Attachment 5 - Geotechnical Report · MCU18/0015

J000635-002-R-Rev1                                                                                               November 2018


and suitable founding materials. It is our opinion that an appropriately designed micropile or CFA pile
structure will provide acceptable factors of safety against global slope instability.
It is understood that underground services will be installed via HDD. Unsupported open trenching for the
installation of services should not be undertaken.

6.2     Retaining Wall Design and Parameters
Retaining walls must be founded as described in Section 6.3 and may be designed using the parameters in
Table 3, and in accordance with AS4678-2002 Earth retaining structures.
Allowance should be made for construction loading, up-slope footing loadings, the effects of sloping ground
(if not supported on piles), hydrostatic loads, and backfill compaction stresses.
Table 3: Retaining Structure Design Parameters.
                                                             Unit           Friction
                                                                                       Lateral Earth Pressure Coefficient
                                                            Weight           Angle
                 Retained Material                                                        Ka             Ko
                                                             (t/m3)        (Degrees)   (Cantilever   (Non yielding     Kp
                                                                                         Wall)          wall)

Loose Sand                                                    1.7              30         0.3            0.5          3.0
Medium Dense Sand                                             1.8              34        0.25           0.45          3.4
Dense sand                                                    1.9              38         0.2            0.4          4.2
Stiff (or stiffer) Clay                                       1.8              27         0.4            0.6          2.6
Engineered Fill (future)                                      1.9*             34*       0.28*          0.4*          3.5*
Note:     *Preliminary only; depends on fill material type and level of compaction.


Positive permanent drainage must be installed behind all walls unless they are designed for development of
full hydrostatic pressures.

6.3     Foundation Design and Parameters
      6.3.1     High-level footings
Where suitable stiff (or stiffer) clay is present at shallow depth (i.e. proposed Lot 3), the proposed buildings
may be supported on conventional high-level strip or pad footings. Such footings may be designed using an
allowable bearing pressure of 100 kPa.
To achieve the design recommended pressures, footing excavations must be dry and cleaned of any loose,
disturbed or saturated materials prior to pouring concrete.
All existing and proposed footings should found such that they are not adversely affected by any adjacent
excavations, batter slopes, trenches, or retaining walls that are not designed to support building or fill loads.
To minimise the potential for any adverse interaction effects, footings should found at least below a plane
extending 1 m horizontally from the base of trenches/batter slopes/excavations/ retaining walls, then rising
up at 1V:1H. This requirement is illustrated in the following diagram.




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