Changes Application - MCU15/0023.02

                        AUSTRALIAN GEOGUIDE LR8 (CONSTRUCTION PRACTICE)

                    EXAMPLES OF POOR HillSIDE                                             CONSTRUCTION PRACTICE
                                                                           Unstabi!ised   rock topples and travels downslope          ----;,
                                                                                                  Vegetation removed         -                 \

                                                                 Sleep unsupported          cut fails :\                          \                \
                           Discharges of roofwater soak away rattler than                                                             .
                           conducted offsile or to secure storage for re-use ----\                                                    ~
                                          Structure unable to lolerale
                                          settlement    and cracks           ..--...l                                             /
                                                                                                                                      .....
                                  Poorly compacted IiII settles                                                        '.
                                  unevenly and cracks pool                                                               -

                            Inadequate walling unable
                            to support fill




                                                                                                                        Dwelling not founded in
                                                                                                                        bedrock

                                                                                                                   Absence of subsoil drainage
                                                                                                                   within fill

                                                                                                              Loose, saturated fill slides and
                                                                                                              possibly flows downslope
                                                       '--    Ponded water enters slope and activates landslide
                                                                                                                                                       '£1 AGS (2007)
                             '-     Possible lravel downslope     which impacts other development      downhill                  Seea/sQ•••GS(2000)~              •.J


     WHY ARE THESE PRACTICES POOR?
     Roadways and parking areas - are unsurfaced and lack proper table drains (gutters) causing surface water to pond and
     soak 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 walis 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 herring bone,
I,   pattern. This may conflict wijh 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 likeiy 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 Informatlon   relevant to your particular          situation   may be found in other Australian            GeoGuides:

               GeoGuide LR1 - Introduction                                         GeoGuide LR6 - Retaining Walls
               GeoGuide LR2 - landslides                                           GeoGuide LR7 - Landslide Risk
               GeoGuide LR3 - Landslides in Soil                                   GeoGuide LR9 - Effluent & Surface Water Disposal
               GeoGuide LR4 - Landslides in Rock                                   GeoGuide LR1 0 - Coastal Landslides
               GeoGuide lR5      - Water & Drainage                                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.




                                       Australian Geomechanics Vol 42 No 1 March 2007                                                                                   175