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为探讨中间主应力与层理方向对页岩力学和渗透特性的影响,运用自主研制的多功能真三轴流固耦合试验系统,以含气页岩为研究对象,进行真三轴应力条件下不同中间主应力加卸载试验。研究结果表明:中间主应力对页岩渗透率的影响在中间主应力垂直于层理面时最大,最小主应力垂直于层理面时次之,最大主应力垂直于层理面时最小;当中间主应力垂直于层理面或平行于层理面时,中间主应力与渗透率呈负相关。中间主应力垂直于层理面时渗透率对中间主应力的敏感性明显大于中间主应力平行于层理面时的敏感性,二者相差1~2个数量级;此外,定义损伤变量D表达式,发现加载过程中损伤变量–中间主应力曲线斜率变化不大,而在卸载过程中斜率变化明显,中间主应力垂直于层理面时损伤变量全程大于中间主应力平行于层理面时的损伤变量。
In order to explore the influence of the middle principal stress and bedding direction on the mechanics and permeability of shale, a self-developed multi-functional true three-axis fluid-solid coupling test system was used to study gas bearing shale under true triaxial stress Different intermediate principal stress loading and unloading test. The results show that the influence of intermediate principal stress on shale permeability is the highest when the principal principal stress is perpendicular to the bedding plane, the minimum principal stress is perpendicular to the bedding plane, and the maximum principal stress is the minimum when perpendicular to the bedding plane. When the middle principal stress is perpendicular to the bedding plane or parallel to the bedding plane, the middle principal stress has a negative correlation with the permeability. When the middle principal stress is perpendicular to the laminar plane, the sensitivity of the permeability to the middle principal stress is obviously greater than that of the middle principal stress parallel to the laminar plane, and the difference between them is 1-2 orders of magnitude. In addition, the D variable expression , It is found that during the loading process, the damage variable - the slope of the main stress curve does not change much, but the slope changes obviously during the unloading process. The damage variable is larger when the main principal stress is perpendicular to the bedding plane than the middle principal stress parallel to the bedding plane variable.