Geotechnical Report

                          EXAMPLES FOR POOR HILLSIDE CONSTRUCTION PRACTICE




WHY ARE THESE PRACTICES POOR?
Roadways and parking areas - are unsurfaced and lack proper table drains (gutters) causing surface water to pond and soaks into the ground.
Cut and fill - has been used to balance earthworks quantities and level the site leaving unstable cut faces and added large surface loads to
the ground. Failure to compact the fill properly has led to settlement, which will probably continue for several years after completion. The
house and pool have been built on the fill and have settled with it and cracked. Leakage from the cracked pool and the applied surface loads
from the fill have combined to cause landslides.
Retaining walls - have been avoided, to minimise cost, and hand placed rock walls used instead. Without applying engineering design
principles, the walls have failed to provide the required support to the ground and have failed, creating a very dangerous situation.
A heavy, rigid, house - has been built on shallow, conventional, footings. Not only has the brickwork cracked because of the resulting ground
movements, but it has also become involved in a man-made landslide.
Soak-away drainage - has been used for sewage and surface water run-off from roofs and pavements. This water soaks into the ground and
raises the water table (GeoGuide LR5). Subsoil drains that run along the contours should be avoided for the same reason. If felt necessary,
subsoil drains should run steeply downhill in a chevron, or herringbone, pattern. This may conflict with the requirements for effluent and
surface water disposal (GeoGuide LR9) and if so, you will need to seek professional advice.
Rock debris - from landslides higher up on the slope seems likely to pass through the site. Such locations are often referred to by geotechnical
practitioners as "debris flow paths". Rock is normally even denser than ordinary fill, so even quite modest boulders are likely to weigh many
tonnes and do a lot of damage once they start to roll. Boulders have been known to travel hundreds of metres downhill leaving behind a
trail of destruction.
Vegetation - has been completely cleared, leading to a possible rise in the water table and increased landslide risk (GeoGuide LR5).

           DON'T CUT CORNERS ON HILLSIDE SITES - OBTAIN ADVICE FROM A GEOTECHNICAL PRACTITIONER

More information relevant to your particular situation may be found in other Australian GeoGuides:
        GeoGuide LR1 - Introduction                                    GeoGuide LR7 - Landslide Risk
        GeoGuide LR3 - Soil Slopes                                     GeoGuide LR8 - Hillside Construction
        GeoGuide LR4 - Rock Slopes                                     GeoGuide LR9 - Effluent & Surface Water Disposal
        GeoGuide LR5 - Water & Drainage                                GeoGuide LR10 - Coastal Landslides
        GeoGuide LR6 - Retaining Walls                                 GeoGuide LR11 - Record Keeping

The Australian GeoGuides (LR series) are a set of publications intended for property owners; local councils; planning authorities; developers;
insurers; lawyers and, in fact, anyone who lives with, or has an interest in, a natural or engineered slope, a cutting, or an excavation. They
are intended to help you understand why slopes and retaining structures can be a hazard and what can be done with appropriate professional
advice and local council approval (if required) to remove, reduce, or minimise the risk they represent. The GeoGuides have been prepared
by the Australian Geomechanics Society, a specialist technical society within Engineers Australia, the national peak body for all engineering
disciplines in Australia, whose members are professional geotechnical engineers and engineering geologists with a particular interest in
ground engineering. The GeoGuides have been funded under the Australian governments’ National Disaster Mitigation Program.

February 2019