Mechanism And Prevention And Control Of Rockburst In Extra Thick Coal Seams Under Super Thick Conglomerate Stratum

Taking Qianqiu Coal Mine as the engineering background, this dissertation uses stress estimation, numerical modelling, theoretical analysis and on-site measurement to study the mechanism and, prevention and control of the rockburst in extra thick coal seams under super thick conglomerate stratum based on overlying strata spatial structure theory, elastic-plastic mechanics, rock mechanics and material mechanics. The conclusions are as follows:To reveal the abutment stress distribution rule in extra thick coal seams under super thick conglomerate, the method of estimating the breaking angle of overlying strata was presented based on microseismic data, and stress transfer estimation model of super thick conglomerate stratum was established according to the abutment stress estimation model and the overlying strata spatial structure.The judgement criterion and evaluation method of rockburst risk were proposed based on stress superimposition estimation, and the evaluation result was verified to be consistent with the actual conditions by application in the No.21221and No.21141longwall panels in Qianqiu Coal Mine.Three kinds of rockburst mechanism in extra thick coal seams under super thick conglomerate in Yima coal field were presented, rockburst induced by coal plastic slip, rockburst induced by roof and floor shearing, and rockburst induced by floor buckling.①After the formation of the plastic slip line field, the coal(rock) with burst liability will burst violently along with the plastic slip plane under the effect of external force, and thus lead to rockburst.②the thin hard strata in the roof and floor will suffer from shear failure under high vertical and horizontal stress, and release huge amounts of elastic energy thus to result in rockburst.③the floor acts as a strut under the horizontal stress, and it will fracture and burst violently when it is impacted by mining and excavation disturbance.By on-site investigation and theoretical analysis, the mechanism of creep-induced rockburst was presented that the high external stress from static overlying strata spatial structure leads to creep-induced rockburst in the coal seam around dip roadways. Based on the mechanism, the technology system of creep-induced rockburst prevention and control was established in terms of rockburst evaluation, on-site monitoring, rockburst control and verification of destressing effect.The method and judgement criterion of rockburst early warning based on dynamic microseismic and stress contours was presented to concisely and visually achieve regional rockburst forecast and local rockburst early warning. This method has been applied in the Qianqiu Coal Mine and Yuejin Coal Mine and successfully implemented rockburst early warning for over20times.Combining the research results mentioned above, the technology system of rockburst prevention and control in extra thick coal seams under super thick conglomerate stratum was established and it has been applied in the Yima coal field with great effects.