INVESTIGATION OF THE EFFECTS OF PILE JETTING AND PREFORMING

Both jetting and preforming of piles cause substantial disturbance to the surrounding soil resulting in a notable change in the lateral load behavior. This report presents the results of an experimental study performed with similar model piles installed using (1) impact driving, (2) jetting, and (3) preforming in a sandy soil (with 10% clay) compacted to different unit weights under unsaturated and saturated conditions. The effects of jetting pressure and preformed borehole diameter on the lateral load behavior of piles are presented in terms of normalized design curves. In addition, a computational model that can predict the effects of preforming on the lateral load behavior of piles is also formulated. Then, the measured load-deformation behavior of preformed piles is compared to the computational predictions. The zone of influence of jetting on existing piles is also explored. This is achieved through a testing program where the effects of axial and lateral load characteristics of existing driven piles, due to jetting of other piles at designated locations, are monitored. The results indicate that the influence of jetting under dry soil conditions extends up to about five times the pile diameter with respect to the lateral load characteristics. On the other hand, no significant jetting influence zone was detected in completely saturated soils.