A method for treating lagging water inrush disaster of water-rich floor rock stratum goaf

Abstract

This invention discloses a method for controlling delayed water inrush disasters in goaf areas of water-rich floor strata, belonging to the field of coal mine water hazard control technology. The method includes the following steps: Step S1, determining the water-rich floor strata at risk of water inrush by analyzing hydrogeological data; Step S2, investigating the spatial distribution of water-richness in the floor strata using the TSP method and transient electromagnetic method; Step S3, drilling core samples from the roadways on both sides of the coal mine working face towards the water-rich floor strata; Step S4, analyzing the mineral composition, microstructure, and physical and mechanical properties of each floor stratum in the laboratory; Step S5, establishing a goaf floor water inrush failure model under the coupled influence of mining stress and floor hydrostatic pressure using theoretical calculations combined with discrete element numerical analysis, and conducting a risk assessment; Step S6, carrying out advanced drainage treatment on the water-rich floor strata; Step S7, implementing pre-mining grouting reinforcement of the coal mine working face floor strata and thin-layer filling of the floor strata after mining delay.

Description

Technical Field

[0001] This invention belongs to the field of coal mine water hazard control technology, specifically relating to a method for controlling delayed water inrush disasters in goaf areas of water-rich bottom rock strata. Background Technology

[0002] Coal mine floor water inrush is one of the major hazards threatening safe production in mines, especially in mining areas with water-rich floor strata. Mining disturbances can easily induce pressurized water in the floor to break through the aquitard, causing water inrush accidents. Delayed water inrush is characterized by its suddenness, concealment, and high destructiveness, often occurring some time after mining, making prediction and prevention difficult. Traditional water inrush control methods mostly focus on in-process monitoring and post-incident sealing, lacking systematic proactive identification, risk classification, and targeted treatment methods. The treatment effects are limited, and they are often accompanied by long treatment cycles, high costs, and insufficient reliability. While existing technologies have applied hydrogeological exploration, geophysical exploration, and grouting reinforcement, the connections between various links are not tight, data integration is insufficient, and treatment measures lack systematic coordination. Therefore, there is an urgent need for an integrated prevention and control method that can systematically assess the risk of water-rich floor water inrush and achieve precise drainage and enhanced treatment to improve the initiative and scientific nature of coal mine water hazard prevention and control. Summary of the Invention

[0003] In view of this, this application provides a method for treating delayed water inrush disasters in goaf areas of water-rich floor strata. This method is used to systematically assess the risk of water inrush in water-rich floor strata and to achieve an integrated prevention and control method that combines precise drainage with enhanced treatment. This method aims to solve the problems of poor connection between various links, insufficient data integration, and lack of systematic coordination of treatment measures in existing technologies, thereby improving the initiative and scientific nature of coal mine water hazard prevention and control.

[0004] To achieve the above objectives, this application adopts the following technical solution: This application provides a method for controlling delayed water inrush disasters in goaf areas of water-rich bottom rock strata, the method comprising the following: Step S1: By organizing and analyzing hydrogeological data, determine the water-rich strata of the base layer at risk of water inrush. Step S2: Investigate the spatial distribution of water-bearing properties in the bottom strata using the TSP method and transient electromagnetic method; Step S3: Drill core samples from the roadways on both sides of the coal mine working face toward the water-rich floor. Step S4: Analyze the mineral composition, microstructure, and physical and mechanical properties of each bottom rock layer in the laboratory; Step S5: Using theoretical calculations combined with discrete element numerical analysis, establish a model of goaf floor water inrush failure under the coupled influence of mining-induced stress and floor hydrostatic pressure, and conduct a risk assessment. Step S6: Based on the risk assessment results of step S5, carry out advanced drainage treatment on the water-rich foundation slab. Step S7: Implement pre-mining grouting reinforcement of the bottom plate of the coal mining face and thin-layer filling of the bottom plate after mining.

[0005] In this way, a systematic method for treating water inrush in water-rich foundations is provided, covering the entire process of assessment, detection, testing, simulation, drainage, and reinforcement.

[0006] In some embodiments, step S1 specifically involves: collecting and organizing preliminary geological exploration reports, hydrogeological data from adjacent coal mining areas and coal mining faces; analyzing the main water-rich rock strata in the bottom strata of the coal mining face; and classifying the water inrush risk of the water-rich bottom strata into four levels: no water inrush risk, weak water inrush risk, moderate water inrush risk, and strong water inrush risk, based on the hydrostatic pressure, water inflow, stratum thickness, thickness and strength characteristics of the overlying direct bottom strata.

[0007] This allows for the classification of sudden water inrush risks, providing a basis for subsequent precise management.

