Methods to reduce water inflow at the working face by coordinating roof drainage with mining progress

Abstract

This invention discloses a method for coordinating roof drainage with mining progress to reduce water inflow at the working face. The method includes: collecting design data, geological and hydrogeological data of the working face to be mined; calculating the development height of the water-conducting fracture zone at the working face to determine the aquifers to be drained; determining the layout parameters of the drainage boreholes; constructing the drainage boreholes; determining the advance drainage distance and planning the division of drainage sections at the working face; drilling and draining the first drainage section; mining the first section of the working face while simultaneously drilling and draining the second drainage section; mining n sections of the working face sequentially while simultaneously drilling and draining the (n+1)th drainage section; and mining the last section of the working face. This method establishes a dynamic matching mechanism between mining and drainage, ensuring real-time safe drainage at the mining face and in key areas ahead, effectively reducing the amount of work and total underground drainage, ultimately achieving a balance of safety, economy, 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 reducing water inflow at the working face by coordinating roof drainage with mining progress. Background Technology

[0002] In underground coal mining, thick layers of water-bearing rock in the roof are a common geological condition in many mining areas of my country. These rock layers are rich in water and have hydrostatic pressure. If not properly managed, they can easily cause water hazards such as roof water inrush and water surge, resulting in equipment damage, work interruption, and even threatening personnel safety. Therefore, roof water hazard prevention is a key aspect of safe coal mine production. To prevent water hazards and ensure continuous and safe mining, roof drainage technology has become a mature core method and is widely used in relevant coal mines across the country. Its core logic is to actively drain roof water to reduce water pressure. The implementation method is as follows: before mining, drainage boreholes are drilled in the mining roadways and roadways towards the water-bearing rock layers in the roof to form drainage channels to guide the water into the underground drainage system. Mining is only resumed after the water volume has been drained to a safe threshold, thus eliminating the potential water hazard at its source.

[0003] Currently, the mainstream water drainage operations in the industry mostly involve drilling in the roadway and generally adopting a pre-emptive full-face drainage model. This means that the roof water in the entire mining area is drained before mining begins, ensuring that there is no water hazard threat throughout the entire mining process. This model requires the drainage of two parts of water: first, the static water reserves of the roof aquifer itself, which is the inherent water volume of the strata and is not affected by external recharge; second, the dynamic recharge water from surrounding aquifers to the mining area, which is affected by hydrogeological factors, atmospheric precipitation, and other factors, and has the characteristics of continuous recharge and dynamic change. Among them, the static water reserves are the core source of water hazard risks and must be drained to a safe threshold, which is the foundation of mining safety; while the dynamic recharge water, due to continuous recharge, results in a mismatch between the drainage demand and the mining progress.

[0004] While the existing advanced drainage model can ensure safety, it has significant drawbacks: Firstly, it requires long-term dynamic water replenishment, resulting in large drainage volumes and increased operational cycles and intensity due to continuous replenishment. Secondly, mining only needs to ensure the safety of the water body at the current face and a certain range ahead; the current model prematurely drains all dynamic water replenishment from the entire working face, constituting excessive drainage. This extensive model not only increases the workload of drilling and equipment maintenance, raising mining costs, but also wastes groundwater resources, increases the load on underground drainage systems, and increases drainage energy consumption and treatment costs, contradicting the concept of green and efficient coal mining.

[0005] Therefore, the water drainage operation under the condition that the coal mining face is arranged along the monoclinal direction still needs further research in order to carry out reasonable drainage, save water resources, and achieve a balance between safety, economy and environmental benefits. Summary of the Invention

[0006] To address the problems of excessive drainage, water waste, and high costs associated with existing methods, this invention proposes a method to reduce water inflow at the working face by coordinating roof drainage with mining progress. This method is mainly applicable to coal mining faces arranged along a single inclination. By establishing a dynamic matching mechanism between the two, only the mining face and key areas ahead are guaranteed safe drainage in real time, without the need for advance drainage of dynamic water supply to the entire working face, thereby effectively reducing ineffective discharge.

