Slope Stability Report-21190-001-Rev0 Pomona Kin Kin Rd

Phil Brierley                                                                                    21190-001-Rev0
C/- NDD Constructions Pty Ltd                                                                       21 June 2021

4.2.2 Excavations
Excavations within the natural soils and very low to low strength weathered argillite/phyllite, should be
achievable using small to medium sized conventional earthmoving plant (e.g. 5 to 14 tonne excavators) with
toothed buckets. The use of larger earthmoving plant with ripper attachments may be required for efficient
excavations into stronger rock. Excavations into any medium strength (or stronger) weathered rock may
require the use of hydraulic rock breaking attachments or other specialised excavation techniques.
Temporary batter slopes may be formed at 1V:1H in the existing soils and weathered rock. Flatter batters
may be required if groundwater seepage is encountered, or if earthworks are undertaken during a period of
heavy rainfall.

Permanent batter slopes may be formed at 1V:2H in stiff (or stiffer) clays, medium dense sands, very low
strength rock and future controlled fill. Where such battering is not possible, fill batters and cuts will need to
be retained. All existing cut/fill batters should be trimmed back to the permissible grades outlined above,
otherwise must be retained by an engineer designed retaining wall (Ref. Section 4.4).

All batters should be protected from erosion by surface protection, the type of which will be dependent upon
a number of factors including batter slope, material type, aspect, aesthetic finish required, etc. As a
minimum, all soil batters should be topsoiled and seeded (or hydromulched) to establish a permanent grass
(or similar vegetation) cover.
Any excavations which may be required adjacent to existing structures will need to be specifically designed
to ensure that the structures are not adversely affected (e.g. 'undermined').

The above recommendations do not supersede any existing safety regulations or legislation applicable to
excavations (e.g. limits on personnel entry into trenches).

4.2.3 Filling
The existing natural soils where free of deleterious materials (e.g. vegetation, oversize etc.), are expected to
be suitable for re-use as structural fill, subject to appropriate moisture adjustment. It should be noted that
due to the highly reactive nature of the existing clay soils, the impacts on site classification must be
considered.

Should importation of fill be required, it is recommended that such fill should comply with the following:

       Minimum CBR of 10%
       Maximum plasticity index of 15%
       Shrink-swell index ≤ 1%
       Maximum particle size of 100 mm
Controlled fill materials should be compacted at moisture contents within the range of -2% to +2% of OMC for
Standard Compaction. Confirmatory testing must be carried out at regular intervals and further details for
control and testing of fill are given in Australian Standard AS 3798-2007 Guidelines on Earthworks for
Commercial and Residential Developments. Select fill should have a maximum particle size of 100 mm for
an uncompacted layer thickness of 200 mm and shall be compacted by repeated rolling with a small
compactor to achieve a dry density ratio of at least 95% of the Standard Maximum Dry Density for cohesive
soils, or 70% Dry Density Index for any imported cohesionless soils.

Fill must be ‘benched’ into the natural slope, over-filled by 0.5 m (horizontally) and then trimmed back to the
well compacted material.




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