An assessment of the geotechnical strength reduction factors specified In the new Australian piling standard

Harry Chambers and Barry M. Lehane


The two most common forms of pile load testing currently used in practice are the Static Load Test (SLT) and High Strain Dynamic Load Test (DLT). The Australian Piling Standard AS2159 applies a geotechnical reduction factor (φg) to the load capacities obtained from these tests to derive the pile’s design ultimate geotechnical strength. However, recommendations for assessment of φg in the current (2009) edition of AS2159 differ significantly from those in the previous 1995 edition. This paper investigates differences in φg that are related to the method of pile testing by examining the reliability of load capacity predictions from DLTs with respect to the capacity measured in a SLT. It is shown that the increased φg value allowed by AS2159 (2009) for dynamic testing may be un-conservative compared to the corresponding increase allowed for static load testing.