[0008] In some embodiments, step S2 specifically involves: using the TSP method and transient electromagnetic method to detect the water-bearing characteristics of the bottom rock strata below the coal mining face in the roadways on both sides of the coal mining face, and drawing a spatial distribution plan of the water-bearing properties of the bottom rock strata based on the detection results, so as to determine the key treatment areas for water inrush in the water-bearing bottom rock strata.

[0009] This allows for precise identification of water-rich areas, improving the targeted nature and efficiency of governance.

[0010] In some embodiments, step S3 specifically involves: drilling a core sample from the bottom corner of the sidewall of the coal mine working face towards the bottom rock stratum below the working face; extending the borehole to the bottom of the water-rich bottom rock stratum; testing the hydrostatic pressure and single-hole inflow of the water-rich bottom rock stratum on-site; calculating the thickness of the water-rich rock stratum; and comparing and analyzing the collected hydrogeological data and correcting the data.

[0011] In this way, by obtaining the actual parameters in situ, errors in previous data can be corrected, and the reliability of the data can be improved.

[0012] In some embodiments, step S4 specifically involves: performing qualitative and semi-quantitative analysis of the chemical composition and mineral composition of the rock core using an X-ray fluorescence spectrometer and an X-ray diffractometer; The rock cores were processed into cylindrical specimens and Brazilian split specimens to form rock core specimens; An electro-hydraulic servo universal testing machine was used to conduct uniaxial compression tests, Brazilian splitting tests, and variable angle compression-shear tests on the rock core specimens to obtain the uniaxial compressive strength, tensile strength, cohesion, and internal friction angle physical and mechanical parameters of the rock core specimens.

[0013] In this way, by obtaining rock mechanics parameters, support can be provided for numerical simulation and theoretical calculation.

[0014] In some embodiments, in step S5, the maximum damage depth of the water-rich bottom rock layer in the goaf is calculated using a formula. Discrete element numerical models were established based on the engineering geological conditions of the coal mine working face. The numerical simulation parameters of each floor stratum were corrected with reference to the physical and mechanical parameters obtained in step S4. Fluid-structure interaction analysis was conducted based on the measured hydrostatic pressure and aquifer thickness of the water-rich floor stratum to analyze the characteristics of floor crack propagation, stress evolution, and floor displacement failure under the combined influence of mining-induced stress and hydrostatic pressure of the water-rich floor stratum. Safety factor analysis was performed on the failure process of each floor stratum. The safety factor obtained from the simulation analysis under the engineering geological conditions and the maximum failure depth of the goaf floor obtained from theoretical calculation were used to assess the risk of water inrush in the goaf floor. Targeted treatment was carried out for conditions with water inrush disaster risk. The maximum failure depth of the bottom rock strata in the goaf is calculated using the following formula:

[0015] in, This represents the maximum damage depth of the base plate. The length of the working face in a coal mine; This represents the average mining depth. The average unit weight of the overlying strata; The average cohesion of the bottom rock mass; The average internal friction angle of the base rock mass is given.

[0016] This enables quantitative analysis of the water inrush mechanism and precise risk assessment, guiding the formulation of treatment plans.

[0017] In some embodiments, step S6 specifically includes: In coal mines at risk of water inrush, advanced long-bore fracturing and aquifer drainage projects are carried out. Drainage holes are drilled long distances from the bottom corners of the roadways near the working face, extending towards the aquifer beneath the working face floor. These holes reach the lower part of the water-rich floor strata. Hydraulic jet fracturing and hydraulic fracturing operations are then performed on the water-rich floor strata section with the drainage holes. The effectiveness of the hydraulic fracturing is verified by digital television observation after the fracturing. Additional drainage holes are deployed in key areas for water inrush control, focusing on drainage and treatment. A submersible pump is inserted into the bottom of the drainage hole to drain the water flowing into the hole until the drainage volume of a single hole is less than the preset value. At this point, the drainage work of the water-rich bottom rock layer is completed. The TSP method and transient electromagnetic method were used to test the water drainage effect in the roadways on both sides of the coal mining face. Based on the results of geophysical exploration methods, supplementary local long borehole fracturing water drainage was carried out in the test anomaly area. After all the drainage work is completed, random verification holes are drilled at the coal mine working face to check the drainage effect. The number of drainage pores, n, in the pre-drilled long borehole fracturing aquifer is evenly distributed on both sides of the coal mine working face and is calculated according to the following formula:

[0018] Where Q is the inflow of water into the water-rich bottom rock layer; q is the inflow of water into the drainage borehole.

[0019] This allows for efficient aquifer dredging, reducing the risk of sudden water pressure and volume from the source.

