基于Mohr-Coulomb理论的地基极限承载力公式，没有考虑中间主应力的影响．利用双剪强度理论建立了考虑中间主应力影响时的地基极限承载力公式．推导了凝聚力和基础两侧土的超载影响及自重作用影响的理论公式．以条形基础为例，计算了考虑中间主应力对地基极限承载力的影响．研究结果表明，考虑中间主应力影响，地基极限承载力将提高．

The ultimate bearing capacity of foundation based on Mohr-Coulomb strength criterion does not consider the influence of intermediate principal stress on yield and failure of soil. In this paper, the influence of mean principal stress on the ultimate bearing capacity of foundation was taken into account based on twin shear strength theory. Formulae were derived with the influence of soils cohesive strength, over-burden loads on both sides of foundation and the self weight of soils. Taking strip foundation as an example, the influence of intermediate principal stress on the ultimate bearing capacity of foundation was calculated. The ultimate bearing capacity of foundation will be improved, when the influence of intermediate principal stress on the bearing capacity of foundation is considered.