210533 - 108 Black Mountain Range Road, BLACK MOUNTAIN - Slope Stability Report

Total Concept Homes                                                                                20332-003-Rev0
                                                                                                      16 June 2022

level on the upslope side of the pad. Such materials may require the use of ripping attachments, or selected
hydraulic breaking.

Temporary batters in natural soils of stiffer (or stiffer) consistency, and future controlled fill may be formed at
1V:1H; with permanent batters formed no steeper than 1V:2H. Flatter batters may be required if
groundwater seepage is encountered. Permanent batters will require erosion protection such as covering
with erosion matting or vegetation. Where spatial constraints prevent adoption of the above recommended
batter slopes, cut or fill batters would need to be supported by retaining walls. All existing batters must be
trimmed back to permissible grades as outlined above, or otherwise retained.

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

Any excavations required adjacent to existing structures, will need to be specifically designed to ensure that
the structures are not undermined.

Ground surfaces should be graded to shed surface water runoff away from construction areas. It should be
noted that during wet weather, the natural soils may cause turbid stormwater run-off. Appropriate erosion
and sediment control measures must be installed prior to commencement of earthworks at this site,
especially given the presence of natural gullies and dams within the site boundary downslope of the
proposed construction areas.

4.3    Footing Design
Footings for the proposed building and any ancillary structures (e.g. retaining walls) must penetrate through
any future fill to ‘socket’ at least 1 m into natural residual soil comprising stiff (or stiffer) clay or a minimum of
0.3 m in to very low strength (or stronger) weathered phyllite. Based on the Ground Drill boreholes,
depending on the construction methodology adopted, normally dimensioned, conventional high-level footings
would be appropriate in areas of cut exposing very low strength (or stronger) phyllite, or extended on the
downslope side via the use of steel reinforced concrete bored piles (or ‘bucket piles’).

Footings could be designed with an allowable bearing capacity of 100 kPa when founded in stiff (or stiffer)
natural residual clays or 400 kPa in very low strength (or stronger) weathered phyllite.

Footing design should also account for the characteristic surface movement (ys), indicated by the site
classification report by Ground Drill to be equivalent to Class H1. The re-use of the site-won clay materials
for filling works could result in greater estimates of characteristic ground surface movement and should be
considered by the design engineer if further earthworks are planned.

All footings should found such that they are not adversely affected by any adjacent excavations, trenches, or
retaining walls that are not designed to support building loads. Footings should found at least below a plane
extending 1 m horizontally from the base of trenches/excavations/retaining walls, then rising up at 1V:1H, as
illustrated in Text Figure 10 overleaf.




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