Joint Closure Under Dynamic Normalload And Propagation Of Stress Waves Across Joints

Funded by "973" project of China, the author carried out systematic investigation on the joint closure behavior under dynamic normal load and propagation of stress wave across joints by laboratory experiments, theoretic analysis and numerical simulation in the present dissertation.At first, normal compression tests on artificial joints with different saw-teeth at four kinds of different loading frequencies were performed using Instron 1342 servo-controlled material testing machine. For comparison the same tests on intact samples were conducted. Based on the analysis of test results, effect of surface asperities and loading frequency on the joint closure was discussed.By comparison of the fitting potential of five empirical functions to the closure curve of rock joints under normal loads with different frequencies, it was suggested power function and exponent function give the best fit. Quantitative relations between fitting parameters and strain rate were developed, so new closure models of joint coupling strain rate effect were proposed. Parametric studies and verifications with testing results show that the established models give reasonable estimations of normal stress-closure deformation behavior of rock joint under quasi-dynamic loading.The linear displacement discontinuity model was derived from elastic displacement functions of wave, and then a nonlinear displacement discontinuity model was established by introducing the equivalent displacement hypothesis. Based on the established model, the analytic solutions of transmitted and reflected coefficients were obtained when wave propagates to nonlinear normal deformation joint. Effect of parameters such as initial joint stiffness, quantitative ratio of joint closure to maximum joint closure and frequency of incident wave on transmitted and reflected coefficients was investigated. The analytic results agree well with other's numerical calculations.