Inclined coal seam mining hyperbolic fracture field storage mine water quantity prediction and grading calling method

Abstract

The invention provides an inclined coal seam mining hyperbolic fracture field storage mine water quantity prediction and grading calling method, and aims at the problems of water resource loss and ecological degradation of western arid / semi-arid mining areas, a key layer theory and a hyperbolic fracture field distribution rule are combined, and a mine water storage quantity accurate prediction formula is established. And limitation of traditional empirical estimation is broken through. The gridding water storage structure is constructed through the soft mold bag pouring cutoff wall technology, and the design of the grouting waterproof curtain and the artificial dam body is matched, so that the water storage stability and the utilization rate are effectively improved. According to the method, a multi-stage grading calling system is innovatively designed, and grading purification and efficient calling of ecological restoration, industrial production and domestic water are achieved through valve control and underground in-situ filtration. Meanwhile, the water storage and transfer scheme is scientifically optimized, and the construction and operation cost is remarkably reduced. According to the method, economic, efficient and sustainable technical support is provided for green development and ecological restoration of a mining area while the utilization efficiency of mine water resources is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of mining area ecological protection and water resource reuse. Aiming at the problem of groundwater resource loss and ecological damage caused by inclined coal seam mining in arid / semi-arid mining areas in the west, a method for predicting and grading the amount of mine water stored in a hyperbolic fracture field in inclined coal seam mining is proposed. Background Art

[0002] Green, safe and efficient are the three major themes of coal mining today. As my country's coal development strategy shifts westward, large-scale mining of inclined coal seams in arid / semi-arid areas in the west has led to a sharp loss of groundwater resources and serious degradation of the ecological environment. Traditional horizontal coal seam technical means lack adaptability to the unique spatial morphology of goafs and the evolution of fissures in inclined coal seams, resulting in low mine water storage efficiency and high leakage risk, which cannot meet the diverse needs of ecological restoration and water resource utilization in mining areas. Therefore, it is particularly urgent to develop a new method for accurate water volume prediction and graded call for inclined coal seam mining scenarios.

[0003] The coal seams in the western mining areas of my country are thick and have a wide range of inclination angles. The large-scale development of inclined thick coal seams has caused a series of severe and complex ecological and water resource problems. On the one hand, mining activities have caused a large amount of mine water to be directly discharged and lost, and failed to be effectively retained and utilized. At the same time, the groundwater level in the mining area has dropped sharply, forming a groundwater drop funnel with the mining area as the core, which continues to expand and the depth of the funnel continues to deepen. This directly leads to the growth of surface vegetation being suppressed due to lack of water, gradually withering and dying, which in turn accelerates the process of land sandification and desertification, intensifies soil erosion, and frequently occurs. The landforms are severely damaged, the ecological landscape is fragmented, and the ecosystem service functions are greatly weakened or even lost. On the other hand, the existing technical means for the storage and utilization of mine water have significant limitations. Most traditional technologies focus on the horizontal coal seam mining scene, and lack in-depth and accurate analysis and adaptation strategies for the unique spatial morphology of the goaf and the complex fracture field distribution characteristics formed by the mining of inclined coal seams. For example, in the design of water storage structures, the asymmetric stress-deformation characteristics and anisotropic seepage laws of the rock strata in the goaf of inclined coal seams were not fully considered, resulting in poor stability of the water storage facilities, high risk of leakage, and difficulty in efficiently storing mine water; in the water quality treatment and water use distribution links, a scientific and reasonable hierarchical purification and call system was not established based on the diversified water use needs of the mining area, and the differentiated and stringent water quality standards for ecological restoration, industrial production and residents' lives could not be met, resulting in inefficient use of water resources and serious waste of value.

[0004] In summary, it is urgent to develop an innovative method for the storage and hierarchical utilization of mine water that suits the actual situation of inclined coal seam mining in western mining areas. This method needs to deeply integrate the theories of multiple disciplines such as geomechanics, hydrogeology, mining engineering, and environmental science, accurately control the overburden movement, fracture evolution, and mine water runoff mechanism caused by inclined coal seam mining, and build a stable, reliable, efficient, and intelligent mine water ecological utilization system in order to achieve a win-win situation between the economic benefits of coal mining and the ecological protection of the mining area, and lay a solid foundation for the sustainable development of western mining areas.

