Research On The Law Of Rock Fragmentation And Swelling And Water Storage Characteristics In Goa Fareas Of Underground Reservoirs In Coal Mines

The technology of underground reservoir in coal mine is based on the idea of water preservation of "guiding storage" as the core.Using the rock caving void of goaf formed by coal mining as the main water storage space,the construction of artificial dam and mine water storage and water collection facilities at the same time,forming underground reservoir project has become an important method to solve the utilization and protection of water resources in western mining areas.The formation process of coal mine underground reservoir void water storage space is influenced by the movement of overlying rock strata in the "two zones" during mining,which is closely related to the scale and depth of mining working face,the mechanical properties of overlying rock in mining area,the rock size of caving rock and the distribution of crushing dilatancy.In this paper,the rock mass in the "two zones" of mining is taken as the research object.By means of laboratory test and numerical simulation,the related research on the rock mass dilatation,water storage coefficient and the dynamic change characteristics of water storage space in the "two zones" of overlying rock under multi-factor mining conditions is carried out.The main achievements of the paper are as follows:(1)The water storage characteristics of rock mass in mining-induced fracture zone of roof are tested.The test results show that:under the post-triaxial state of rock in the fracture zone of roof,the water storage coefficient of sandstone and mudstone samples is about 6.6%and 3.4%respectively.The initial porosity characteristics of rock samples are positively correlated with the dilatancy and water storage coefficient after triaxial loading.In different stress stages,the variation of the water storage coefficient of rock samples is dominated by the initial porosity,gradually transitioning to the stress,and finally dominated by the stress and the degree of dilatancy of rock mass and tends to be stable.The relationship between rock water storage coefficient and strain follows Weibull distribution with two parameters.(2)Tests on water storage characteristics of pore and fissure structure of rock mass in roof caving zone were carried out,and the test results showed that:Under the impact of 10-30J gradient energy,the water storage coefficients of sandstone,sandy mudstone and mudstone samples increase in the range of 10.29%-28.82%,6.19%-20.80%and 11.12%-40.89%,respectively.The relationship between impact energy and rock dilation and water storage coefficient follows the Logistic function variation rule.Under the impact condition,the water storage characteristics of rock samples are mainly water storage space of the main through fracture surface,supplemented by the surrounding shedding space and local dense fracture defect area.The impact energy is positively correlated with the fractal dimension of fragmentation and negatively correlated with the average fragmentation.(3)The paper carried out a lateral water storage compaction test for the falling rock cataclastic body,and concluded that the residual crushing coefficient and water storage coefficient of the cataclastic body had a negative correlation with the load and compaction time,and increased with the increase of the cataclastic body gradation;Under long compaction time,the cataclastic body shows the characteristics of large and small void compaction,rapid compaction after deformation and failure,and small deformation compaction.In the water storage environment,compared with sandy mudstone and mudstone,sandstone-like rock samples show obvious water-saturated softening characteristics,and broken rock blocks are more prone to deformation and destruction,further filling water storage space.(4)udec numerical simulation software is used to simulate the roof caving process of coal seam mining with different mining heights and different roof lithology.The simulation results show that:under the condition of large mining heights and weak roof,the distribution range and size of the simulated "arch" stress field are large,and the crushing and expansibility of the caving rock is relatively large.According to the stress change of simulated caved rock mass,the goaf is divided into low stress zone,stress lifting zone and high stress compaction and stability zone,and the water storage structure characteristics of caved rock mass in the zone are analyzed and evaluated.