Study on thickness of safety for cave roofs suffered bending failure in karst areas

Considering the impact of the shaft friction on rock-socketed section in karst area, a series of methods was developed to determine the safe thickness of cave roof. Firstly, considering the bending stiffness of the entire rock roof, the equation of anti-bending thickness can be acquired by using elastic theory and the first strength theory. Secondly, considering the contribution of the shaft friction for altering the distribution of the load on pile, the Griffith criterion and Mohr criterion were introduced to check computations of the anti-punch-shearing and the anti-shearing capacities of the cave roof respectively. Then, the accuracy and correction of the method verified by ABAQUS, and the integrated analyzing model for the cave roof and the rock-socketed pile is simulated. The calculated result agreed well with the simulation's result. Finally, the effect of the ratio of roof thickness and span on the thickness of the safe roof were investigated, while the effect of the nature roof thickness on anti-punch-shearing and anti-shearing capacities and the effect of coefficient of rock-socketed friction on safe cave roof thickness were analyzed as well.