Over-consolidation effect on shear behavior of rock joints

Although many researchers have studied the normal and shear behavior of fractures under stresses, the over-consolidation effect on the slip/shear behavior of discontinuities has not been considered. The over-consolidation behavior of non-planar rock fractures should be considered when deposition-consolidation-erosion (or excavation) sequences occur. Plaster replicas of representative natural rock joint surfaces were prepared for this study. In this case, the surface roughness and other geometrical properties remain constant during the laboratory direct shear tests. It was observed that the shear strength within a large range of roughness, joint wall strength and normal stress values significantly increases with increasing over-consolidation ratio. According to the test results, a new model is developed as an extended form of Barton's shear failure criterion for rock joints. This model considers the effect of various paths of normal loading/unloading before shearing and over-consolidation ratio in a fracture. A new joint over-closure (JOC) parameter is also introduced as the ratio of closure in over-closed to normally closed conditions. (C) 2011 Elsevier Ltd. All rights reserved.