Abstract: Due to the merits of strength reduction method, it has been broadly used in nonlinear numerical analysis of the slope stability. In general, the rock and soil are regarded as to be an idealized elastoplastic model; and Mises yield criterion is used. The stability analysis of densely jointed rock slopes using ubiquitous-joint model , the joint property can be considered as well as the rock, thus fitting better with the practical engineering. It is assumed that failure might occur first either in rock or along joint or in both during the rock strength reduction. According to a real engineering project and based on strength reduction method with ubiquitous-joint model, the calculation results show that the potential slip surface appears in style of a polygonal plane; and the dip angle of the potential slip near slope foot is similar to the equivalent friction angle of joint, while the potential slip near the top slope is related to tension failure of rock. The results also show that the dip angle of the joint determines the slope safety factor and the potential slip range. The steeper joint sets affect less the slope stability. Throughout the investigation of the slope failure criteria and the slip surface, it is recognized that the case of the force or displacement becoming not convergent can be properly used as the failure criteria of slope. The shear strain rate in slope can also be used as the criteria for confirming the potential slip of slope because its physical meaning is very explicit.

Key words: strength reduction method, rock slope, Ubiquitous-Joint model, stability, failure criteria, potential slip face