Abstract: At present, the research on uplift pile mainly uses pile side friction to reflect the bearing behavior of pile, and there is little research on the normal pressure of pile-soil interface. In view of this, through the PLAXIS 3D, the changes of pile ultimate uplift bearing capacity, pile side friction, pile shaft axial force and pile normal stress after foundation pit excavation were studied. The results show that: for the bearing capacity of pile, the influence of cohesion and friction angle of soil around pile is great; the excavation range has little impact on the bearing capacity characteristics of the pile, for silty clay, when the width of the foundation pit excavation is greater than 37.5 times the pile diameter, compared with the non excavation, the loss ratio of bearing capacity is 10.82%~17.83%; for sandy soil, when the width of the foundation pit excavation is greater than 40 times the pile diameter, compared with no excavation, the bearing capacity loss ratio is 15.37%~33.01%. Linear fitting on the normal pressure curve of the pile soil interface and normalization analysis on the slope in the unexcavated state were performed and the ratio of the slope after excavation to the slope in the unexcavated state was obtained, which is 9.18 for silty clay and 34.92~40.94 for sandy soil.

Key words: uplift pile, uplift capacity, foundation pit excavation, the normal pressure of pile-soil interface