[0007] The present invention adopts the following technical solution: a method for reducing the water inflow at the working face by coordinating roof drainage with mining progress, including the following steps: Step 1, collecting design data, geological and hydrogeological data of the working face to be mined.

[0008] 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.

[0009] Step 3: Determine the layout parameters of the drainage boreholes, establish a numerical calculation model of the area for simulation, and obtain the borehole spacing.

[0010] Step 4: Perform drainage drilling according to the hole spacing.

[0011] Step 5: Determine the advance dredging distance, plan the division of dredging sections in the working face, and determine the time required for borehole dredging to reach a stable flow based on the Theis formula.

[0012] Step 6: Drill holes to release the first release section.

[0013] Step 7: The first section of the working face is mined, and the second dredging section is drilled and dredged simultaneously.

[0014] Step 8: Sequentially carry out the back mining of the nth section of the working face, and simultaneously carry out the drilling and dredging of the (n+1)th dredging section.

[0015] Step 9: Conduct the final section of the working face mining.

[0016] As a preferred option, in step 1, design data of the working face to be mined is collected, including: plan layout, mining strata, coal thickness, structural features of the working face, roof strata structure, location of aquifer, permeability coefficient of aquifer, and recharge and drainage conditions.

[0017] As a preferred option, in step 2, the method for determining the aquifer that needs to be drained is as follows: First, the height of the water-conducting fracture zone in the overlying rock of the working face is determined based on the coal thickness and the fracture-mining ratio using conventional empirical formulas, numerical simulations, or model experiments.

[0018] Based on the geological and hydrogeological data of the working face, the aquifer affected by the water-conducting fracture zone is determined. The strata within this range are the aquifers that will directly fill the working face during mining and also need to be drained in advance.

[0019] As a preferred option, in step 3, the layout parameters of the drainage boreholes are determined as follows: based on the layout of the working face in the area to be mined, boreholes are arranged outward in the relatively low-lying roadway. The depth of the boreholes needs to penetrate all aquifers affected by the water-conducting fracture zones. The spacing of the drainage boreholes is determined by numerical simulation.

[0020] First, a numerical calculation model is established using numerical simulation. Then, the sparse effect on the working face under different hole spacing is simulated. Finally, the hole spacing is determined, which is the maximum spacing of the holes under the condition of achieving complete sparseness in the face.

[0021] As a preferred option, in step 4, a special drilling rig for coal mine water exploration and drainage is used to construct the drainage boreholes according to the borehole spacing. 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 embodiment, in step 5, the time required for borehole drainage to reach a 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. To reduce the initial water head of the borehole before mining at the working face Control head of the drainage hole.

[0023] Among them, time in the Theis formula If the necessary parameters for calculation are missing, select 2-3 existing drainage holes and drain water to observe the changes in the borehole inflow. The borehole inflow will gradually decrease until it reaches a stable flow rate. The time period from the start of water drainage to the stable flow rate is the [period of flow rate]. .

[0024] The expected mining speed at this working face is Then, the distance required for advance evacuation is... for: .

[0025] As a preferred embodiment, in step 6, the first dredging section is drilled for dredging, and at time t before the working face is mined, the borehole is opened at a distance... Drainage boreholes are drilled in the first advanced drainage section within the range to drain water, thus ensuring that water within a distance L ahead is drained during working face mining.

[0026] As a preferred embodiment, in step 7, the working face mining and dredging are carried out simultaneously. The mining of the first section of the working face is started, and all dredging boreholes of the second dredging section are opened for dredging. The length of the second dredging section is the advance dredging distance L.

[0027] As a preferred option, in step 8, mining and dredging are carried out sequentially. According to the mining plan, when the mining of the first section is completed, the dredging work of the second dredging section is completed at the same time. At this time, the working face continues to move forward to carry out the mining of the second dredging section, and at the same time, the dredging of the third dredging section is started.

[0028] By sequentially mining n sections of the working face and simultaneously drilling and dredging the (n+1)th dredging section, mining can always be carried out in the dredging section that has been completed.

[0029] As a preferred option, in step 9, when mining the penultimate section, the release of the last section begins simultaneously. When mining reaches the last section, the release of the last section has been completed, and the mining of the last section of the working face can then proceed normally, thus completing the mining of the working face.

