Study On Mechanism Of Rock Localization Deformation And Bifurcation Instability Of Roadway Surrounding Rock

With the increase of mining depth in mine, the instability mechanics and control technology in deep mining and high pressure, soft rock, big deformation roadway are still crucial in underground engineering. Coal and rock system is a high nonlinear and complex one. So the roadway stability has great susceptivity on deformation degree. When the deformation of roadway surrounding rock is bigger than deformation threshold value, the variety and non-exclusivity of instability and failure will happen in system. It has important theory significance and practicality value that the mechanics process and physics essence of rock again deformation and again failure are studied. The study of allowable failure and control development has the same meaning.Because the surrounding rock failure is needed for roadway instability, the startup and develop of localization deformation of rock material loaded are studied firstly. In mechanics experimentation, localization deformation of rock is divided four stages: continuous bifurcation, non-continuous bifurcation, stress grads steady increase and stress grads fast increase. Based on constitutive equations with non-coaxial theory of rock material, the startup condition and initial direction angle of shear band are obtained using discontinuous theory. It is shown that the localization shear band resulted from loading is parallel with the direction of the second principal stress. The square of first vector of shear band direction angle' cosine increases with Poisson radio and has double-hyperbola connection with plasticity tangent rigidity modulus of non-coaxial plasticity stress radio of rock material. Elastoplastic discontinuous bifurcation characteristics critically dependent on the rigidity rule.Localization shear band figures are simulated using ANSYS software(FEM). Size effect of localization deformation is studied on height, width and size aspects.