Numerical modeling of parallel seismic method for detecting existing piles in layered soil

For piles connected to superstructures, whose pile tops are inaccessible, a lateral horizontal impact on the side of the piles through the generation of a flexural wave of the pile shaft is a more feasible approach. This paper presents a parallel seismic (PS) method based on the flexural wave of the pile shaft that combines down-hole tests for the length and an integrity evaluation of existing piles in layered soil. It is suggested that two PS tests be conducted by horizontal striking on the side surface of the pile along and perpendicular to the pile-to-borehole direction, respectively. The first arrivals of the transmitted P-wave and S-wave at the pile-soil interface obtained in these two PS tests and the results of down-hole tests are combined to analyze the pile length and to distinguish the embedded defects for the pile integrity evaluation. A simplified theoretical model for PS tests in layered soil is established, and a correction formula is proposed to correct the initial estimated pile length accordingly. A three-dimensional finite element model is then established to verify the effectiveness and reliability of the proposed PS method in layered soil and the correction formula.