Accurate positioning of water-rich area of coal mine roof and long-distance targeted water drainage method

Abstract

The application discloses a kind of coal mine roof water-rich area accurate positioning and long-distance target water drainage method, comprising: based on the construction of mining area hydrogeological condition, the feasibility of roof aquifer water drainage is comprehensively analyzed;Based on the target mining area working face reagent top and bottom plate condition, the damage situation of plastic zone in the area near working face after coal seam mining is analyzed and the communication condition of "two zones" and overlying filling, aquifer is determined;Collect the geological exploration data and geophysical exploration data of target mining area, locate the water-rich area of working face aquifer region;Long-distance target water drainage scheme of aquifer region is researched, and the water disaster prevention scheme and parameters of target mining area target working face are established.The significant effect is: the above scheme can effectively reduce the cost of water disaster control, improve the recovery efficiency and safety level, and provide a popular technical route and engineering demonstration for coal mine working face roof water disaster prevention under similar hydrogeological conditions.

Description

Technical Field

[0001] This invention relates to the field of coal mine water hazard prevention and control technology, specifically to a method for precise positioning and long-distance targeted drainage of water-rich areas in the roof of a coal mine. Background Technology

[0002] Water hazards in coal mines have always been a key factor restricting safe and efficient mining, especially in Jurassic coalfields and areas with multiple aquifers in western my country. These areas are characterized by high water content in the roof aquifers, uneven spatial distribution, and significant disturbance from mining activities, making them highly susceptible to water inrush, seepage, and large-scale water surges. As mining depth and intensity continue to increase, the traditional "experience-based judgment + localized exploration and drainage" management model has revealed significant shortcomings under complex geological conditions. On the one hand, water-rich areas in the roof often present as lenticular, strip-shaped, or fracture-sandstone composite water-rich bodies, with blurred boundaries and strong heterogeneity, leading to low efficiency and frequent misjudgments in conventional drilling. On the other hand, the layout of roadways and working faces in mining areas is spatially constrained, requiring drainage projects to traverse long distances to reach the target area. Problems such as borehole deviation, uncontrolled trajectory, insufficient effective drilling depth, and unstable sealing quality directly affect the targeted drainage effect and mining safety. Therefore, conducting research on key technologies for precise positioning and long-distance targeted drainage of water-rich areas in coal mine roofs is of great theoretical and engineering value for achieving source control of water hazards, ensuring mining continuity, and improving the inherent safety level of mines.

[0003] The formation and evolution of water-rich areas in the roof are controlled by a combination of factors, including sedimentary facies zones, lithological combinations, the degree of development of tectonic fractures, and recharge-runoff-drainage conditions. The redistribution of mining-induced stress further alters the fracture network and seepage channels, causing the water-rich body to shift from a static distribution to a dynamic response, characterized by enhanced water-richness, the connection of water-conducting channels, and a continuous or abrupt drop in water level. Against this backdrop, accurately locating water-rich areas requires not only a detailed characterization of the aquifer's spatial structure but also the identification of the "main control channels" and "critical boundaries" that are crucial for controlling water inrushes. This makes "finding water accurately" a prerequisite for drainage engineering design. Furthermore, for long-distance targeted drainage projects, it is essential to overcome the limitations of traditional straight-hole or short-distance directional boreholes, achieving controllable trajectories, reliable target entry, stable pumping and drainage, and long-term effectiveness in complex strata. Ultimately, this aims to achieve the goal of "peak shaving and valley leveling" of water inflow during mining and reducing the risk of instantaneous water inrushes.

[0004] In recent years, geophysical exploration, geological modeling, and directional drilling technologies have been widely applied in the field of mine water hazard control. However, several key issues remain to be addressed: First, multi-source exploration results vary significantly in scale, accuracy, and uncertainty, lacking a fusion interpretation and verification loop for water-rich target areas, making it difficult to achieve the leap from "anomaly identification" to "quantitative delineation of water-rich boundaries." Second, long-distance directional drilling is prone to borehole instability, stuck drill bits, and accumulated deviations in areas with interbedded soft and hard layers, fractured zones, and fracture development, resulting in a decrease in target area hit rate. Third, the evaluation of targeted drainage effects often focuses on single-hole water output or short-term drawdown, lacking comprehensive criteria that combine aquifer reservoir water release characteristics, dynamic recharge, and mining evolution, leading to insufficient basis for parameter optimization and process control. These problems hinder the realization of "precise, on-demand, and dynamic governance" in water-rich areas of the roof. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for precise positioning and long-distance targeted drainage of water-rich areas in the roof of coal mines. Taking the aquifer in the roof of the working face as the research object, and based on the actual hydrogeological conditions of the working face and the failure law of the roof overburden, this invention systematically studies the drainage technology of the aquifer in the roof of the working face using theoretical analysis, numerical simulation, and field engineering practice, and formulates a construction plan for drainage of the aquifer in the roof of the working face during mining.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for precise location and long-distance targeted drainage of water-rich areas in the roof of coal mines, the key of which includes the following steps:

[0008] Step 1: Based on the hydrogeological conditions of the construction mining area, combined with the on-site pumping test of the mine, the water level changes of the aquifer long observation hole, and the water drainage situation of the surrounding mine working faces, conduct a comprehensive analysis of the feasibility of draining water from the roof aquifer.

[0009] Step 2: Based on the top and bottom conditions of the working face in the target mining area, theoretical analysis and numerical simulation are used to predict the development height of the water-conducting fracture zone and caving zone of the coal mining face, analyze the damage of the plastic zone in the area near the working face after coal seam mining, and determine the communication between the "two zones" and the overlying aquifers.

[0010] Step 3: Collect geological exploration data and geophysical exploration data of the target mining area to locate the water-rich area of ​​the aquifer region of the working face;

[0011] Step 4: Based on the evaluation results of the aquifer on the roof of the working face in the target mining area and the prediction results of water inrush, and taking into account the water-bearing properties of the aquifer and the development height of the water-conducting fracture zone, conduct research on the long-distance targeted drainage scheme for the aquifer area, and establish the water hazard prevention scheme and parameters for the targeted working face in the target mining area.

[0012] Furthermore, the comprehensive analysis of the feasibility of draining water from the roof aquifer, as described in step 1, based on the hydrogeological conditions of the construction mining area, combined with on-site pumping experiments, changes in the water level of the aquifer through long-term observation holes, and the drainage situation of surrounding mine working faces, includes:

[0013] Obtain surface and underground condition data of the target area;

[0014] Water release tests were conducted in the vertical shaft and the mining area, respectively.

[0015] Based on the data from mine borehole pumping tests and the experience of mining areas with similar conditions, a feasibility analysis of aquifer drainage is conducted based on the criteria for judging the feasibility of drainage.

[0016] Based on the changes in water level at long boreholes, the aquifer's permeability was analyzed to obtain the evaluation results of the aquifer on the roof of the working face in the target mining area and the prediction results of water inrush.

[0017] Furthermore, the feasibility criteria for dredging are as follows:

[0018] >10, weak supply, easy to be dispersed and subdued;

[0019] 3≤ ≤10, with strong supply, can be dispersed and subdued;

[0020] <3, with strong supply lines, direct evacuation is not advisable;

[0021] in, It is the ratio of drawdown to inflow rate; The water level drawdown within the main controlled release area; This refers to the inflow rate within the main controlled release area.

[0022] Furthermore, step 2, which involves predicting the development height of the water-conducting fracture zone and caving zone of the coal mining face based on the roof and floor conditions of the target mining area using theoretical analysis and numerical simulation, analyzing the damage of the plastic zone near the working face after coal seam mining, and determining the communication between the "two zones" and the overlying aquifers and water-bearing strata, includes:

[0023] Establish the basic theory of overlying rock strata collapse in goaf areas;

[0024] Based on the "masonry beam" theory and structural model, the overlying strata above the goaf are divided into caving zones and fracture zones, and the heights of the caving zones and fracture zones are calculated respectively.

[0025] Based on the measurement data of basic coal and rock mechanics parameters and the test data of Brazilian splitting experiments, a numerical simulation calculation model was established to conduct numerical simulation analysis on the evolution law of fractures in the overlying strata of the goaf. The predicted results of the development height of the water-conducting fracture zone and the caving zone of the coal mining face were obtained. Based on the prediction results, the damage of the plastic zone in the area near the working face after coal seam mining was analyzed, and the communication between the "two zones" and the overlying aquifers and water-bearing strata was determined.

[0026] Furthermore, the height of the landslide zone is calculated as follows:

[0027] When the coal seam dip angle is small and the overlying strata are extremely hard rock, the calculation formula is:

[0028]

[0029] in, The height of the landslide zone is in meters (m). is the coefficient of rock fragmentation during collapse, dimensionless; The coal seam mining height is in meters (m). The dip angle of the coal seam;

[0030] If the overlying rock strata consist of hard, medium-hard, soft, and extremely soft rock strata, the calculation formula is as follows:

[0031]

[0032] in, This refers to the amount of roof subsidence.

[0033] The formula for calculating the height of the fracture zone is:

[0034]

[0035] in, It is a constant; This is a correction factor.

[0036] Furthermore, step 3, which involves collecting geological and geophysical exploration data of the target mining area and locating the water-rich zone of the aquifer region at the working face, includes:

[0037] Collect geological and geophysical exploration data of the target mining area and perform data preprocessing;

[0038] The main control factors were analyzed on the preprocessed exploration data, and an indicator system was constructed based on the analysis of the main control factors.

[0039] A water-bearing index evaluation model based on AHP and local variable weight model was constructed, and the local variable weight water-bearing index was calculated.

[0040] Based on the obtained local variable weight water-bearing index, contour lines of the water-bearing index are drawn, and by analyzing the spatial distribution pattern of the water-bearing index, the water-bearing zoning of the aquifer area is determined, thus realizing the location of the water-bearing zone in the aquifer area of ​​the working face.

[0041] Furthermore, the mathematical expression of the water-richness index evaluation model is as follows:

[0042]

[0043] in, The water-richness index, For the first Standardized values ​​of the main control factors These are local variable weights that change with the state of the factors.

