Response to Info Request - Attachment 5 - Geotechnical Report MCU18-0015 & RAL18-0001 · MCU18/0015

J000635-002-R-Rev1                                                                                      November 2018


     6.3.2       Piles
Where loose sand is present (i.e. Proposed lots 1 and 2), structures should be supported on the underlying
medium dense (or denser) sand. Grout-injected CFA or bored piles are considered suitable. Bored piles may
encounter significant fall-in of loose sand unless a casing/liner is used during construction.
Drilling spoil or fluid should not be stockpiled or discharged on site.
Table 4 shows representative values of ultimate (unfactored) geotechnical parameters for bored/CFA pile
design. A sensitivity analysis should be undertaken to assess effects for the range of parameters.
Table 4: Pile Design Parameters.
                                Ultimate skin       Ultimate base
      Material type
                                friction (kPa)     resistance (kPa)
Loose sand                            10                  NR
Medium dense sand                     20                  NR
Dense sand                            40                  NR
Very dense sand                       60                 1800
Stiff clay                            30                  500
Very stiff or hard clay               50                 1300
Low strength (or
                                      100                2200
stronger) rock
Notes:
     1)      NR – Not recommended
     2)      Skin friction should be discounted for sections of pile shafts where liners are in place

Piles should be designed to resist lateral loads from the movement of loose sand, in the event of localised
slope instability. Lateral forces should be estimated on the assumption that lateral movement occurs along
the interface between loose and medium dense sand, using an assumed depth of 3 m. Calculation of lateral
forces on piles may be carried out in accordance with the method outlined below:




Ultimate geotechnical capacities (Rd,ug) determined from the parameters provided must be multiplied by a
geotechnical strength reduction factor (øgb) in accordance with Section 4 of AS 2159-2009 Piling – Design
and installation to determine the design geotechnical strength (Rd,g). The geotechnical strength reduction
factor should be determined in accordance with AS 2159-2009 and is expected to be in the range of 0.45 to



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