Abstract: Under the punching shear failure mode, the experiments were conducted on the karst cave roof to study the bearing capacity under different roof thicknesses and load eccentricities in the laboratory. The failure mode of karst cave under eccentric loading was assumed to be axisymmetric according to the experimental results. Based on the upper bound limit analysis method and Griffith strength criterion, a new method was proposed for calculating the ultimate bearing capacity of karst cave roof both under axial symmetrical and eccentric loading. Besides, a method was given for estimating the range of the punching failure area. The experimental results show that at the same eccentric distance, the ultimate bearing capacity of the roof increases linearly with the increase of the roof thickness before reaching the ultimate bearing capacity of the bedrock. When the roof thickness is constant, the ultimate bearing capacity increases nonlinearly with the increase of eccentricity. In addition, the eccentricity e tends to be gentle and reaches the ultimate bearing capacity of the bedrock at the outside the range of punching shear failure. The theoretical calculation results are in good agreement with the experimental results.

Key words: karst area, limit analysis method, ultimate bearing capacity, failure mode, experimental study