A method for controlling roof drainage in multi-mining faces in monoclinal structural regions

Abstract

This invention discloses a method for controlled roof drainage in multi-face coal mining in monoclinic structural regions. Taking advantage of the characteristic that water level increases with depth in monoclinic structures, a layered and graded controlled drainage strategy is employed based on the differences in working face depth: firstly, the drainage water level is controlled at a preset water head threshold to ensure it is lower than the floor elevation of the first shallow working face being mined, meeting the safe mining conditions for the shallow working face; after the shallow working face is mined, the drainage water volume is gradually increased and the drainage water level is gradually decreased to adapt to the mining needs of the next deeper working face, and so on, achieving orderly mining of multiple working faces from shallow to deep. This method involves a one-time arrangement of drainage boreholes in the low-level roadway, using a controlled drainage approach to orderly prevent roof water hazards in each working face, reducing the dynamic water inflow of the working face, and exhibiting significant economic, safety, and environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of water hazard prevention and control in coal mining, and in particular to a method for controlling roof drainage in multi-faceted coal mining faces in monoclinic structural areas. Background Technology

[0002] In coal mining, roof water hazards are one of the major disasters threatening safe production. For water-bearing roof geological conditions characterized by thick roofs, high water content, and strong water abundance, existing mature water hazard prevention technologies generally employ a combination of pre-drilling drainage and delayed working face mining. Specifically, before mining, specialized boreholes are drilled in the roof area to drain water from the aquifer. Mining operations only commence after the roof water level has dropped to a safe threshold and the water hazard risk has been eliminated. This technology effectively reduces water inrush accidents caused by roof water during mining and has been widely applied in various water-rich roof mining scenarios. The technology is mature and stable, providing a fundamental guarantee for safe coal mining.

[0003] However, in multi-face mining scenarios within monoclinic structural regions, existing technologies have significant limitations, making it difficult to simultaneously ensure mining safety, economic efficiency, and water resource utilization. On one hand, when the working faces are arranged along a strike direction consistent with the monoclinic structure, traditional techniques require separate drainage boreholes for each working face area, resulting in large workloads, high costs, and long construction periods. On the other hand, while some improvements propose concentrating borehole construction in relatively low-lying areas of the monoclinic structure to achieve centralized drainage of water across multiple working faces to the lowest possible level, thus coordinating the mining of multiple faces, this improvement still has drawbacks. A single, full-volume drainage would significantly increase the dynamic water supply within the area, leading to excessive drainage volume and water resource waste.

[0004] Therefore, it is necessary to develop a new roof drainage method that is adapted to the characteristics of monoclinic structures and takes into account safety, efficiency and water resource protection, so as to further meet the actual needs of efficient and safe mining in multi-faceted monoclinic areas. Summary of the Invention

[0005] The problem to be solved by this invention is to provide a method for controlled roof drainage in multi-face coal mining in monoclinal structural areas. Combining the characteristic that the water level of monoclinal structures increases with burial depth, and taking advantage of the differences in burial depth of the working faces (low water pressure in shallow working faces and high water pressure in deep working faces), a layered and graded controlled drainage strategy is adopted to achieve orderly mining of multiple working faces from shallow to deep.

[0006] The present invention adopts the following technical solution: a method for controlling roof drainage in multi-coal mining faces in monoclinic structural areas, comprising the following steps: Step 1, collecting working face design data, geological and hydrogeological data of the area to be mined.

[0007] Step 2: Calculate the development height of the water-conducting fracture zone at the working face to determine the aquifers that need to be drained.

[0008] Step 3: Determine the location and depth of the drainage boreholes, establish a numerical calculation model of the area for simulation, and obtain the borehole spacing and total span.

[0009] Step 4: Using the numerical calculation model established in Step 3, determine the control head of the drainage holes before mining for each working face.

[0010] Step 5: Based on the hydrogeological parameters of the aquifer and the drawdown data of the working face, determine the time to start the drainage before mining for each working face using the Theis formula.

[0011] Step 6: Based on the hole spacing and total span, carry out drainage drilling construction, and arrange drainage holes in the low-level roadway in one go.

