Yossef H Hatzor

Instability of overhanging cliffs depends mainly on rock mass structure and on tensile stresses that develop at the base of the slope. In this paper we present stability analysis of a 34m high overhanging cliff, transected by closely spaced horizontal beddings and three sets of vertical joints. The upper third of the cliff is cantilevered and extrudes more than 11m beyond the toe of the slope, giving rise to eccentric loading at the base of the slope and buildup of tensile stresses within the rock mass. Field observations suggest that the vertical joints which transect the entire cliff form "tension cracks" at the back of the cliff, but their distance from the face is uncertain. Yet, the nature of deformation depends upon the exact location of the vertical tensile crack. The stability of the cliff under different geometrical configurations was studied using continuous 2-D FEA and 2-D Discontinuous Deformation Analysis. Both FEA and DDA are shown to agree with field observations. Based on computational results rock bolt reinforcement was added to the DDA model. Optimal reinforcement scheme was determined using kinematical based criterions.