Study on the Influence of Lateral Pressure Coefficient on Coal Seam Water Injection Borehole Based on FDM-DEM
Coal seam water injection is widely used in underground mining of coal mines.After water injection,the coal body is wet,which weakens its strength and brittleness,increases its plasticity,and reduces the amount of floating dust.For deep low-permeability and difficult-to-inject coal seams,the deformation and damage characteristics of coal body around the coal seam water injection boreholes affect the coal seam water injection effect.Based on the finite difference method(FDM)and discrete element method(DEM),a fluid-solid coupling model was constructed to analyze the deformation and damage law of the coal body around the borehole and the seepage law of coal seam water injection under different lateral pressure coefficient conditions.The results show that the deformation and damage range around the borehole and the water pressure of water injection borehole are roughly distributed in a circular shape under the two-way isobaric conditions,while they are distributed in an elliptical shape under the two-way non-isobaric conditions,and the stress concentration phenomenon is more obvious in the smaller stress direction.As the lateral pressure coefficient increases within 1.6,the fracture area on both sides of the upper and lower sides of the borehole expands accordingly,but there is no significant difference in the fracture distribution area when the lateral pressure coefficient is 1.6,1.8 and 2.0.The water pressure distribution and effective wetting range are similar to the distribution of the damage area.The vertical wetting range changes greatly with the increase of the lateral pressure coefficient,and the overall trend is increasing first and then changing less.When the lateral pressure coefficient is 1.0-1.6,the vertical wetting range is influenced by the lateral pressure coefficient.Then,the stress concentration on both sides of the upper and lower sides increases,resulting in the local area of strong extrusion on both sides of the upper and lower sides,and the wetting range will not be significantly expanded.The research results can provide a reference basis for the design of water injection boreholes in deep low-permeability and difficult-to-inject coal seams.
Discrete elementFinite differenceCoal seam water injectionLateral pressure coefficientDamage characteristicsWetting range
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