Instability Mechanism Of The Coal Wall In Coalface With Large Dip Angle And Great Mining Height And Its Control

Due to abundant reserves of thick coal seam in our country, fully-mechanizedmining of coalface with great mining height, with increasingly prominent merits of itstechnology and significant improvement of the matching equipment, has alreadybecome the important development direction in terms of the mining of thick coal seam.However, the complicated occurrence conditions, such as the increase of the dip angleand the buried depth of the coal seam, and―three softness‖coal seam, pose greatchallenge for controlling the surrounding rock of the stope, leading to serious instabilityof the coal wall in the coalface, which greatly limit the exertion of the of advantages ofsafe and high-efficient mining of coalface with great mining height. Therefore,launching studies on the stability of the coal wall and the technology for safe andhigh-efficient mining in coalface with great mining height is of great realistic andtheoretical significances.Based on the investigations and statistics of the main instability forms of the coalwall and its instability characteristics, in view of the different mechanisms of theinstability of the coal wall in the coalface with great mining height, the present paperconducts scientific classifications of the instabilities, puts forward the concept ofstress-controlled instability and structure-controlled instability, and interprets theirconnotations.With the adoption of fundamental theories in elasticity, the present paper conductstheoretical studies to investigate the mechanism of the stress-controlled instability of thecoal wall, and analyzes the stress distribution law in the coal mass in front of thecoalface. According to the distribution law of the maximum principle stressσ1andmaximum shear stressτmax in the coal mass in front of the coalface, the author findsthat the splitting failure, leading to stress-controlled instability，is very likely to happenin the middle and upper part of the coal wall in coalface with great mining height, andthe shear failure, leading to structure-controlled instability, is likely to happen in theupper part of the coal wall. Using slide failure theory of wedge-shaped object combinedwith limit equilibrium method, we launch theoretical studies on the mechanism ofstructure-controlled instability, obtaining its judgment equation. In line with the volumeeffects of the structural plane in rock mechanics, we established the discriminantmechanism of stress-controlled instability and structure-controlled instability of the coalwall. Using theoretical studies, RFPA and PFC and UDEC numerical software, thepresent paper studies deep into the influences of the coal seam dip angle on the stress-controlled instability and structure-controlled instability of the coal wall incoalface with great mining height, acquiring its influencing law under followingconditions, different mining height, different coal mass intensity, different buried depthand different occurrence of structural planes, et al, providing technical train of thoughtfor controlling the stability of the coal wall in coalface with great mining height andlarge dip angle. Utilizing AHP-FCE comprehensive evaluation model, this paperconducts the evaluation of the stability of the Y110206coalface with great miningheight in Yangchangwan coal mine. According to the occurrence of the seam and thefully-mechanized technology of the coalface with great mining height as well as itsequipped level, the present paper conducts reasonable designing and equipmentselection, puts forward the security technology for the coalface with6.2m height andlarge dip angle and free burning seam, realizes the expected goal of producing10million of the coal, yielding significant technical and economic benefits.