[0012] Step 7: Conduct controlled evacuation. Before mining the first working face, carry out the necessary evacuation and then start mining the first working face.

[0013] Step 8: Conduct controlled dredging in sequence before mining the subsequent working faces to complete the mining of the corresponding working faces.

[0014] As a preferred option, in step 1, design data of the working face in the area to be mined is collected, including: plan layout, mining strata, coal thickness, structural features of the area, roof strata structure, location of aquifer, aquifer permeability coefficient, and recharge and drainage conditions.

[0015] As an alternative, in step 2, conventional empirical formulas, numerical simulations, model experiments, and other methods are used to determine the height of the water-conducting fracture zone in the overlying rock of the working face. Then, based on the geological and hydrogeological data of the working face, the water-bearing rock strata affected by the water-conducting fracture zone are determined. The rock strata within this range are the aquifers that directly fill the working face during mining and also the aquifers that need to be drained in advance.

[0016] As a preferred option, in step 3, based on the layout of the working faces in the area, boreholes are arranged outward in the relatively low section of the lowest working face. The depth of the boreholes must penetrate all aquifers affected by the water-conducting fracture zones. The spacing and total span of the drainage boreholes are determined by numerical simulation.

[0017] A numerical calculation model of the region was established to simulate the sparse effect on the working face of the region under different hole spacing and total span, and to determine the hole spacing and total span of the boreholes.

[0018] As a preferred option, in step 4, the numerical calculation model established in step 3 is used to calculate the drainage effect on the area under different drainage pressure conditions of the drainage borehole, and observe the position of the line where the water pressure is 0, so as to determine the control head of the drainage hole required to achieve 0 pressure in each working face area.

[0019] As a preferred option, in step 5, the time t required for borehole drainage to reach a steady flow is determined according to the Theis formula; In the formula: The water storage coefficient; denoted by ρ, where ρ is the hydraulic conductivity and r is the radius of influence.

[0020] Furthermore, , Permeability coefficient, The drawdown for each working face is obtained by subtracting the control head of the drainage holes before mining from the initial water head of the drainage boreholes.

[0021] As a preferred option, in step 6, a special drilling rig for coal mine water exploration and drainage is used to carry out the construction of drainage boreholes according to the borehole spacing and total span. During the drilling construction, the borehole pipe and blowout preventer valve are installed in accordance with the relevant regulations and specifications. After the construction is completed, the borehole valve is in the closed state.

[0022] As a preferred option, in step 5, the required drainage is completed before the first working face is mined: at time t before the working face with the highest altitude and lowest water pressure is mined, the drainage hole is opened for drainage. A normally open pressure reducing valve is installed at the drainage hole opening. The closing pressure of the valve is set to the pressure corresponding to the control water head of the drainage hole of the first working face. That is, the drainage borehole continuously drains water. When the water head is lower than the set pressure, the borehole is closed to achieve controlled drainage.

[0023] As a preferred option, in step 5, controlled dredging is carried out sequentially before the subsequent working face mining. According to the set time for starting dredging before the working face mining and the control water head of the dredging hole before each working face mining, controlled dredging is carried out in an orderly manner before the mining of the high area working face, so as to complete the mining of the corresponding working face.

[0024] Compared with existing technologies, the present invention has the following technical effects: 1. The method of the present invention combines the characteristic that the water level of a monoclinic structure increases with burial depth, and utilizes the difference in burial depth of the working face (low water pressure in shallow working faces and high water pressure in deep working faces) to adopt a layered and graded controlled drainage strategy: first, the drainage water level is controlled at a preset water head threshold to ensure that the water level is lower than the bottom plate elevation of the first shallow working face to be mined, thus meeting the safe mining conditions of the shallow working face; after the shallow working face is mined, the amount of water drained from the borehole is gradually increased and the drainage water level is reduced to adapt to the mining needs of the next deeper working face, and so on to achieve orderly mining of multiple working faces from shallow to deep.

