Fully Coupled Model And Engineering Application For Deformation And Pressure-relief Gas Flow Of Remote Coal And Rock Mass Due To Mining

The pressure-relief gas drainage technique is the most effective and economical regional method to decrease gas content and eliminate coal and gas outburst from many years'practices and studies. In recent decades, many field tests was operated on pressure-relief gas drainage due to mining, however, the interaction between the deformation and pressure-relief gas flow of coal and rock mass is not considerate enough to provide the theory and method for efficient pressure-relief gas drainage. By taking coal and rock mass due to mining as the research object in the paper, the combination methods of laboratory experiment, filed experiment, theoretical analysis and numerical analysis are used to research on mechanical characteristic, movement, deformation, pressure relief and seepage characteristic of overlying coal and rock masses. The paper carried on the interaction between the deformation and pressure-relief gas flow, and then set up elasto-brittle- plastic constitutive model of coal rock mass damage due to mining and fully coupled model and numerical solution for deformation and pressure-relief gas flow. The research provides theoretical basis and reference for the design of protective layer mining and relief-pressure gas drainage. The main aspects can be seen as the following:1) A similar experiment for fissure evolution of remote coal and rock mass due to mining, obtained the space-time change law of mine-induced stress, fracture development and deformation in the remote protected layer.2) The elasto-brittle- plastic constitutive model of coal rock mass damage due to mining was set up based on the plastic flow format of Drucker-Prager constitutive model by introducing the inscribed circle criterion and the ideal brittle-plastic model, and validated by comparing with the traditional constitutive models through uniaxial and triaxial compression numerical tests.3) Considering the nonlinear characteristics of the pressure-relief gas flow effecting by the mine-induced fracture and separation, the generalized power law was set up to study the pressure-relief gas migration, depending on the local Reynolds number.4) A fully coupled model and numerical solution for deformation and pressure-relief gas flow were established to simulate the low-permeability coal and rock mass under high-strength underground mining. Then the correctness and rationality of this model was validated by COMSOL Multiphysics software, through the simulation of single borehole gas drainage and three boreholes gas drainage.5) The classification and judgment method of the protective layer was brought out by the equivalent relative interval between the protective layer and the protected layer, considering the occurrence condition and mining parameters of the protective layer working face and the effluence of hard rock in the overburden. The under protective layer is classified into three kinds, and the upper protective layer two kinds.6) A technical system was brought out of pressure-relief gas drainage for the protective layer and the protected layer. The chosen methods were successfully applied in Xinjing coal mine of Yangquan coal field, and the relieved gas in the remote protected layers was better drained utilizing the mining influence of the protective layer, which validates the fully coupled model for deformation and pressure-relief gas flow.