[0044] Furthermore, step 4, based on the evaluation results and water inflow prediction results of the aquifer roof of the target mining area, combined with the aquifer's water-bearing capacity location results and the development height of the water-conducting fracture zone, studies a long-distance targeted drainage scheme for the aquifer region, and establishes a water hazard prevention scheme and parameters for the target mining area's targeted working face. This process includes:

[0045] Based on the evaluation results of the aquifer on the roof of the working face in the target mining area and the water inrush prediction results, the key parameters of the targeted drainage scheme are determined by comprehensively considering the water-bearing properties of the aquifer and the development height of the water-conducting fracture zone.

[0046] Construct a long-distance targeted water drainage scheme for aquifer regions;

[0047] Based on the targeted drainage scheme, the layout of drainage boreholes, the final borehole level, the vertical distance of boreholes, as well as the borehole parameters and structure are determined.

[0048] The drilling technical requirements, drilling sequence, project content, and drilling process are determined based on the conditions for commencement of construction.

[0049] The final water hazard prevention and control plan and parameters for the target working face in the target mining area were formulated.

[0050] Furthermore, the key parameters of the targeted drainage scheme include: borehole space layout parameters and drainage cycle and time control parameters.

[0051] This invention constructs a complete technical system based on the main lines of "feasibility evaluation of roof aquifer drainage - precise determination of the height of mining-induced zones - precise positioning through multi-source information fusion in water-rich areas - regional long-distance directional targeted drainage". This system enables a shift from traditional extensive management to refined, targeted, and engineering-based applications, effectively reducing water hazard management costs, improving mining efficiency and safety levels, and providing a scalable technical route and engineering demonstration for roof water hazard prevention in coal mine working faces under similar hydrogeological conditions.

[0052] The significant effects of this invention are:

[0053] (1) This invention conducts a feasibility study on drainage of the aquifer in the roof of the working face, clarifying the necessity, feasibility, and control indicators of drainage, and avoiding blind drilling and ineffective drainage; combined with the study on the development height of the "two zones" of the coal mining face, it accurately grasps the development range of the caving zone and the fracture zone and their spatial relationship with the aquifer, guiding the coordinated optimization of drainage and mining sequence, and reducing the risk of water inrush and production stoppage losses from the source. Furthermore, through the application of precise positioning in water-rich areas and long-distance targeted drainage technology, the treatment effect can be significantly improved, the repeated construction and overload operation of the drainage system can be reduced, thereby reducing the overall treatment cost and improving the production continuity and safety factor during the working face mining period.

[0054] (2) The implementation of this invention will reduce the amount of ineffective engineering and production losses: On the one hand, the precise positioning of water-rich areas can reduce the number of boreholes and trial and error costs, and reduce ineffective drainage and excessive pumping; on the other hand, the long-distance targeted drainage technology can achieve targeted treatment of key water-rich areas at a greater distance and under more complex boundary conditions, release water volume in advance, reduce water pressure, and reduce the economic losses caused by risks such as water inrush, flooding, and production stoppage during mining; at the same time, it can reduce the peak load of the drainage system, achieve "peak shaving and valley leveling" of water inflow, and save electricity consumption and operation and maintenance costs.

[0055] (3) By systematically studying the feasibility of draining water from the roof aquifer, the development height of the two zones and the precise location of the water-rich area, this invention can significantly improve the predictability and controllability of coal mine water hazard risks, reduce the probability of water inrush accidents, and protect the lives of workers and the safety of mine property. At the same time, by forming a standardized and normalized governance plan, it can improve the level of safe production and management capabilities of the mining area, and promote the progress of water hazard prevention and control technology and the upgrading of engineering applications in the coal mining industry.

[0056] (4) The targeted dredging of this invention emphasizes "on demand, by area, and by target" treatment, which can reduce unnecessary pumping and water waste, and reduce disturbance to the surrounding groundwater system. At the same time, by improving treatment efficiency and reducing repeated construction and material consumption, it indirectly reduces energy consumption and carbon emissions, which meets the requirements of green mines and sustainable development. Attached Figure Description

[0057] Figure 1 This is a flowchart of the method of the present invention;

[0058] Figure 2 This is a schematic diagram showing the division of the "two zones" in the goaf area;

[0059] Figure 3 This is a schematic diagram of the geometric model and mesh division of the goaf. Detailed Implementation

[0060] The specific embodiments and working principles of the present invention will be further described in detail below with reference to the accompanying drawings.

[0061] Example:

[0062] This invention uses the drainage construction plan of Ningtaota Coal Mine as an example for illustration. Ningtaota Coal Mine is one of the three pairs of extra-large mines invested and constructed by Shaanxi Coal and Chemical Industry Group Co., Ltd. in the southern area of ​​Shenfu Mining Area. The southern wing of the mine has 2... -2 The coalfield face in the eastern coal area is overlain by a confined aquifer in weathered bedrock fissures, with a unit yield of 0.06087~1.606 L / s·m and a permeability coefficient of 0.4911~2.133 m / d, indicating weak to moderate water abundance. South Wing 2 -2 The overlying bedrock thickness at the working face in the eastern coalfield ranges from 27.2m to 88.53m, and the height of the water-conducting fracture zone ranges from 114.8m to 207.7m. This fracture zone extends through the weathered bedrock fissure aquifer down to the soil layer. Furthermore, based on previous hydrogeological data, the water-bearing capacity increases further south, posing a safety hazard to the working face during mining operations due to the threat of the overlying Zhiluo Formation weathered bedrock aquifer.

[0063] like Figure 1 As shown, a method for precise positioning and long-distance targeted drainage of water-rich areas in the roof of a coal mine includes the following specific steps:

[0064] Step 1: Feasibility study on drainage of the roof aquifer in the working face: Based on the actual hydrogeological conditions of Ningtaota Coal Mine, a comprehensive analysis of the characteristics of the roof aquifer and aquitard, as well as the development characteristics of faults and folds, and other influencing factors, combined with the mine's on-site pumping experiments, the water level changes of the aquifer through long-term observation holes, and the drainage situation of the working faces of surrounding mines, is conducted to comprehensively analyze the feasibility of drainage of the roof aquifer.

[0065] Step 2: Research on the Development Height of the "Two Belts" in the Coal Mining Face: Coal mining disturbance will generate fractures in the overlying strata of the coal seam. These fractures may develop into the overlying aquifer, thus creating a water-conducting fracture zone, which poses a significant threat to the safe production of the coal mine. Therefore, based on the south wing 2... -2Based on the actual roof and floor conditions of the coal face in the East Coal District, theoretical analysis and numerical simulation were used to predict the development height of the water-conducting fracture zone and caving zone of the coal face. The damage of the plastic zone in the vicinity of the working face after coal seam mining was analyzed and the communication between the "two zones" and the overlying aquifers was determined.

[0066] Step 3: Precise Location of Water-Rich Zones in the Aquifer at the Working Face: Based on the actual conditions of the 2-2 coal seam in the eastern part of the south wing, collect geological exploration data (such as borehole core data, geological structure information, etc.) and geophysical exploration data (such as transient electromagnetic method, radio wave penetration method, etc.). Conduct comprehensive analysis of these data from different sources, and construct a local variable weight water-rich index model for each spatial point using the local variable weight model and the analytic hierarchy process (AHP). Plot contour lines for the local variable weight water-rich index to determine the water-rich zone zoning of the aquifer area.

[0067] Step 4: Formulate a long-distance targeted water release plan for the aquifer area: Based on the analysis of the southern wing 2 -2 Based on the evaluation results and water inrush prediction results of the roof aquifer in the coal mining area of ​​Dong District, the comprehensive analysis results of the water-bearing zoning of the aquifer, and the development height of the water-conducting fracture zone, a study was conducted on the long-distance targeted drainage scheme of the aquifer area. A scientific and reasonable water hazard prevention and control technical scheme and parameters were established for the targeted working face of Ningtaota Coal Mine. Through centralized and unified drainage, the static storage of the aquifer was reduced, the instantaneous peak water inrush intensity during the working face mining was reduced, and the safe mining number of the working face was ultimately ensured.

[0068] In this embodiment, the specific implementation process of step 1 is as follows:

[0069] Step 1.1: Determine the surface conditions of the mine.

[0070] The exploration area is located in the 2-2 coal seam east area of ​​the southern wing of the Ningtaota Coal Mine. The terrain is high in the southeast and low in the northwest. The highest elevation is near the cut-off points of the S1235, S1236, and S1237 working faces, at 1314m, while the lowest elevation is in the western part of the S1236 and S1237 working faces, at 1257m, with a relative elevation difference of approximately 57m. The overall terrain is relatively flat. Most of the surface in the area is covered by modern aeolian sand, with some areas exposing Quaternary loess.

[0071] Step 1.2: Determine the downhole conditions

[0072] The mine is located in the southern wing of the mining area. -2 The eastern coalfield is bordered by the S1234 working face to the north, the southern boundary of the coalfield (adjacent to the Hongliulin coalfield) to the south, the eastern boundary of the coalfield (adjacent to the Zhangjiamao coalfield) to the east, and the southern wing 2 coalfield to the west. -2 The southern section of the auxiliary haulage roadway in the East Coal Mine area. The area explored in this survey is approximately 5177m long from east to west and approximately 1100m wide from west to east.

[0073] South Wing 2 -2 The coal seam thickness in the eastern coalfield ranges from 4.1 to 8.46 meters, with an average of 6.70 meters. The coal seam is black with a weak bituminous luster, short columnar, and semi-bright. Generally, the coal seam slopes from east to west, extending upwards with some local undulations. There are no faults, and the structure is relatively simple and stable. The working face floor elevation ranges from +1123.52 to +1164.18 meters, and the coal seam burial depth ranges from 113.55 to 157.71 meters. The sand layer is 1.8 to 8.5 meters thick, the soil layer is 37.9 to 96.8 meters thick, and the overlying bedrock is 27.2 to 88.53 meters thick. The coal seam structure is simple and stable, with a hardness coefficient f = 1.22.