[0025] 2. The method of the present invention only requires the construction of a small number of drainage boreholes in a single roadway in a low-lying area of ​​a monoclinic structure, which can comprehensively cover the water hazard prevention needs of multiple working faces, significantly reducing the amount of drilling, shortening the preparation period, and reducing mining costs; at the same time, by controlling the drainage water level in layers and grades, it avoids the waste of a large amount of water resources caused by a one-time full drainage, effectively controls the amount of dynamic water replenishment, and achieves the rational utilization of water resources.

[0026] 3. The method of the present invention can realize the orderly advancement of multiple working faces according to the mining progress, taking into account both safety and economic benefits, and solves the problem of overall planning and economy in the prevention and control of roof water hazards in multiple working face areas of monoclinic structures. Attached Figure Description

[0027] Figure 1 This is a plan view of the construction block of the numerical calculation model in an embodiment of the present invention.

[0028] Figure 2 This is a schematic diagram of the numerical calculation model and boundary condition settings in an embodiment of the present invention.

[0029] Figure 3 This is a cloud diagram showing the initial water pressure calculation of the numerical calculation model in an embodiment of the present invention.

[0030] Figure 4 This is a cloud map showing the water pressure drainage effect in an embodiment of the present invention when the spacing between drainage holes is 50m and the total span is 2800m.

[0031] Figure 5 This is a cloud map of the water pressure field in the region when the water head controlled by the drainage hole is 55m according to an embodiment of the present invention.

[0032] Figure 6 This is a flowchart illustrating the steps of the method for controlling roof drainage in multi-mining faces in monoclinic structural areas according to the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the application will be further described in detail below with reference to the accompanying drawings. The described embodiments are only a part of the embodiments involved in this invention. All non-innovative embodiments based on these embodiments by other researchers in the art are within the protection scope of this invention. Furthermore, the step numbers in the embodiments of this invention are only set for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0034] In one embodiment of the present invention, the method of the present invention was used in the 110505 and 110507 working faces of a certain mine to prevent water hazards in the thick-layered sandstone aquifer in the roof. The specific implementation process is as follows: Figure 6As shown, this includes: 1. Collecting design data, geological and hydrogeological data for working faces 110505 and 110507: Specifically, working face 110505 adopts fully mechanized longwall mining technology, with a mining elevation of +1282m to +1151m and a relative ground elevation of +1638m to +1822m. The working face has a strike length of 2358m, a dip length of 250m, a dip angle of 8 to 34°, an average of 22°, and a coal seam thickness of 8 to 11m, with a designed mining thickness of 10m. The distance from the roof of coal seam 5 to the Zhiluo Formation within the working face is 20 to 163m, and the thickness of the Zhiluo Formation within the working face is 140 to 330m.

[0035] The 110507 working face mines the No. 5 coal seam, with a thickness of 10m, using the strike-longwall full-thickness single-pass top coal caving method. The average elevation of the coal seam in the working face is +1086m, with a strike length of 2128m and a dip length of 360m. According to the statistics from boreholes X602, K2004, X702, and K2105, the average elevation of the Zhiluo Formation floor is +1297.96m, and the thickness of the Yan'an Formation aquifer in the No. 5 coal seam floor is 75.63m. Notably, the area where this working face is located has a monocline structure with an average stratum dip angle of 8.3°, and the average permeability coefficient of the Yan'an Formation and Zhiluo Formation aquifers in the roof is 0.8192m / d.

[0036] 2. Calculate the development height of the water-conducting fracture zone in the working face and determine the aquifer that needs to be drained: Based on the measured data of the development height of the water-conducting fracture zone in the mining area, the fracture-to-mining ratio of coal seam No. 5 in the mine is 19. The development height of the water-conducting fracture zone is calculated as the coal thickness multiplied by the fracture-to-mining ratio, i.e., 10×19=190m.

[0037] Based on the structure of the top strata, it was determined that the fracture zone developed through the Yan'an Formation and entered the Zhiluo Formation. Therefore, it is necessary to drain the water in the sandstone aquifers of the Yan'an and Zhiluo Formations.

[0038] 3. Determine the location and relevant parameters of the drainage boreholes: Based on the location of the two working faces in the mining area, the stratigraphic level of the working faces, design data, etc., a numerical calculation model was constructed using finite element numerical analysis software. The numerical calculation range is as follows: Figure 1 As shown.

