水力冲孔造穴作用下煤体增透效应与瓦斯流态转捩规律研究OA

To investigate the permeability enhancement mechanism of coal and the law of gas migration under the action of hydraul-ic punching and cavity-making,based on the characteristics of multi-flow regime coexistence and multi-physical field coupling in coal seams,the influence mechanism of cavity-making parameters on the evolution of coal permeability and the response of gas drainage was systematically revealed.Based on the idea of multi-flow regime transition,a fully coupled multi-physical field model integrating gas seepage theory with stress field and adsorption deformation field was constructed.The gas flow regimes in coal seams were distinguished,and the characteristics of gas flow transition from laminar flow to turbulent flow were revealed.Based on the spherical particle assumption,the permeability expression of the broken zone after cavity-making was derived.Combined with the effective stress principle and adsorption-induced deformation theory,a dynamic evolution model of permeability in the elastic zone was established.By coupling the gas flow field and coal-rock stress field,a unified description of the multi-flow regime transition process and the interaction of stress-seepage-adsorption was realized.Taking Well SX006-1 in Qinshui Basin as an engineering ex-ample,the model was verified by using field-measured gas pressure data.The calculation results of the model were in good agree-ment with the field pressure monitoring data,which could accurately reflect the spatiotemporal evolution characteristics of pressure during gas drainage under the condition of hydraulic punching and cavity-making.The results show that hydraulic punching and cav-ity-making significantly changes the local stress distribution of coal seams,forming a columnar plastic broken zone centered on cav-ity-making,which strengthens the unloading and structural fragmentation effects,and induces a wider range of micro-fracture expan-sion and pore connectivity,thus improving the overall permeability of coal.With the increase of cavity-making aperture,an annular permeability enhancement zone is gradually formed inside the coal seam,the influence range continues to expand,the permeability is significantly enhanced,and the gas migration capacity and drainage efficiency are improved synchronously.The gas flow in the broken zone shows the characteristics of flow regime transition from laminar flow to turbulent flow,and neglecting the turbulent ef-fect will lead to obvious deviations in flow velocity and pressure distribution.Hydraulic punching and cavity-making realizes coal permeability enhancement through the synergistic effect of stress unloading,structural fragmentation and pore connectivity,and the permeability enhancement effect is significantly affected by the cavity-making aperture.The increase of aperture can strengthen the unloading permeability enhancement and gas pressure drop effect,but the permeability improvement presents a nonlinear character-istic.When the aperture exceeds a certain range,the permeability enhancement benefit tends to be saturated,and an excessively large aperture may cause problems such as reduced slag discharge efficiency and increased construction risks.