[0074] Step 1.3, Vertical well water release test

[0075] The main inclined shaft of the coal mine revealed a water inflow of 63 m³ / h when it exposed the Zhiluo Formation aquifer (154 m). 3 / h, during the excavation of the upper roadway of the coal bunker, there is a 30m... 3 The water inflow rate was / h. Pre-grouting was carried out on both shafts before excavation, with the auxiliary shaft receiving 9144m³ of grout. 3 The slurry injection volume of the ventilation shaft was 7652m³. 3 During the tunneling process, when the auxiliary shaft reached the aquifer in the lower section of the Zhiluo Formation, the water volume in a single borehole reached 64 m³. 3 The water inflow of the ventilation shaft is also relatively large. Therefore, a dewatering project was implemented for the auxiliary shaft, involving 6 boreholes with a single borehole water volume of 20-34 m³ / h. 3 / h, with water flowing from both holes simultaneously, the water inflow reaches 40m³ / h. 3 / h, with water flowing out from all three holes simultaneously, the water inflow reaches 80m³ / h. 3 / h, when adding more outlet holes, the water flow increases only slightly; when all six holes are discharging water simultaneously, the maximum flow rate reaches 92m³ / h. 3 / h. Next, eight dewatering wells were constructed outside the vertical shaft, and single-well and group-well pumping tests were conducted, with single-well water volumes reaching 40-70 m³ / h. 3 / h, when pumping water through a group of wells, the water volume increases with the number of wells up to 4, with a maximum of 140m³ / h. 3 / h; the water flow rate with 4 or more wells changes little with the increase of the number of wells, with a maximum flow rate of 106m³. 3 / h. The ventilation shaft also carried out multi-hole and multi-combination dewatering projects. The water level in the dewatering wells was lowered to the bottom plate of the Zhiluo Formation, but at this time the water level in the observation holes in the ventilation shaft was still 30m higher than the top interface of the aquifer. After the dewatering wells stopped draining, the water level returned to the original level after one month.

[0076] Step 1.4, Water Release Test in the Mining Area

[0077] South Wing East Zone 2 of the Mine -2 The water release test involved drilling 12 boreholes, with the FS0 boreholes capable of carrying up to 80m³ of water.3 / h, the water flow in borehole G1 reached 140m³. 3 The water level in the observation well did not decrease within a short period of time. After the valve was closed, the water level recovered to 40-50% of the maximum drawdown within 10 minutes, indicating that the permeability and water-bearing capacity of the aquifer in the mining area are weak to moderate, and the aquifer's recharge source is generally average. According to the single-hole water release test of the FS0 borehole, the water volume in the single-hole of the FS0 borehole in the lower section of the Zhiluo Formation reached 106 m³ / h. 3 The water level decreased rapidly within a short period (121h) and rebounded quickly after the valve was closed, indicating that the permeability and water-bearing capacity of the lower section of the Zhiluo Formation aquifer are weak to moderate, and it has a very good source of recharge. According to the single-hole water release test of the FS0 borehole in the lower section of the Zhiluo Formation aquifer, the water level elevation of this layer is +1232.5~+1295.0m, and the groundwater flow direction is from west to northeast, east, and southeast. The unit yield of the aquifer is q=0.0078~0.4461L / s·m, the water-bearing capacity is weak to moderate, the permeability coefficient is K=0.0179~2.277m / d, the mineralization is 142.2~373.3mg / L, and the hydrochemical type is mainly HCO3-Ca and HCO3-Ca·Na type.

[0078] Step 1.5: Feasibility analysis of releasing water from the aquifer based on the pumping test.

[0079] Based on the data from mine borehole pumping tests and the experience of mining areas with similar conditions, the ratio of drawdown depth to water inflow is used as the criterion for judging the feasibility of drainage, as shown in Formula 3-1.

[0080] (1)

[0081] Where S is the drawdown (m) within the main controlled release area; Q is the inflow rate (m3 / min) within the main controlled release area.

[0082] (1) >10, weak supply, easy to be dispersed and subdued;

[0083] (2) 3≤ ≤10, with strong supply, can be dispersed and subdued;

[0084] (3) <3, the supply is very strong, and it is not advisable to directly disperse and surrender.

[0085] Based on the hydrogeological borehole data of the mining area, the aquifer's drainage capacity was analyzed. As shown in Table 1, the lower section of the Zhiluo Formation in the coal roof of the mining area has good drainage capacity.

[0086] Table 1. Analysis of the aquifer permeability of the lower section of the Zhiluo Formation based on pumping tests.

[0087] ZL1 49.22 1232.59 30.61 5.243 0.1713 97.30 Easy to dredge and descend ZL2 27.33 1233.81 47.58 9.032 0.1898 87.80 Easy to dredge and descend ZL3 37.57 1245.97 47.70 5.747 0.1205 138.33 Easy to dredge and descend ZL4 21.31 1266.77 63.25 0.610 0.00964 1728.14 Easy to dredge and descend ZL5 29.88 1234.33 29.47 5.492 0.1863 89.43 Easy to dredge and descend ZL6 49.69 1234.16 140.20 5.878 0.0382 397.53 Easy to dredge and descend ZL7 10.32 1254.10 44.24 10.268 0.2312 71.81 Easy to dredge and descend ZL8 23.79 1294.57 36.44 6.983 0.3916 86.97 Easy to dredge and descend ZL9 23.40 1288.60 126.76 4.458 0.1352 473.90 Easy to dredge and descend ZL10 40.00 1257.51 69.66 5.492 0.2788 211.40 Easy to dredge and descend

[0088] Step 1.6: Aquifer Resilience Analysis Based on Long-Range Hole Water Level Changes

[0089] Based on the time-varying water level curves of the lower section of the Zhiluo Formation in the coal mine, the aquifer permeability analysis was conducted.

[0090] In this example, step 2, based on the top and bottom conditions of the target mining area's working face, uses theoretical analysis and numerical simulation to predict the development height of the water-conducting fracture zone and caving zone of the coal mining face, analyzes the damage of the plastic zone near the working face after coal seam mining, and determines the communication between the "two zones" and the overlying aquifers and water-bearing strata. The specific implementation method is as follows:

[0091] Step 2.1: Determine the basic theory of overlying strata collapse in the goaf.

[0092] During coal seam mining, the caving and fracture evolution patterns of the overlying strata determine the distribution, shape, and evolution of the caving and fracture zones, serving as crucial evidence for determining the extent of gas migration in the goaf. The fragmentation and subsidence characteristics of the caving rock determine the porosity and permeability distribution in the goaf, thus influencing the gas migration process. These factors form the foundation for studying the gas migration and enrichment patterns in layered goafs over coal seams.

[0093] After coal seams are mined, the original stress balance around the goaf is broken, causing a redistribution of stress, which leads to deformation, damage and movement of the rock strata. Based on the mine pressure hypothesis proposed by his predecessors, Academician Qian Minggao proposed the "masonry beam" theory through extensive production practice and field observation of internal rock strata movement. Because the rock mass morphology in front of and behind the mining face is similar to that of masonry, it is called "masonry beam". This theory fully explains the manifestation law of mine pressure in the mining area and provides a theoretical basis for mine pressure control in the mining area.

[0094] Above the immediate overlying strata lie multiple layers of rock of varying thickness and strength. Practice has shown that during overlying strata movement, one or more hard, thick rock layers play a major controlling role; these layers are called key layers. Fracturing a key layer can cause a significant portion or all of the overlying strata to move as a whole. Based on the "masonry beam" theory, the "key layer theory of rock strata control" was developed, focusing on key layers. This theory organically unifies the study of rock strata movement with the study of gas flow in mined coal and rock masses, laying a solid foundation for a more comprehensive and in-depth explanation of the laws governing mining rock mass activity and the exploration of fluid flow patterns within coal and rock masses.

[0095] Coal seam mining activities cause the movement and fracturing of overlying strata, thus forming mining-induced fractures within the overlying strata. Engineering applications such as pressure relief and gas drainage are closely related to the distribution patterns of these mining-induced fracture fields in the overlying strata. Under the influence of coal seam mining, the overlying strata form delamination fractures and fracture fractures. The former causes the coal seam to expand and deform, thereby relieving gas pressure, which then flows out along the delamination fractures. The latter connects the gas channels between two vertical strata. Based on the key stratum theory, previous researchers have conducted in-depth studies on the distribution of fractures during the movement of overlying strata through extensive theoretical analysis, physical experiments, numerical simulations, and field measurements. The following conclusions were drawn: Before the first failure of the key stratum, the amount of delamination increases with the advancement of the working face, with the largest delamination occurring in the center of the goaf. After the initial failure of the key stratum, the key stratum in the center of the goaf is gradually compacted, but a delamination zone remains on each side of the goaf. The delamination zone closer to the working face moves forward continuously with the advancement of the working face, and its maximum width and height decrease to about one-third of that before the initial failure of the key stratum. From a planar perspective, there are delamination development zones that are laterally connected along the bedding plane around the goaf, called the mining-induced fracture "O" rings. The "O" rings, to a certain extent, refine the development and classification of fractures in the overlying strata, providing a theoretical basis for the design of gas drainage systems.

[0096] Step 2.2: Division of the "two zones" in the goaf and calculation of their height

[0097] According to the "masonry beam" theory and structural model, as the coal cutting and roof caving work proceeds, the overlying strata above the goaf will subside and fracture under the influence of mining activities. This phenomenon will exhibit significant zoning characteristics, with the part closest to the coal seam collapsing first because this area bears a large confining pressure. This area is defined as the collapse zone (Ⅰ). Based on the integrity and deformation of the fractured rock, the upper part of this zone can be further divided into the fracture zone (Ⅱ) and the bending subsidence zone (Ⅲ). According to the internal porosity, the area from the working face support to the cut can be divided into three parts, namely the coal wall support zone (A), the delamination zone (B), and the recompaction zone (C). Figure 2 As shown.

[0098] (1) Collapse zone

[0099] In the initial stage of caving, the immediate roof and the old roof maintain the stability of the overburden. Due to the strength of the coal and rock itself and the supporting effect of the coal wall, the coal and rock mass above the immediate roof can remain relatively stable within a certain length of the working face. As the advance length increases, the immediate roof will first experience periodic caving. After reaching its tensile limit, the old roof will break and collapse under the combined action of its own weight, the load above, and the mining below. The height of the caving zone in the natural accumulation state is mainly determined by factors such as the overburden's breccia coefficient, the mining height, and the coal seam dip angle. The height of the caving zone with a soft roof is about 2 to 4 times the mining height, while it can reach 5 to 6 times the mining height when the roof is hard rock.

