Abstract: Soils around structures such as shafts, tunnels, and chambers are usually under a non-limit state in deep underground engineering. The earth pressure on structure in the non-limit state cannot be predicted accurately by existing theories. In this paper, a model for earth pressure between slip surfaces in non-limit state is established considering soil arching effect. According to the principal stress rotation theory and the simplified parabolic slip surface, the lateral earth pressure coefficient on the slip surface is deduced. Based on the assumption of major principal stress arch, the analytical solution is obtained from the differential equation of average vertical stress in the soil using the limit equilibrium method. The accuracy of this analytical solution is validated by comparing the predicted earth pressures with those values observed from physical modelling under the limit equilibrium state, and calculated from other classical theories. An example of earth pressure analysis between non-limit state of slip surfaces suggested that the presented theory is applicatable to evaluate earth pressures both on the structure and inside soil between slip surfaces under the non-limit state.

Key words: soil arching effect, non-limit state, inclined slip surface, principal stress rotation, major principal stress arch