[0039] Specifically, the upper boundary is defined by the +1290m water level line, the left and lower sides extend 1500m beyond the working face boundary, and the right side is defined by the F2 reverse fault. The model is trapezoidal in shape, with upper and lower side lengths of 4464m and 7759m respectively, and a height of 2459m.

[0040] like Figure 2As shown, the upper boundary of the model is a non-ingress boundary with a water pressure of 0; the right side is a reverse fault with a non-ingress boundary; the left side is a variable head boundary, and the entire numerical model region is monoclinal with an average dip angle of 8.3° (tan8.3°=0.146). The water pressure at the left boundary is (2459-y)×1460 Pa; the lower boundary is an ingress boundary with a water pressure of 2459×1460 Pa.

[0041] like Figure 3 As shown, the model has a natural water pressure field. Before mining, the original water head height in the area was +1290m, corresponding to the upper boundary water pressure. The overall tilt angle of the model is 8.3°, and the calculated lower boundary water pressure is 3.59MPa.

[0042] Furthermore, a drilling site was arranged in the relatively low-lying transport roadway of the 110507 working face, with boreholes extending outwards. These boreholes needed to reach the Zhilu group. The water pressure field cloud map formed when the borehole spacing was 50m and the total span of the borehole arrangement was 2800m, assuming all boreholes were fully discharged, is shown below. Figure 4 As shown, it can be seen that the 110505 and 110507 working face areas can be completely cleared, and the final drilling spacing is determined to be 50m with a total span of 2800m.

[0043] 4. Determine the control head of the drainage boreholes before mining of working faces 110505 and 110507: Using the numerical analysis model in step 3, and setting the control head of the drainage boreholes at 55m, the calculated water pressure field cloud map of the area is as follows. Figure 5 As shown in the figure. It can be seen that this control head can achieve safe mining at 110505 m. Under the condition that the control head of the drainage borehole is set to 0 m, the calculated water pressure field cloud map of this area is shown in the figure. Figure 4 As shown, this control head is sufficient to ensure safe mining of the 110507 face. Therefore, the control heads for the drainage holes before mining of the 110505 and 110507 working faces are determined to be 55m and 0m, respectively.

[0044] 5. Determine the time for starting drainage before mining each working face: Based on the hydrogeological parameters of the aquifer and the drawdown data of the working face to be drained, the drainage time before mining of working faces 110505 and 110507 is calculated to be 120 days and 130 days respectively, by substituting into the Theis formula.

[0045] 6. Drainage drilling construction: Based on the hole spacing and total span, a special drilling rig for coal mine water exploration and drainage is used to carry out drainage drilling construction. The drainage drilling hole is equipped with a 16m orifice pipe. During construction, a blowout preventer valve is installed. After construction is completed, the orifice valve is in the closed state.

[0046] 7. After completing the required drainage before the first working face is mined, the 110505 working face will be mined: 120 days before the 110505 working face is mined, the drainage hole will be opened for drainage. A normally open pressure reducing valve will be installed at the drainage hole opening. The valve is set to close at 0.55 MPa. That is, the drainage borehole will continuously drain water. When the water head is lower than 0.55 MPa, the borehole will be closed to achieve controlled drainage.

[0047] 8. Continue controlled dredging before mining the 110505 working face to complete the mining of the working face.

[0048] If a controlled drainage method is not used, and the water head in the drainage borehole is directly reduced to 0 at the beginning, then the total water volume of the drainage borehole calculated based on numerical values ​​is 1447.28 m³. 3 / h; After adopting the method of the present invention, during the mining at 110505, the total water volume of the drainage borehole was 803.31m. 3 / h, relatively reducing drainage by 643.97m 3 / h. The 110505 working face is 2230m long, designed for 23.7 months of mining, and can relatively save 643.97 × 24 × 23.7 × 30.5 = 11171849.148m of drainage. 3 .

[0049] It is evident that the method of the present invention is designed for working conditions with multiple working faces arranged in a single inclined area. It arranges drainage boreholes in the low-level roadway in one go and adopts a controlled drainage method to orderly realize the prevention and control of roof water hazards in each working face, effectively reducing the dynamic water inflow of the working face, and has significant economic, safety and environmental benefits.