[0100] When the coal seam dip angle is small and the overlying strata are extremely hard rock, the empirical formula for calculating the height of the caving zone is:

[0101] (2)

[0102] In the formula: The height of the landslide zone is in meters (m). is the coefficient of rock fragmentation during collapse, dimensionless; The coal seam mining height is in meters (m). The dip angle of the coal seam is , in °.

[0103] If the overlying rock strata consist of hard, medium-hard, weak, and extremely weak rock layers, the empirical formula is:

[0104] (3)

[0105] In the formula: The value is the amount of roof subsidence, expressed in meters (m).

[0106] (2) Fracture zone

[0107] As the caving zone expands, the overlying rock strata shift and deform, disrupting the original structure. This results in horizontal delamination and vertical separation, generating numerous fractures and forming a fracture zone. The vertical fractures in the lower strata of the fracture zone connect with interlayer fractures, allowing groundwater to easily accumulate and migrate. The fracture zone lies above the caving zone, and the direction of delamination extends far along the key strata. Its height is also related to lithology and mining depth; the harder the overlying rock, the greater the height of the fracture zone.

[0108] Based on the hardness of the roof lithology, the height of the caving zone and fracture zone in thick coal seam mining can be calculated using the following empirical formula:

[0109] (4)

[0110] In the formula: a and b are constants; q is a correction coefficient.

[0111] Table 2 Formulas for calculating the height of caving and fracture zones in thick coal seam mining

[0112]

[0113] Note: The cumulative mining thickness of the coal seam is in meters (m). The formula is applicable to layered mining thicknesses of 1 to 3 meters and cumulative mining thicknesses of less than or equal to 15 meters. The ± term in the formula represents the error term.

[0114] According to the empirical formula for fracture zone height in Table 2, this embodiment uses a 6 times caving-to-production ratio to predict the development height of the caving zone and a 28 times guiding-to-production ratio to predict the development height of the water-conducting fracture zone.

[0115] In summary, South Wing 2 -2 The height of the coal seam caving zone in the eastern coalfield ranges from 27.1 to 44.52 meters, and the height of the water-conducting fracture zone ranges from 114.8 to 207.7 meters. -2 The bedrock overlying the coal seam is 27.2m to 88.53m thick, and the water-conducting fracture zone extends all the way to the soil layer.

[0116] Step 2.3: Numerical simulation of the evolution of fractures in the overlying strata of the goaf.

[0117] (1) Introduction to numerical simulation software

[0118] FLAC is a simulation software developed by ITASC that uses the Lagrange difference analysis method. There are two versions, FLAC2D and FLAC3D. The former is used for two-dimensional calculations, while the latter can be extended to three-dimensional space based on it. It can simulate the plastic failure characteristics of materials such as coal and rock when they reach the yield limit based on their mechanical parameters. It is widely used in many fields such as mining and tunnel engineering, and geotechnical mechanics.

[0119] (2) Determination of basic coal and rock mechanical parameters

[0120] The mechanical properties of coal reservoirs are greatly influenced by their fundamental mechanical parameters, and the accurate acquisition of these parameters is crucial for a deeper understanding of gas migration behavior and reservoir stability. Therefore, coal samples were collected from adjacent working faces and boreholes and transported to the laboratory. A rigorous wet coring procedure was implemented according to the authoritative standards issued by the International Society for Rock Mechanics (ISRM).

[0121] To minimize the impact of coal sample heterogeneity and anisotropy on experimental results, strict screening criteria were adopted during coal sample selection to ensure that the selected coal samples represented the typical characteristics of coal seams within the study area. During sample preparation, the original structure and orientation of the coal samples were preserved as much as possible to reduce the impact of human factors on the anisotropy of the coal samples. Before conducting the experiments, coal samples with significant wave velocity differences were eliminated through wave velocity testing to minimize the influence of individual abnormal values ​​on the overall conclusions. Furthermore, extensive experimental data was collected through repeated experiments, and statistical analysis methods were used to process the data. These measures ensured the reliability and accuracy of the experimental results, providing strong support for the study of the mechanical seepage characteristics of coal.

[0122] 1) Uniaxial compression test

[0123] Uniaxial compression tests were conducted using a high-performance dynamic testing machine from Chongqing University. Standard cylindrical sandstone samples were used, with a radial deformation measuring device installed at the circumferential position in the center of the specimen. After sample installation, the test chamber was sealed and all data acquisition sensors were connected, and a contact load was pre-applied. The test employed a displacement control mode, setting the axial loading rate to 0.15 mm / min, while simultaneously activating the real-time monitoring and safety protection system for axial force, axial displacement, and circumferential deformation. After confirming all protective devices were in place, the loading program was initiated, continuously recording various mechanical response parameters until macroscopic failure of the specimen occurred.

[0124] 2) Brazilian splitting test

[0125] The Brazilian splitting test used the AG-250kNIS testing system manufactured by Shimadzu Corporation of Japan. This modular system mainly consists of a servo-hydraulic drive unit, a high-rigidity frame structure, and digital control components, enabling it to meet complex testing needs, including uniaxial compressive strength determination, indirect tensile testing (Brazilian disc method), and cyclic loading and unloading. Experimental data showed that after reaching the strength critical point, it exhibited typical brittle fracture behavior.

[0126] (3) Establishment of numerical simulation calculation model

[0127] According to the South Wing East District 2 -2 The geological data of the coal seam and relevant parameters of the working face are as follows: the length along the positive x-axis strike is 600m, and the length along the positive y-axis dip is 440m. Considering the boundary effect of the model excavation, a 100m protective coal pillar needs to be reserved around the strike and dip of the working face. The entire model consists of 9 coal and rock layers, with close contact between each layer. The simulation starts excavating from x=100m, and proceeds 10 times, each time advancing 40m, for a total advance of 40m. After the first layer is excavated, the second and third layers are excavated in the same manner. The established geometric model and mesh generation are as follows. Figure 3 As shown.

[0128] Since gravity exists in the actual mining area, it needs to be considered. The magnitude of gravity is set to 9.8 m / s². 2 The direction is along the negative z-axis.

[0129] The established model was meshed, with a total of 208,640 mesh elements and 338,611 nodes. The model was assigned values ​​based on the measured mechanical parameters of each coal and rock stratum. The numerical simulation calculation adopted the Mohr-Coulomb model.

[0130] (4) Analysis of stress evolution in overlying strata

[0131] The established model was meshed, with a total of 208,640 mesh elements and 338,611 nodes. The model was assigned values ​​based on the measured mechanical parameters of each coal and rock stratum. The numerical simulation calculation adopted the Mohr-Coulomb model.

[0132] After the working face is mined, the overlying strata are damaged. The working face is excavated 10 times, each time for a certain length. The stress inside the overlying strata changes, and the redistribution of stress reduces the pressure inside the overlying strata, thus creating stress relief zones and stress concentration zones. Therefore, this section will study the stress changes in the overlying strata by observing the stress relief distribution on the transverse section of the model in the simulation results, based on the numerical simulation above, in order to analyze the damage of the overlying strata. Generally, because the strata in the caving zone collapse, the stress they experience is much smaller than the original rock stress. Therefore, the stress magnitude of the strata in the caving zone is shown as 0 in the simulation results, and the stress of the strata in the fracture zone is generally less than the original rock stress.

[0133] (5) Analysis of the evolution of plastic deformation of overburden

[0134] When the load on a rock is stopped, the deformation that cannot return to its initial state due to the destruction of its internal structure is called plastic deformation of the rock. Coal and rock strata, under the influence of mining, form plastic zones under shear and tensile stress. Generally, by calculating the plastic range of the coal seam, the area of ​​damage to the overlying strata caused by mining is analyzed, thus determining the range of the caving zone and fracture zone in the vertical "three zones". The FLAC3D simulation software displays the distribution range of plastic failure of the overlying strata in units of grid cells. The state of each cell is represented by three methods: None, shear, and tension. None indicates no tensile or shear failure, shear indicates shear failure, and tension indicates tensile failure. Shear failure and tensile failure each have two different descriptions: shear-n and shear-p, and tensile failure includes tension-n and tension-p. A suffix of -n indicates that the rock is currently undergoing failure; a suffix of -p indicates that failure occurred in a previous cycle. In FLAC3D numerical simulations, regions where only shear failure occurs are typically considered as fracture zones, while regions where both shear and tensile failure occur simultaneously, with tensile failure being dominant, are considered as collapse zones.

[0135] To determine the plastic failure zone of the overlying strata in the goaf, plastic failure cloud maps of the overlying strata on the Y-axis section were selected and analyzed during 10 excavation processes.

[0136] Combining the results calculated using empirical formulas for caving zones and fracture zones with the numerical simulation results in this section, it is found that the caving zone height in the goaf under fully mechanized top-coal caving mining technology is at least three times the coal seam mining thickness. Therefore, the range of caving zone height calculated using empirical formulas has a large error. Thus, it can be concluded that the height of the caving zone in the south wing 2... -2 The caving zone of the coal seam goaf in the eastern coalfield ranges from 23.21 to 30.22 meters, and the water-conducting fracture zone ranges from 189.33 to 200.47 meters in height. -2 The bedrock overlying the coal seam is 27.2m to 88.53m thick, and the water-conducting fracture zone extends all the way to the soil layer.

[0137] (6) Analysis of the evolution of overlying displacement

[0138] The displacement of the surrounding rock can reflect the development of coal and rock fractures to some extent, and vertical displacement directly reflects the delamination fractures in the coal and rock mass. Analysis shows that after the first layer of excavation, the displacement of the lower coal and rock strata in the goaf is positive, indicating expansion and bulging of the coal seam floor, with the largest bulging located in the middle of the goaf. Conversely, the vertical displacement of the upper coal and rock mass in the goaf is negative, showing a clear gradation phenomenon and generating delamination fractures. Along the strike of the coal seam, the vertical displacement of the strata in the middle of the goaf is the largest, while the displacement of the strata at both ends of the working face is relatively smaller. After the second layer of excavation, the vertical displacement of the coal and rock mass within a certain depth range in the lower part of the coal seam decreases, and the vertical displacement of the coal seam is no longer symmetrically distributed.

