Geotechnical Stability Assessment · MCU19/0008

Project No. PG-2096                                                                                                               Page | 7
April 2019
Ref: PG-2096, 2019-02-21, GR VER 2
Andrew and Michelle Douglas – Geotechnical Stability Assessment - Proposed Residence, 22 Arakoon Crescent, Sunshine Beach




An assessment of a single pile's lateral capacity is provided by using Broms Charts as
shown in Figure 1. Refer to Table 2 for applicable parameters. Piles are usually
deemed to be classed as short when the L/B ratio is less than 10 to 12.




                       FIGURE 1               ULTIMATE LATERAL RESISTANCE OF PILES

TABLE 2                DESIGN VALUES FOR LATERAL PILE CAPACITY CALCULATION

                                                                                                                     Bulk Density 
                              Material                                               Design Kp
                                                                                                                        (kN/m3)
                                              Loose                                       2.56                             18
            Sands                          Medium Dense                                   3.0                             18.5
                                              Dense                                       3.25                             19

Should a 'working stress' approach be adopted, a factor of safety of between 2.5
and 3.0 should be adopted.

Lateral capacity may be achieved through the use of raked screw piles etc. if
required.

Construction Considerations

Given the non cohesive soil conditions encountered on site, it is likely that a bored
pier type foundation system will not be appropriate as side wall collapse of the piers
is likely to occur. Appropriate piling solutions could include CFA piles or possibly
screw piles, however screw piles are unlikely to provide significant lateral capacity
and a combination of vertical and raked piles may be required.

During construction, all piles must be inspected by a geotechnical engineer to
confirm the geotechnical strength parameters presented in Table 1 and Table 2 and
to check the capacity of the piles.