Understanding the Energy Transfer Mechanism in the Near Field of Impact Driven Piles

Abstract

Pile installation by applying an impact to the top of a pile appears to be a simple construction process but analysis of that process is complicated as it involves a source of energy, the structural member (pile), and the ground into which the pile is driven. Codes and regulatory standards suggest some basic guidance to analysis but much is still unknown. Pile driving creates vibrations in the surrounding ground that can cause direct damage to nearby structures, cracking in underground utilities or dynamic settlement of loose sands with attendant potential damage. It is customary to monitor surface ground motions starting as close as 1.5 m from the pile and use the surface vibration data to interpret energy propagation. The work described here, however, presents ground motion measurements from impact pile driving not only along the surface but also in the body of the ground at different radial distances and depths. Ground motion data during impact pile driving was obtained by installing motion sensors starting very close to the pile, 0.2 m, and moving away to about 0.8 m and 2 m at the same depth as well as along the ground surface at greater distances. Extensive analysis of the ground motion amplitude and dominant frequencies was performed. Shear wave velocity degradation in the near field of an impact driven pile was