Abstract: The procedures of calculating the limit bearing capacity of pile foundation above karst caves are provided in this paper based on MatLab using the theorem of the lower bound solution with finite element method. A plain strain model in no consideration of 3D space effect is built with the rock mass material assumed to obeying the Mohr-Coulomb criterion with plastic associated flow rule. A dimensionless parameter N is defined to describe the effect of different parameters on the bearing capacity of pile foundation. According to the position relation between piles and karst caves, the variation of limit bearing capacity of pile foundation in six different cases are examined in detail. The influences of rock-socketed pile depth h_r, self-weight q_s of overlying soil, and diameter D of karst caves on the bearing capacity of pile foundation are also investigated. Results reveal that the limit bearing capacity of pile foundation increases with the increase of h_r, but decreases with increasing of D, while the influence of q_s is negligible. In addition, the failure modes of pile foundation in different cases are also analyzed. The computation method in this paper is verified correct through two examples in the presence and in the absence of karst caves.

Key words: pile foundation above karst caves, limit bearing capacity, MatLab, lower bound finite element method, failure mode