Attachment C - Soil Survey Report · MCU18/0013

Project No. 1-20119                                                                                                                  Page | 28
March, 2018
Ref: 1-20119, 2018-03-02, BR VER 2
Sam Hopper – Slope Stability Assessment and Geotechnical Report - Proposed Residence, 24 Arakon Crescent, Sunshine Beach




TABLE 8 RETAINING WALL DESIGN PARAMETERS (UNFACTORED)
                                                               Earth Pressure Coefficient Vertical
                                           Density                                                                          Long Term
          Material                              3                            Wall                                                     o
                                           (kN/m )                                                                         Drained Ø ( )
                                                                 Ka            Ko            Kp
      Back Fill                              17                 0.27          0.43          NR                                  35
              2
       Gravel                                19                 0.33          0.50           3.0                                30
    Loose Sand                               17                 0.33          0.50           3.0                                30
 Medium Dense Sand                           18                 0.29          0.46           3.4                                33
    Dense Sand                               20                 0.27          0.43           3.0                                35
  Very Dense Sand                            22                 0.21          0.36           4.7                                40
Note: 1) NC – Not considered, NR Not recommended.
      2) Infers granular free draining material placed behind the retaining wall as a drainage layer.




                                   TRAPEZOIDAL DISTRIBUTION
                   Lateral Earth Pressure                          Lateral Earth Pressure due to Surcharges
                                0.65KaH




                                                  hw


                                                           hw

                         Earth Pressure                     Water               UDL             Point Load or
                                                                                                Strip Footing


                                                                   FIGURE 6

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 i.e.
on site clay or concrete, etc. with a slope towards an open drain.

Due to possible long term problems with blocking of gravel filters and drains and short term
storm conditions that could flood the fill behind retaining walls, it is recommended that all
retaining walls be designed for some water pressure distribution. For ultimate limit state the
suggested water pressure distribution for retaining walls on this site would be half height water
pressure.

During installation of any retaining walls, the in-situ soils should be battered back to minimise
fall-in and subsequent disruption of works. Temporary batter angles should be requested from
Soil Surveys should any battering on site be proposed. Suitable precautions to satisfy Health &
Safety requirements must also be adhered to.