Evaluation of static capacity of piles from rapid load testing

The unloading point method (ULM) is a simple technique for determining equivalent static load-settlement behaviour of piles from rapid load tests. Since the ULM assumes piles to be rigid, it does not consider the effects of elastic shortening and the lag in response along pile shaft. This assumption can be improved by increasing measurement points, e.g. adding an accelerometer at pile toe. In this article, the stress-wave theory was used instead of the additional sensor for estimating the response at pile toe. By considering the lag in response along pile shaft, a better estimate of the stationary point can be obtained and used in the ULM. The refined ULM was verified by comparing with the non-linear model using rapid load test results in literatures. Predictions by the proposed method agreed well with the results from static pile load tests and were better than other methods in this study.