A fractal multi-field model and numerical simulation of rough coal rock fractures
Topological characteristics of coal rock fractures have a crucial impact on gas accumulation,migration,and production.Based on the fractal theory of porous media,a new interdisciplinary analysis model was constructed to quantitatively characterize the roughness of coal rock fractures.Meanwhile,the permeability of coal rock was defined by a function of fracture roughness.In this way,the influences of fracture roughness and fractal behaviour on gas seepage,coal rock stress and coal rock permeability un-der the coupling of multiple physical fields(coal deformation,gas adsorption,and gas pressure)were quantitatively analysed.The research results demonstrate that the proposed four fractal parameters can ef-fectively characterize the number,length,tortuosity,and roughness of rough cracks.When the physical parameters of coal rock remain unchanged,its permeability is inversely proportional to the fractal dimen-sion of fracture tortuosity and directly proportional to the fractal dimension of fractures.Compared to the other microscopic parameters,changes in the fractal dimension of fracture tortuosity have the greatest impact on coal rock permeability and gas pressure.This study provides a new interdisciplinary method for evaluating extraction rates and mining safety in related engineering projects.
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