Laboratory and numerical modelling of shear behaviour of natural rock joints under CNS

The shear behaviour of natural rock joints was investigated in the laboratory under Constant Normal Stiffness (CNS) condition. Shear tests were performed on irregular profiles under initial normal stresses (sigma(no)) between 0.56 and 2.16 MPa, and a normal stiffness (k(n)) of 450kPa/mm. Laboratory direct shear behaviour under CNS condition was numerically modelled for a simplified 2D joint profile using the Universal Distinct Element Code (UDEC). The predicted and laboratory results of shear and normal stresses corresponding to horizontal displacements were compared for various initial normal stresses (sigma(no)). The model predicted shear and normal stresses for 2D profile are in acceptable agreement with the laboratory data. However, the dilation behaviour under sigma(no) exceeding 1.10 MPa is overestimated in the UDEC model.