1-22276-01 site plan

Project No. 1-22276                                                                                                                  Page | 23
February, 2020
Ref: 1-22276, 2020-02-28, BR VER 2
Wessel Petroleum Pty Ltd – GEOTECHNICAL INVESTIGATION - Proposed Service Station Reconstruction, 52-54 Mary Street and Weyba Road,
Noosaville




           6.4.3       Deep Foundations

Given the subsurface conditions encountered, bored piers are not recommended due to the
potential for sidewall collapse and high groundwater issues.          Refer construction
recommendations. Screw piers are recommended.

General

It is recommended that the deep foundations used on this project be designed in accordance
with AS 2159-2009 Piling - Design and installation. This code uses the limit state design
method. In the limit state design method the following must be taken into account:-

          Ultimate strength - the design of a single pile or a pile group must be such that both the
           design geotechnical strength (Rd,g) and the structural strength (Rd,s) are greater than or
           equal to the Design action effect (Ed) i.e.:-

                                             Rd,g ≥ Ed and Rd,s ≥ Ed
          Serviceability - Single piles and pile groups shall be designed for serviceability by
           controlling or limiting pile movements
          Durability - This is outlined in Section 6 of AS 2159-2009 and will not be discussed any
           further here
          Any other factors that need to be considered i.e. stability, scour, fatigue, cyclic loading or
           seismic actions - As we are not aware that any of these factors will affect the pile design
           they will not be considered any further.

Ultimate Strength Design

The design of a deep foundation system should consider the following:-

          Compressional capacity i.e. base bearing and skin friction design values, this will also
           include negative skin friction effects.
          Tensional capacity and effects i.e. potential uplift due to expansive clays.
          Lateral capacity of the piles
          Construction considerations - See Section 6.4.4.

Compressional Capacity

The design geotechnical strength (Rd,g) can be calculated as the design ultimate geotechnical
strength (Rd,ug) multiplied by the geotechnical strength reduction factor g). The ultimate
geotechnical strength parameters for the materials encountered on the site are outlined in Table
5.




                                                                                                            SOIL SURVEYS