PROPAGATION OF P-WAVES IN DUAL NONLINEAR ELASTIC MEDIUM FOR JOINTED ROCK MASS

Based on the nonlinear rock mechanics with third order nonlinearity and nonlinear normal deformation behaviour joint model,by using wave equation characteristic method,the semi-numerical solutions of P-wave across single joint in dual nonlinear elastic medium are obtained.Computational programs are compiled.Studies of parameters of joint and wave source,nonlinear coefficient of soft rock,position of joint are conducted to get an insight into transmitted waveform,transmission coefficient and frequency spectra distribution under the influence of dual nonlinear elasticity.The results show that the nonlinear coefficient of rock affects the high-frequency filter of joint and displacement recovery path of particle on joint surface.The wave propagation is not only affected by the same factors in linear wave,but also by the nonlinear coefficient and joint position.When P-wave with the same frequency is influenced greatly by the nonlinear behaviour of rock;the transmission coefficient of P-wave with smaller amplitude is bigger.When P-wave with large amplitude is influenced by dual nonlinearity;a series of higher harmonics are produced in transmitted wave;and this higher harmonics is affected by the combined effect of rock and joint.