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.

The deformation of retaining structures induced by the excavation will cause the change of the earth pressure, which will have an adverse impact on the additional deformation and internal force of adjacent tunnels. Combining the earth pressure with the deformation of the diaphragm wall, a three-dimensional unloading earth pressure calculation model is established considering the spatial effect of excavation. Mindlin’s solution is used to calculate the additional stress at the tunnel axis. The tunnel is regarded as a continuous Euler-Bernoulli beam resting on the Pasternak foundation which considers the continuity of soil deformation, and the response of the tunnel under additional load is obtained. Applying the additional load caused by the excavation to the adjacent tunnel, theoretical method for calculating the additional deformation of tunnels considering spatial effect is obtained. Compared with the history case, the reliability of the method is proved. By applying the method, the influence laws of the maximum deformation of the retaining wall, the distance between the tunnel and the foundation pit and the soil modulus are further analyzed. The research results show that: the increase of the maximum deformation of the diaphragm wall will further increase the deformation and internal force of the tunnel, while the increase of the soil modulus and distance between the tunnel and foundation pit will reduce the additional deformation and internal force of the tunnel.