Theoretical and Practical Application of Tube Seismic Method for Pile Integrity Testing

In recent years, a tube seismic method has been proposed to assess pile integrity by analyzing the water pressure response at different depths within the tube under vertical excitation. However, the theoretical framework for this method remains underdeveloped. Therefore, this paper aims to propose a coupled vibration model between the pile surrounding soil, pile, and fluid in-tube. By combining the three-dimensional vibration governing equations of the pile with Biot’s fluid potential function, the expression for the water pressure response at different depths is derived. The dynamic response of the pile obtained in this study is nearly identical to the existing solutions under degenerated conditions. Based on the verified analytical solution, this study investigates the water pressure propagation mechanism in the tube. It can be observed that the water pressure in the tube propagates at two different speeds, which results from the combined effects of both stress wave propagation along the pile body and Stoneley wave propagation within the tube. Parametric analysis of the soil-pile-fluid in tube system under different conditions is conducted to investigate the factors influencing the water pressure response. The field test results demonstrated the feasibility of the tube seismic method and provided theoretical support for the application in the pile integrity test.