FINITE ELEMENT LIMIT ANALYSIS OF BRIDGE DOUBLE-PILES FOUNDATION IN KARST AREAS

This paper aims to calculate ultimate bearing capacity of bridge double-piles foundation in karst areas and combines the theorem of the limit analysis with finite element method. The computation procedure is provided on the basis of MATLAB. The modified Hoek-Brown criterion is employed to describe the characteristic of rock mass. The method of hyperbolic approximation is used in the process of optimization computation to solve the problem that singular point can not be differentiated. Based on the numerical results, the effects of different parameters on the bearing capacity factor N_σ are evaluated. The results reveal the follows. (1)The value of N_σ increases with increasing the subcharge over rock mass, with an increase in the rock socketed depth, and the rate of increase in N_σ is insensitive. (2)The value of N_σ decreases with increasing the radius of the cave, and first decreases, then increases with increasing the horizontal distance between piles and caves. (3)The value of N_σ increases non-linear with increasing the value of GSI, and the relationships between N_σ and m_i, and the vertical distance are approximately linear. (4)The rock unit weight has a neglible effect on N_σ, when the larger distance between piles and caves exist. (5)Three types failure pattern are provided, including general shear failue, punching failure controlled by the left pile, punching failure with bearing failure. At last, the method proposed in this paper is verified by comparing the results reported by the previous investigations.