Abstract: Field investigations and studies indicate that the stability of a cutting slope along Qing-Chang Line, Yizheng City, is mainly controlled by the thick silty clay layer including a large amount of gravel. The maximum height of the cutting slope would reach 20 m. The gravel content in the clay varies greatly, the strength of the soils is strongly affected by the gravels. Combined with the site topography and landslide investigation, it is found that the sliding surfaces were through the layer of silty clay, so the strength parameters along the sliding surface were inversely evaluated, the soil strength parameter values with the change of gravel content were obtained. According to the strength parameters of the soil under different conditions, the stability coefficients of slopes under different slope ratio were analyzed. It is recommended that the slope ratio should be 3H:1V or 2H:1V, if the slope is cut in the cohesive soil layer. 

Key words: gravelly clay, cutting slope, excavation plans