[0030] Compared with the prior art, the present invention has the following technical effects: 1. The present invention provides a method for coordinating roof drainage with mining progress to relatively reduce the water inflow of the working face. It is mainly applicable to the working condition where the coal mining face is arranged along a single inclination. The core is to divide the working face into sections to realize the coordinated operation of mining and drainage, thereby relatively reducing the dynamic water inflow of the working face, which has significant economic, safety and environmental benefits.

[0031] 2. This invention establishes a dynamic matching mechanism between roof drainage and mining progress, ensuring safe drainage only at the mining face and key areas ahead, without the need for advance drainage of dynamic water supply to the entire working face. This effectively reduces ineffective discharge, lowers the workload and total underground drainage, saves water resources, reduces energy consumption and treatment costs, and ultimately achieves a balance of safety, economy and environmental benefits, meeting the needs of green, safe and efficient coal mining. Attached Figure Description

[0032] Figure 1 This is a plan view of the construction block of the numerical calculation model in an embodiment of the present invention.

[0033] Figure 2 This is a schematic diagram of the numerical calculation model and boundary condition settings in an embodiment of the present invention.

[0034] Figure 3This is a cloud diagram showing the initial water pressure calculation of the numerical calculation model in an embodiment of the present invention.

[0035] Figure 4 This is a cloud map showing the water pressure drainage effect when the spacing between drainage holes is 50m, according to an embodiment of the present invention.

[0036] Figure 5 This is a water pressure cloud diagram after drainage in the first drainage section of this embodiment of the invention.

[0037] Figure 6 This is a water pressure cloud map formed in the second dredging section of an embodiment of the present invention.

[0038] Figure 7 This is a water pressure cloud diagram formed in the third dredging section of an embodiment of the present invention.

[0039] Figure 8 This is a water pressure cloud map formed in the fourth dredging section of an embodiment of the present invention.

[0040] Figure 9 This is a water pressure cloud map formed in the fifth dredging section of an embodiment of the present invention.

[0041] Figure 10 This is a water pressure cloud diagram formed in the sixth dredging section of an embodiment of the present invention.

[0042] Figure 11 This is a water pressure cloud diagram formed in the seventh dredging section of an embodiment of the present invention.

[0043] Figure 12 This is a water pressure cloud diagram formed in the eighth dredging section of an embodiment of the present invention.

[0044] Figure 13 This is a flowchart of the method for reducing water inflow at the working face by coordinating roof drainage with mining progress according to the present invention. Detailed Implementation

[0045] 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.

[0046] In one embodiment of the present invention, the method of the present invention is used to prevent water hazards in the thick sandstone aquifer on the roof of a certain coal mine working face 110504. Here, 110504 is the number of a specific working face in the coal mine. The specific implementation process is as follows: Figure 13As shown, the steps include: (1) collecting design data, geological and hydrogeological data of working face 110504.

[0047] In this embodiment, the 110504 working face mines the No. 5 coal seam with a thickness of 12m, using the strike-longwall full-thickness single-pass top coal caving method. The coal seam elevation of the working face is located between +1164.706m and +1296.932m, with a strike length of 2530m and an oblique length of 192m.

[0048] The working face is mainly threatened by the Yan'an Formation and Zhiluo Formation sandstone aquifers in the roof. Specifically, the Yan'an Formation sandstone is 10-30m thick and approximately 0.5-20m vertically from the roof of coal seam 5; the Zhiluo Formation sandstone is 50-150m thick and approximately 70-80m vertically from the roof of coal seam 5. The area where the working face is located has a monocline structure with an average dip angle of 8.3°, and the average permeability coefficient of the Yan'an and Zhiluo Formations aquifers in the roof is 0.8192m / d.

[0049] (2) Calculate the development height of the water-conducting fracture zone at the working face and determine the aquifers that need to be drained.

[0050] 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. Therefore, the development height of the water-conducting fracture zone is calculated as the coal seam thickness multiplied by the fracture-to-mining ratio: 12 × 19 = 228 m.

[0051] 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, so it was necessary to drain the water from the sandstone aquifers of the Yan'an and Zhiluo Formations.

