Appendix B - Global Stability Assessment Report

                                                - 12 -
                                                                                    Job No: ME21/032

      Any temporary cut batters in the natural clay (CH) (extremely weathered granite) must be no
       steeper than 1H:1V, and no steeper than 1.5H:1V in the existing controlled fill. Care must be
       taken to ensure that large cobbles and boulders within the extremely weathered rock profile
       do not impact on the safety of persons on or off the Site, or roll down the slope. The
       temporary batter angle adopted should be determined by an experienced qualified
       geotechnical engineer or engineering geologist following assessment and inspection of the
       batters.
      Unsupported permanent cuts are not anticipated. Information can be provided regarding
       maximum permanent batter cut angles and heights where notified and required.
      All cut and fill batters must be designed for the imposed loads from any adjacent or proposed
       structures.
      Depressions formed by the removal of vegetation, underground elements and any other
       features, etc. should have all disturbed and weakened soil removed. All backfilling works
       should be carried out in accordance with AS3798 – 2007 under ‘Level 1 Supervision’.
      All additional fill must be placed in thin layers under ‘Level 1 Supervision’ in accordance with
       AS3798– 2007 to form ‘Controlled Fill’. Each fill layer must be compacted to 95% Standard
       Maximum Dry Density at Optimum Moisture Content +2% at Optimum Moisture Content +2%.
       In areas of sloping ground steeper than 15% or 80, the fill must be ‘keyed’ or benched in to
       the existing Controlled Fill, the natural stiff or stronger clay profile or extremely weathered
       rock to limit the potential for fill instability and sliding down the hill slope. Fill batters and
       slopes must not exceed the heights and slope angles stated in Table 5 of this report.
      All temporary and permanent batters must be assessed by a competent, suitably qualified
       engineer during earthworks operations.
      Unless the soils at the Site have previously been tested as non-dispersive, consideration
       should be given to either applying a gypsum material in to the upper 300mm soil profile, or
       importing a non-dispersive clay capping material. Further testing would be required to
       determine gyspum application rates. Suitable vegetation would then be required to be
       established over the gypsum treated surface or over the non-dispersive soil capping layer.
      A 10kPa surcharge has been allowed for in this assessment, acting behind the batter and
       retaining wall crests to simulate the loading of the proposed shed. A reassessment will be
       required where higher surcharge pressures are expected, and/or where surcharges are
       expected in different areas to that shown on the global stability models presented in Appendix
       F.
      Batters must be no higher and no steeper than that described in Table 5. All cut and fill
       batters must be checked onsite by a competent and suitably qualified geotechnical engineer
       or enginreering geologist during construction.
      All retaining wall footings must found to the minimum depth and in the foundation materials
       described in Table 5. Refer to the global stability models attached as Appendix F for further
       information.
             o Additional retaining wall foundation embedment depth may be required to suit
                 structural engineering design and this should be checked by the designer.
      Retaining wall and footing design must be suitably designed by a competent and qualified
       structural engineer, and further geotechnical advice must be sought regarding the design
       parameters prior to construction.
      Retaining walls must be suitably designed to ensure that long term internal stability is
       achieved and maintained. Internal stability issues such as overturning, sliding and base
       capacity failure must be suitably addressed by the retaining wall designer. The retaining walls
       must be designed with adequate and suitably designed drainage to limit the build-up of
       groundwater pressures behind the walls. It is noted that the global stability assessments have
       been run assuming no groundwater behind or in close proximity beneath the retaining walls or
       batters for long term conditions. The retaining walls must also be designed for the imposed
       loads from any adjacent or proposed structures. Excavations are not allowed adjacent to the
       bases of the retaining walls so as to reduce the potential for undermining of the retaining wall
       foundations.
      The retaining wall must be structurally connected to the foundation and/or pile. The global
       stability modelling assumes that the slip circle passes beneath the base of the pile within the
       fill batter area. Structural connection design is the responsibility of the retaining wall
       designer/structural engineer.



Ref: 27222-rev 1                                                           MORRISON GEOTECHNIC
Mr Geoff Hussin