Research On Water Inrush Prevention Technology Of Coal Seam Floor Lagging In Baizhuang Mine

On January 25,2016,at 4:15 am,an ordovician ash water inrush accident occurred in the east wing of the Baizhuang coal mine in Feicheng city,Shandong province.The Baizhuang mine is located in the Permian coal field of north China,which accounts for one third of the total coal production in China.However,due to its unique karst hydrogeological conditions,the carboniferous Permian coal field in north China is significantly endangered by the high confined water of deep ordovician limestone,and has an increasingly serious situation.In order to reduce the frequency of water inrush accidents or eliminate the occurrence of water inrush accidents,inestimable economic losses and adverse social effects on production and life can be avoided,the mechanism research and prevention and control practice of water inrush accidents between Austria and China should be carried out in depth.This paper adopts the research methods of theoretical analysis,field test,numerical simulation and engineering practice,etc.,with the purpose of explaining the mechanism of the large floor water inrush accident at the 8105 working face of baizhuang mine,and practices the key technologies for the prevention and control of the ordovician ash water damage on the floor.The main achievements are as follows:?1?Based on the analysis of geological and hydrogeological conditions of the mine and the working face,the characteristics of water inrush accidents on the 8105 working face are preliminarily analyzed.The stoppage time of water inrush from the overlying 7101 working face is 14 days,and the action of ore pressure shows the hysteresis of water inrush.?2?According to the theory of plastic slip to partition of mining face,could be divided into?mining working face in clusters,?mining stress before zero tensile fracture zone,inflation pressure relief after?mining area,?goaf stress compression region and other four areas.Then,according to the zero damage theory of the floor,the damage depth of the floor caused by the influence of coal mining is calculated,and the maximum damage depth of the floor is 15.2m.The critical water inrush coefficient of Ts was used as the hypothesis,and the rebuttal method was used in theory to prove the imperfection of the water-proof layer of coal floor during water inrush and the existence of hidden structural fracture zone,so that the effective water-proof layer thickness of the floor was less than the actual thickness.Therefore,it is theoretically determined that the cause of this water inrush accident is the ordovician limestone water inrush in the hidden structure of floor under the action of mining pressure.?3?Rfpa^2d-seepage numerical simulation software was used to simulate the evolution process of floor water inrush in the process of advancing the working face of baizhuang coal mine.A numerical model was established based on the stratum distribution in the comprehensive column diagram of the baizhuang mine field,and the evolution characteristics of cracks,distribution rules of mining stress and seepage characteristics of the working face floor were analyzed based on the simulation results.In the continuous mining process of coal seam,the working face floor will appear failure zone under the influence of ore pressure,and the failure depth will gradually increase.There is enough safe layer between the working face floor and the confined water of wuhui aquifer,but there is a hidden structural fracture zone in the axial part of syncline axis.The action of ore pressure breaks the equilibrium state of water pressure and pressure difference in the hidden broken zone of working face floor,and forms the hydraulic relation between wuhui aquifer and ordovician limestone aquifer.The mining-induced failure depth of the floor and the leading height of the aquifer increase suddenly,forming an integrated water inrush channel.At the same time,the buried fault structural fracture zone formed by the axial part of the synclinal axis of the coal seam passes through the section of the 8105 track channel directly below the working face of 7101,thus forming the 8105 track channel to block the five ash water,resulting in water inrush from the 8105 track channel,while the working face of 7101 has only a small amount of seepage.?4?The key technologies for the treatment of the synclinal fracture zone of the floor after water inrush in baizhuang coal mine are summarized,including the precision construction of the grouting borehole using the directional"closure roadway"on the ground,the drainage grouting and the backflow plugging.This treatment speed is quick,the effect is good,saved a lot of time for resuming mine safety production.