Comparison of design values to dynamic load testing results for bored piles in Bringelly Shale in Western Sydney

The Sydney Basin is one of the most well-documented geological regions in Australia. Comprising of different rock formations consisting of a geological profile of varying sandstones and shales. These formations vary between classes from I to V based on the overall properties of the rock mass, the compressive strength determined from UCS testing and the overall roughness of the material. These rock properties determine the design parameters for piling applications, namely skin friction and end-bearing stress values. One of the most common formations in the Western Sydney region is Bringelly Shale, most of the correlations used currently are determined from soil sampling and static load testing performed from the 1970’s to the late 1990’s before the introduction and acceptance of pile dynamic load testing to assess pile capacity.

High Strain Dynamic (PDA) load testing and CAse Pile Wave Analysis Program (CAPWAP) can be used to produce a reliably accurate comparison of pile capacity to an ultimate static load test and so help determine the skin friction and end bearing stress values on a tested pile. This paper aims to compare recent dynamic load test data with CAPWAP analysis to design values based on the geotechnical information provided on-site in the Western Sydney area. From the presented comparisons the potential variance in design values compared to the frictions and base resistance achieved during testing for Bringelly Shale can be demonstrated.