South Australia & NT Chapter

Screw Pile Anchors

Peter Yttrup & Ron Lochert

Screwpiling has been used since the early 1990’s in Australia. Screwpiling is not new having been used in England in the 1830’s and in Indonesia by the Dutch in colonial days.

Screwpiles can be used in piled foundations as an alternative to other piling systems. However, the strength of screwpiles is often limited by the yielding of the helix plate at loads less than the geotechnical strength of the foundation. That is, the design strength of screwpiles is limited by the structural strength of the helix, which is unlike other piling systems.

Screwpiles have tension strength that is relatively high as well as a ductile response at high loads. This makes screwpiles an attractive piling system for expansive soil foundations. Such foundation will often induce tensile actions in piles. Further, the prediction of pile actions in expansive soil is difficult and unreliable, therefore the ductile behaviour of screwpiles is an advantage.

The review of AS2870 will probably contain a section dealing with screwpiling for residential construction. Peter Yttrup’s presentation will discuss the current proposal for this section.

The use of screwpiles as a ground-reinforcement system to deal with the very difficult situations in expansive soil foundations will be discussed. An investigation of ground-reinforcement using screwpiles to improve foundations for heavy silos will be presented.

Case studies of screwpiling and Screw-anchoring will also be presented to demonstrate the possibilities of ‘screw-technology’, which is not limited to screwpiling.

Ron Lochert will discuss commercial applications of screwpiling as offered to the SA Housing Trust as “complete systems” for residential footings with particular reference to their use on highly reactive soils.

Engineers Australia members participating in AGS technical sessions can record attendance on their personal CPD logs. Members should refer to Engineers Australia CPD policy for details on CPD types, requirements and auditing guidelines.