基于关键层位置的导水裂隙带高度预计方法

在深入研究覆岩关键层对导水裂隙发育高度影响规律的基础上，提出了通过覆岩关键层位置来预计导水裂隙带高度的新方法.工程实测和理论研究结果表明：覆岩关键层位置会影响导水裂隙发育高度，只有当关键层位置距开采煤层小于某一临界高度时，该关键层破断裂缝才会贯通成为导水裂隙，且受该关键层控制而同步破断的上覆岩层破断裂缝也会贯通成为导水裂隙.关键层破断裂缝贯通的临界高度可以粗略按（7～10）M（M为煤层采厚）估算.当覆岩主关键层位于临界高度（7～10）M以内时，导水裂隙将发育至基岩顶部，导水裂隙带高度等于或大于基岩厚度；当覆岩主关键层位于临界高度（7～10）M以外时，导水裂隙将发育至临界高度（7～10）M上方最近的关键层底部，导水裂隙带高度等于该关键层距开采煤层的高度.上述基于关键层位置的导水裂隙带高度预计方法能适应不同采厚条件下的导水裂隙带高度预计，同时可以对由于覆岩关键层结构变化引起的导水裂隙带高度异常发育情况作出判别，其可靠性得到了工程实测结果的验证。

New method to predict the height of fractured water-conducting zone by location of key strata

Based on depth study of the influence law of key strata on the height of fractured water-conducting zone,this paper proposed a new method to predict the height of fractured water-conducting zone by location of key strata.The engineering measurements and theoretical research results show that the key stratum location affects the height of fractured water-conducting zone in the roof,when the distance from key stratum to the coal seam is less than a critical value,the fracture of key stratum will develop to water-conducting fracture,and the same goes to the fracture of the overlying strata controlled by key stratum leading to a synchronous breakage with key stratum.The critical height of key stratum fracture can be roughly estimated to be(7～10)M,where M is coal mining height.When it is less than(7～10)M from the primary key stratum to coal seam,water-conducting fracture will grow to the location above the roof of the bed rock,then the height of fractured water-conducting zone is equal to or greater than the height of the bed rock.When the distance from the primary key stratum to coal seam is greater than(7～10)M,water-conducting fracture in the roof will develop to the position below the nearest key stratum being(7～10)M more away from the coal seam,and then the height of fractured water-conducting zone equals to the distance of the key stratum to coal seam.The prediction method is able to predict the height of fractured water-conducting zone in the roof with different mining heights,meanwhile,it also can be utilized to distinguish the abnormal development of the height of fractured water-conducting zone induced by structural changes of key stratum,and its reliability is verified by engineering measurements results.