Safe Mining Of Overlying Coal Seams In Gob Mining Area Of Hai Wan Coal Mine

It is necessary to analyze the overmining feasibility in order to ensure safe ovemaining.In order to study the feasibility of overmining under the conditions of room mining gob,based on the specific geological and mining conditions in the below coal gob of 5-2 coal seam and upper coal overmining of 4-2 coal seam in Hai Wan coal mine,the influential factors affecting the overmining were analyzed,and it is indicated that the room mining gob area is the main factor.With reference to the judgment methods of the longwall caving method,including the ratio judgment method,the "three zone" discriminating method,the surrounding rock balance method and the mathematical statistics method,it is feasible for overming of Hai Wan coal mine while considering the influence of coal mining time interval.In view of the dynamic disasters caused by the instability of coal pillar and roof in the room mining gob area,it is pointed out that the influence of coal pillar and roof stability on overmining should be analyzed,in addition to the feasibility analysis of the continuity of upper coal seam before overmining under the condition of room mining gob.The coal pillar safety factor is 1.37 and coal pillar is in a basically steady state by using the calculation method of coal pillar stability safety coefficient.With reference to the experience of roof stability analysis in Datong coal mine area,the area ratio of coal pillar is calculated to be 57%,which remained in room mining gob area of 5-2 coal seam in Hai Wan coal mine.It is concluded tha roof is stable under overmining in the lower coal mine gob area.At the same time,in order to reveal the influence of the overmining process on the stability of the below room gob,the mining influence depth of the floor induced by coal mining and the development height of the caved and fracture zone were respectively analyzed,The distance sum of the maximum floor failure height of 4-2 coal seam and the caved and fracture height of 5-2 coal seam is less than that the upper and lower coal seams.It is pointed out that the room mining gob area of 5-2 coal seam is still stable.Furtherly,through the combination of numerical simulation and analogical scores methods,a comprehensive demonstration of the feasibility of overmining were carried out.,it is feasible for overmining under room mining gob of Hai Wan coal mine.Finally,a number of safety technical measures in the process of overmining have been formulated in order to ensure the safety of the overmining.