Research On Overlying Rock Structure And Near-far Roof Control Technology In Extra Thick Coal Seam

Over the past ten years,the overburden structure,strata pressure mechanism and control technology of extra-thick coal seam in Datong mining area have been explored.On the basis of surface deformation measurement,the vertical fracture characteristics of high-level overlying strata are inverted.Based on the large-scale three-dimensional physical similarity simulation of extra-thick coal seam,which reproduces the transformation of “longitudinaltransverse” fracture morphology of overlying rock visually;Combined with two-dimensional physical similarity simulation of overburden fracture.It is confirmed that the overlying strata of extra-thick coal seam have horizon structure and unified mechanical model of overburden structure is constructed.The mechanism of mine pressure in large space stope is revealed and the idea of collaborative control of overlying strata in extra-thick coal seam is proposed.Combined with specific engineering cases,the implementation process of far and near field classification control technology for overburden is introduced in detail.(1)The fracture pattern of roof in extra-thick coal seam is directional.From the transverse “O-X” fracture of overlying strata near the coal seam to the longitudinal “O-X”fracture pattern,the existence of roof fracture turning to critical layer is determined,the critical layer discrimination index is given theoretically,and the fracture height of overburden zone is obtained.(2)The overlying strata of extra-thick coal seam have “low-middle-high” layer structure characteristics,the high roof structure corresponds to the longitudinal fracture zone of overburden rock;The “low-middle” structure corresponds to the irregular and regular collapse zones of the blocks in the lateral fault zone of the overlying rock,respectively.The movement between layers is not synchronous,the separation between layers is significant,and the displacement curve of the same layer shows a step change.(3)The mechanical model of overburden structure in extra thick coal seam stope is established,which reveals the mechanism of complex strata pressure.The given overburden load and the force expression of support body are obtained.The effective control way of strata pressure in large space stope is found,and the idea of collaborative control of overlying strata in extra-thick coal seam is proposed.(4)The ground drilling repeated blasting technology is developed,and the ground drilling hydraulic fracturing engineering practice was carried out,which enriches the extra thick coal seam overburden far field control method;The near-field control technology and applicability of overburden are classified and analyzed,and the application practice is carried out in combination with specific engineering environment.The effect of roof pre-splitting pressure relief is remarkable.The location structure model of overlying strata is universal,which is suitable for general coal seam thickness conditions and enriches the stope pressure theory.Based on the research and development of coal mine permissible water gel liquid explosive,it provides conditions for repeated blasting of overburden ground drilling and broadens the technical level of overlying rock roof control;Chain arm saw continuous cutting machine fully realizes the mechanized top cutting operation of hard roof.This paper has 148 graphs,24 tables,128 references.