Study On Propagation Law Of Stress Wave Across Rough Joints Under Different In-situ Stresses

Joints have an important influence on the strength characteristics and deformation characteristics of rock mass.Joints in deep rock mass under the action of ground stress are closed recessive features.They will open and slip under the action of earthquake,explosion and other loads,which is extremely unfavorable to the stability of the rock mass.Considering the natural joint roughness,this paper combines numerical simulation and theoretical analysis methods to study the propagation law of stress wave across rough joints under different in-situ stresses.The specific research work is as follows:(1)By comparing with the theoretical solution,the feasibility of using the discrete element software UDEC to simulate the propagation of shear wave across filled joints is verified.The average value of midline intercept and the root mean square of fluctuation are used to generate a joint with different roughness.The influence parameters of S-wave vertical incidence rough filled joints was numerically studied.It is found that the influence of the roughness of joint on transmission coefficient is closely related to filled thickness,and the influence of the root mean square of fluctuation of the joint is greater.When considering the failure of the filling material,it is found that after the sliding of the planar filled joint,the amplitude of the transmission wave is related to the strength of filled joints,but independent of the incident wave amplitude.(2)Considering the influence of in-situ stress,based on the time-domain recursive method,and the wave propagation equations of the nonlinear joint of S and P wave are derived for the continuously yielding model and the BB model,respectively.The theoretical solution and simulated solution by UDEC have good consistency.(3)Based on the joint continuously yielding model,The effects of joint stiffness,roughness,incident wave amplitude and frequency on the propagation of S-waves across joints in deep rock mass were studied by UDEC.It is found that the transmission coefficient increases with the increase of joint tangential stiffness,roughness and in-situ stress.The influence of the lateral pressure coefficient on the transmission coefficient is phased.When the lateral pressure coefficient is not more than 1,the transmission coefficient increases as the lateral pressure coefficient increases.When it exceeds 1,the transmission coefficient decreases as the lateral pressure coefficient increases.When considering the nonlinear and plastic deformation characteristics of joints,the stress wave attenuation law is affected by the combination of amplitude and in-situ stress.When the in-situ stress is large enough,the stress wave propagation law is basically independent of the incident wave amplitude.(4)Based on the BB model,Considering the influence of parameters such as joint stiffness,incident wave amplitude and angle,the propagation law of a set of parallel nonlinear rough joints with P wave oblique incidence under different in-situ stress is studied.It is found that the rougher joints are,the larger the initial normal stiffness is,and the smaller the attenuation of the P wave across the joint is.The transmission coefficient increases as the lateral pressure coefficient increases,and when the lateral pressure coefficient is greater than 1,the increase amplitude decreases.The influence of the incident angle has a large dependence on the in-situ stress.Before the in-situ stress is small and the amplitude of the incident wave reaches a certain value,the transmission coefficient increases with the increase of the amplitude,and the smaller the in-situ stress is,the larger the increase amplitude is.After the in-situ stress is greater than 30 MPa,the influence of the incident wave amplitude on the attenuation law of the stress wave can be neglected.