A 3D analytical model for distributed low strain test and parallel seismic test of pipe piles

In this study, the authors proposed a new dynamic integrity test method of piles, namely, distributed low strain integrity test (DLSITs). The basic idea of DLSITs is that a series of accelerated sensors connected by cables are preinstalled on the steel reinforcement cage of cast-in-place pile or attached on the shaft of precast piles. Compared with the conventional methods (LSITs), the efficient detection depth of the DLSITs can be doubled and its detection accuracy is significantly improved. Accordingly, a coupled 3D analytical model is established for the theoretical analysis of the DLSITs. The developed theoretical model is also applied to investigate the 3D effect of the parallel seismic test (PSTs). A vibration mode analysis is conducted to clarify the forming mechanism of the high frequency interference during the DLSITs and PSTs. The main findings can be drawn as: Both the DLSITs and PSTs suffer obvious high frequency interference arisen from the 3D effect of piles. To reduce this adverse influence, the radius angle between the impact force location and the axial line of receiving sensors is advised to set as 90 degrees.