Changes Application - MCU15/0023.02

Project No. 112-14608
January, 2013    REF: 1-14608, 2013-01-15, BR VER O.                                         Page 12


      It is recommended that the deep foundation system on this project be designed in
      accordance with AS 2159-2009 'Piling. Design and Installation'. This code uses the limit
      state design method.


      Compressional Capacity


      The design of a single pile or a pile group must be such that both the geotechnical design
      strength R•., and the structural design strength R., are greater than or equal to the design
      action effect Ed, ie.




      The design geotechnical strength (R..,) can be calculated as the ultimate geotechnical
      design strength (R.",) multiplied by the geotechnical strength reduction factor O,.


      However, specialist piling contractors should make their own assessment of pile type and
      founding levels/length considering pile load requirements and subsurface conditions.


      It is recommended that piled foundations should extend to a depth of at least 1.0m below
      a 25 degree line from the toe of the slope, and into medium dense sands (as a minimum).
      Any shaft friction values should be calculated below the 25 degree line only.


      The design of piles in cohesionless soils may be carried out using the following method:


                 Rj.g = Rd.ug X tPg      tPg . Refer Table 4.3.2 (c) AS2159
                                                (For design tP = 0.45 is considered appropriate)


                                                ultimate pile resistance


        where:


                 Qb=Ab    'Pd.(Nq-l)            ultimate base resistance
                 Qs = As . Pd' Ks . (tan6)      ultimate skin friction


                 As =     area of pile shaft
                 Ab =     area of pile base
                 Pd =     effective overburden pressure at depth d (Pd = Y X d)




                                                            ~    SOIL SURVEYS ENGINEERING