Abstract: The key to researching the seepage characteristics and stability of slopes containing soft interlayers is to construct a reasonable seepage model. On the basis of saturated-unsaturated seepage-stress coupling theory, we established a slope seepage model by assuming that the intersection surface between soft interlayers and upper rock mass is equivalent to a single fracture surface of certain width. The modelling result is in general consistent with the simulation results of classical saturated-unsaturated model in terms of the seepage characteristics of slopes with soft interlayers under rainfall conditions. The permeability coefficient of the equivalent fissure surface at the foot of the slope grows rapidly, which is more consistent with the actual growth of the slope permeability coefficient. By comparing the curve of stability coefficient between the proposed model and classical model, we found that the inflow of the equivalent fissure surface has a significant influence on the stability coefficient of slopes with soft interlayers. The model offers a basis and reference for the design of slopes with soft and weak inclusions in practical projects.

Key words: soft interlayers, seepage modelling, equivalent fracture surface, slope stability, rainfall