Obtaining Cyclic Load-Transfer Curves

Load-transfer curves are commonly used in the design of piled foundations subjected to substantial lateral loads. There currently exists a need to develop a database of this information for the calcareous sediments present on the North West Shelf of Australia. In particular, the behavior of piles subjected to cyclic loading in these soils needs to be understood and quantified.

A geotechnical centrifuge can be used to experimentally determine load-transfer curves. Instrumented model piles have been tested at high acceleration levels to simulate prototype conditions. In order to model cyclic conditions accurately, the pile has to be loaded at high frequencies. This necessitates a suite of pile loading hardware as well as an automated load control system.

The necessary rate of pile lateral loading creates a requirement for data acquisition at frequencies higher than 10 kHz. In order to accommodate this, and other data logging requirements, a 32 channel data acquisition system has been developed and installed in the geotechnical centrifuge facility at the University of Western Australia.

Post processing of the experimental data involves curve fitting bending moment data followed by numerical differentiation and integration to obtain profiles of deflected shape and pile force per unit length. These results can be combined to form load-transfer curves for piles subjected to monotonic and cyclic loading conditions.