Pore water pressure of clay soil around large-diameter open-ended thin-walled pile (LOTP) during impact penetration

This study investigates the pore water pressure (PWP) behavior of soil around large-diameter open-ended thin-walled piles (LOTPs) during impact driving using a large deformation finite-element method. A comparative analysis of the PWP accumulation curves of the soil inside, outside, and below the LOTP tips with different diameters and wall thicknesses during impact driving is conducted under the same hammering solution. The PWP development is dependent on the absolute distance from the pile surface to the location of the soil and the dimensions of the LOTP. The excess pore water pressure (EPWP) accumulates and gradually dissipates, and its level decreases with increasing pile diameter. However, a negative excess pore water pressure (Ne-EPWP) is identified during hammering. Based on the above findings and analyses, a PWP prediction equation for LOTP during driving is proposed, and the predicted curves are compared with the numerical results. The influence of PWP accumulation after penetration of 2d (d is the LOTP internal diameter) does not increase significantly. This equation can provide the initial distribution field of PWP in saturated clay for LOTPs, thereby facilitating pile drivability analyses.