[0050] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for controlling roof drainage in multi-mining coal faces in monoclinal structural regions, characterized in that, Includes the following steps: Step 1: Collect working face design data, geological and hydrogeological data for the area to be mined; Step 2: Calculate the development height of the water-conducting fracture zone at the working face to determine the aquifers that need to be drained; Step 3: Determine the location and depth of the drainage boreholes, establish a numerical calculation model of the area for simulation, and obtain the borehole spacing and total span. Step 4: Using the numerical calculation model established in Step 3, determine the control head of the drainage holes before mining for each working face; Step 5: Based on the hydrogeological parameters of the aquifer and the drawdown data of the working face, determine the time to start drainage before mining for each working face using the Theis formula. Step 6: Based on the hole spacing and total span, carry out drainage drilling construction, and arrange drainage holes in the low-level roadway in one go. Step 7: Conduct controlled evacuation. Before mining the first working face, carry out the necessary evacuation and then start mining the first working face. Step 8: Conduct controlled drainage sequentially before mining the subsequent working faces to complete the mining of the corresponding working faces; in Step 2, the aquifers that need to be drained are determined as follows: The height of the water-conducting fracture zone in the overburden of the working face is calculated based on the coal thickness and the fracture-mining ratio, using empirical formulas, numerical simulations, and model experiments. Based on the geological and hydrogeological data of the working face, the aquifers affected by the water-conducting fracture zone are identified, and the strata within the affected range are identified as aquifers that need to be drained in advance. In step 3, the location of the drainage drill holes is determined as follows: Based on the layout of the working face in the area to be mined, boreholes are arranged outward in the low-level roadway of the lowest working face. The borehole depth needs to penetrate all aquifers affected by water-conducting fracture zones. A numerical calculation model is established by numerical simulation method to simulate the drainage effect on the working face of the area under different borehole spacing and total span, and to determine the layout spacing and total span of the drainage boreholes. In step 5, the time t required for borehole drainage to reach steady flow is determined according to the Theis formula: ； In the formula: The water storage coefficient; The coefficient of conductivity; To affect the radius, , The permeability coefficient represents the drawdown at each working face. The initial water head of the drainage borehole is minus the control water head of the drainage borehole before the working face is mined. In step 7, the necessary drainage is carried out before the first working face is mined. At time t before the working face with the highest altitude and lowest water pressure is mined, the drainage hole is opened for drainage. A normally open pressure reducing valve is installed at the drainage hole opening. The valve is set to close at the pressure corresponding to the control water head of the drainage hole of the first working face. The drainage borehole continues to drain water. When the water head is lower than the set pressure, the borehole is closed to achieve controlled drainage. In step 8, controlled dredging is carried out sequentially before the subsequent working face is mined. According to the set time for starting dredging before the working face is mined and the control water head of the dredging hole before each working face is mined, controlled dredging is carried out sequentially before the mining of the high area working face, and the mining of the corresponding working face is completed.

2. The method for controlling roof drainage in multi-mining coal faces in monoclinal structural areas according to claim 1, characterized in that, The working face design data for the area to be mined includes: plan layout, mining strata, coal thickness, structural features of the area, roof strata structure, location of aquifers, aquifer permeability coefficient, and recharge and drainage conditions.

3. The method for controlling roof drainage in multi-mining coal faces in monoclinal structural areas according to claim 1, characterized in that, In step 4, the control water head of the drainage holes before mining of each working face is determined as follows: Based on the numerical calculation model, under different drainage pressure conditions of the drainage borehole, the drainage effect of the corresponding area is calculated, the water pressure field cloud map of the area is obtained, the position of the line where the water pressure is 0 is observed, and the control head of the drainage hole required to achieve 0 pressure in each working face area is determined.

4. The method for controlling roof drainage in multi-mining coal faces in monoclinal structural areas according to claim 1, characterized in that, In step 6, according to the hole spacing and total span, a special drilling rig for coal mine water exploration and drainage is used to carry out the construction of drainage holes, and the orifice pipe and blowout preventer valve are installed. After the construction is completed, the orifice valve is in the closed state.

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