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Rock slopes with intermittent joints in open-pit mines are complex geological bodies composed of intact rock and discontinuous structural planes, and their stability analysis are necessary for mine disaster prevention. In this study, a series of base friction tests were performed to determine the failure process and displacement field evolution of rock slopes with intermittent joints using the speckle technique of a noncontact measurement system. Next, stability calculation models of the slopes were established from the energy perspective using the plastic limit analysis theory, and the effects of the joint inclination angle and coalescence coefficient of rock bridges on the slope stability were evaluated. The four main conclusions are as follows: (1) The failure of rock slopes with intermittent joints shows the feature of collapse-lower traction-upper push. (2) Based on the failure modes of rock bridges in slopes, the failure of rock slopes with intermittent joints could be divided into three types: tensile coalescence (type A), shear coalescence (type B), and tensile–shear coalescence (type C). (3) Among the three slope types, the stability of the type A slope is significantly influenced by rock cohesion, whereas that of the type B slope is significantly influenced by joint cohesion. The stability of type C slope is significantly influenced by the joint inclination angle and joint friction angle. (4) The local-stable slope is unstable while the first through-tensile crack in the zone of the potential sliding body higher than the critical instability height appeared. This study guides the stability evaluation and instability prediction of jointed rock slopes in open-pit mines.

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Fault properties have an important influence on the sliding mode and long-term stability of slopes. In this paper, a cusp catastrophe theoretical model of an open-pit slope is established based on the mechanical model of plane sliding slope instability. The model considers time effects, the rheological properties of fault locking sections, and the strain softening properties of fault softening section. A rheological constitutive model is constructed based on the fractional derivative according to fractional calculus. A slope instability criterion is proposed within catastrophe analysis. The influences of the fault medium length, stiffness ratio, and different orders of the fractional derivative on slope stability are discussed. The critical height and critical safety factor of the dynamic slope instability are derived, and the catastrophe instability time is predicted. The results show that longer softening stages are associated with smaller stiffness ratio values, higher fractional orders, and a greater possibility of slope instability. Slope stability is dynamic under the rheological action of the fault medium.

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