[0005] Therefore, it is necessary to design a method for predicting the storage volume of mine water in a hyperbolic fracture field during inclined coal seam mining and its hierarchical utilization. Through in-depth research on the fracture field distribution and goaf spatial morphology caused by inclined coal seam mining, the present invention innovatively proposes a precise prediction model for mine water reserves based on a hyperbolic fracture field and a grid-based water storage and hierarchical utilization system. Through the combined application of flexible mold bag water isolation walls, hierarchical filtration, and self-purification technologies, the efficient storage, hierarchical purification, and reasonable utilization of mine water are realized, significantly improving the ecological restoration efficiency and the comprehensive utilization efficiency of mine water, breaking through the technical bottleneck of traditional methods in the inclined coal seam scenario, and providing an economic, efficient, and sustainable solution for mine area environmental governance. Drill vertically from the ground to the coal seam in the center of the goaf to test and obtain the physical and mechanical parameters of each rock layer, and calculate the theoretical fracture block length of each key layer according to the parameters; the inclined coal seam working face is arranged along the dip and advanced along the strike. During the advancement of the working face, a concrete water isolation wall is poured parallel to the goaf at a certain interval using a flexible mold bag; calculate the subsidence of the rock layer at the water level based on the water level height obtained by drilling, and then according to the subsidence of the rock layer at the water level, the advancement distance of the working face, the coal seam thickness, and the dip angle, etc., the water storage volume in the goaf after the mining of coal seams with different dip angles can be obtained; the mine water stored in the inclined goaf is divided into multiple grid areas by the water isolation concrete wall, and the grids are connected in the artificial dam area, and the mine water utilization is controlled by valves. The mine water passes through multiple in-situ underground filtrations of iron nets and filter nets installed on both sides of the valves to achieve the purpose of multi-level utilization. Summary of the Invention

[0006] The present invention proposes a method for predicting the storage volume of mine water in a hyperbolic fracture field during inclined coal seam mining and its hierarchical utilization. Through in-depth research on the fracture field distribution and goaf spatial morphology caused by inclined coal seam mining, the present invention innovatively proposes a precise prediction model for mine water reserves based on a hyperbolic fracture field and a grid-based water storage and hierarchical utilization system. Through the combined application of flexible mold bag water isolation walls, hierarchical filtration, and self-purification technologies, the efficient storage, hierarchical purification, and reasonable utilization of mine water are realized, significantly improving the ecological restoration efficiency and the comprehensive utilization efficiency of mine water, breaking through the technical bottleneck of traditional methods in the inclined coal seam scenario, and providing an economic, efficient, and sustainable solution for mine area environmental governance.

[0007] In order to achieve the above purpose, a method for predicting and grading the amount of water stored in the mine in the hyperbolic fracture field of inclined coal seam mining is designed:

[0008] (1) Parameter acquisition: Drill a hole in the center of the goaf to obtain a core to measure the physical and mechanical parameters of the rock strata. The length of the fractured block in the key layer is calculated according to the key layer theory, laying the foundation for subsequent water storage calculations.

[0009] (2) Setting of water-blocking wall: The working face is arranged in a forward-leaning manner, and a flexible mold bag-cast water-blocking wall (spacing 300-500m, C30-C40 concrete) is set up in parallel with the goaf. The water is stored in a grid, with a coal pillar width of 40m-60m at the bottom and 20m-30m at the top, to enhance structural stability and prevent disorderly flow and leakage of mine water.

[0010] (3) Calculation of water storage capacity: The amount of rock layer subsidence is obtained by observing the water level in the borehole, and the water storage expression is derived in combination with the coal seam parameters (inclination 0°<α<60°), so as to accurately control the water storage capacity of the goaf. The parameters of the formula supporting water resource planning are derived from core experiments and actual mining area measurement data. Its accuracy is significantly higher than that of traditional estimation models, providing a scientific basis for ecological restoration and industrial water use planning.

