Research On Deformation And Failure Character And Yielding Support Mechanism In High Stress Soft Rock Roadway

With coal mining depth increase, the support and maintenance problem of high stress soft rock roadway becomes more and more prominent, the deformation and failure of surrounding rock and its control mechanism becomes a problem needing solve urgently. Therefore, based on the massive soft rock triaxial compressive test, viscoelastic plastic strain softening creep constitutive model of soft rock was first proposed in the paper, and the model was inserted to the FLAC built-in construction relations, then the deformation and failure mechanism and the yield pressure support mechanism of high stress soft rock roadway were analyzed by numerical simulation. The research production was successfully used in the project practice. Its main innovative achievement manifests in the following five aspects:(1)Based on curve of tri-axial compression test under different confining pressure, mechanics model of strain softening is builded, generalized cohesive force c and generalized internal friction angle ? of different equivalent plasticity shear strainεpsand different confining pressureσ3 is determined by Mohr stress circle, then softening rule of mechanic parameters on soft rock are embedded into the softening constitutive relation in FLAC simulation software, which are obtained by least surface fit and are approved be fit to describe the mechanic characteristics of soft rock after peak value.(2) Based on rules and ageing behavior of creep curve of soft rockmass sample under every level of load, a new creep mechanic model of soft rock series connected by classic visco-elasticity and plasticity mechanic model and strain softening mechanic model is builded up firstly, then the tri-dimension creep constitutive equations is deduced and the 7 parameters of the above model is identified by nonlinear regression analysis. Based on this, insert this model to FLAC built-in creep construction relations, through the numerical simulation, the result indicates that the model can describe the three stage mechanics conditions of soft rock.(3) Based on viscoelastic plastic strain softening creep constitutive model, the deformation and failure characters at the high vertical stress and the high level stress condition was analyzed using numerical simulation method. The evolution rule of the deformation, stress, plastic and crush zone along with time was got.(4)The control action at different support intensity for the high stress soft rock roadway was studied using numerical simulation. The result shows that the initial deformation of high stress soft rock roadway was insurmountable. So the"yield pressure support"is proposed. The yield pressure support mechanics model was established, and the support effects influenced by different yield distance and different limited deformation amount was analyzed.(5) Aims at the problem of high stress soft rock roadway in Li Yazhuang Coal Mine, Huozhou Coal Electricity Group, the high-resistance and yield stress support system taking high strength with yield stress function bolt and ribbed anchor as the core is proposed. Through the scene observation, the result indicates that the support system has controlled the roadway fierce deformation and continue creep effectively, and the roadway security enhances greatly.