Research On Effective Anchoring Mechanism And Technology Of Roadway Roof Under Close/Very Close Coal Seam

The overburden coal seams are prone to spontaneous combustion,and the interlayer spacing varies greatly(1.7-13.5 m)In this paper,taking the 7₂ and 7₃ close/very close coal seams in the second level?₂ mining area of a mine in Huaibei mining area as an example,the overlying strata structure,migration law and mining damage characteristics of stope floor under the close/very close coal seam mining are systematically studied,and the effective roof anchor of the roadway under the close/very close coal seam is proposed Based on the concept of fixed support nursing,the regional classified support technology system of near/very close coal seam was established.By using the research methods of physical similarity,numerical simulation and theoretical analysis,this paper reveals the mechanism of sliding and instability of the high-level key strata of the stable overlying coal seam caused by the mining of the underlying coal seam,and grasps the damage evolution law of the floor strata after the mining of the overlying 7₂ coal seam,The temporal and spatial evolution law of roof stress in adjacent sections under different thickness of interlayer and in the mining process of upper coal seam working face is obtained,which lays a theoretical foundation for the roof stability control of underlying 7₃ coal seam;The support concept based on"effective anchoring layer thickness"is proposed to evaluate the actual anchoring ability of bolt(cable)to roof in roadway support.In order to control the stability of roof surrounding rock,a certain"effective anchoring layer thickness"must be achieved.The minimum effective anchoring layer thickness of 7₃ coal seam roof and the feasibility of coal bolt support are calculated theoretically;According to the thickness and structural characteristics of the interlayer,the effective anchoring conditions and the difficulty of surrounding rock control of the roadway,the adjacent two coal seams are divided into the close distance coal seam and the very close distance coal seam,and the roof of the underlying coal roadway is divided into the damage interlayer,the fracture interlayer and the block fracture interlayer.The regional classification support technical scheme of the underlying coal roadway in the close/very close distance coal seam is proposed.The industrial test results show that:the proposed sub regional classified support technology scheme for the coal roadway under the close/extremely close coal seam not only realizes the effective control of the roof,but also effectively prevents the spontaneous combustion of the residual coal in the goaf of the overlying coal seam,and achieves good technical and economic benefits,It provides a reference for the safe mining of coal resources under such conditions in Huaibei mining area.There are 47 figures,18 tables and 105 references in this paper.