RFI - Attachment C - Slope Stability Assessment and Geotechnical report · MCU20/0026

Project No. 1-22543                                                                                                                    Page | 26
June, 2020
Ref: 1-22543, 2020-05-20, BR SSA VER 1
Sanya Holdings – Slope Stability Assessment and Geotechnical Report - Proposed Residence, 40 Park Crescent, Sunshine Beach




TABLE 8 RETAINING WALL DESIGN PARAMETERS (UNFACTORED)
                                                               Earth Pressure Coefficient Vertical
          Material                         Density                          Wall
                                                                                                                              Long Term
                                                 3
                                            (kN/m )                                                                          Drained Ø (o)
                                                                 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
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.
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.




                                                                                                               SOIL SURVEYS