the effect of intermediate principal stress is ignored by the critical pressure and the formula of ultimate bearing capacity of shallow foundation
so its results are usually smaller than real values and that the potential of soil’s strength is not fully utilized. From unified strength theory that considers the effect of intermediate principal stress
the common formula of ultimate bearing capacity of foundation was deduced and the unified solutions was obtained. The formula of Terzaghi ultimate bearing capacity of foundation is the specific case of the unified formula. Through changing parameter of unified strength theory
a series of solutions can be obtained. The results indicate that bearing capacity of foundation is greater than Terzaghi ultimate bearing capacity of foundation because of the effect of intermediate principal stress.