Testing Method for Existing Engineering Pile Behavior Based on Side Hole Shear Waves

For solving the difficulties in the bottom depth and integrity evaluation of existing piles, a parallel seismic (PS) test in existing research is proposed. The existing PS testing of using the first arrival of P wave transmitted from the pile shaft to evaluate the bottom depth and integrity is invalid in saturated soil, as it is difficult to excite the pile shaft with inaccessible pile tops in vertical direction. This paper is to provide a PS testing approach using the shear wave induced by horizontal impact on the lateral surface of a pile. Under appropriate excitation-testing hole arrangement in PS testing, the first arrival of shear wave (F-S wave) received at a certain depth of testing hole transmitted from the pile shaft, can be used to evaluate the bottom depth and integrity of existing piles in saturated soil. Finite element method is used to verify PS testing limitations of the first arrivals of P wave and the effectiveness of the first arrivals of shear wave in evaluating pile bottom and integrity for existing piles by horizontal impact on the lateral surface of a pile in saturated soil. The results show that: (1) When the testing holes are arranged perpendicular to the excitation direction in saturated soil, the first arrival of F-S wave in the received signal can be identified easily. By reading the first F-S wave travel time, the two fitting lines and their intersection points are determined and the intersection points are corrected by the recommended method, so as to determine the pile bottom depth more easily with higher precision. When there is a segregation defect in the pile body, the first F-S wave arrivals present a broken line consisting of two parallel lines and a connecting line in between. It is recommended that the depth of the top of the defect can be estimated based on the beginning point of the connecting line. The proposed PS testing method provides an effective means for evaluating the depth of pile bottom and the integrity of pile body in saturated foundation.