The expression of effective stress principle suitable for the micro-structural features of saturated concrete is established. The theoretical equation of pore water pressure coefficient under three-dimensional stress state is proposed. By this model, the compressive strength of concrete under different confining pressures is predicted, and the influential mechanism of pore water pressure on the strength of concrete under complicated stress states is investigated. The results indicate that the existence of pore water pressure changes the loading path of the matrix’s true stress in the principal stress space, therefore it modifies the compressive strength when the stress state of the concrete reaches its limit.