[0052] (3) Determine the layout parameters of the drainage boreholes.

[0053] Based on the location of the working face in the mining area, its stratigraphic position, and design data, a numerical calculation model was constructed using finite element numerical analysis software. The numerical calculation range is as follows: Figure 1 As shown in the figure, the coordinate system is a geodetic rectangular coordinate system, with the horizontal and vertical coordinates corresponding to the geodetic horizontal and vertical coordinates, and the unit is meters.

[0054] The upper boundary is defined by the +1290m water level line, the left side extends 1500m beyond the working face boundary, the lower side extends 2000m 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 sides measuring 6964m and 10259m respectively, a height of 2459m, and a total area of ​​21.18 million square meters. 2 .

[0055] 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, the 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)×1460Pa; the lower boundary is an ingress boundary with a water pressure of 2459×1460Pa.

[0056] Furthermore, the initial water pressure calculation cloud diagram of the numerical calculation model in this embodiment is as follows: 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.

[0057] Drilling sites are arranged in the relatively low-level transport roadway of the 110504 working face, with boreholes extending outwards. These boreholes must reach the straight guide rail assembly. For example... Figure 4 As shown, the water pressure field cloud map is formed when the borehole spacing is 50m and the boreholes are completely cleared. It can be seen that the 110504 working face area can be completely cleared, and the final borehole spacing is determined to be 50m.

[0058] (4) Conduct drainage drilling.

[0059] A special drilling rig for coal mine water exploration and drainage was used to carry out the construction of drainage boreholes. The borehole was equipped with a 16m borehole pipe and a blowout preventer valve was installed during construction. After the construction was completed, the borehole valve was closed.

[0060] (5) Determine the advance evacuation distance and plan the division of evacuation sections in the working face.

[0061] Based on the hydrogeological parameters of the aquifer, the time required for borehole drainage to reach a stable flow was calculated using the Theis formula: 98 days. The average daily mining distance at the 110504 working face is 3.05m, therefore the calculated advance drainage distance L = 98 × 3.05 ≈ 300m.

[0062] (6) Drill holes to release the first release section.

[0063] 98 days before the start of mining operations, the first pre-drainage borehole within a 300m radius was opened for water drainage. The drainage effect was as follows: Figure 5 As shown, this ensures that water within a 300m radius ahead is drained during mining operations.

[0064] (7) The first section of the working face is mined, and the second dredging section is drilled and dredged at the same time.

[0065] Start the first section of the working face to start mining, and at the same time open all the dredging boreholes in the second dredging section for dredging. The length of the second dredging section is the distance L of the advance dredging, that is, the working face mining and dredging are carried out at the same time.

[0066] (8) The working face is mined in n sections in sequence, and the drilling and dredging of the (n+1)th dredging section is carried out simultaneously.

[0067] According to the mining plan, when the first section is completed, the dredging work of the second dredging section is also completed. At this time, the working face continues to move forward to carry out the mining of the second dredging section, and at the same time, the dredging of the third dredging section is started. That is, mining and dredging are carried out in sequence.

[0068] The working face is mined in n sections sequentially, while simultaneously drilling and releasing the (n+1)th release section. This ensures that mining always continues within the already released sections. The water pressure cloud diagram formed by the second to eighth release sections (the last release section) is shown below. Figures 6 to 12 As shown.

[0069] (9) Carry out the last section of the working face mining.

[0070] When mining the penultimate section, the clearing work of the last section is carried out simultaneously. When mining reaches the last section, the clearing work of the last section has been completed, and then the mining of the last section of the working face can be carried out normally to complete the mining of the working face.

[0071] In this embodiment, the calculation results of the water volume for segmented drainage are shown in Table 1.

[0072] Table 1 Calculation Results of Water Volume for Segmented Drainage

[0073]

[0074] The table shows that the 110504 working face has a length of 2550m, and the average water volume released in 8 stages is 207.45m³. 3 / h, if drained in one go, the water volume is 490.67m³. 3 / h, an average reduction of 283.22m 3 / h, for a coal mining time of 27.5 months at the 110504 working face, a total relative saving of drainage volume of 283.22×24×27.5×30.5≈5701219m³ can be achieved. 3 .

