Undrained Shear Strength and Pore Pressure Changes Due to Prestress Concrete Pile Installation in Soft Clay

This study focuses on the changes of undrained shear strength (Su) and pore pressure (u2) due to the installation of prestress concrete pile (PCP) in Fujian marine soft clay in China. The changes of Su values due to PCP installation are measured by vane shear test (VST) investigation. The piezocone penetration testing (CPTU) is conducted for detecting the change of pore pressure when the PCPs are driven one by one according to the predesigned PCPs construction sequence. The results show that the Su-post values of Fuzhou soft clay are lost about 17% and the Su-post300 value is 1.36 times as much as Su-pre value. It is also shown that three fitting straight lines of Su-pre, Su-post, and Su-post300 are almost parallel which helps predicting the Su value with different depths. The relationship between the normalized excess pore pressure, ∆u/σ′v0, and the ratio of radial distance to pile radius, lg(r/R), is also proposed based on CPTU data, which can be used to predict the excess pore pressure from different distance.