[0020] In some embodiments, after the drainage of the bottom rock strata of the coal mine working face is completed, verification holes for drainage effect are randomly drilled on the coal mine working face. The verification holes are arranged in groups, and the number of groups of verification holes is 5% to 10% of the number of drainage holes. Randomly sample 5% to 10% of the drainage holes in the side roadways, and drill verification holes in the roadway sidewall area 1 to 3 meters around the drainage holes. Verification holes account for 30% to 40% of the total number of verification holes in the key areas for floor water inrush control, and verification holes account for 60% to 70% of the total number of verification holes in the remaining areas of the floor of the coal mine working face. The water inflow and head height of the verification borehole were measured, and the borehole water inflow was less than 1m. 3 / h, the water head height is lower than the bottom rock layer of the goaf, and the water-bearing state of the bottom layer is identified as the dewatering state; The advanced long borehole fracturing aquifer drainage project involves drilling long drainage boreholes evenly on both sides of the coal mining face before the formal mining of the coal mining face. The drainage holes are drilled at an angle of 15° to 45° with the horizontal plane along the normal direction of the roadway side until the bottom of the water-rich rock layer. The diameter of the drainage borehole is 150mm to 300mm, and the horizontal position of the borehole end is as close as possible to one-third of the coal mining face.

[0021] In this way, the hydrophobic effect is scientifically verified to ensure that the base plate reaches a safe and dry state.

[0022] In some embodiments, the hydraulic jet fracturing and hydraulic pressure fracturing operations on the water-rich rock strata with drainage holes serve to fracture the water-rich rock strata, expand the fractures in the water-rich rock strata, and connect the artificially fractured fractures with the natural joint fractures. By utilizing the fracture network of the water-rich base rock strata under natural pressure difference, the water existing inside the rock strata seeps into the drainage borehole. The submersible pump at the bottom of the drainage borehole discharges the water gushing from the drainage borehole into the drainage channels on both sides of the side trench, forming a natural pressure difference again, enriching the water in the water-rich base rock strata. This operation is repeated until the rock strata are quickly drained.

[0023] In this way, by constructing a continuous water-conducting fracture network, the drainage speed and drainage efficiency are greatly improved.

[0024] In some embodiments, the installation, fixing, and operation steps of the submersible pump are as follows: The submersible pump is connected to a plastic drain pipe and suspended, and lowered to the bottom of the drainage borehole. The drain pipe is fixed to the wire mesh on both sides of the trough, with the drain outlet facing the drainage ditch. The steel rope is connected to the anchor bolts of the adjacent side. Turn on the submersible pump to drain the water flowing from the drainage hole into the drainage ditch. The fissure water will continuously accumulate at the bottom of the hole under the natural pressure difference. The working cycle of the submersible pump is 1 to 4 hours, depending on the water flow rate of a single hole. After the water-rich bottom rock layer reaches the drainage state, the submersible pump will be stopped and the equipment will be retrieved. The outer diameter of the submersible pump should be smaller than the inner diameter of the drainage hole with sufficient margin. The drainage head should be greater than the vertical depth of the drainage hole. If the bottom rock layer is a weakly cemented rock layer with low strength, consider inserting a rigid casing to prevent large deformation and hole collapse of the borehole, which could jam the submersible pump. The rigid casing in the water-rich bottom rock layer section is designed as a perforated pipe.

[0025] This ensures the safe and stable operation of the drainage equipment and adapts it to complex geological conditions such as weak cementation.

[0026] In some embodiments, the specific operation of grouting reinforcement in step S7 is as follows: several sets of grouting holes are evenly distributed on both sides of the coal mine working face. Each set of grouting holes consists of a grouting distal hole and a grouting proximal hole. The depth of the grouting distal hole extends to the middle of the direct bottom stratum overlying the water-rich rock layer. The horizontal position of the end of the grouting distal hole is as close as possible to three-eighths of the coal mine working face. The depth of the grouting proximal hole extends to the middle of the direct bottom stratum overlying the water-rich bottom stratum. The horizontal position of the end of the grouting proximal hole is as close as possible to one-sixth of the coal mine working face. The direction of the grouting hole is at 20° to 30° with the normal direction of the side wall. The grouting distal hole and the grouting proximal hole are arranged in opposite directions. The grouting uses single-liquid cement grout and CS two-liquid grout.

[0027] In this way, the water-conducting channels are blocked by strengthening the integrity and strength of the bottom rock mass.