[0139] In this case, taking the coal mining face of the 2-2 coal seam in the south wing as the research background, the study combined indoor mechanical experiments with three-dimensional numerical simulation to verify the evolution law of the overburden spatial structure and the development height of the "two zones" (caving zone and water-conducting fracture zone) during the coal seam mining process.

[0140] First, to ensure the authenticity and reliability of the numerical simulation results, this embodiment conducted systematic indoor basic rock mechanics experiments. By standard processing and testing of coal and rock cores collected in the field, the basic mechanical parameters of the top and bottom rocks at each stratum were accurately obtained, laying a solid physical and mechanical foundation for constructing a high-precision numerical model.

[0141] Based on this, this step utilizes FLAC3D finite difference numerical simulation software to establish a three-dimensional geomechanical model that conforms to the actual stratigraphic structure and boundary conditions of the study area. The simulation process employs the Mohr-Coulomb yield criterion and realistically reproduces the full-cycle dynamic mining process of the working face's self-cutting advance through step-by-step excavation commands. To comprehensively reveal the overburden failure mechanism, this step focuses on in-depth analysis from three core dimensions: In terms of stress evolution, it reveals the formation process of the pressure relief zone above the goaf and the dynamic concentration and transfer law of the supporting pressure before and after the working face; in terms of the evolution of overburden plastic deformation, it tracks in detail the entire process of the rock strata transforming from elastic deformation to tensile and shear plastic yielding, visually demonstrating the initiation, expansion, and connection paths of the fracture network; in terms of overburden displacement evolution, by monitoring the subsidence curves of different layers of the roof, it analyzes the asynchronous nature of rock strata displacement and the evolution characteristics of the delamination space.

[0142] The simulation ultimately quantitatively determined the South Wing 2 -2 The boundary of overlying strata failure in the working face of the eastern coalfield: the development range of the goaf caving zone is 23.21–30.22 m, and the height of the water-conducting fracture zone reaches 189.33–200.47 m. Of particular concern is that the thickness of the bedrock overlying the coal seam in the study area is only 27.2 m–88.53 m, meaning the water-conducting fracture zone will completely penetrate the overlying bedrock and develop entirely into the loose surface soil layer.

[0143] Finally, the developmental height of the "two zones" obtained from FLAC3D numerical simulation was cross-compared with the theoretical calculation results from traditional empirical formulas. The two results showed a high degree of agreement, mutually confirming the scientific validity and rationality of the research methods and parameter values ​​used in this step.

[0144] In this embodiment, the specific implementation process of collecting geological exploration data and geophysical exploration data of the target mining area in step 3, and locating the water-rich area of ​​the aquifer region of the working face, is as follows:

[0145] Step 3.1: Multi-source data collection and preprocessing

[0146] (1) Geological exploration data acquisition

[0147] Geological exploration data is the fundamental information source for water-bearing assessment. This applies to the southern wing 2. -2 In the eastern coalfield, it is necessary to systematically collect borehole core data, including key parameters such as aquifer thickness, lithological assemblage characteristics, rock quality index (RQD), core recovery rate, and borehole leakage. Borehole core data directly reflects stratigraphic lithological variations and fracture development, serving as the fundamental basis for determining aquifer water storage capacity. Simultaneously, detailed regional geological structural information needs to be collected, including fault scale index, fault influence radius, and fold development degree. Studies show that the fault scale index is positively correlated with aquifer water-bearing capacity; the fault influence radius can reach 700–750 m, and areas with well-developed structures are often concentrated areas of aquifer anomalies.

[0148] (2) Geophysical exploration data acquisition

[0149] Geophysical exploration is an effective means of identifying water-rich anomaly zones, offering advantages such as wide detection range and high resolution. (Regarding the southern wing 2...) -2 In the eastern coalfield, a combined detection scheme integrating transient electromagnetic (TEM) and radio tunneling methods is recommended. TEM is highly sensitive to low-resistivity bodies (water-bearing structures) and can effectively detect the spatial distribution of aquifers in the floor or roof. Radio tunneling methods can delineate hidden geological anomalies within the mining area, such as faults and collapse columns. Both methods have been successfully applied in hydrological detection at coal mine faces. Studies have shown that the combined application of radio tunneling and TEM can improve the accuracy and precision of detecting water seepage hazards at the working face. Furthermore, audio-frequency electromagnetic (ETEM) can also be used as a supplementary detection method to analyze the specific hydrological characteristics of anomaly areas.

[0150] Step 3.2: Analysis of Controlling Factors and Construction of Indicator System

[0151] (1) Identification of controlling factors

[0152] The water-bearing capacity of an aquifer is controlled by a combination of geological factors, requiring a systematic analysis from aspects such as lithological differences, hydraulic characteristics, tectonic factors, and geophysical parameters. (Combined with the southern wing 2) -2 Based on the actual geological conditions of the East Coal Mine area, the following key controlling factors are recommended: Aquifer thickness: The greater the thickness, the richer the water-bearing space, and the stronger the water-bearing capacity. Lithological characteristics: Brittle rocks such as sandstone have well-developed fractures and strong water-bearing capacity; plastic rocks such as mudstone have weaker water-bearing capacity. The brittle-plastic ratio of the rock strata can be used for quantitative characterization. Tectonic development degree: Including fault scale index, fold intensity, etc., reflecting the effect of tectonic activity on water-bearing space. Borehole leakage: The amount of mud lost during drilling directly reflects the degree of fracture development and is closely related to water-bearing capacity. Geophysical parameters: Transient electromagnetic apparent resistivity, pit penetration attenuation coefficient, etc., can indirectly reflect the water-bearing situation.

[0153] (2) Construction of indicator system

[0154] Based on the above analysis of the main controlling factors, an indicator system capable of comprehensively and accurately depicting the distribution pattern of water-bearing properties is constructed. Each factor indicator needs to be standardized and dimensionless to lay the foundation for subsequent multi-factor information fusion.

[0155] Step 3.3: Construction of the water abundance index model based on AHP and local variable weight model

[0156] (1) Determining basic weights using the Analytic Hierarchy Process (AHP)

[0157] The Analytic Hierarchy Process (AHP) is a multi-criteria decision-making method that combines qualitative and quantitative approaches, suitable for weight allocation in complex geological problems. Its basic steps include: establishing a hierarchical structure, constructing a judgment matrix, calculating weight vectors, and conducting consistency checks. By inviting hydrogeological experts to compare the relative importance of each controlling factor pairwise, the basic weights of each factor can be determined. However, the traditional AHP method determines constant weights, meaning the weights of each factor remain fixed throughout the evaluation area, failing to reflect changes within a single controlling factor or changes under combined conditions of multiple factors.

[0158] (2) Introduction of the local variable weight model

[0159] To address the limitations of the constant weight model, a variable weight theory is introduced to construct a local variable weight water-bearing index model. The core idea of ​​the variable weight model is that the weights are dynamically adjusted according to the changes in the state values ​​of factors. When a factor is in an abnormal state (such as particularly high fault density or particularly low apparent resistivity), its weight is automatically increased, thereby improving the model's response to geological anomalies.

[0160] The key steps in constructing a local variable weight model include:

[0161] Weighting interval division: Using the K-means clustering method in dynamic clustering, the threshold values ​​for weighting intervals are divided based on the distribution characteristics of the measured data of each main control factor. State-based weighting vector construction: The weighting parameters for each factor under different state values ​​are determined, and a mathematical expression for the state-based weighting vector is established. Weighting parameter determination: The weighting parameters that optimize the model's sensitivity are determined through optimization algorithms or empirical formulas. Research shows that the sensitivity undergoes an inflection point change when the weighting parameters vary by ±5%.

[0162] (3) Calculation of local variable weight water-bearing index

[0163] Based on the above theory, a local variable-weight water-bearing index evaluation model is constructed:

[0164] (5)

[0165] in, The water-richness index, For the first Standardized values ​​of the main control factors This model represents locally variable weights that change with the state of the factors. It can determine not only the weights of different evaluation indicators, but also the different weights of the same indicator at different state values.

[0166] Step 3.4: Drawing contour lines of water-bearing index and evaluating regional distribution.

[0167] (1) GIS-based spatial analysis

[0168] Thematic data for each controlling factor are input into a Geographic Information System (GIS) platform to create their respective thematic layer maps. Using the spatial overlay analysis function of GIS, multi-source geological information is compositely overlaid to calculate the local variable-weight water-bearing index for each spatial unit. Research shows that GIS technology can be used to perform multi-factor overlay calculations and generate quantitative zoning maps of water-bearing hazard.

[0169] (2) Contour drawing and regional division

[0170] Using professional mapping software such as Surfer, contour lines were plotted on the calculated local variable-weight water-bearing index. By analyzing the spatial distribution pattern of the water-bearing index, the water-bearing zoning of the aquifer region was determined. The water-bearing classification standard can refer to existing research results, such as classifying water-bearing into different levels such as weakly water-bearing, moderately water-bearing, and strongly water-bearing.

[0171] (3) Verification and correction of evaluation results

[0172] To ensure the reliability of the evaluation results, pumping test data can be used to verify and correct them. Studies show that correcting the evaluation results using five sets of pumping test data can significantly improve the evaluation accuracy. Compared with traditional constant-weight evaluation results, the variable-weight model's evaluation results better reflect the heterogeneous characteristics of the aquifer and have higher prediction accuracy. In practical applications, the vulnerability index is positively correlated with aquifer water pressure and fault scale, and negatively correlated with the thickness of the impermeable layer. The consistency of the zoning results can be verified by comparing the locations of known water inrush points or inflow points.

[0173] The aquifer water-bearing capacity evaluation method based on multi-source information fusion and a local variable weight model has the following technical advantages: Multi-source information fusion: Integrating geological drilling data and geophysical exploration data, fully utilizing the complementarity of various information sources improves the comprehensiveness of the evaluation. Dynamic weight adjustment: The variable weight model overcomes the limitations of traditional constant weight models, enabling more sensitive responses to local geological anomalies. Visual output: Generating intuitive water-bearing capacity zoning maps based on the GIS / Surfer platform provides direct basis for water control engineering design. Engineering guidance value: The evaluation results can directly support decisions on water control engineering such as grouting modification and depressurization. The following analysis combines specific research findings.

