Rapid pile load tests in the geotechnical centrifuge

Centrifuge experiments were conducted to learn about the factors that affect mobilised resistance during rapid load testing of piles in sand. We studied the influence of pore water pressure during rapid load tests and its effect on the widely used unloading point method to derive static pile capacity. This paper describes the testing programme and the test set-up. We present typical measurement results from a total of 36 rapid and 12 static load tests, as well as the effects of the loading rate and excess pore pressures on pile resistance. The tests confirm that a rapid load test can overestimate static capacity due to pore water pressure when testing piles in medium to fine sands. The results of the pore pressure measurements show a combination of positive and negative excess pore pressure in the zone around the pile base, which can be explained by compression, volumetric behaviour during shearing and pore fluid flow around the pile.