[0028] In some embodiments, the specific operation of thin-layer filling in step S7 is as follows: during the mining advance of the coal mining face, the lagging coal mining face is uniformly sprayed with high water and fast-setting material slurry in the goaf; the high water and fast-setting material is composed of materials A and B in equal proportions; full-area filling or partial filling is selected according to the division of the floor water inrush risk area, and the filling thickness is 5cm to 10cm.

[0029] In this way, the deformation of the base plate can be controlled in real time during mining, crack development can be suppressed, and dynamic protection can be achieved.

[0030] Compared with existing technologies, the beneficial effects of this invention are as follows: It provides a systematic and proactive treatment method to address the problems of delayed water inrush in water-rich goaf areas, including its sudden onset, high concealment, passive and lagging traditional treatment methods, disconnected multi-stage processes, and limited treatment effectiveness. Through hydrogeological analysis, comprehensive geophysical exploration, in-situ sampling, laboratory testing, and fluid-structure interaction numerical simulation, it achieves precise risk classification and delineation of key areas for delayed water inrush, solving the problems of unpredictable and unclear risks associated with delayed water inrush. It deeply integrates geological, geophysical, experimental, and simulation data to form a closed-loop system of assessment, detection, analysis, treatment, and verification, overcoming the shortcomings of existing technologies such as poor coordination and insufficient synergy. By employing proactive water drainage and pressure reduction, pre-mining grouting reinforcement, and delayed thin-layer filling during mining, it reduces water pressure and volume at the source, enhances the strength of the goaf, dynamically inhibits fracture propagation, and achieves a shift from passive sealing to proactive prevention. Simultaneously employing targeted treatment and quantitative construction, the treatment cycle is effectively shortened, costs are reduced, and mine safety and treatment reliability are significantly improved, providing a scientific and efficient integrated solution for delayed water inrush in water-rich bottom strata. Attached Figure Description

[0031] Figure 1 A flowchart for the treatment of delayed water inrush disaster in a water-rich bottom rock goaf provided for embodiments of this application; Figure 2 A plan view of the working surface provided for an embodiment of this application; Figure 3 A cross-sectional schematic diagram of the working surface provided for an embodiment of this application. Attached Figure

[0032] 1. Opening cut; 2. Return airway; 3. Transport roadway; 4. Drainage hole; 5. Grouting near hole; 6. Grouting far hole; 7. Grouting hole; 8. Key treatment area for water inrush in the floor; 9. Coal mining face; 10. Direct floor; 11. Water-rich strata; 12. Fracturing zone of aquifer. Detailed Implementation

[0033] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0034] In the embodiments of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0035] In the description of the embodiments of this application, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, at least one of a, b, or c can mean: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, and c can be a single item or a plurality of items.

[0036] In the description of the embodiments of this application, the term "and / or" refers to and covers any and all possible combinations of one or more of the associated listed items. The term "and / or" describes an association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this application generally indicates that the preceding and following related objects have an "or" relationship.

[0037] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, "linking" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. "Fixed connection" refers to a connection where the relative positional relationship remains unchanged after the connection. Furthermore, the directional terms mentioned in the embodiments of this application, such as "inner" and "outer," are only for reference to the directions in the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of this application, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0038] In the description of embodiments of this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0039] Please see Figure 1 , Figure 2 and Figure 3 , Figure 1 A flowchart illustrating a method for mitigating delayed water inrush disasters in water-rich goaf areas provided in embodiments of this application. Figure 2 A plan view of the working surface provided for an embodiment of this application. Figure 3 A cross-sectional schematic diagram of the working surface provided for an embodiment of this application.

[0040] in, Figure 2 The first one is the cutting eye, also called the cutting eye. It is a special roadway that is excavated between the transport roadway and the return airway and along the starting line of the coal seam before the coal mining face is mined in the underground coal mining face. Figure 3 Zhong 12 is the aquifer fracturing zone. The aquifer fracturing zone refers to the spatial range in which the rock of the aquifer and its surrounding rock is compressed and forms a network of interconnected fractures under the action of hydraulic fracturing or mining stress. The permeability and water-bearing capacity of the rock mass in this area are significantly improved, making it a key channel for groundwater enrichment and migration.

[0041] The method includes the following steps: Step S1: By organizing and analyzing hydrogeological data, the 11th layer of the water-rich bottom plate with the risk of water inrush was determined.

[0042] Specifically, we collected and organized the preliminary geological exploration report, the hydrogeological data of the adjacent coal mining area and the coal mining face 9, analyzed the main water-rich floor 11 of the rock strata of the coal mining face 9, and classified the water inrush risk of the water-rich floor 11 into four levels: no water inrush risk, weak water inrush risk, medium water inrush risk, and strong water inrush risk based on the hydrostatic pressure, water inflow, rock stratum thickness, thickness and strength characteristics of the overlying direct floor 10.

