Stability Evaluation of Rock Slopes with Cracks Using Limit Analysis

Cracks are commonplace on slope crests. It has been found that cracks have a significant influence on the stability of slopes in soil with strength governed by a linear criterion; rock slopes with cracks are analyzed in this study using a nonlinear rock model. The kinematic approach of limit analysis is utilized because it straightforwardly considers open cracks and provides rigorous bounds to limit loads. The depth range of a vertical crack in the Hoek–Brown rock mass is derived for dry and wet crack boundary conditions. The stability number and factor of safety are provided by assuming the most adverse crack location, and the presence of water is considered as pore-water pressure acting on the boundaries of the crack and failure surface. When the inclination angle of the rock slope is less than 60°, the influence of cracks on the slope stability is negligible (< 5%). However, it increases to 33.9% when the slope angle is increased to 85°. Based on the critical collapse mechanism, the most adverse vertical cracks appear to be deeper in steeper slopes. Examinations of stress vectors on rupture surfaces and principal stresses indicate that the tensile stress components are eliminated by the presence of cracks, whereas the compressive stresses are maintained as they are. Cracks introduced in rock slopes cause the removal of tension in slopes without adjusting the strength envelope to eliminate the tensile strength of rock.