Study On Fracture Conduction Characteristics And Water And Energy Storage Of Overburden Strata In Abandoned Mines

Coal resource of shallow part is becoming gradually exhausted in China,and a large number of coal mines are on the verge of closure.Meanwhile,there is a lot of space formed by mining in the abandoned coal mines.If the underground energy storage station could be built in the abandoned mine using the natural elevation difference between remaining mine roadway and goaf,it could not only preserve and use groundwater resources,but also bring huge economic benefits.Therefore,study on the abandoned mines reuse is not only the inevitable requirement for the development of its technology,but also meets the major needs of the national energy strategy.According to fracture development and water and energy storage of overburden strata after full mining in the abandoned coal mines,this paper uses many research methods such as theoretical analysis,numerical simulation and geophysical method to build the fractured rock mass model,simulate the evolution of mining-induced fracture in overburden strata,and analyze the fracture transmission and its evolution under coupled stress.This paper also measures the mining-induced fractures distribution of overburden strata in the abandoned mining area of a mine in the range of 1000 m×1000m,and deduces the hydraulic conductivity of fractured rock mass in abandoned mine,which provides the guidance for abandoned mines reuse.The main innovative points are as follows:(1)Based on the discrete medium model,the spatial distribution of discrete fracture network in the rock mass is studied.According to the basic fracture parameters in the research area,the probability model for the distribution of fracture parameters is designed and the fracture network reconstruction method is optimized.On this basic,the more suitable fractured model in the srudy area is reconstructed.(2)The spatial model of fractured rock mass is constructed.On this basic,the influence of rock mass integrity on its deformation is studied.Meanwhile,the block size and its distribution in the research area are analyzed,showing the rock mass attribute of small block in the study area.The development of mining-induced fractures and its evolution in overburden strata are also simulated.On this basic,the characteristic of mining-induced fracture in overburden strata after mining is revealed,that is,its shape is similar to an irregular "O".Meanwhile,the sensitivity factors of the distribution of mining-induced fractures are also analyzed.(3)Based on the optimized reconstruction method of fractured rock mass,this paper establishes a composite fractured medium model of groundwater seepage,simulates the movement of groundwater in fractured rock mass,and analyzes the transmission characteristics of fractured rock mass and its sensitivity factors.This paper also establishes the function relationship between the transmission characteristics and fracture parameters,such as fracture aperture,size and density.Meanwhile,the crack propagation under coupling stress is deduced.(4)Using the transient electromagnetic method(TEM),the mining-induced fractures distribution of overburden strata within 1000 m×1000 m in the abandoned mining area,Shanxi province,is measured,and the establishes the fracture model after fully mining with strong universality,that is,the fractures are distributed in the form of cracks.Meanwhile,this paper reveals the migration trajectory of groundwater in the abandoned mine,and deduces the hydraulic conductivity of overburden strata.It also puts forward the calculation criterion of the abandoned mines transmission,which should be based on the large-scale and macroscopic fractures.This paper provides theoretical guidance for the reuse of abandoned coal mines.The dissertation includes 99 figures,29 tables and 247 references.