An Insertion Rate Model for Pile Installation in Sand by Jetting

摘要

The use of jetting is an approach to aid the installation of piles, especially in areas that have hard but relatively shallow subsurface soil layers. Jetting piles for a portion of their installation depth minimize their exposure to excessive driving stress and provide energy savings and noise reduction. However, the literature offers little information regarding the appropriate selection of jetting parameters, such as flow rate and jet velocity, which are needed to produce the desired installation times as a function of soil strength. This paper presents a model for estimating pile jetting parameters based on the results from laboratory and field testing. The model is based on an idealization of the applied shear stress that is produced by the jet as well as the soil resistance to pile insertion. The model is applied to 19 field installations where the jetted depths of the piles range from 10-34 ft. The field data yield ratios of 6-20 for the jet flow rate (Qw) to the rate of the pile volume insertion in terms of time (Qp), with the lower ratios associated with higher jet velocities. The proposed model yields an estimated Qw/Qp that is within +/- 20 % of the measured values.