[0011] The formula for rock subsidence is:

[0012]

[0013] The water storage capacity expression is

[0014]

[0015] Among them, D is the distance along which the working face advances along the strike, M is the thickness of the coal seam, α is the inclination of the coal seam, and H is c is the burial depth of the goaf center, H w is the critical layer thickness, is the average length of the broken blocks in the key layer below the water level;

[0016] (4) Gradual call mechanism: Mine water is graded and filtered, self-purified water is used for ecological reclamation, filtered water is supplied to industry once, filtered water is supplied to daily life twice or more, and water quality characteristics are optimized. Pumping wells are placed deep in the goaf to ensure water quality and quantity, and valves and dams coordinate to control water flow.

[0017] (5) Auxiliary engineering measures: artificial dam (C60-C70 concrete mixed with steel fiber) to retain water and prevent leakage; grouting to build water-blocking curtains at intervals of 300m-500m to reduce the cost of surface ecological water replenishment, prevent water outflow, improve the water storage efficiency of the mining area, and build a comprehensive mine water ecological utilization system.

[0018] Compared with the traditional method, the present invention has the following characteristics:

[0019] First, the accurate prediction model of mine water reserves: Based on the key layer theory and the hyperbolic distribution characteristics of the fissure field in the goaf of inclined coal seams, a mine water storage prediction formula was constructed. This model can replace the traditional empirical estimation, realize the accurate and scientific planning of water storage, and significantly improve the efficiency of water management for ecological restoration in mining areas.

[0020] Second, grid water storage and graded water use system: innovatively designed grid water storage layout based on flexible mold bag water barrier wall,

[0021] Combined with artificial dams and graded filtration technology, the ecological reclamation of mine water and the graded use of industrial water and residential water are achieved, providing an efficient and flexible water use solution for ecological restoration in mining areas.

[0022] Third, the whole process cost reduction and efficiency improvement design: through the flexible mold bag casting watertight wall and the grouting watertight curtain design with optimized spacing,

[0023] While ensuring structural stability, it reduces construction and operating costs and alleviates the problems of long-term water diversion energy consumption and equipment loss in the mining area.

[0024] Fourth, ecological and economic benefits are given equal weight: Combining hydrogeology and mining engineering theory, a full life cycle management model for mine water in inclined coal seam mining scenarios has been formed, which has achieved a significant increase in water resource utilization and provided a sustainable path for green development in mining areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A method for predicting and grading the amount of mine water stored in hyperbolic fracture fields during inclined coal seam mining

[0026] Figure 2 Plane surface

[0027] Figure 3 Concrete dam

[0028] Figure 4 flow chart

[0029] The components in the attached figure are marked as follows: 1. Surface monitoring borehole (optical fiber is arranged inside), 2. Separation layer grouting, 3. Aquifer, 4. Main key layer, 5. Goaf, 6. Aquifer, 7. Coal seam inclination, 8. Concrete dam body, 8.1 Valve switch, 8.2 Valve, 8.3 Filter, 8.4 Concrete trough, 8.5 Wire mesh, 9. Concrete water barrier, 10. Coal seam, 11. Monitor, 12. Monitoring borehole (optical fiber is arranged inside), 13. Grouting hole DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0031] (1) Drill a hole vertically from the ground surface to the coal seam in the center of the goaf, use professional drilling equipment to ensure that the diameter, depth and verticality of the hole meet the requirements, and obtain core samples. Test and obtain the physical and mechanical parameters of each rock layer, including rock density, elastic modulus, compressive strength, etc.

[0032] (2) According to the key layer theory and the physical and mechanical parameters of the overlying rock layers, the key layers in the overlying rock layers are determined, and the theoretical fracture block lengths of each key layer are calculated.

[0033] (3) The working face of the inclined coal seam is arranged along the dip and advanced along the strike. During the advancement of the working face, a concrete watertight wall is cast in parallel with the working face in the goaf at a certain distance using a flexible mold bag.

[0034] (4) The water level in the water storage void area is observed by drilling holes, and the amount of subsidence of the horizontal rock layer where the water level is located is calculated using the following formula.

