to the placement of a coarse granular working
       surface over the exposed subgrade. The required layer thickness will depend on the type of plant proposed
       to traffic the site and should be determined on a case by case basis however, a layer thickness of
       approximately 0.15m would be anticipated for ‘light’ equipment.

       5.4       Groundwater Control

       5.4.1     Temporary

       It will be necessary to obtain groundwater samples for testing to confirm disposal water quality, prior to
       finalisation of groundwater control methods.




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