Plane failure in rock slopes – A review on stability analysis techniques

In stratified sedimentary and meta-sedimentary rock formations ‘plane mode’ of rock failure is very common. The plane failure occurs when a structural discontinuity plane such as; bedding plane, fault plane or preferred orientations of a joint set dips or daylight towards the valley or excavation at an angle smaller than the slope angle and greater than the angle of friction of the discontinuity surface. The stability of the slope, having plane mode of failure, depends on the geometry, rock type, potential failure plane characteristics, groundwater conditions, dynamic loading and the surcharge conditions. The slope may demonstrate these conditions in a simple uniform manner or there may be complex conditions owing to variability in the slope geometry and heterogeneity in the slope material. The stability of the slope, having plane mode of failure, can be assessed by different methods which can be broadly classified as conventional and numerical methods. Conventional methods include; kinematic methods, empirical methods, limit equilibrium and probabilistic methods, whereas numerical methods include continuum, discontinuum and hybrid methods. Each of these methods has their own advantage and limitations owing to the slope conditions, application requirement and capability of an expert. In this paper a comprehensive review on governing parameters and various stability analysis techniques for plane mode of failure in rock slopes is presented. Keywords: Rock slope stability, Plane failure, Limit equilibrium, Numerical methods