Abstract: The cut slope loses its stability more frequently than the filled one during the operation of cohesive canals. The denser the soil and the deeper the excavation, the more frequently the slide occurs because of the swelling and softening of soils under the action of unloading. The expansive soils intensify the loss of shear strength, and the stiff-fissure clay accelerates the loss of strength as well as enlarges the softening zone. Slope protection placed on the bank surface not only effectively prevents the surface erosion even for dispersive clay, but also in certain degree restricts the expansion of soils, as a result, the superficial slide decreases. Moreover, the slope protection may reduce the frost action of silty soils. The proposed method for determining the shear strength of cohesive cut slopes is somewhat different from the current method used in China.