Bearing Pressure Of Hard Roof In Guo Zhuang Coal Mine Study On The Mechanism Of Water Inrush From Floor Mining In Water

With the rapid development of China's economy,energy plays an increasingly important role in China's national economy.As the largest energy source in China for a long time,coal plays an important role in China's economic development.As a result,with the increase of coal mining volume in China,it is inevitable to encounter the double threat of mining coal seam in the process of hard roof and floor aquifer high pressure water.After the hard roof working face is mined,because the roof strength is too high,a large area of the roof will be suspended,resulting in the roof hanging and not collapsing.With the development of coal mining,the hanging distance of the hard roof becomes larger and larger,and the roof finally reaches the bearing limit,resulting in a large area of roof collapse.The impact caused by the large area collapse of the hard roof makes the problem of water inrush more prominent.However,the research on floor water inrush is mainly focused on the damage of floor water isolation caused by coal mining process.There is little research on the coupling effect of hard roof collapse on floor impact and floor failure in mining process of pressure water face.In view of the above problems,this paper provides a new idea for the prediction and prevention of water inrush from the bottom floor of coal mine.The specific research contents of this paper are as follows:(1)By using the method of similar material simulation,this paper studies the deformation and failure characteristics of coal seam floor in the process of hard roof caving,which has gone through four stages:the stress concentration of the floor before coal mining.the stress unloading of the floor after coal mining,the impact of hard roof caving on the floor and the compaction.Based on the analysis of the data collected by stress meter and the actual collapse situation,it is considered that the development and failure of the floor cracks are mainly concentrated in the second and third stages,and the phenomenon of delayed failure of the floor will occur.(2)Based on the mechanical theory,this paper analyzes the secondary deepening failure of the floor caused by the backwardness of the hard roof.First,the collapse form of roof is analyzed.According to the hard condition of roof,the collapse of roof can be divided into break type and pull bend type.Among them,the pull bend type failure form which is easy to cause the floor water inrush and other serious coal mine accidents is mainly studied.According to the theory of half space inelastic collision,the relation curve between roof impact stress and time is deduced by mechanical formula.Finally,according to the theory of elasticity,the mechanical model of floor failure under the superposition of floor confined water and roof collapse is analyzed.From the view of mechanical model,the mechanical failure mechanism of floor under the impact of hard roof is analyzed.(3)The dynamic module and seepage module of FLAC3D are used to simulate the floor failure under different conditions.The parameters of the roof impact stress and time in the derivation of the theoretical formula are adjusted to simulate the stress characteristics of the floor under different impact strength and the development of the floor cracks.According to the parameters of the seepage module,the water pressure of the floor of different aquifers is adjusted to analyze the fracture development and the change of floor pore water pressure under different water pressure.Finally,through the analysis of the different buried depth of the hard top plate mining face under the pressure of water floor cracks development.Through the analysis of the above three schemes,the failure rule of the floor under different parameters is provided a theoretical basis for the mining face above the pressure water of the hard roof.(4)In the mining practice of the working face above the pressure water of the hard roof,through the above theoretical analysis,the floor cracks are secondary developed due to the impact of the collapse of the hard roof,and the difficulty of floor treatment is further improved.In practice,the combination of transient electromagnetic method dynamic detection and drilling verification is used to judge the damage of the floor and to reinforce the floor with grouting technology,which effectively inhibits the development of the floor cracks and improves the water inrush resistance of the floor.It realizes the safe mining of working face and creates huge economic value.