Reasearch Into The Dynamic Characteristics Of Stress Wave Propagation In Jointed Rock

The research on wave propagation and attenuation in rock mass is a profound andsignificant issue, and many practical problems of large underground projects have closerelation to the rock instability under stress wave or impulse load and the stress wavepropagation in rock mass; therefore, the research has become one of foreland problemsin the field of underground engineering area. It is well known that rock joints are widelyexisted in the rock mass, and rock joints generally affect or determine the mechanicalcharacteristic and dynamic property of rock mass. Consequently, considering theinfluence of the rock joint is important and necessary to solve the issues of undergroundrock engineering, and the interaction between rock joints and stress waves becomecrucial in rock engineering. In the paper, firstly numerical simulation by FLAC3D isadopted to study the influence of nonlinear rock joint and multiple parallel joint sets on1D wave propagation; and then, based on the time-domain method proposed byJianchun Li and Guowei Ma in2009, the work aims at expanding the new method tosolve the nonlinear problems of wave propagation in nonlinear rock joint and multiplerock joints systematically, and theoretical researches are carried out to meet the targets.In addition, the nonlinear property of rock joint embodies the following aspects: thenonlinear normal deformation of rock joint, the shear-slip phenomenon and dynamicproperties of open rock joint. The contents of the paper are summarized as follows:(1) With FLAC3D program, the paper systematically simulate the propagationprocess of1D stress wave in jointed rock with single rock joint and multiple parallelrock joints for the first time. Firstly, according to the parametric study on the rock-stem3D model without rock joints, the achievements provide the basis for the selection ofappropriate parameters applied to the dynamic FLAC3D models. In addition, three rockjoint models are existed to simulate the actually working state of rock joint in FLAC3D program: the joint model considering the tensile, the spring model and the shear-slipmodel. Afterwards, appropriate simulation models are established to analyze thepropagation process in jointed rock with single rock joint and two parallel rock joints.Finally, combined with the theoretical results obtained from the previous chapters, theaccuracy of simulation model is discussed, and the conclusion obtained is valuable tomake FLAC3D program better applied to1D wave propagation across the practicalnon-continuous medium in the field of underground rock engineering.(2) Considering the nonlinear normal deformation of rock joints, the constitutivemodel (BB model) is introduced by comparing various nonlinear constitutive models,and the nonlinear displacement discontinuity model is conducted in time domain. Andthen, by using the relationship between the wave front and joint surface, wavepropagation equations of2D longitude wave impinging on a rock joint are derived intime domain, which is superior to consider both the influence of incident angle andnonlinear deformation of rock joint on the wave propagation.(3) Considering the shear-slip phenomenon of rock joints, the linearization modelof shear-slip behavior is employed to conduct the propagation model in jointed rockwith2D P-wave and S-wave, wave propagation equations of P-wave and S-waveobliquely impinging on a rock joint are derived in time domain, which can not onlyconsider the influence of incident angle and shear-slip behavior of rock joint, but alsoanalyze the effect of shear-slip behavior on the wave attenuation.(4) With correcting the analytical model of wave propagation in open joint, theactually state of open joint can be reflected involving the mechanical properties. On thebasis of the existed analytical model, spring model of rock joint are proposed to reflectthe interaction between stress wave and open joint, subsequently, wave propagationequations are derived to obtain the wave amplitude of transmitted wave and reflectedwave. The correction model is valuable to analyze the energy propagation attenuation inopen joint subjected2D explosive wave and reflect the actually working state of openjoint.(5) Due to the diversity and complexity of2D wave propagation in multipleparallel joint sets, there is an initially new attempting to conduct numerical differencemodel on wave propagation in two parallel rock joints. With the consideration ofnonlinear deformation of rock joint, wave propagation equations are derived to reflectthe wave propagation process in jointed rock with two parallel joints. The deducedequations can analyze the influence of various parameters on wave propagation,including nonlinear deformation of rock joint, incident angle and joint spacing between two parallel joints.Though finite differential software FLAC3D and the theoretical method, theresearch works are systematically carried out on the propagation process of stress wavein jointed rock with single rock joint and multiple parallel rock joints, and focus on theinfluence of the nonlinear characteristics of rock joint and multiple parallel joints onwave propagation.The obtained conclusions are the further supplement of dynamic theory of rockmechanics, and have the important theoretical significance, guiding significance andpractical significance to the underground rock engineering and structure engineering.