Influence of intermediate principal stress on correction formula of bearing capacity of rock foundation

Generally the bearing capacity of rock foundation is high, and practically it's very hard to figure out the exact value of the bearing capacity. As a result the researches related to the bearing capacity of rock foundation are less likely to be taken. However with the increasingly growing load of buildings, the requirements for the bearing capacity of rock foundation are improving in response. The bearing capacity of rock foundation involves the structure of the rock mass and strength of rock, thereby the solution of the bearing capacity of rock foundation is far less perfect compared with the theory of the bearing capacity of soil foundation which is developed from the theory of plasticity. Presently the method of limit equilibrium and the slip line field theory and the limit analysis are available to explore the ultimate bearing capacity of rock foundation, nevertheless the results derived from these theories are most likely to be on the small side. The paper employs the Twin Shear Theory to obtain the theoretical formula of the ultimate bearing capacity of strip-type rock foundation, considering the impacts of intermediate principle stress to the bearing capacity of rock foundation. With the comparison of the project case, it indicates that the results are bigger than the ones applying the Mohr-Coulomb strength theory, and it will bring great economic benefits in the event it is put into the practical projects.