Geotech Report - Initial Findings

Essence of Peregian
215-219 David Low Way, Peregian Beach
Project No. 007-160A,
27 April 2010



       5.3       Earthworks

       5.3.1     Excavation

       Excavation of the sands encountered in the bores should be readily achieved in bulk excavation using a
       medium sized hydraulic excavator, possibly supplemented by ripping in any significantly cemented zones.

       5.3.2     Temporary Batter Stability

       If movement sensitive services are not located ‘close’ to excavations, and geometry permits, battered slopes
       may be adopted. Stable (cut) batter angles will need to be properly assessed once design and earthworks
       procedures have been finalised. However, as a preliminary guide, the values given in Table 3 are suggested
       for unsurcharged batters, up to 3m in height, where some movement behind batter crests is acceptable and
       the sands are fully dewatered. Detailed stability analysis prior to bulk earthworks design finalisation will be
       required on a location by location basis (as part of bulk earthworks design) to confirm stable batter slopes
       and detailed inspection by an experienced geotechnical engineer will be required at the time of construction
       to confirm the stability of batter faces.

       The batter angles given in Table 3 are based on the assumption that batter faces are protected from erosion
       and that drainage is designed to keep surface and groundwater away from the slopes. If free water is
       allowed to emanate from batter faces, slopes will be unstable at the nominated batter slopes.
       Table 3: Maximum Temporary Unsurcharged Cut Batter Slopes

                        Material                           Strength                       Temporary Cut Batter*
                                                      very loose to loose                       1V : 3H
                        Sands
                                                    medium dense to dense                      1V : 1.5H
       * Dewatered

       If insufficient space exists for the construction of cut batters at the maximum slopes given in Table 3, positive
       excavation support will be required in order to prevent excavation instability.

       If buildings etc. are proposed close to slope crests, specific slope stability analysis will be required on a
       structure by structure basis to establish stable slope angles and foundation requirements etc. to minimise the
       potential for crest movements to adversely affect buildings and to minimise building surcharge loading to
       slopes.

       Fill batters should be formed by over-filling by a minimum distance of not less than 1m and cutting back to
       profile, to ensure proper compaction of batter faces. All exposed fill should be protected from weathering,
       erosion and groundwater seepage.

       5.3.3     Batter Erosion Protection

       It is anticipated that cut and fill batters at the site will erode and require ongoing maintenance. It will be
       necessary to install concrete lined collector drains at the crest of slopes and to fully protect batter faces to
       minimise future erosion and maintenance requirements.




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