Papers by Keyword: Rock Joint

Abstract: Infilling rock joints widely exist in natural rock masses, and the shear failure of infilling rock joints plays an important role in the instability of rock masses. In order to study the shear failure mechanism of infilling rock joints, Particle Flow Code is used to simulate the direct shear test of infilling rock joints. The PFC models with different infilling thickness are established firstly, and then the procedures of PFC simulation are described. In the end, the shear failure process of infilling rock joints with different infilling thickness is simulated. Based on the PFC simulation results, it can be concluded that the shear failure mode changes with increasing infilling thickness, and the shearing of the infilling rock joint rarely gives birth to microcracks in rock due to the existence of the infilling material.

Abstract: According to the displacement discontinuity method and the conservation of momentum at the wave fronts, analysis for cylindrical P-wave propagation across a linear elastic rock joint is carried out. Considering the energy variation for wave propagation in one medium, the wave propagation equation was derived and expressed in an iterative form. The transmission and reflection coefficients are then obtained from the equation. By verification, the results agree very well with those from the existing results.

Abstract: The three-dimensional roughness characteristics of the tensile granite joint surfaces are studied. Firstly, the tensile granite joints are prepared by splitting cubic granite blocks, and the triangular networks of the joint surfaces are established based on the topographic data collected by laser scanner. Then, the roughness characteristics of the two-dimensional profiles in different positions and different directions are studied. It proves that the roughness of the tensile granite joint surface is position and direction depended, and the roughness parameters based on the profiles are inadequate to characterize the roughness of the three-dimensional joint surfaces. Some new roughness parameters to characterize the three-dimensional joint surfaces are finally calculated on the basis of the triangular networks, these parameters can reflect the spatial and anisotropic characteristics of the joint surfaces. The results in this paper will lay the foundation for further study of the roughness characteristics and mechanical properties of the tensile rock joints.

Abstract: The Joint Roughness Coefficients, JRC, is presented Barton and Choubey in 1977. A series of different rock joint profiles were reconstructed by means of the independent cut method (Voss, 1988) using the programs written by MATLAB language. The reconstructed joint profiles have different amplitude and roughness. JRC values of the joint profiles were calculated on the basis of an empirical formula founded by Tse & Cruden in 1979 using measure interval space 0.5mm on the profiles. The fractal dimension values of the joint profile were calculated by means of stick-measuring methods suggested by Xu in 1996. The relationships between JRC and fractal dimension for all joint profiles were analyzed and exist strong correlations. A new empirical equation describing the relationships was established based on nonlinear fitting analysis and can predict JRC values accurately.

Abstract: Three cases for 1-D wave propagation in ideal elastic rock, through single rock joint and multiple parallel rock joints are used to verify 1-D wave propagation in rocks. For the case for 1-D wave propagation through single rock joint, the magnitude of transmission coefficient obtained from UDEC results is compared with that obtained from the analytical solution. For 1-D wave propagation through multiple parallel joints, the magnitude of transmission coefficient obtained from UDEC results is compared with that obtained from the method of characteristics. For all these cases, UDEC results agree well with results from the analytical solutions and the method of characteristics. From these verification studies, it can be concluded that UDEC is capable of modeling 1-D dynamic problems in rocks.

Abstract: Theoretical investigation on incident elastic P-wave transmission across rock fracture is presented by using an optimization method. It’s assumed that the rock fracture is of nonlinear constitutive model for normal deformation, and the hyperbolic elastic model (BB model) is introduced to descript this nonlinear property. Based on the theory of momentum conservation and discontinues condition, wave propagation equation for P-wave transmission across nonlinear fracture is obtained. Parameter studies, including initial normal stiffness, the ratio of given closure to maximum allowable closure and frequency, are carried out and graphically presented.