[0043] Step S2: The spatial distribution of water-bearing properties in the bottom strata is investigated using the TSP method and transient electromagnetic method.

[0044] Specifically, the water-bearing characteristics of the bottom rock strata below the coal mining face 9 were detected by the TSP method and transient electromagnetic method in the roadways on both sides of the coal mining face 9. Based on the detection results, a spatial distribution plan of the water-bearing properties of the bottom rock strata was drawn to determine the key treatment area 8 for water inrush in the water-bearing bottom 11. The two side roadways are the return air roadway and the transport roadway, respectively.

[0045] Step S3: Drill core samples from both sides of the coal mine working face 9 into the water-rich bottom plate.

[0046] Specifically, rock cores were obtained by drilling obliquely from the bottom corner of the side roadway on both sides of the coal mining face 9 to the bottom rock strata below the coal mining face 9 as samples. The drilling extended to the bottom of the water-rich bottom plate 11. The hydrostatic pressure, single-hole water inflow of the water-rich bottom plate 11 were tested on site, and the thickness of the water-rich bottom plate 11 was calculated. The collected hydrogeological data were compared and analyzed, and the data were corrected.

[0047] Step S4: Analyze the mineral composition, microstructure, and physical and mechanical properties of each base stratum in the laboratory.

[0048] Specifically, X-ray fluorescence spectrometry and X-ray diffraction were used to perform qualitative and semi-quantitative analysis of the chemical composition and mineral composition of the samples to determine the mineral composition of the specimens. Cores collected from field drilling were processed into standard cylindrical specimens of ф50mm×100mm and ф50mm×50mm, and standard Brazilian splitting specimens of ф50mm×25mm. It should be noted that the cores were sealed with plastic wrap before and after processing to maintain the in-situ moisture content and prevent weathering. Furthermore, an electro-hydraulic servo universal testing machine was used to conduct uniaxial compression tests, Brazilian splitting tests, and variable-angle compression-shear tests on the bottom rock layer specimens to obtain the uniaxial compressive strength, tensile strength, cohesion c, and internal friction angle φ, among other physical and mechanical parameters, for each rock layer specimen.

[0049] Step S5: Using theoretical calculations combined with discrete element numerical analysis, establish a model of water inrush failure of the goaf floor under the coupled influence of mining stress and hydrostatic pressure of the floor, and conduct a risk assessment.

[0050] Specifically, the maximum failure depth of the water-rich floor 11 in the goaf is calculated using a formula. A discrete element numerical model is established based on the engineering geological conditions of the coal mine working face 9. The numerical simulation parameters for each floor stratum are corrected using the physical and mechanical parameters obtained in step S4. Fluid-structure interaction analysis is performed using the measured hydrostatic pressure and aquifer thickness of the water-rich floor 11. The analysis examines the characteristics of floor crack propagation, stress evolution, and floor displacement failure under the combined influence of mining stress in the coal mine working face 9 and hydrostatic pressure in the water-rich floor 11. A safety factor analysis is conducted on the failure process of each floor stratum. The safety factor obtained from the simulation analysis under these engineering geological conditions and the theoretically calculated maximum failure depth of the goaf floor are used to assess the risk of water inrush in the goaf floor. Targeted treatment is then implemented for conditions with the risk of water inrush disasters. The maximum failure depth of the bottom rock strata in the goaf is calculated using the following formula:

[0051] in, This represents the maximum damage depth of the base plate. The oblique length of the coal mine working face (9); This represents the average mining depth. The average unit weight of the overlying strata; The average cohesion of the base rock mass; The average internal friction angle of the base rock mass is given.

[0052] Step S6: Based on the risk assessment results of step S5, carry out advanced drainage treatment on the water-rich bottom plate (11).

[0053] Specifically, in the coal mine working face 9 at risk of water inrush disaster, an advanced long-bore fracturing aquifer drainage project is carried out. From the bottom corner of the roadway near the side of the coal mine working face 9 on both sides, advanced long-distance drainage holes 4 are drilled towards the aquifer below the bottom plate 9 of the coal mine working face. The drainage holes 4 extend to the lower part of the water-rich bottom plate 11. Hydraulic jet fracturing and hydraulic fracturing operations are carried out on the water-rich bottom plate 11 section of the drainage holes 4. After fracturing, the hydraulic fracturing effect is inspected by digital television observation. In the key water inrush control area 8 of the bottom plate, additional drainage holes 4 are deployed for key water drainage control.

