Abstract: The construction of PHC pipe piles in marine soft soils strongly will induced a strong buildup of the excessive pore water pressure and a strong disturbance on the strength of the soft soil, thereby negatively affecting the bearing capacity of the foundation soils. To better understand the influence of PHC installation on the soil pore water pressure and on the soil strength before and after pile installation, this paper presents a series of testing results such as, pore water pressure monitoring tests, static penetration tests and cross plate shear tests at different depths during PHC pipe pile construction in the site with marine soft soils in Zhejiang. These tests and evaluations may be beneficial to the optimizing construction schedule and ensuring construction safety. The test results show that the changes of the excess pore water pressure after PHC installation in the testing area undergoes three typical processes, namely, shortterm increase, longterm stability, and finally dissipation. The pore pressure dissipation with time relationship basically presents an inverted "U" shape. The increase of the pore pressure greatly reduces the insitu shear strength of soil, leading the soil shear strength to be changing in a "U" shape with soil depth. The shear strength of soil after the PHC pile installation in soft clays depends on the dissipation of excess pore water pressure, soil characteristics, and construction method. This research may be useful for the optimizing the construction timing of the PHC pipe piles in marine soft soils and ensuring the stability of the excavation close to the pile construction site.

Key words: Marine Soft Soil, Excess Pore Water Pressure, Shear Strength, Bearing Capacity, PHC Pipe Pile