Pore Water Pressure and Stress Changes During the Construction of Stiffened Deep Cement Mixing Piles

Investigations on the changes in pore water pressures and stress during the construction of stiffened deep cement mixing (SDCM) piles are scarce, resulting in an unsatisfactory understanding of the bearing capacity formation process. Thus, this paper presents a preliminary field study to investigate the variation characteristics of pore water pressures, total stress and effective stress during the construction of SDCM piles derived from field tests. In the meantime, cone penetration tests (CPTs) were conducted before and after the construction of SDCM piles. The results show that the variation ranges of pore water pressure, total stress and effective stress of soils around piles decreased with increasing distance between the measuring point and piles when the depths of the measuring points were the same. During the piling process, the effective stress increased by approximately 53–103%, and the pile side frictions increased accordingly, while the tip resistance and side resistance values of soils around piles increased by 27–106% and 2–145%, respectively. Additionally, SDCM piles successively formed different load-bearing components with decreasing bearing capacity along the pile diameter direction, which realized a better bearing efficiency than conventional piles made with homogeneous materials. In essence, they were also the source of significant economic advantages of SDCM piles. Through this study, we expect to provide a reference for further studies on the bearing mechanism of SDCM piles in soft soil regions.