Research On Roof Failure Law And Water Inrush Risk Evaluation Of Coal Seam Mining

As the mine proceeds deeper,it faces the problems of high geostress,high water pressure and the damage of aquifers produced by mining of overlying coal seams and the accumulation of mined-out water,and the potential danger of water inrush from the roof is correspondingly increased.At the same time,for a coal mine where limestone is directly roofed,how is the roof rock layer broken and what is the law of destruction?When the next group of coal seams are mined,will the goaf water,sandstone water and limestone water be poured into the underground?And so on are all topics worth studying.Based on the National Natural Science Foundation of China and the project commissioned by the enterprise,the paper studies the rock breaking law of roof rock under the condition of 10#coal seam mining in Xinzhi Mine,establishes a water inrush risk assessment model for limestone roof,and conducts water inrush danger Sexual evaluation,and put forward targeted water control measures.The following research and work results have been achieved:(1)Through analysis of mine hydrogeological conditions,on-site coal mining practice and rock sample water sample test and other data,combined with the theory of"masonry beam"and key layer,we get:1)K2 limestone strength at the top of coal bed 10#in Xinzhi mine Mainly affected by water rock action,the stronger the action,the lower the strength;2)The critical condition of instability is the angle between the broken rock blocks of the roof,the smaller the angle,the more stable;3)The height of the collapse zone is follower The destruction height of the rock layer and the fracture zone fracture height depend on the fracture penetration of the old roof.(2)The step-by-step fine simulation of the failure process of the roof under mining disturbances was performed using Flac3D,and the following conclusions were obtained:1)Compared with the failure characteristics of mudstone and sandstone roofs,under the same conditions,the initial breaking step of the old roof of the limestone roof was larger,The failure cycle of the rock roof is longer,which is more likely to cause the phenomenon of slipping and instability of local blocks;2)The height of the collapse zone of the limestone roof is about 12m,and the height of the fracture zone is about 62m,which is basically consistent with the empirical formula;Under the conditions,the damage of the roof and floor of the coal seam will be intensified.Under the influence of large-distance water-conducting faults or water-conducting sinking columns,there is a possibility that the bottom Ordovician limestone water replenishes the roof aquifer.(3)On the basis of theoretical analysis and numerical simulation,the"three figures and two predictions"method was used to construct the limestone roof water inrush risk evaluation model,and the water inrush risk of the roof directly filled aquifer and old empty water was calculated in detail and evaluation.it was concluded that:1)There are four zones of the water-filled aquifer directly on the roof of the 10#coal seam.Most of the zone is in the water inrush danger zone,and only the water inrush threat at the boundary is small;2)Under normal conditions,the old empty water in the 2#coal seam goaf is safe throughout the study area,and there is basically no threat of water inrush;3)The water-rich coefficient comparison method predicts that the water inrush in the+450 level 10#coal seam face is less than 50m~3/h.