[0174] In this embodiment, step 4, based on the evaluation results and water inrush prediction results of the aquifer roof of the target mining area, combined with the aquifer water-bearing location results and the development height of the water-conducting fracture zone, studies a long-distance targeted drainage scheme for the aquifer area, and establishes a water hazard prevention scheme and parameters for the target mining area's targeted working face. The specific implementation process is as follows:

[0175] Step 4.1: The meaning and necessity of targeted water drainage

[0176] (1) The core concept of targeted water drainage

[0177] Targeted drainage refers to the precise location of aquifer anomaly zones based on the spatial distribution of aquifer water abundance and the development characteristics of water-conducting fracture zones. Drainage boreholes are then strategically and selectively deployed to proactively control roof water hazards. Compared to traditional extensive drainage, targeted drainage emphasizes the principle of "draining where water is abundant and treating where there is a threat," effectively avoiding over- or under-drainage and significantly improving the economy and effectiveness of water control projects.

[0178] (2) The engineering necessity of targeted release

[0179] According to South Wing 2 -2Previous research in the eastern coalfield revealed significant spatial heterogeneity in the water-bearing capacity of the weathered bedrock aquifer. The S1232 working face, the one least affected by the fire zone in the southern wing, experienced an initial underground water release rate as high as 1697 m³ / h, with particularly high water levels in boreholes near the fire zone. This data clearly indicates that without targeted pre-drainage measures, the working face will face a significant threat of instantaneous water inflow peaks during mining operations, not only increasing mine drainage costs but also potentially triggering water inrush and sand collapse accidents, seriously threatening mining safety. Therefore, it is essential to conduct refined and targeted research on water-bearing zoning and the development of water-conducting fracture zones.

[0180] Step 4.2: Determination of key parameters for the targeted drainage scheme

[0181] (1) Optimization of borehole space layout parameters

[0182] The layout of borehole space is the core of the targeted drainage scheme, and it is necessary to comprehensively consider multiple factors such as the characteristics of water-rich zones, the development morphology of water-conducting fracture zones, and the economics of drilling projects.

[0183] Determination of the final borehole level: Studies have shown that the water-conducting fracture zone is the main channel for roof water to enter the working face. Therefore, the upper limit of the water-conducting fracture zone should be used as the final borehole control level for drainage boreholes. Based on the analysis of the South Wing 2... -2 Accurate prediction of the development height of the water-conducting fracture zone in the coal roof (by correcting empirical formulas with measured data to obtain a calculation formula that conforms to the actual situation in the study area) can determine the reasonable depth of borehole penetration into the aquifer, ensuring effective exposure of the water-rich section while avoiding engineering waste caused by excessive drilling.

[0184] Drilling elevation angle design: The drilling elevation angle should be designed based on the fracture angle formed by the mining-induced fracture zone. The fracture angle reflects the dip characteristic of the mining-induced fracture, and matching the drilling elevation angle with it can maximize the exposure of the fracture development direction and improve the drainage efficiency. At the same time, the drilling elevation angle design must also consider the terrain conditions and the drilling rig's construction capabilities to ensure the feasibility of the project.

[0185] Borehole group layout: Within a single drilling site, the borehole layout should balance drainage efficiency and engineering economy. Research results indicate that a layout of ≤3 boreholes with an included angle of 60° within a single drilling site is the optimal solution. This layout can form a three-dimensional drainage network within a limited space, ensuring sufficient exposure of the aquifer while avoiding engineering overlap caused by excessively small borehole spacing. Furthermore, based on the roof water inflow characteristics of different subsequent mining faces, differentiated borehole construction modes can be determined for first-mining type two-way drainage and adjacent-mining type single-way drainage.

[0186] Applications of long-distance directional drilling: For areas with high water abundance, long-distance directional drilling technology can be introduced for tracking and releasing water. This technology can extend long distances along the target strata, precisely control the borehole trajectory, and achieve targeted drainage of water-rich areas at a distance. Combined with the South Wing 2... -2 The working face layout in the East Coal Mine area features diversion boreholes in the outer roadway and interception boreholes in the adjacent face, forming a governance pattern of "combining dredging and blocking, and regional prevention and control".

[0187] (2) Control of release cycle and timeliness

[0188] Prioritizing the reduction of static reserves: The water inflow in a water-bearing aquifer on the roof of a coal seam consists of two parts: static reserves and dynamic recharge. Static reserves refer to the volume of groundwater contained in the aquifer, characterized by a large initial inflow and rapid decay. Dynamic recharge, on the other hand, is the portion continuously supplied by lateral runoff from the periphery, manifesting as a stable, long-term inflow. A reasonable approach to preventing roof water hazards is to pre-emptively reduce (dry) the static reserves of groundwater within the influence range of water-conducting fractures to the greatest extent possible before mining, thereby reducing the intensity of concentrated water inflow during the mining process.

[0189] Identification and Control of Drainage Cycle: Drainage projects need to be carried out continuously until the borehole inflow stabilizes. This study proposes using the quasi-stable borehole inflow cycle as a basis to determine an optimized "time"-based drainage principle. In practical engineering, by continuously monitoring changes in borehole inflow, a key criterion for achieving the drainage target is that the total drainage volume exceeds the static aquifer reserve and the stable borehole inflow is less than the dynamic reserve. For working faces with similar geological conditions, an effective drainage period of approximately 18 months is typically required to meet safe mining requirements.

[0190] Step 4.3: System Construction of Regional Targeted Water Discharge Scheme

[0191] (1) Differentiated release strategy based on water-rich zones

[0192] Based on the preliminary water-bearing capacity assessment results, the south wing 2 -2 The coal roof aquifer is divided into weakly aquifer-rich, moderately aquifer-rich, and strongly aquifer-rich zones. Different drainage strategies are implemented for each zone:

[0193] In areas with abundant water, dense drilling groups will be deployed, and long-distance directional drilling will be used for tracking and exploration to implement high-intensity, high-flow-rate concentrated drainage. This area is the core source of water inrush risk, and it is essential to ensure sufficient drainage and reduction of static reserves before extraction.

[0194] In moderately water-rich areas: conventional drainage boreholes are arranged according to the optimized borehole layout pattern to maintain an appropriate drainage intensity and prevent the risk of water inrush.

[0195] In areas with low water abundance, the number of observation wells should be appropriately increased, with monitoring as the primary focus and drainage as a secondary measure, to avoid engineering waste.

[0196] (2) Engineering organization for centralized and unified evacuation

[0197] To achieve systematic management of the aquifer on the roof, a centralized and continuous drainage engineering organization model should be adopted.

[0198] (3) Evaluation and dynamic optimization of evacuation effect

[0199] A robust evaluation and feedback mechanism must be established during the dredging process. Methods such as grey relational analysis should be employed to propose criteria for judging dredging effectiveness. The dredging effect should be dynamically assessed by comparing changes in borehole inflow, water pressure drop, and aquifer recharge intensity before and after dredging. If the dredging effect in a certain area is found to be substandard, additional boreholes should be drilled or dredging parameters adjusted promptly to ensure the achievement of overall remediation goals.

[0200] By implementing the above-mentioned targeted water drainage scheme, the following engineering objectives are expected to be achieved: Reducing the static storage of the aquifer: Centralized drainage can significantly reduce the static storage of the roof aquifer, weakening the energy reserve for water hazards. Reducing the peak water inflow intensity during mining: Pre-drainage ensures that the water inflow during mining primarily relies on dynamic replenishment rather than the release of static storage, thus significantly reducing the peak water inflow intensity. Referring to the treatment experience of the S1232 working face, a combination of grouting curtain and drainage measures can achieve a good effect of less than 10 m³ / h in measured water inflow at the working face. Ensuring safe mining of the working face: Through systematic targeted drainage, the safe mining of the south wing 2 can ultimately be ensured. -2 During the mining process, the water inflow at each working face in the East Coal Mine area is controllable and the risks are preventable, thus achieving safe and efficient production.

[0201] Based on South Wing 2 -2 Based on the evaluation results of the water-bearing capacity of the roof aquifer in the East Coal Mine area and the research findings on the development height of the water-conducting fracture zone, targeted water drainage scheme research is conducted, which is a key measure to implement the concept of "scientific water management and precise prevention and control". By optimizing borehole spatial layout parameters (final borehole position, borehole elevation angle, and group layout pattern), scientifically controlling the drainage cycle (prioritizing static reserve reduction and identifying quasi-stable water inflow cycles), and constructing differentiated regional drainage strategies, a systematic and operable roof water hazard prevention and control technology system has been formed. The implementation of this scheme will effectively reduce the static reserve of the aquifer, lower the instantaneous peak water inflow intensity during working face mining, and provide protection for the South Wing 2... -2 The safe mining in the eastern coalfield provides a reliable guarantee and also offers useful lessons for the prevention and control of water hazards in mines with similar geological conditions.

[0202] Step 4.4: Determining the Drilling Layout

[0203] (1) Drilling site location

[0204] According to South Wing 2 -2Based on the actual conditions of the East Coal Mine area and considering the principles of optimizing construction workload and facilitating construction, the drilling site will be located at the auxiliary haulage roadway of the S1234 working face, the cut-out of the S1236 working face, the cut-out of the S1237 working face, and the South Wing 2. -2 The rubber transport tunnel in the eastern coalfield, and the southern wing 2 -2 The drainage measures in the eastern area allow for proactive water exploration and release, while also facilitating centralized and unified drainage work later on.

[0205] (2) Drilling layout

[0206] The Zhiluo Formation weathered bedrock fissure confined aquifer is characterized by uneven water abundance and permeability, and multidirectional water flow. Based on the hydrogeological conditions of the exploration area, the overall water abundance of the Zhiluo Formation weathered bedrock fissure confined aquifer is moderate, with a relatively large static reserve. The coal seam caving zone height ranges from 27.1 to 44.52 m, while the thickness of the overlying normal bedrock is only 8.1 to 36.53 m, with an average thickness of 25.05 m. The caving zone, formed by collapse, is characterized by fragmented blocks, numerous voids, and strong connectivity, which facilitates water passage.

