Abstract: The Jurassic sand-mudstone alternating stratum is one of typical sliding-prone layers in Three Gorges Reservoir region, where the landslides occur with high frequency. Due to this characteristic lithology combination and architectural feature, the stratum is one key area of landslide control in Three Gorges Reservoir region. In order to further study the stability of rock slope with soft-hard alternating layers, the paper presents a new calculation model of soft-hard interbedding rock slope by means of the analysis on an idealized model. Besides, a shear strength parameter degradation model of soft-hard interbedded rock slope is proposed with considering the effect of weathering for shear strength parameter degradation of the discontinuity plane and a space variation function. Moreover, function expression of shear strength parameter degradation is educed along surface of the layer. The function presented the relationship between weathering thickness and strength parameters, which was in favour of the quantitative analysis of slope stability. Then, utilizing this function weakened the shear strength parameters along surface, evaluating slope stability with the weakened parameters, obtaining the relation curve of stability coefficient and distance from the analyzed point to slope surface. Finally, it is proved that the shear strength parameter degradation of the discontinuity plane of soft-hard interbedded rock slope is significant to its stability assessment with slope case study in Three Gorges Reservoir region. It is concluded that the assumption that shear strength parameters remain constant distribution along layer surface has certain limitation in the stability analysis of single sliding surface slope. Moreover, if the degradation of shear strength parameters of structural planes is not under consideration, it may lead to the result of stability calculation unsafe.

Key words: rock slope, stability evaluation, soft-hard interbedding strata, variation function, degradation of parameters