Study On The Strain Localization Phenomenon And Roadway Surrounding Rock Failure Mechanism

The strain localization is that the strong strain concentration occurs in the loading process of rock-like materials, resulting in the forming of deformation localization or narrowband phenomenon. If a large amount of shearing deformation is centered at the narrowband, we call it the shear zone. The shear zone is considered to be the result of the strain localization and cause or precursors of the material instability and failure. Have a in-depth study of the strain-localization shear-zone phenomenon will be very important practical significance for rock engineering and mining engineering.In this paper, the formation and development of the deformation localization shear zone for rock-like materials were studied by the two methods of theoretical analysis and numerical simulation. In addition, the surrounding rock localization phenomena of deep roadway was discussed briefly.1. The trigger mechanism, launch condition and formation stage at the plane strain state of the strain localization shear zone in the rock-like materials were analysed in theory. Based on the gradient plasticity theory, it is found that along with hard (soft) modulus changed from a positive value to negative value, the qualitative characteristic of differential equation is changing. At the same time, the deformation model will change from uniform deformation into the non-uniform deformation. That is the localization deformation pattern and trigger mechanism of shear zone.The spring-slider combination mechanics models were established. The launch condition of shear zone model was obtained by the mechanical response for the formation process of shear zone.By the use of Mohr-Coulomb theoretical analysis, we can found that the localization shear zone appears in the range of strain hardening of the whole-process stress-strain curve for rock under the condition of plane strain.2. Based on the numerical simulation software of FLAC, the localization shear zone of rock was simulated numerically under the condition of plane strain. It is found that end-face effect, size effect, loading mode and speed, defect position and quantity have influence on the final shape of localization shear zone and strength of rock specimens. The numerical simulation research of localization shear zone for rock was done under the condition of axisymmetric compression, which was divided into two cases of uniaxial compression and conventional triaxial. 3. The shape of localization shear zone and the specific influence degree of rock strength on cylinder specimens were discussed by contrast from three aspects of end-face effect, high effect and confining pressure. It shows that part of study results obtained by simulation are similar with trials or numerical analysis results in previous literatrue.4. The surrounding rock localization phenomena of deep roadway was discussed by the methods of numerical and drilling imaging. The results show that the strain localization shear zone appeared inside the surrounding rock is an important reason of surrounding rock failure of deep roadway.