基于CT三维重构煤体变开度裂隙渗流特性研究

Study on seepage characteristics of coal fissures with variable apertures based on CT 3Dreconstruction

煤层注水过程中会发生水沿着煤体原生孔裂隙滤失现象,影响注水现场施工效果.为进一步从微观层面探讨煤体裂隙变开度对其渗透特性的影响,结合CT三维重构技术构建6种不同开度的裂隙模型,分析裂隙体积、形状因子等结构参数以及煤体渗透率与裂隙开度的关系.基于Navier-Stokes方程开展变开度裂隙的渗流模拟研究.研究结果表明:形状因子随着裂隙开度变化逐渐减小,这表示随着开度增加,三维裂隙模型趋近于标准球体,空间形态更加简单,更有利于渗流的持续进行;沿渗流方向裂隙压力逐渐降低,水流速度逐渐增加,其中截面整体的速度分布密度保持不变,平均渗流速度随开度增加呈现增大趋势;渗透率与裂隙开度之间呈非线性关系,裂隙开度在60μm以下时,渗透率随裂隙开度增速缓慢,此时裂隙粗糙度对整体渗流的阻碍作用较强,裂隙开度在60μm以上时,渗透率随着裂隙开度的增加迅速提高,也会导致部分区域发生回流、涡流现象,最终裂隙空间将对渗流起主导作用.

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 volume 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 fissure model approaches the standard sphere and the spatial form is simpler,which is more conducive to continuous seepage.The fissure pressure decreases gradually along the seepage direction,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 apertures.There is a nonlinear relationship between permeability and fissure aperture.When the fissure aperture is below 60μm,the permeability increases slowly with the fissure aperture,and the fissure roughness is a strong hindrance to the overall seepage.When the fissure aperture is above 60μm,the permeability increases rapidly with the increase of the fissure aperture,which will also lead to backflow and eddy current phenomena in some areas,and finally the fissure space will dominate the seepage.