[0054] Insert a submersible pump into the bottom of drainage hole 4 to drain the water flowing into drainage hole 4 until the drainage volume of a single hole is less than the preset value. Then the drainage work of the water-rich base plate 11 is completed. The installation, fixing, and operation steps of the submersible pump are as follows: The submersible pump is connected to the plastic drainage pipe and suspended, and lowered to the bottom of the drainage borehole. The drainage pipe is fixed to the wire mesh of the side slope on both sides, with the drainage outlet facing the drainage ditch. The steel rope is connected to the anchor rod of the adjacent slope. The submersible pump is turned on to discharge the water flowing in the drainage hole 4 into the drainage ditch. The fissure water continuously accumulates at the bottom of the hole under the natural pressure difference. The working cycle of the submersible pump is 1 to 4 hours, depending on the water flow of a single hole. The submersible pump is stopped and the equipment is retrieved after the water-rich bottom plate 11 reaches the drainage state. The outer diameter of the submersible pump should be smaller than the inner diameter of the drainage hole 4 with sufficient margin. The drainage head should be greater than the vertical depth of the drainage hole 4. If the bottom rock layer is a weakly cemented rock layer with low strength, consider inserting a rigid sleeve to prevent large deformation and hole collapse of the borehole and to jam the submersible pump. The rigid sleeve in the water-rich bottom plate 11 section is designed as a perforated pipe.

[0055] The TSP method and transient electromagnetic method were used to test the water drainage effect in the roadways on both sides of the coal mine working face 9. Based on the results of geophysical exploration methods, supplementary local long borehole fracturing water drainage was carried out in the test abnormal area. After all the drainage work is completed, random drilling of drainage effect verification holes is carried out on coal mine working face 9. Among them, the number n of the pre-drilled long borehole fracturing aquifer drainage holes 4 is evenly distributed on both sides of the roadway of the coal mine working face 9, and is calculated according to the following formula:

[0056] Where Q is the water inflow of the water-rich base plate 11; q is the water inflow of the drainage borehole.

[0057] Furthermore, after the drainage of the bottom rock strata of the coal mine working face 9 is completed, drainage effect verification holes are randomly drilled on the coal mine working face 9. The verification holes are arranged in groups, and the number of groups of verification holes is 5% to 10% of the number of drainage holes. In some examples, 5% to 10% of the drainage holes 4 on both sides of the roadway are randomly sampled, and verification holes are drilled in the roadway sidewall area 1 to 3m around the drainage holes 4. Verification holes account for 30% to 40% of the total number of verification holes in the key treatment area 8 for water inrush in the floor. Verification holes account for 60% to 70% of the total number of verification holes in the remaining area of ​​the floor of the coal mine working face 9.

[0058] The water inflow and head height of the verification borehole were measured, and the borehole water inflow was less than 1m. 3 / h, the water head height is lower than the bottom rock layer of the goaf, and the water-bearing state of the bottom layer is identified as the dewatering state.

[0059] In some examples, the advanced long borehole fracturing aquifer drainage project involves uniformly drilling long drainage boreholes on both sides of the coal mine working face 9 before formal mining. The drainage holes 4 are drilled at an angle of 15° to 45° to the horizontal plane along the normal direction of the roadway side, extending to the bottom of the water-rich floor 11. The diameter of the drainage boreholes is 150mm to 300mm, and the horizontal position of the borehole end is as close as possible to one-third of the distance from the coal mine working face 9. The long boreholes can be long-distance conventional straight boreholes or long-distance directional boreholes.

[0060] In some examples, the hydraulic jet fracturing and hydraulic pressure fracturing operations on the water-rich base plate 11 section of the drainage hole 4 are intended to fracture the water-rich base plate 11, expand the fractures in the water-rich base plate 11, and connect the artificially fracturing fractures with the natural joint fractures. Using the fracture network of the water-rich base plate 11 fractures, the water existing inside the rock strata seeps into the drainage hole under the natural pressure difference. The submersible pump at the bottom of the drainage hole discharges the water gushing from the drainage hole 4 into the drainage channels on both sides of the side trench, forming a natural pressure difference again and enriching the water in the water-rich base plate 11. This operation is repeated until the rock strata are quickly drained.

[0061] Step S7: Implement pre-mining grouting reinforcement of the bottom plate of coal mining face 9 and thin-layer filling of the bottom plate of coal mining face 9 after mining.

