1-22276-01 site plan

Project No. 1-22276                                                                                                                  Page | 31
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




outlets to subsoil pipe drains must be located beyond the ends of the walls and connected to a
proper drainage system. It is suggested the pipes be wrapped in filter fabric to minimise silting.

Adequate surface and subsoil drainage should be provided for all retaining walls on the site.
Cut-off / interceptor drains should also be provided around the high side of the wall to ensure
stormwater runoff from the area above the wall is suitably diverted.

In weather exposed locations, to reduce infiltration by surface runoff, the surface of the backfill
should be sealed. This can be achieved by either compacting a material of low permeability or
concrete, etc. with a slope towards an open drain.

It is essential that backfill be properly placed to avoid drains being blocked by fines washed out
of the fill. However, within 0.5m behind the wall the backfill should be loose as research has
shown that compaction directly behind the wall can significantly raise the earth pressure against
the wall to above the 'at rest' case.

During installation of any retaining walls, the insitu soils should be battered back to minimise
fall-in and subsequent disruption of works. Temporary batter angles are given in Section 6.2.8.
Suitable precautions to satisfy Health & Safety requirements must also be adhered to.

    6.7 Pavements
Final pavement levels have not been detailed but are expected to be similar to existing site
surface levels and as such the subgrade would be the existing sandy fill material or future fill.

Dynamic cone penetrometer test results indicate insitu CBR values, in the upper level fill and
natural soils are quite variable/consistent across the site, ranging from 4% to in excess of 10%.

Based on the investigation findings and providing that the recommendations outlined in the
following section are complied with, the following pavement design values may be adopted for
the development.

TABLE 8                 DESIGN VALUES
                                                                                                        Modulus of Subgrade Reaction
                    Material                                    CBR Value (%)
                                                                                                                 (kPa/mm)
                                                    Use CBR value of material, see
                Controlled Fill                                                                               Based on CBR value
                                                            Section 6.2
                                   (2)
          Existing Sand Fill                                     5                                                         30
Note:-         (1) Assume minimum CBR value of 10%.
               (2) Existing material appropriately treated (conditioned and compacted).

Along with recommendations contained in Section 6.2 the following general earthworks
recommendations are made:-

           i)       Incorporate a perimeter drain at the pavement edges to prevent possible
                    deterioration under wet weather.
         ii)       Pavements should be well drained both during and upon completion of construction.
                   Water should not be allowed to pond on or near pavement surfaces.
         iii)      Pavement gravel should comply with the Local Council quality specifications for sub
                   base and base course material.
       iv)         Subgrades should be compacted to achieve the minimum density ratios as outlined
                   in Section 6.2 'Civil Works'.
         v)        It is recommended that inspection and testing be carried out following general
                   earthworks to confirm subgrade conditions.


                                                                                                            SOIL SURVEYS