Geotechnical Investigation Report

J001369-001-R-Rev0                                                                                                August 2021


If any soil conditions encountered during the footing excavations are found to differ from those noted in the
geotechnical investigation, Core should be notified immediately, and an inspection of the footing excavations
should be carried out to assess if changes to footing design are required.
Adequate site drainage should be carried out to ensure that natural runoff is directed away from the building
walls and footings.
All 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.




                                      Diagram 1: Exclusion zone for base of footings.

7.5     Retaining Wall Design Parameters
Design for retaining structures could be carried out using a triangular pressure distribution applicable to the
wall type (i.e. active pressures for a cantilever wall or ‘at rest’ pressures for a propped wall) and based on the
parameters in Table 33. These values do not include an allowance for hydrostatic pressures, construction
loading, adjacent foundation loadings, the effect of sloping ground, or backfill compaction stresses.
Table 3: Retaining Wall Design Parameters.
                                      Unit           Friction                   Lateral Earth Pressure Coefficients
      Retained Material             Weight            Angle          Cantilever Wall        Non-yielding Wall
                                                                                                                      Kp
                                     (t/m3)        (Degrees)              (Ka)                    (Ko)
Loose Sand                             1.7              28                0.36                    0.53                2.77
Medium Dense Sand                      1.9              34                0.27                    0.43                3.61
Dense Sand                             2.0              39                0.22                    0.36                4.5
Compacted Fill                          *                *                  *                       *                  *
*: Variable depending on the type of material used and the degree of compaction achieved.

7.6     Drainage and Erosion
Site drainage should be designed to readily remove surface water, minimise water infiltration into the slope,
and to prevent ponding of water on subgrade areas during construction and also adjacent to foundations,
perimeter slabs, and driveways once construction is completed.
Roof water, including overflow from rainwater tanks, and water collected from hard surfaces (e.g. driveways)
must be directed by pipes or lined channels to a legal point of discharge.
Shallow subsurface cut-off drains should be installed upslope of building areas in order to intercept and
divert potential subsurface seepage. Diversion drains should be constructed above the crest of any cut or fill
embankments.
Any exposed soil on sloping ground must be protected from erosion (e.g. through re-vegetation).




                                                                11