Laboratory Tests on Open-Close Pile Jacking and Load Bearing Characteristics in Saturated Clay Soil

The stress characteristics of the pile-soil interface have an important influence on the effect and long-term bearing capacity of jacked piles. In order to obtain the stress characteristics of the pile-soil interface of the jacked pile in clay, the development law of pore water pressure and earth pressure for open- and closed-end jacked piles during the pile jacking process was studied using indoor model tests based on a saturated soft clay foundation. Test results show that, during the pile jacking process, the excess pore water pressure, earth pressure, and effective earth pressure at the pile-soil interface all increase gradually along penetration depth, and the increasing trend first increases linearly and then increases sharply at the pile end. The excess pore water pressure at the pile-soil interface of an open-end pile is smaller than that of a closed-end pile. The earth pressure and effective earth pressure at the pile-soil interface of the closed-end pile show a “lateral pressure degradation,” and the degradation becomes more and more significant with increasing depth. The pile-soil interface adhesion coefficient increases with increasing penetration depth, and the greater the adhesion coefficient is, the higher the tightness between the pile and soil will be. As a method of determining the interfacial tightness between the pile and soil, the adhesion coefficient is closely related to the excess pore water pressure and earth pressure generated during the pile jacking process and can accurately reflect the mechanical mechanism of pile jacking in saturated viscous soil. Results of this contribution can provide reference for theoretical research on the mechanical pile jacking mechanism in saturated viscous soil.

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