采动裂隙形态响应及覆岩渗透性演变试验研究

Experimental study on mining-induced fracture form response and permeability evolution of overlying strata

采场覆岩岩层移动和裂隙发育产生的卸压增透作用是实现瓦斯高效抽采的保障,为了探究回采中采动裂隙的分布和覆岩渗透性的演变,基于相似模拟技术,分析了裂隙的形态响应过程,并利用瞬态流量法以空气为介质对覆岩渗透性进行了测试,研究结果表明:裂隙布展在频数上,近开切眼区域高于采场内部;在形态上,裂隙角度多集中在水平夹角0°~10°、90°~110°和170°~180°三个区域,近开切眼区域裂隙角度与岩层卸压角表现出一致性,而在采场内部裂隙角度多以正交方向为主。回采过程中,测点流量数据与采动影响密切相关,水平方向上各测点流量均经历了波动—激增—稳定3个阶段,而垂向上流量激增阶段较不明显,最终稳定流量与测点与回采层位层间距呈负相关。利用数据拟合,获得了描述覆岩渗透性与层间距关系的三参数对数式,并对各参数的物理意义进行了解释。研究成果可对瓦斯抽采的工程参数布置提供一定的指导。

The pressure relief and permeability enhancement effect caused by the movement of the overburden strata and the development of cracks in the stope is the guarantee for efficient gas drainage.In order to explore the distribution of mining cracks in the stope and the evolution of the permeability of the overburden,based on similar simulation technology,the morphological response process of fractures was analyzed,and the permeability of the overlying rock was tested using the transient flow method with air as the medium.The results show that the fractures are distributed in frequency,and the near-open cut area is higher than the inside of the stope.On morphology,the angles are mostly concentrated in the horizontal angles of 0°~10°,90°~110°and 170°~180°.The angle of cracks in the near-open cut area is consistent with the pressure relief angle of the rock formation,but in the inner place the angle is orthogonal.During the mining process,the air flow data at the measurement point is related to the impact of mining.The flow at each measurement point in the horizontal direction has experienced three stages of fluctuation-surge-stability,and the stage of vertical flow surge is less obvious.The final stable flow is negatively correlated with the interval between the measuring point and the recovery horizon.Based on the data fitting,the relationship between overlying rock permeability and interlayer spacing can be described by the three-parameter logarithmic formula.The physical meaning of the three parameters are stated.The research results could provide some guidance for the arrangement of engineering parameters of gas drainage.