[0207] The drilling layout followed the principles of zoning, even distribution, and overall drainage. It employed a combination of long-distance directional drilling and short-distance conventional drilling to proactively drain water, increase the drainage area, reduce drainage blind spots, and ultimately ensure safe mining operations at the working face.

[0208] 1) Directional drilling

[0209] The design includes 13 drilling sites and 61 drainage boreholes, including 13 main boreholes and 19 branch boreholes, with an estimated total length of 23,742 m.

[0210] 2) Conventional drilling

[0211] This design includes 3 drilling sites and 12 drainage boreholes, with an estimated total length of 1612m.

[0212] Step 4.5: Selection of Final Hole Layer

[0213] This drilling project requires the effective drainage of all aquifers within the overlying bedrock, especially the aquifers in the fractured zone of the weathered bedrock, which are the main target aquifers for drainage. All directional borehole trajectories must be controlled in the upper and middle parts of the weathered bedrock, with the main borehole trajectory 10-20m from the bottom interface of the laterite layer and the final borehole 5-10m from the bottom interface of the laterite layer. All conventional boreholes must penetrate all the overlying bedrock on the working face and terminate when they enter the laterite layer 1.0-2.0m.

[0214] Step 4.6: Determine the vertical distance of the borehole.

[0215] Based on the borehole data of SB42, BK48, SB43, BK46, etc. in the working face, the vertical distance of the boreholes was determined. The thickness from the roof of coal seam 2-2 to the bottom boundary of the laterite layer is 27.2m to 88.53m, with an average thickness of 51.3m.

[0216] The vertical and horizontal distances of the borehole can determine the elevation angle and hole depth. In actual construction, dynamic adjustments and information-based construction should be made according to the actual situation.

[0217] Step 4.7: Determine the parameters and structure of the drainage borehole.

[0218] Directional drilling: The drilling design is a two-stage process, i.e., opening with a Φ152mm drill bit and sealing with cement. A 10.5m long Φ127mm borehole casing is then lowered, and a Φ94mm drill bit is used to close the hole.

[0219] Conventional drilling: The borehole is designed with a two-stage structure, i.e., a Φ152mm drill bit is used for opening, and the hole is sealed with cement. A 10.5m long Φ108mm borehole casing is lowered, and a Φ94mm drill bit is used to close the hole.

[0220] Step 4.8: Determine drilling technical requirements

[0221] (1) Conditions for commencement of construction

[0222] S1234 working face auxiliary transport roadway, S1236 working face cut-out, S1237 working face cut-out, South Wing 2 -2 The rubber transport tunnel in the eastern coalfield, and the southern wing 2 -2 With the drainage measures in the East District well-maintained, the monitoring video functioning normally, and ventilation, water supply, power supply, drainage, and communication in place, and with standardized on-site preparations in place, construction can commence after passing the acceptance inspection by the Department of Geological Survey and Water Control.

[0223] (2) Drilling rig positioning

[0224] The YHZ90 / 360 intrinsically safe mining drilling rig borehole positioning instrument was used for this drilling positioning. When determining the borehole location, it must be strictly determined and marked by specialized surveyors according to the design. The personnel responsible for construction must be present on-site to jointly mark the borehole's opening position, azimuth, and inclination angle according to the design. The drilling rig must be installed stably and securely. When connecting the power to the drilling rig, the power-on / off procedure must be strictly followed. After drilling, the azimuth and inclination angles must be corrected again, and drilling can only proceed after confirmation. No changes are allowed without the designer's approval.

[0225] (3) Aperture requirements

[0226] Construction was carried out strictly in accordance with the designed hole diameter and drilling structure, and the final hole diameter of all holes was Φ94mm.

[0227] (4) Length, installation and fixing of the orifice pipe

[0228] According to Article 48 of the "Detailed Rules for Water Prevention and Control in Coal Mines," when the expected water pressure during water exploration and drainage in rock strata is 1.0 ≤ P < 2.0 MPa, the length of the borehole sealing casing should be greater than 10m. Based on the borehole data (SB42, BK48, SB43, BK46, etc.) within the working face, the vertical distance of the boreholes was determined. The thickness from the roof of coal seam 2-2 to the bottom boundary of the laterite layer is 27.2m to 88.53m, with an average thickness of 51.3m. Therefore, the expected hydrostatic pressure of the borehole is less than 1.5 MPa, and the length of the sealing casing is 10.5m. A section of hard and intact rock strata was selected for drilling, and the borehole diameter should be 1-2 levels larger than the diameter of the borehole pipe. For this design, a Φ152mm drill bit was selected for directional drilling. After drilling to the predetermined depth, a 10.5m long Φ127mm casing was lowered, and the borehole was sealed with cement with a water-cement ratio of 0.6:1 (ensuring the casing is secure and leak-proof). After 72 hours of solidification, the gate valve was installed.

[0229] (5) Pressure resistance test

[0230] All borehole casings must undergo a pressure test after consolidation. According to Article 46 of the "Detailed Rules for Water Prevention and Control in Coal Mines," the water-stopping casing must undergo a pressure test, with the pressure value not less than 1.5 times the expected static water pressure. For boreholes also used for grouting, the pressure value should be determined based on the final grouting pressure and stabilized for at least 30 minutes. The vertical distance of the boreholes is determined based on borehole data from SB42, BK48, SB43, and BK46 within the working face. -2 The thickness from the coal roof to the bottom boundary of the laterite layer is 27.2m to 88.53m, with an average thickness of 51.3m. The expected hydrostatic pressure of the borehole is less than 1.5MPa. The pressure for this pressure test is 2.5MPa, and the pressure stabilization time is not less than 30 minutes. Drilling can only continue after confirming that the pressure can be held up without leakage and that the water-stopping sleeve is firm and not loose. Otherwise, the sleeve must be re-fixed.

[0231] (6) Water pressure and flow rate observation

[0232] Considering the need to collect data such as water volume and pressure during water discharge, a ball valve and a high-precision acid and alkali resistant pressure gauge should be installed at the outer end of the orifice pipe. After the drilling is completed and the water flow from the borehole stabilizes, the water volume should be measured. One week after the drilling is completed and the water pressure stabilizes, the water pressure should be measured.

[0233] (7) Borehole surveying

[0234] According to Article 55 of the "Shaanxi Province Coal Mine Water Prevention and Control Management Regulations (Trial Implementation)," inclination measurement should be conducted after the completion of water exploration and drainage boreholes, and the number of boreholes measured should not be less than 30% of the total number of water exploration and drainage boreholes. The ZYL-6000D kilometer directional drilling rig used in this directional drilling project is equipped with a YSX20 mining-grade measurement-while-drilling device, which meets the inclination measurement requirements for all boreholes. A total of 12 ordinary boreholes were drilled, and inclination measurements were conducted on boreholes D1, D3, D5, and D7.

[0235] After each drilling site is completed, a pressure gauge is installed on the ball valve. A U-shaped pipe is connected and fixed to the top of the tunnel via a flange connection. Then, a water discharge hose is connected; the hose type is Φ127mm for directional drilling and Φ108mm for conventional drilling. The water discharge hose is laid along the roof and both sides of the tunnel to the floor, secured every 1.5m with pipe clamps to ensure the hose is horizontal and vertical. Finally, a gate valve is installed at the end of the water discharge hose. If the borehole water volume is greater than 20m³, a gate valve is installed. 3 / h, install a flow meter on the gate valve.

[0236] After the drilling site construction is completed, the drilling site identification management board and the drilling water inflow observation board are hung. The water volume and water pressure are observed before the water volume of a single hole stabilizes. After the water volume and water pressure stabilize, the working face drilling construction summary report is prepared, and the on-site management of drainage is transferred to the responsible unit.

[0237] (10) Pay attention to checking whether there are signs of water in the surrounding area of ​​the drilling site. If it is found that the drilling site is very close to the water accumulation point or the surrounding rock of the drilling site is unstable, which may cause unsafe construction, another safe location should be selected as the new drilling site for drilling construction.

[0238] (11) During the drilling process, observe the water volume and pressure when the borehole starts to produce water, the water volume and pressure during the water production process, the water volume and pressure when the water production reaches its maximum, as well as the stable simple hydrological observation and drilling original records.

[0239] (12) Close monitoring is required. If any of the following phenomena are found: soft coal and rock, spalling, pressure buildup, backflow of water into the borehole, sudden increase in water pressure or volume in the borehole, or drill bit jacking, drilling must be stopped immediately. However, the drill rod must not be pulled out. The borehole depth should be recorded and the drill rod should be secured at the same time. The technical personnel should be notified immediately, and a dedicated person should be assigned to monitor the water situation. In case of a critical situation, personnel threatened by water should be evacuated immediately.

[0240] (13) If harmful gases are found to be emitted during drilling, ventilation should be increased while sealing the borehole with yellow mud and wooden plugs (prepared in advance). If this cannot be dealt with, work should be stopped immediately, the power supply should be cut off, and personnel should be evacuated to a fresh airflow section.

[0241] (14) When encountering high pressure water to top the drill rod, use slips and valves to control the drill rod alternately to make it slowly withdraw from the hole. During operation, personnel are prohibited from standing directly in front of the drill rod.

[0242] (15) Before the start of each directional drilling site, a monitoring video is installed at the drilling site and connected to the mining industry video system to ensure that the video is recorded throughout the drilling process and uploaded in real time or recorded throughout the process using a mobile camera; for conventional drilling, the key strata are recorded during the construction process, and after the completion of a borehole, the drilling process is recorded using an explosion-proof mobile phone.

[0243] (16) Completion conditions

[0244] Once the designed number of boreholes is completed, or the design objectives are achieved and the design task is completed, relevant as-built documentation is submitted, and video and image data is preserved, an application for completion can be submitted.

[0245] Step 4.9: Determine the drilling sequence and project scope.

[0246] The overall construction sequence of the project is arranged according to the working face sequence, with construction proceeding from north to south, face by face.

[0247] The drilling process is as follows: drilling positioning → drilling to the designed depth of the borehole pipe → lowering the borehole pipe and fixing it with cement → continuing drilling to the designed layer after solidification.

[0248] The drilling work includes:

[0249] ① After drilling the core tube, pre-embedding the borehole pipe, and fixing the pipe, a pressure test is conducted;

[0250] ② After the pressure test is passed, install the valve and carry out drilling. For each water exploration and drainage hole, first construct the main hole, and then construct the branch holes in sequence.

