【目的】为更好地理解应力作用下煤系层状砂质泥岩的渗透率变化,在应力渗流耦合室内试验的基础上使用离散元模拟研究层状砂质泥岩的力学特征与渗透性。【方法】首先,通过加载方向平行和垂直岩样层理方向的应力渗流耦合室内试验,研究砂质泥岩全应力应变加载过程的破坏形式以及与渗透性间的相互关系。其次,在离散元软件PFC2D中首次提出通过求解有限差分法来表征流场流动的方法,该方法能很好地反映砂质泥岩应力应变响应与渗透率变化,所得模拟应力应变及渗透率曲线与试验结果一致,流体沿主裂缝集中流动。最后,基于校准后的参数进行不同层理角度岩样应力与渗透率模拟,探究最大渗透率和峰值强度与层理角度的关系。【结果】结果表明:层状砂质泥岩强度与渗透率具有各向异性;岩样中流场方向、流量大小和接触力链与裂纹密切相关,其中强接触力链集中分布在试样节理处的剪切带附近;随层理角α的增大,峰值强度呈“U”型变化,最大渗透率呈线性减小。【结论】本数值模拟研究方法可充分考虑岩石力学与渗流特性的影响,为围岩防渗加固项目提供理论基础并为离散元模拟流固耦合提供一个新思路。

【Purposes】In order to better understand the permeability changes of coal measure bed⁃ ded sandy mudstone under stress, the mechanical characteristics and permeability of bedded sandy  mudstone were studied by discrete element simulation on the basis of the stress seepage coupling labo⁃ ratory tests.【Methods】 First, the failure mode and the relationship between the full stress-strain load⁃ ing process and the permeability of sandy mudstone were studied by the stress-seepage coupling labo⁃ ratory tests in the bedding directions of parallel and perpendicular rock bedding. Second, in the dis⁃ crete element software PFC , a method to characterize the flow field by solving the finite difference  method is proposed for the first time, which can well reflect the stress-strain response and permeabil⁃ ity changes of sandy mudstone, and the simulated stress-strain and permeability curves obtained are  consistent with experimental results, with the fluid flowing intensively along the main fracture. Fi⁃ nally, according to the calibrated parameters, the stress and permeability of rock samples at different  bedding angles are simulated, and the relationships between the maximum permeability or peak  strength and bedding angles are explored. 【Findings】The results show that the strength and perme⁃ ability of layered sandy mudstone are anisotropic. The flow field direction, flow rate, and contact  force chain in the rock sample are closely related to the crack, and the strong contact force chain is con⁃ centrated near the shear zone at the joint of the sample. With the increase of the bedding angle α, the  peak intensity changes in a “U” shape, and the maximum permeability decreases linearly.【Conclusions】 This numerical simulation method fully takes into account the influence of rock mechanics and seepage  characteristics, which provides a theoretical basis for the surrounding rock seepage prevention and rein⁃ forcement project, and a new idea for the fluid-structure interaction of discrete element simulation.