西部生态脆弱矿区煤炭开采过程中的地下水资源保护与利用是实现该区域煤炭绿色开采的前提和必要条件。其中，保水开采与地下水库技术的广泛应用为解决煤水共采问题提供可能。本文以煤矿地下水库煤岩边界在水反复浸入条件下稳定性变化为研究背景，以神东矿区乌兰木伦矿3-1号煤层顶板砂质泥岩为研究对象，通过无损浸水试验获得试样的自然吸水性规律，获得试样含水率到达饱和状态的浸水时间。根据浸水时间，对试样进行干燥-饱和反复浸水，得到不同循环浸水试样含水率随浸水次数呈指数增加关系，而试样抗剪强度和浸水次数呈指数降低关系。黏聚力随浸水次数的增加呈下降趋势，而内摩擦角先增加后减小，表明材料的均一性以及破裂面的形态及裂隙发育的形态、尺寸、方向变化造成了内摩擦角增加,而后期循环浸水占主导因素，表现为内摩擦角减小。根据黏聚力、内摩擦角与干燥-饱和循环次数的关系，建立了基于干燥-饱和循环次数的Mohr-Coulomb准则。声发射计数曲线与剪应力曲线有较强的对应性，在试样破坏时刻声发射事件明显增加，对应声发射累计计数曲线的明显上升阶段。试样在破坏过程中以低RA值为主，破坏时刻对应高RA值，即试样破坏过程中的基础裂隙类型是张拉裂隙，破坏时刻对应明显的剪切裂隙。研究结果表明，地下水库边界煤岩柱在地下水库蓄水-抽水过程中，在浸水-失水作用下其强度发生显著变化，建议在构建地下水库时应考虑水作用引起的边界煤岩柱强度弱化作用。

The protection and utilization of groundwater resources in coal mining process is the prerequisite and neces- sary condition for realizing green mining at the ecological fragile mining area in western China. Among them,the exten- sive application of water-preserved mining and underground reservoir technology provides the possibility for solving the problem of coal-water co-production. In this paper,with the background that the stability of the coal and rock boundary of underground reservoir changed under the conditions of repeated immersion in water,the sandy mudstone of the No.3-1 coal seam roof of Wulanmulun Mine was investigated. The natural water absorption law of the sample was obtained by non-destructive water immersion test,and the water immersion time of the sample water content reaching saturation state was obtained. According to the immersion time,the sample was dried-saturated and repeatedly immersed in wa- ter. It was found that the water content increased exponentially with the number of immersion, whereas the shear strength and the number of water immersion in the sample decreased exponentially. The cohesive force decreased with the increase of the number of immersion times,while the internal friction angle increased first and then decreased,in- dicating that the uniformity of the material,and the shape of the fracture surface and the shape,size and direction of the fracture caused the internal friction angle to increase. The cycle immersion later was the dominant factor to make the internal friction angle decrease. Based on the relationship between cohesion,internal friction angle and number of dry-saturated cycles,the Mohr-Coulomb criterion was established based on the number of dry-saturated cycles. The a- coustic emission counting curve had a strong correspondence with the shear stress curve. The acoustic emission event increased significantly at the moment of sample failure,corresponding to the obvious rising phase of the cumulative a- coustic emission counting curve. The sample mainly had a low RA value during the failure process,and the failure time corresponded to a high RA value,i. e. ,the common type of crack in the failure process of the specimen was tensile crack,and the moment of failure corresponded to the obvious shear crack. These results show that the strength of coal and rock pillars in the groundwater reservoir boundary changed significantly under the action of water immersion-water loss during the impoundment-pumping process in the groundwater reservoir. It is suggested that the weakening effect of water on the strength of boundary coal and rock pillars should be considered when constructing the underground reser- voir.