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

Abstract：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.