| With the coal mining extending to the deep,the problem of limestone water damage in coal seam floor has become one of the biggest technical problems in North China type coalfield mining.Yongcheng mining area is located in the hinterland of Huanghuai Plain,which is a typical area of North China type coal field threatened by water inrush from Carboniferous and Ordovician limestone in the floor.From 1982 to 2019,19 large limestone water inrush accidents occurred,including 9 in Chensilou Coal Mine.Through the case analysis and research of water inrush accidents in Chensilou Coal Mine over the years,and the checking calculation based on the theory of water inrush coefficient,the water inrush points of each mining head in the coal mine calculated according to the water pressure and the thickness between the coal seam floor and the upper water bearing section of Taiyuan formation are all not greater than 0.06mpa/m of the abnormal stratum block,and no fault or fold with obvious breakpoint is exposed near the water inrush point The comprehensive analysis shows that the mine outburst has the typical characteristics of karst fissure water inrush in the limestone of deep Taiyuan formation.Therefore,based on the collection and analysis of the geological and hydrogeological conditions in the study area,the paper takes the typical 2517 fully mechanized face with large buried depth and high pressure bearing in Chensilou Coal Mine as the research object,and adopts the methods of plastic theory and empirical formula calculation,numerical simulation of the stress change of the roof and floor and the damage characteristics of the roof and floor,underground field test and indoor rock sample test In this paper,the deformation and failure of deep mining coal seam floor and the mechanism of water inrush from limestone fracture of Taiyuan Formation under high pressure are studied systematically.The main achievements are as follows:(1)The representative 2517 fully mechanized coal face with large buried depth and high pressure water in the floor is selected as the research object.By using theoretical formula,plastic theory,indoor FLAC~3DD numerical simulation and underground working face drilling combined with high-density electrical method,the maximum damage depth values of the mining floor are obtained respectively.It is revealed that under the condition of large buried depth and high pressure water,coal seam Two 2 is under the condition of large buried depth and high pressure water The evolution characteristics of the floor failure in the mining process,the influence scope of the deformation failure form and the horizontal direction of the coal seam floor are drawn,and the corresponding modified empirical formula is put forward.(2)Based on the characteristics of deformation and failure evolution of mining floor in deep buried area,the water inrush mode of limestone fracture type expansion of Taiyuan Formation of mining floor in the whole section of the study area is established.The water inrush concept that the deformation and failure of mining floor gradually develop downward and the fracture of high water pressure aquifer gradually develop upward and even connect under the combined action of high ground stress and high water pressure is analyzed.The critical water inrush mode is proposed The expression of effective aquifer thickness is given and checked according to the actual data.(3)Based on the study of the failure evolution characteristics of the deep mining floor and the mechanism of water inrush of limestone fracture type in Taiyuan formation,through the comparison and analysis of the core sample observation before and after the underground grouting and the limestone sample strength measurement in the ground laboratory,the target rock layer,grouting material and the diffusion radius of the slurry are determined,and it is clear that the pure cement slurry is the mine The best material for grouting transformation of coal seam floor.(4)It is found in the laboratory experiment that under the action of high pressure water erosion,the cracks in the limestone rock of Taiyuan formation without grouting develop,resulting in the decrease of the compressive strength of the rock mass;after the reinforcement of the coal seam floor with cement slurry,all kinds of pores in the coal seam floor are filled,and the mechanical strength of the rock increases obviously.In this project,the construction grouting drilling and investigation drilling are combined to measure the slurry diffusion radius on site.The length of the slurry diffusion radius is closely related to the development scale of the rock fracture network,the length and width of the fracture development and the main agent material of the slurry.The migration diffusion radius of the slurry injected with montmorillonite and cement as the main agent of the grouting is larger than that of the slurry injected with pure cement as the main agent,but the rock after the grouting is stronger The former is lower than the latter.(5)According to the grouting horizon,grouting radius and grouting materials determined by the study,three typical deep and high pressure working faces in the South five mining area are selected for the project to carry out the grouting transformation of the floor of coal seam 22.The transient electromagnetic detection was carried out before the grouting reinforcement of the bottom plate of each test fully mechanized working face,and the abnormal water rich area was found out.After the grouting reinforcement of the working face,the transient electromagnetic detection technology was used to verify the grouting transformation effect of the working face,so as to guide the grouting transformation design and construction,and realize the safe mining of the working face under the condition of large buried depth and high pressure.The project basically established the technological process of water prevention and control in the research area for the water inrush of the Taiyuan limestone fracture type.This dissertation includes 93 figures,24 tables and 157 references. |
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