隔水关键层下不同开采尺寸对覆岩移动规律的影响研究

Study on influence of different mining sizes on movement law of overlying rock under waterproof key layer

导水裂隙带的高度是煤矿在“三下”开采时最关注的因素之一,为了探究隔水关键层下同开采尺寸与导水裂隙带发育高度之间的联系,以邵寨矿作为研究对象,通过变形分析法确定工作面上覆导水裂隙带发育的影响因素,采用数值模拟软件对邵寨煤矿2号煤层开采时不同长度下工作面回采后的覆岩垮落形态进行模拟。研究结果表明,2号煤层上覆厚65 m及112 m的隔水关键层为该煤层的导水裂隙带发育的抑制层,其都由中间一层较坚硬岩层作骨架,上下覆盖各一层软弱岩层而组成。导水裂隙带发育至抑制层时,抑制层抑制了导水裂隙带的纵向扩展,转而倾向于横向扩展,同时增加覆岩的垮落角,当垮落岩体范围超过抑制层的极限跨距时导水裂隙带便会倾向于向上发育扩展;不同切眼长度的工作面其覆岩的跨落仅发生在工作面开采空间范围内,对两侧60 m范围内的覆岩无明显影响;影响整体覆岩运移规律的因素主要为工作面的推进,而当工作面切眼长度小于180 m时,上覆岩层移动主要表现在延安组的垮落,而当切眼长度增加至220 m时,安定组岩层开始随工作面推进加速下沉,但并未完全垮落,切眼长度增加至300 m时,安定组及洛河组在工作面后方120 m处就已经完全垮落。研究结果可以指导矿井在保护隔水层的条件下,合理的设计工作面切眼长度,对于矿井水害防治有一定借鉴作用。

The height of the water conducted zone is one of the most concerned factors in the"three under"mining of coal mines.In order to explore the relationship between different mining sizes and the development height of the water conducted zone,taking the Shaozhai Coal Mine as the research object,the deformation analysis method was used to determine the influencing factors of the development of the overlying water conducted zone on the working face.The numerical simulation software was used to simulate the caving morphology of the overlying rock after the mining of the working face with different lengths during the mining of the No.2 coal seam in Shaozhai Coal Mine.The research results indicate that the waterproof key layers covering 65 m and 112 m thick above the No.2 coal seam are the inhibition layers for the development of the water conducted zone of the coal seam.They are all composed of a harder rock layer in the middle as the skeleton,and the upper and lower layers are covered with each layer of soft rock.When the water conducted zone develops to the inhibition layer,the inhibition layer inhibits the longitudinal expansion of the water conducted zone and tends to expand laterally.At the same time,it increases the caving angle of the overlying rock.When the range of the caving rock mass exceeds the limit span of the inhibition layer,the water conducted zone tends to expand upward.The caving of the overlying rock of the working face with different open-off cut lengths only occurs within the mining space of the working face,and has no obvious effect on the overlying rock within the range of 60 m on both sides;the main factor affecting the overall overlying rock movement law is the advancement of the working face,when the length of the working face open-off cut is less than 180 m,the overlying rock movement is mainly manifested in the caving of the Yan′an Formation,when the length of the open-off cut increases to 220 m,the rock layers of Anding Formation begins to accelerate and sink with the advancement of the working face,but it has not completely collapsed,when the length of the open-off cut increases to 300 m,the Anding Formation and the Luohe Formation have completely collapsed at 120 m behind the working face.The research results can guide the reasonable design of the open-off cut length of the working face under the condition of protecting the waterproof key layer,which has a certain reference for the prevention and control of mine water damage.