In order to comprehensively explore the ultimate bearing capacity of uplift piles in combined soil and rock masses

combined with engineering geotechnical parameters and experimental data

the Flac3D numerical analysis software is adopted to carry out numerical simulation analysis to obtain the ultimate bearing capacity of uplift piles in the composite rock mass. The Kotter limit equilibrium passive equation is employed to solve the pull-out force provided by the soil layer. And based on the rock strength

the strength of the rock mass embedded in the rock pile can be determined by the Hoek-Brown failure criterion. In turn

the pull-out force of the rock mass embedded in the rock can also be obtained. In addtion

based on the principle of force balance

the ultimate bearing capacity of rock in lay uplift piles in the combined rock mass can be obtained by superimposing the pull-out resistance provided by failure rock layer and the rock mass on the gravity of failure cone. The theoretical calculation value obtained from the analytical formula is close to the numerical simulation analysis value in the case of small rock-socketed depth. However

with the increase of the rock-socketed depth

the theoretical calculation value fluctuates within a certain range around the experimental value. Therefore

combining with the numerical results

the theoretical formula of the ultimate bearing capacity is modified. Finally

by taking the consideration of the effect of rock wathering

rock-sockering depth

soil thickness and pile length

the improved ultimate bearing capacity analytical formula is obtained. The modified analytical formula is used to predict the ultimate bearing capacity of different uplift piles under different geological conditions. The predicted results show that the numerical simulation results are consistent with the theoretical calculation results

which means the analytical method of the ultimate bearing capacity of uplift piles in this paper is feasible. Based on a part of test result

the ultimate bearing capacity of different rock-socked piles with different rock-socked depths in similar projects can be determined by this method.