| The Jurassic coalfield in northern Shaanxi has thick coal seams,many layers,shallow burial,good coal quality and relatively simple mining conditions,making it one of the seven largest coalfields in the world.Since the large-scale development of Jurassic coalfields in northern Shaanxi,the scale and output of coal production have increased year by year.Under the condition of repeated mining of shallow buried coal seams,coal mining will cause serious leakage of groundwater in the overlying rock,aggravate surface water and soil loss,and huge impact on the surface ecological environment.Therefore,it is of great significance to explore the temporal and spatial evolution law of water-conducting channels under the condition of repeated mining of shallow-buried coal seams,which is of great significance for the safe and efficient mining of coal mines and the effective protection of the ecological environment of the mining area.In order to study the development law and influencing factors of the water-conducting fissure zone under the conditions of repeated mining of shallow buried coal seams in northern Shaanxi,revealing the temporal and spatial developmental characteristics of aqueducts.This paper takes the Anshan mine field in the Fugumiaohagu mining area of northern Shaanxi as the research object,starting from the three influencing factors of working face layout,working face advancing speed and coal seam spacing,studying its influence on the development law of the water-conducting fracture zone.Theoretical analysis,numerical simulation and physical similar material simulation were used to analyze the spatiotemporal evolution of water diversion channels under the conditions of repeated mining of shallow buried coal seams.By establishing a solid-liquid coupling similar material mold experiment,the seepage characteristics of the water diversion channel under the solid-liquid coupling state were analyzed.The main results are as follows:(1)Mining under the condition of shallow buried double coal seam increases the width of the retained coal column,and the height of the fracture zone and the height of the collapse zone decrease.The height of the water-conducting fissure zone is reduced by 13%compared with the 20m coal column;the mining speed is inversely correlated with the development height of the water-conducting fissure zone;after the coal mining of the lower seam is completed,When the distance between the double coal seams is 40m,compared with the distance of 20m,due to the greater effect of the supporting force of the overlying rock,the development height of the water-conducting fractures is reduced by 45%,and the height of the water-conducting fracture zone is more difficult to penetrate to the upper coal goaf.(2)During the repeated mining of shallow buried coal seams,the fissures develop more intensively,but the development rate is stable,and the fissures are“double trapezoidal"longitudinal distribution.From mining to advancing to the ravine,the length of fracture development shows a decreasing-increasing-decreasing trend;when the working surface is pushed through the ravine,the fracture development rate shows a trend of first increasing-stabilizing-incre-asing,the fracture development density decreases,and the development range affects the overburden of the upper coal goaf.(3)After the double-coal seam mining is completed,a large number of water bodies break through the water-resistant laterite layer and infiltrate into the rock layer below the soil-rock junction,resulting in soil and rock formation.The water content of the junction surface layer increases,the water content of the aquifer decreases,the infiltration of the water in the middle part of the overlying rock in the gob is larger than that on both sides of the overlying rock in the gob,and the infiltration rate is also faster.According to the measurement results of water content,the prediction formula of water content of different layers after the completion of double coal seam mining is established. |
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