[0251] ③ Stop drilling and withdraw the drill bit after reaching the designed final hole position. After withdrawing the drill bit at the final hole, measure the water flow once the water output in the borehole stabilizes; measure the water pressure one week after the final hole is completed and the water pressure stabilizes.

[0252] ④ In accordance with the design requirements, after the construction is completed, a unified pre-drainage process shall be carried out until the water volume and pressure stabilize before handover.

[0253] Step 4.10: Determine the construction process

[0254] The drilling process used is a combination of traditional sliding directional drilling and a dual-power composite drilling process using a screw motor and drilling rig rotation, namely, composite directional drilling.

[0255] Composite directional drilling technology includes two forms: sliding directional drilling and composite drilling. In sliding directional drilling, the power for rock breaking during drill bit rotation is provided solely by the mud pump. The drill bit and screw motor rotor rotate, and the directional drilling rig only applies drilling pressure to the drill string. Other parts of the drill string only experience axial sliding, and the screw motor tool face can maintain a stable orientation, thus achieving continuous manual control of the borehole trajectory. In composite drilling, the mud pump delivers high-pressure water to the bottom of the hole, driving the screw motor to rotate the drill bit. Simultaneously, the drilling rig rotates the drill string and applies drilling pressure, achieving composite rock breaking. A measurement-while-drilling (MWD) device is used to measure borehole trajectory parameters in real time, thus controlling the real-time borehole trajectory. The advantages of this drilling method are: high drilling efficiency, smooth borehole trajectory, prevention of drilling accidents, and facilitating deep hole drilling. However, because the screw motor tool face angle changes continuously with the stator's rotation, continuous manual control of the borehole trajectory is not possible. Nevertheless, the bending variation of the borehole trajectory in composite drilling exhibits certain regularities.

[0256] The composite directional drilling process combines sliding directional drilling with composite drilling. By leveraging the borehole trajectory control function of sliding directional drilling and the high efficiency and smooth trajectory of composite drilling, it can improve the borehole formation rate and efficiency of directional long borehole deep hole drilling while allowing for manual control of the borehole trajectory.

[0257] According to the method described in this embodiment of the invention, based on the estimated water release volume at the working face and the analysis of the mine's hydrogeological conditions, 13 directional drilling sites were designed, with 13 main boreholes and 48 branch boreholes, totaling over 40,000 m of work. Three conventional drilling sites were also designed, with over 12 boreholes, totaling an estimated work volume exceeding 1,600 m. A total of 73 boreholes were arranged, with an estimated total work volume exceeding 41,000 m. Furthermore, the static water reserve of the aquifer was successfully reduced through zoned high- and low-pressure combined drainage technology, lowering the instantaneous peak water inflow intensity during working face mining and ensuring safe working face mining.

[0258] In summary, this invention constructs a complete technical system based on the main lines of "feasibility evaluation of roof aquifer drainage - precise determination of the height of the two mining zones - precise positioning through multi-source information fusion in water-rich areas - regional long-distance directional targeted drainage". This system enables a shift from traditional extensive management to refined, targeted, and engineering-based applications, effectively reducing water hazard management costs, improving mining efficiency and safety levels, and providing a scalable technical route and engineering demonstration for roof water hazard prevention in coal mine working faces under similar hydrogeological conditions.

[0259] The technical solution provided by this invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make several improvements and modifications to this invention without departing from the principles of this invention, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. A method for precise positioning and long-distance targeted drainage of water-rich areas in the roof of a coal mine, characterized in that, Includes the following steps: Step 1: Based on the hydrogeological conditions of the construction mining area, combined with the on-site pumping test of the mine, the water level changes of the aquifer long observation hole, and the water drainage situation of the surrounding mine working faces, conduct a comprehensive analysis of the feasibility of draining water from the roof aquifer. Step 2: Based on the top and bottom conditions of the working face in the target mining area, theoretical analysis and numerical simulation are used to predict the development height of the water-conducting fracture zone and caving zone in the coal mining face, analyze the damage of the plastic zone in the area near the working face after coal seam mining, and determine the communication between the "two zones" and the overlying aquifers. Step 3: Collect geological exploration data and geophysical exploration data of the target mining area to locate the water-rich area of ​​the aquifer region of the working face; Step 4: Based on the evaluation results of the aquifer on the roof of the working face in the target mining area and the prediction results of water inrush, and taking into account the water-bearing properties of the aquifer and the development height of the water-conducting fracture zone, conduct research on the long-distance targeted drainage scheme for the aquifer area, and establish the water hazard prevention and control scheme and parameters for the target working face in the target mining area.

2. The method for precise positioning and long-distance targeted drainage of water-rich areas in coal mine roofs according to claim 1, characterized in that: Step 1, which involves a comprehensive analysis of the feasibility of draining water from the roof aquifer based on the hydrogeological conditions of the mining area, combined with on-site pumping experiments, changes in water level at long-term observation holes in the aquifer, and the drainage situation of surrounding mine working faces, includes: Obtain surface and underground condition data of the target area; Water release tests were conducted in the vertical shaft and the mining area, respectively. Based on the data from mine borehole pumping tests and the experience of mining areas with similar conditions, a feasibility analysis of aquifer drainage is conducted based on the criteria for judging the feasibility of drainage. Based on the changes in water level at long boreholes, the aquifer's permeability was analyzed to obtain the evaluation results of the aquifer on the roof of the working face in the target mining area and the prediction results of water inflow.

3. The method for precise positioning and long-distance targeted drainage of water-rich areas in the roof of a coal mine according to claim 2, characterized in that: The criteria for determining the feasibility of evacuation are as follows: >10, weak supply, easy to be dispersed and subdued; 3≤ ≤10, with strong supply, can be dispersed and subdued; <3, with strong supply lines, direct evacuation is not advisable; in, It is the ratio of drawdown to inflow rate; The water level drawdown within the main controlled release area; This refers to the inflow rate within the main controlled release area.

4. The method for precise positioning and long-distance targeted drainage of water-rich areas in the roof of a coal mine according to claim 1, characterized in that: Step 2, which involves predicting the development height of the water-conducting fracture zone and caving zone of the coal mining face based on the roof and floor conditions of the target mining area using theoretical analysis and numerical simulation, analyzing the damage of the plastic zone near the working face after coal seam mining, and determining the communication between the "two zones" and the overlying aquifers, includes: Establish the basic theory of overlying rock strata collapse in goaf areas; Based on the "masonry beam" theory and structural model, the overlying strata above the goaf are divided into caving zones and fracture zones, and the heights of the caving zones and fracture zones are calculated respectively. Based on the measurement data of basic coal and rock mechanics parameters and the test data of Brazilian splitting experiments, a numerical simulation calculation model was established to conduct numerical simulation analysis on the evolution law of fractures in the overlying strata of the goaf. The predicted results of the development height of the water-conducting fracture zone and the caving zone of the coal mining face were obtained. Based on the prediction results, the damage of the plastic zone in the area near the working face after coal seam mining was analyzed, and the communication between the "two zones" and the overlying aquifers and water-bearing strata was determined.

5. The method for precise positioning and long-distance targeted drainage of water-rich areas in coal mine roofs according to claim 4, characterized in that: The height of the landslide zone is calculated as follows: When the coal seam dip angle is small and the overlying strata are extremely hard rock, the calculation formula is: in, The height of the landslide zone is in meters (m). is the coefficient of rock fragmentation during collapse, dimensionless; The coal seam mining height is in meters (m). The dip angle of the coal seam; If the overlying rock strata consist of hard, medium-hard, soft, and extremely soft rock strata, the calculation formula is as follows: in, This refers to the amount of roof subsidence. The formula for calculating the height of the fracture zone is: in, It is a constant; This is a correction factor.

6. The method for precise positioning and long-distance targeted drainage of water-rich areas in coal mine roofs according to claim 1, characterized in that: Step 3, which involves collecting geological and geophysical exploration data of the target mining area and locating the water-rich zone of the aquifer region at the working face, includes: Collect geological and geophysical exploration data of the target mining area and perform data preprocessing; The main control factors were analyzed on the preprocessed exploration data, and an indicator system was constructed based on the analysis of the main control factors. A water-bearing index evaluation model based on AHP and local variable weight model was constructed, and the local variable weight water-bearing index was calculated. Based on the obtained local variable weight water-bearing index, contour lines of the water-bearing index are drawn, and by analyzing the spatial distribution pattern of the water-bearing index, the water-bearing zoning of the aquifer area is determined, thus realizing the location of the water-bearing zone in the aquifer area of ​​the working face.

7. The method for precise positioning and long-distance targeted drainage of water-rich areas in coal mine roofs according to claim 6, characterized in that: The mathematical expression for the water-richness index evaluation model is as follows: in, The water-richness index, For the first Standardized values ​​of the main control factors These are local variable weights that change with the state of the factors.

8. The method for precise positioning and long-distance targeted drainage of water-rich areas in coal mine roofs according to claim 1, characterized in that: Step 4, which involves studying long-distance targeted drainage schemes for the aquifer region based on the evaluation results and water inflow prediction results of the aquifer roof in the target mining area, and comprehensively considering the aquifer's water-bearing capacity and the development height of the water-conducting fracture zone, and establishing the water hazard prevention scheme and parameters for the target mining area's targeted working face, includes: Based on the evaluation results of the aquifer on the roof of the working face in the target mining area and the water inrush prediction results, the key parameters of the targeted drainage scheme are determined by comprehensively considering the water-bearing properties of the aquifer and the development height of the water-conducting fracture zone. Construct a long-distance targeted water drainage scheme for aquifer regions; Based on the targeted drainage scheme, the layout of drainage boreholes, the final borehole level, the vertical distance of boreholes, as well as the borehole parameters and structure are determined. The drilling technical requirements, drilling sequence, project content, and drilling process are determined based on the conditions for commencement of construction. The final water hazard prevention and control plan and parameters for the target working face in the target mining area were formulated.

9. The method for precise positioning and long-distance targeted drainage of water-rich areas in the roof of a coal mine according to claim 8, characterized in that: The key parameters of the targeted water drainage scheme include: borehole space layout parameters and drainage cycle and time control parameters.

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