Progress in the Bearing Performance Research of Underlying Roof in Karst Pile Foundations

Aiming at the bearing capacity of the top plate under karst pile foundation, the influencing factors of the failure form of the top plate under karst pile foundation are summarized, the influence of the sensitive factors of the top plate on its own bearing capacity and the bearing capacity of the pile end are integrated, and the influencing factors of the calculation of the safe thickness of the top plate and the influence of the top plate on the bearing capacity of the pile end are analyzed. The research results show that under ideal conditions, the failure mode of the top plate is mainly divided into shear failure of thin top plate (h≤2d) , shear failure of slightly thick top plate (2d<h≤4d) , bending and tensile failure of very thick top plate (h>4d) , and the influencing factors are mainly the plate thickness; the calculation results of the safe thickness are mostly concentrated in 2~4 times the pile diameter, and the influencing factors are mainly the strength of the rock and soil, the pile diameter, the working conditions, the calculation assumptions, the calculation model, etc.; the degree of the bearing capacity of the pile foundation depends greatly on the strength of the top plate itself and the rock embedding depth, and the other influencing factors generally have thresholds; the calculation method of the safe thickness of the top plate varies depending on the factors considered and the working conditions, and the adoption of reasonable formulas is suggested.