煤矿覆岩裂隙地下水渗流特征的试验研究

Experimental study on characteristics of grounawater fracture in coal mine overlying rock

覆岩裂隙地下水渗流特征是采煤和采空区后期维护需考虑的重点因素,特别是煤矿地下水库修建区,覆岩裂隙场经沉积作用形成稳定形态,具有良好的储水和导水能力,也是煤矿地下水库重要的组成部分。在浅层地下水丰富区域或夏季极端降雨条件下,地下水库形成垂向补给,分析地下水在覆岩裂隙中的渗流特征为煤矿地下水库安全运营及地下水资源保护提供科学依据。此次研究通过固−液耦合相似模型试验获得开采区覆岩裂隙发育稳定规律及导通含水层后地下水渗流特征,分析得出延伸远空间大的离层裂隙和微裂隙多以储水为主,贯穿多个岩层的垂向裂隙具有很强的导水能力,离层裂隙间的水力联系主要靠两侧区域的垂向裂隙形成。垂向补给条件下,地下水先以非饱和方式沿垂向裂隙进行入渗,由上及下覆岩裂隙逐渐区域饱和,最终形成稳定的饱和入渗形式。在此基础上建立饱和渗流状态的地下水渗流数学模型,并依靠数值法求解,与相似模拟试验相互验证得出垂向裂隙是主要的导水通道,其导水量占比最大可达到97%,与此同时垂向裂隙中地下水的运移速度也远超出离层裂隙中的多个数量级。最后通过敏感性分析得出垂向裂隙渗流量与裂隙发育程度和总涌水量成正相关,与岩石渗透性成负相关。覆岩裂隙中地下水的运移时间与裂隙发育程度、岩石渗透性和总涌水量均呈负相关。

The seepage characteristics of groundwater in the overlying fissures are the key factors to be considered in the later maintenance of coal mining and goaf,especially in the underground reservoir construction area of coal mines.It is also an important part of coal mine underground reservoir.In shallow groundwater-rich areas or under extreme summer rainfall conditions,underground reservoirs form vertical recharge,and analyzing the seepage characteristics of groundwater in overlying fissures provides a scientific basis for the safe operation of coal mine underground reservoirs and the protection of groundwater resources.In this study,the solid-liquid coupling similarity model test was used to obtain the development and stability of the overlying fissures in the mining area and the characteristics of groundwater seepage after the aquifer was connected.The analysis showed that the large abscission fissures and micro-fissures that extend far and wide are mostly water storage.,the vertical fissures running through multiple rock layers have strong water conductivity,and the hydraulic connection between the separation layer fissures is mainly formed by the vertical fissures in the two sides.Under the condition of vertical recharge,groundwater first infiltrates along the vertical fissures in an unsaturated manner,and is gradually saturated regionally from the upper and lower overlying fissures,finally forming a stable saturated infiltration form.On this basis,a mathematical model of groundwa-ter seepage in saturated seepage state is established,and the numerical method is used to solve it.It is verified with similar simulation ex-periments that vertical fractures are the main water conduction channels,and their water conduction can account for up to 97%.At the same time,the migration speed of groundwater in vertical fractures is also many orders of magnitude higher than that in abscission frac-tures.Finally,through the sensitivity analysis,it is concluded that the vertical fracture seepage is positively correlated with the fracture de-velopment degree and the total water inflow,and negatively correlated with the rock permeability.The migration time of groundwater in overlying fissures is negatively correlated with the degree of fissure development,rock permeability and total water inflow.