Study on seepage characteristics of coal fissures with variable apertures based on CT 3D reconstruction
In the process of coal seam water injection,water will leak out along the primary pore and fissures of coal,which affects the construction effect of water injection.In order to further explore the influence of coal fissure variable opening on its permeability characteristics at the microlevel,six fissure models with different apertures were constructed by combining CT three-dimensional reconstruction technology,and structural parameters such as fissure vol-ume and shape factor and the relationship between coal permeability and fissure apertures were analyzed.Based on the Navier-Stokes equation,the seepage simulation of fissures with variable apertures is studied.The results show that the shape factor gradually decreases with the change of fissure aperture,which means that with the increase of aperture,the three-dimensional fis-sure model approaches the standard sphere and the spatial form is simpler,which is more con-ducive to continuous seepage.The fissure pressure decreases gradually along the seepage direc-tion,and the flow velocity increases gradually.The velocity distribution density of the whole section remains unchanged,and the average seepage velocity increases with the increase in ap-ertures.There is a nonlinear relationship between permeability and fissure aperture.When the fissure aperture is below 60 μm,the permeability increases slowly with the fissure aperture,and the fissure roughness is a strong hindrance to the overall seepage.When the fissure aper-ture is above 60 μm,the permeability increases rapidly with the increase of the fissure aper-ture,which will also lead to backflow and eddy current phenomena in some areas,and finally the fissure space will dominate the seepage.
CT 3D reconstructionfissure apertureshape factorpermeability
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