[0062] In some examples, the specific operation of grouting reinforcement is as follows: several sets of grouting holes 7 are evenly distributed on both sides of the roadway of the coal mining face 9. Each set of grouting holes 7 consists of a grouting distal hole 6 and a grouting proximal hole 5. The grouting distal hole 6 extends to the middle of the rock stratum of the direct overlying rock stratum 10 above the water-rich bottom slab 11. The horizontal position of the end of the grouting distal hole 6 is as close as possible to three-eighths of the position of the coal mining face 9. The grouting proximal hole 5 extends to the middle of the rock stratum of the direct overlying rock stratum 10 above the water-rich bottom slab 11. The horizontal position of the end of the grouting proximal hole 5 is as close as possible to one-sixth of the position of the coal mining face 9. The direction of the grouting hole 7 is at an angle of 20° to 30° with the normal direction of the side wall. The grouting distal hole 6 and the grouting proximal hole 5 are arranged in opposite directions. The grouting uses single-liquid cement grout and CS two-liquid grout.

[0063] Specifically, the spacing of the grouting holes 7 is selected to be 1.5 to 1.7 times the grouting diffusion radius. The theoretical grouting range of the far grouting hole 6 and the near grouting hole 5 should cover the central floor of the goaf. According to existing theoretical research, the maximum failure depth of the goaf floor is generally located in the middle of the working face floor 9. The distribution spacing, number, and length of the grouting holes 7 in the schematic diagram are only for conceptual illustration. Furthermore, the grouting reinforcement uses single-component cement grout and CS two-component grout. The water-cement ratio of the cement grout is 1:1; the water glass concentration is between 35 and 42 Be, the modulus is 2.3 to 3.0, the volume ratio of single-component cement grout to water glass is 2:1, and the grouting termination pressure is 2 to 3 MPa.

[0064] In some examples, the specific operation of thin-layer backfilling is as follows: during the mining advance of the coal mining face 9, the lagging coal mining face 9 uniformly sprays high-water-content, fast-setting material slurry into the goaf; the high-water-content, fast-setting material is composed of materials A and B in equal proportions; according to the division of the floor water inrush risk area, full-area backfilling or partial backfilling is selected, and the backfilling thickness is 5cm to 10cm.

[0065] Specifically, the thin-layer filling uses a high-water-content, fast-setting material. The main product of the hydration and hardening process is the crystalline hydrate of ettringite. Metal ions will not be released into the water and will not cause pollution. The high-water-content material A and B are used in equal proportions. The stone-setting rate is 100% under a high water-cement ratio. There is no water bleeding during the solidification process. The setting time is short, and the early strength is high and adjustable. Furthermore, thin-layer backfilling can be used to select whether to use full-area backfilling or partial backfilling based on the risk zone of water inrush in the floor. Thin-layer backfilling aims to cover and fill the surface cracks of the floor in the goaf, and block the water inrush path of the floor. A backfilling thickness of 5cm to 10cm can basically achieve the function.

[0066] In summary, the embodiments of this application provide a method for mitigating delayed water inrush disasters in the goaf of a water-rich foundation 11, which solves the following problems: By integrating hydrogeological data, geophysical exploration, and indoor rock mechanics experiments, and through theoretical calculations combined with discrete element numerical simulation, a numerical model of water inrush failure in goaf floor under the coupled influence of mining-induced stress and hydrostatic pressure on the floor is established. This model reveals the failure process of the floor and the evolution law of the water inrush channel, improves the accuracy and reliability of water inrush prediction, realizes the assessment of water inrush risk in water-rich floor, and provides a scientific basis for targeted treatment.

[0067] The aquifer drainage technology, employing long-bore fracturing, enhances the connectivity of natural fractures through hydraulic fracturing, creating efficient drainage channels to rapidly drain the water-rich base plate 11 and significantly reduce hydrostatic pressure. Grouting reinforcement is then implemented on the drainage foundation to seal the fracture network; thin-layer backfilling is carried out after mining to cover surface fractures in the base plate, forming a dual protection system of deep reinforcement and surface sealing, effectively blocking water inrush paths.

[0068] By verifying the effectiveness of well sampling and geophysical re-testing, the drainage effect can be accurately assessed, and supplementary treatment can be carried out for abnormal areas to ensure the quality and reliability of the treatment. This method, through proactive treatment and precise construction, significantly reduces the probability of water inrush accidents and ensures safe production in the mine.

[0069] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the protection scope of the present invention.