[0035]

[0036] (5) According to the horizontal rock layer subsidence where the water level is located, the distance of the working face advancement, the thickness and inclination of the coal seam, etc., the expression of the water storage capacity of the goaf after mining at different inclination coal seams can be obtained:

[0037]

[0038] Among them, D is the distance along which the working face advances along the strike, M is the thickness of the coal seam, α is the inclination of the coal seam, and H is c is the burial depth of the goaf center, H w is the critical layer thickness, is the average length of the broken blocks in the key layer below the water level;

[0039] (6) The mine water stored in the inclined goaf is divided into multiple grid areas by waterproof concrete walls, and the grids are connected in the artificial dam area. The mine water is controlled by valves. The mine water is filtered in situ underground through the iron mesh and filter mesh installed on both sides of the valve, and can achieve multi-level calling purposes.

Claims

1. A method for predicting and grading the amount of water stored in a mine in a hyperbolic fracture field in inclined coal seam mining, characterized in that In order to solve the problem of groundwater loss and ecological damage caused by mining of inclined coal seams in arid / semi-arid mining areas in the west, the method can accurately predict the water storage capacity of the goaf after mining of inclined coal seams and provide a scientific basis for ecological planning of mining areas by storing mine water in a grid-like manner in the goaf and purifying it in stages. The method includes the following steps: (a) Drill a hole vertically from the ground surface to the coal seam in the center of the goaf, take core samples, and test the physical and mechanical parameters of each rock layer; (b) According to the key layer theory and the physical and mechanical parameters of the overlying rock layers, the key layers in the overlying rock layers are determined, and the theoretical fracture block length of each key layer is calculated; (c) The working face of the inclined coal seam is arranged along the inclination and advanced along the strike. During the advancement of the working face, a concrete watertight wall is cast in the goaf parallel to the working face using a flexible formwork bag at a certain distance; (d) The water level in the water storage void area is observed by drilling holes, and the subsidence of the horizontal rock layer where the water level is located is calculated according to the following formula (e) According to the amount of subsidence of the horizontal rock layer where the water level is located, the distance of advancement of the working face, the thickness and inclination of the coal seam, etc., the expression of the water storage capacity of the goaf after mining of coal seams with different inclination angles can be obtained: (f) The mine water stored in the inclined goaf is divided into multiple grid areas by waterproof concrete walls, and the grids are connected in the artificial dam area. The mine water call is controlled by valves. The mine water is filtered multiple times underground in situ through iron mesh and filter mesh installed on both sides of the valve, and can achieve multi-level call purposes.

2. According to the method for predicting and graded calling of mine water volume in hyperbolic fissure fields of inclined coal seam mining as described in claim 1, the water-isolating coal pillars in the inclined water storage goaf are cast using flexible mold bags, with a spacing of generally 300 to 500 m. The strength of the concrete is generally C30 to C40, and fibers are added to avoid cracks that cause water seepage.

3. According to the method for predicting and graded calling of mine water volume stored in hyperbolic fracture fields of inclined coal seam mining described in claim 1, the expansion coefficient of the overlying rock strata gradually decreases from the collapse zone to the fracture zone, and the general value range is 1.1 to 1.

3.

4. According to the method for predicting and grading the amount of mine water stored in a hyperbolic fracture field in inclined coal seam mining as described in claim 1, the coal seam inclination range is 0°<α<60°.

5. According to the method for predicting and graded calling of mine water volume stored in hyperbolic fracture fields in inclined coal seam mining as described in claim 1, the width of the water-blocking coal pillar at the bottom of the inclined water storage goaf is wider than the coal pillar at the top of the goaf. Generally, the width of the bottom water-blocking coal pillar is 40m to 60m, and the width of the top water-blocking coal pillar is 20m to 30m.

6. According to the method for predicting and graded calling of the amount of mine water stored in hyperbolic fissure fields in inclined coal seam mining as described in claim 1, the mine water stored in the goaf can be directly used for ecological reclamation and vegetation irrigation in the mining area after self-purification, the mine water that has been filtered once in situ underground can be used for industrial water in the mine or nearby factories, and the mine water that has been filtered twice or more can be used for domestic water, and the pumping wells for calling mine water should be designed deep in the inclined goaf.

7. According to the method for predicting and graded calling of mine water volume in hyperbolic fracture fields of inclined coal seam mining described in claim 1, under the condition that the water storage goaf is inclined along the strike, grouting is required at intervals of 300m to 500m along the strike to form a water-proof curtain, so as to reduce the cost of water diversion for surface ecological restoration.

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