Dynamic load testing is carried out with two identical bolt-on strain and acceleration transducers attached to a section of pile. The pile is then struck with a driving hammer or a separate drop weight. A hammer mass of about 1 to 2% of the test load is generally sufficient. The generated compressive stress wave travels down the piles and reflects from the pile toe upward. The stress waves, which are picked up by the transducers, are processed and automatically stored in the computer for further analysis and reporting.
The analysis is carried out using the signal matching program CAPWAP. Pile and soil data are modelled and a response is calculated based on one dimensional wave equation theory. The signal matching process utilizes an iterative method in which the results of each analysis are compared to the actual measured pile behavior. Appropriate dynamic soil parameters are refined until a satisfactory match is achieved.
The mobilized static shaft and toe resistance of the pile can hence be derived. The signal matching program also provides a prediction of the static load displacement performance of the pile on the basis of the refined pile and soil model.