Loss ratio of bearing capacity of uplift piles under deep excavation

Bearing capacity of uplift piles would inevitably decrease owing to the change of the ground stress field and the normal stress of pile-soil interface under deep excavation.Unfortunately,due to the limitation of field conditions,it was almost impossible to obtain the bearing capacity of uplift piles under deep excavation from field tests,and theoretical study became the only feasible way to solve this problem.By use of the limit equilibrium method and the simplified Mindlin’s stress solution,a simple formula for predicting the bearing capacity of uplift piles in soft clay under deep excavation was deduced.The calculated results by the proposed formula were in well accordance with the simulated results of FEM.The influence of radius of excavation and effective length of pile on the loss ratio of bearing capacity was finally discussed,and some useful conclusions for engineering design of uplift piles under deep excavation were drawn.