[0075] In summary, the core of this invention is to segment the working face to achieve coordinated mining and water drainage. By establishing a dynamic matching mechanism between the two, only the mining face and key areas ahead are guaranteed safe drainage in real time, without the need for pre-drainage of dynamic water supply to the entire working face. This can effectively reduce ineffective discharge, reduce the amount of work and the total amount of underground drainage, save water resources, reduce energy consumption and treatment costs, and ultimately achieve a balance of safety, economy and environmental benefits, meeting the needs of green, safe and efficient coal mining.

[0076] 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 coordinating roof drainage with mining progress to reduce water inflow at the working face, characterized in that, Includes the following steps: Step 1: Collect design data, geological and hydrogeological data of the working face 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 layout parameters of the drainage boreholes, establish a numerical calculation model of the area for simulation, and obtain the borehole spacing. Step 4: Perform drainage drilling according to the hole spacing. Step 5: Determine the advance dredging distance, plan the division of dredging sections in the working face, and determine the time required for borehole dredging to reach a stable flow based on the Theis formula. Step 6: Drill holes to release the first dredging section; Step 7: The first section of the working face is mined, and the second dredging section is drilled and dredged simultaneously. Step 8: Sequentially carry out the back mining of the n sections of the working face, and simultaneously carry out the borehole dredging of the (n+1)th dredging section; Step 9: Conduct the final section of the working face mining; 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 determined by empirical formulas, numerical simulations, or model experiments, based on the coal thickness and the fracture-to-mining ratio. 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 layout parameters of the drainage boreholes are determined as follows: Based on the layout of the working face in the area to be mined, boreholes are arranged outward in the relatively low-lying roadway. 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 sparse effect on the working face under different borehole spacing and determine the borehole spacing. 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. The expected mining speed at the working face is v, and the distance required for advance clearing is... for: .

2. The method for coordinating roof drainage with mining progress to reduce water inflow at the working face according to claim 1, characterized in that, In step 1, design data of the working face to be mined is collected, including: plan layout, mining strata, coal thickness, structural features of the working face, roof strata structure, location of aquifer, permeability coefficient of aquifer, and recharge and drainage conditions.

3. The method for coordinating roof drainage with mining progress to reduce water inflow at the working face according to claim 1, characterized in that, In step 4, a special drilling rig for coal mine water exploration and drainage is used to construct the drainage boreholes according to the borehole spacing. The borehole pipe and blowout preventer valve are installed. After the construction is completed, the borehole valve is in the closed state.

4. The method for coordinating roof drainage with mining progress to reduce water inflow at the working face according to claim 1, characterized in that, In step 6, the first dredging section is drilled for dredging. At time t before the working face is mined, the borehole is opened at a distance... Drainage boreholes are drilled in the first advanced drainage section within the range to drain water, ensuring that water within a distance L ahead is drained during mining operations.

5. The method for coordinating roof drainage with mining progress to reduce water inflow at the working face according to claim 1, characterized in that, In step 7, the back mining and dredging of the working face are carried out simultaneously. The back mining of the first section of the working face is started, and all the dredging boreholes of the second dredging section are opened for dredging. The length of the second dredging section is the distance L of the advance dredging.

6. The method for coordinating roof drainage with mining progress to reduce water inflow at the working face according to claim 1, characterized in that, In step 8, mining and dredging are carried out sequentially. When the mining of the first section is completed, the dredging work of the second dredging section is completed at the same time. The working face continues to move forward to carry out the mining of the second dredging section, and at the same time the dredging of the third dredging section is started. The working face is mined in n sections in sequence, while the (n+1)th slack section is slackened by drilling, so that mining is carried out in the slack section that has been slackened.

7. The method for coordinating roof drainage with mining progress to reduce water inflow at the working face according to claim 1, characterized in that, In step 9, while mining the penultimate section, the release of the last section begins simultaneously. When mining reaches the last section, the release of the last section is completed, and the mining of the last section of the working face is carried out normally, thus completing the mining of the working face.

Images