Abstract: The offset of load position greatly influences the ultimate bearing capacity of the underlying rock foundation with cavities. Based on double logarithmic spiral curve model, the limit analysis method is adopted to establish the underlying rock foundation with cavities damage body function equation when the load position offset is small. Then, the calculation formula of ultimate bearing capacity of hollow rock foundation is deduced. When the offset of load position is large, Prandtl failure mode is developed in the rock foundation with cavities. Furthermore, the influence of the thickness h of rock foundation, load position offset e and internal friction angle ? on the ultimate bearing capacity of rock foundation with cavities are analyzed. Finally, the model test of the ultimate bearing capacity of the rock foundation with cavities under different load position offset and thickness were carried out, and the results were compared and verified with the theory. The results show that when the offset of position is constant, the ultimate bearing capacity of rock foundation increases linearly and the foundation tends to be complete rock foundation with the increase of h. The ultimate bearing capacity of rock foundation with cavities increases non-linearly with the increase of e when h is a certain value. When the h reaches a certain value, the ultimate bearing capacity is close to the value of complete bedrock. When h and e are constant, the limit bearing capacity of the rock foundation with void increases gradually with the increase of the angle of internal friction ?.

Key words: rock foundation with cavities, limit analysis, ultimate bearing capacity, double logarithmic spiral curve, experimental study