不同水压加载下煤体裂隙渗流数值模拟

为研究煤体在不同水压加载下内部裂隙的渗流运动和孔隙变形规律,应用纽迈核磁共振(nuclear magnetic resonance,NMR)扫描与图像重构技术建立煤岩微孔隙渗流模型,而后借助COMSOL软件,在煤体两侧为固定边界,其上部边界分别进行1～10 MPa水压逐级加载的条件下,对煤体的微观裂隙通道进行渗流运动的数值模拟分析.模拟结果表明:煤体中只有贯通裂隙参与渗流运动,非贯通孔裂隙不参与渗流运动;渗流过程最大流速先是呈现较大速率的正比例增长,在水压达到4 MPa时会突然保持稳定,在水压超过5 MPa后又呈现出较小速率的正比例增长.裂隙介质最大变形会在水压接近4 MPa时到达一个峰值然后突然反弹减小,又逐渐缓慢增大直至最后趋于稳定.应力云图特征表明,渗流过程中应力场变化趋势与裂隙位移变形趋势一致,渗流过程中的水力耦合作用是水压在4 MPa时渗流规律发生改变的主要原因.

Numerical Simulation of Coal Fracture Seepage under Different Pressure Loading

It is significant to study the seepage movement and pore deformation of coal under different pressure. For this purpose, first, the coal micro-pore seepage model was established by the neumaire NMR scanning and image reconstruction technology. Second, and the law of seepage flow in the micro-fracture channel of coal was analyzed using the COMSOL software. The simulation conditions were as follows. (1) Both sides of the model were set as fixed boundary;(2) The upper was set as the hydraulic loading boundary, and the hydraulic pressure ranged from 1 MPa to 10 MPa . The results show that seepage exists only in the through-hole fractures, but not in the non-through-hole fractures. Overall, the maximum flow rate increases proportionally, but, it remains stable when the hydraulic pressure reaches 4 MPa, and then increases in proportion to a smaller velocity after the hydraulic pressure more than 5 MPa. (2) The maximum deformation of the coal reaches a peak when the hydraulic pressure is close to 4 MPa, then decreases suddenly, and then increases gradually and slowly tends to be stable . (3) Stress nephogram features show that the variation trend of the stress field in the seepage process is consistent with the fracture displacement and deformation trend, and the hydraulic coupling in the seepage process is the main reason for the seepage law to change when the water pressure is 4 MPa.