PERFORMANCE OF AXIALLY LOADED STEEL PIPE PILES DRIVEN IN SOFT ROCK

The results of static and dynamic pile testing with open-ended steel pipe piles driven into soft rock are presented. The ground around the piles was instrumented with piezometers and an accelerometer for monitoring the response of the ground throughout the whole test period. The pile testing consisted of dynamic monitoring including initial driving and redriving as well as static load testing. Extensive in-situ soil testing and laboratory soil tests were conducted prior to the pile installation. Tests were also performed after the completion of static load tests. Positive pore pressures were observed adjacent to the pile while negative pore pressures were generated at some distances far from;the pile during the installation process. Remarkable setup, the gain in soil resistance with elapsed time after pile installation, was shown by the redriving and the static load tests. The observations of pore pressure indicated that the setup was associated with the dissipation of pore pressure, which may cause an increase in the effective stresses in the soil around the pile. The effect of the soil plug are discussed with respect to their contribution to soil resistance.