Claims

1. A method for controlling delayed water inrush disasters in goaf areas of water-rich bottom rock strata, characterized in that, Includes the following steps: Step S1: By sorting and analyzing hydrogeological data, determine the water-rich bottom layer (11) of the water inrush risk zone; Step S2: Investigate the spatial distribution of water-bearing properties in the bottom strata using the TSP method and transient electromagnetic method; Step S3: Drill core samples from both sides of the coal mining face (9) toward the water-rich bottom plate (11); Step S4: Analyze the mineral composition, microstructure, and physical and mechanical properties of each bottom rock layer in the laboratory; Step S5: Using theoretical calculations combined with discrete element numerical analysis, establish a model of water inrush failure of the goaf floor under the coupled influence of mining stress and hydrostatic pressure on the floor, and conduct a risk assessment. Step S6: Based on the risk assessment results of step S5, carry out advanced drainage treatment on the water-rich bottom plate (11): Step S7: Implement pre-mining grouting reinforcement of the bottom plate of the coal mining face (9) and thin-layer filling of the bottom plate of the coal mining face (9) after mining.

2. The method for controlling delayed water inrush disasters in goaf areas of water-rich bottom rock strata according to claim 1, characterized in that, The specific steps of step S1 are as follows: collect and organize the preliminary geological exploration report, hydrogeological data of the mine and adjacent coal mining areas, and the coal mining face (9), analyze the main water-rich bottom plate (11) strata of the coal mining face (9), and classify the water inrush risk of the water-rich bottom plate (11) into four levels: no water inrush risk, weak water inrush risk, medium water inrush risk, and strong water inrush risk based on the hydrostatic pressure, water inflow, rock layer thickness, thickness and strength characteristics of the overlying direct bottom plate (10).

3. The method for controlling delayed water inrush disasters in goaf areas of water-rich bottom rock strata according to claim 1, characterized in that, The specific steps of step S2 are as follows: using the TSP method and transient electromagnetic method to detect the water-bearing characteristics of the bottom rock strata below the coal mining face (9) in the roadway on both sides of the coal mining face (9), and drawing a spatial distribution plan of the water-bearing properties of the bottom rock strata based on the detection results, so as to determine the key treatment area (8) of water inrush in the water-bearing bottom (11).

4. The method for controlling delayed water inrush disasters in goaf areas of water-rich bottom rock strata according to claim 1, characterized in that, The specific steps of step S3 are as follows: from the bottom corner of the sidewall of the coal mining face (9) on both sides, drill obliquely to the bottom rock layer below the coal mining face (9) to obtain rock cores as samples; the drill hole extends to the bottom of the water-rich bottom plate (11), and the hydrostatic pressure, single hole flow rate, and thickness of the water-rich bottom plate (11) are tested on site, and compared and analyzed with the hydrogeological data collected in step S1, and the data is corrected.

5. The method for controlling delayed water inrush disasters in goaf areas of water-rich bottom rock strata according to claim 1, characterized in that, Step S4 specifically involves: The chemical composition and mineral composition of the core were qualitatively and semi-quantitatively analyzed using X-ray fluorescence spectrometry and X-ray diffraction. The rock cores were processed into standard cylindrical specimens and Brazilian splitting specimens; An electro-hydraulic servo universal testing machine was used to conduct uniaxial compression tests, Brazilian splitting tests, and variable angle compression-shear tests on the rock core specimens to obtain the uniaxial compressive strength, tensile strength, cohesion, and internal friction angle physical and mechanical parameters of the rock core specimens.

6. The method for controlling delayed water inrush disasters in goaf areas of water-rich bottom rock strata according to claim 1, characterized in that, In step S5, the maximum damage depth of the water-rich bottom plate (11) in the goaf is calculated using a formula. A discrete element numerical model was established based on the engineering geological conditions of the coal mining face (9). The numerical simulation parameters of each bottom stratum were corrected with reference to the physical and mechanical parameters obtained in step S4. Fluid-structure interaction analysis was performed based on the measured hydrostatic pressure and aquifer thickness of the water-rich bottom stratum (11). The crack propagation, stress evolution, and displacement failure characteristics of the bottom stratum under the combined influence of mining stress of the coal mining face (9) and hydrostatic pressure of the water-rich bottom stratum (11) were analyzed. The safety factor analysis was performed on the failure process of each bottom stratum. Based on the safety factor obtained from the simulation analysis under the engineering geological conditions and the maximum failure depth of the goaf bottom stratum obtained from theoretical calculation, the risk assessment of water inrush in the goaf bottom stratum was carried out. Targeted treatment was carried out for conditions with water inrush disaster risk. The maximum failure depth of the bottom rock strata in the goaf is calculated using the following formula: ； in, This represents the maximum damage depth of the base plate. The oblique length of the coal mine working face (9); This represents the average mining depth. The average unit weight of the overlying strata; The average cohesion of the base rock mass; The average internal friction angle of the base rock mass is given.

7. The method for controlling delayed water inrush disasters in goaf areas of water-rich bottom rock strata according to claim 1, characterized in that, Step S6 specifically involves: In the coal mine working face (9) at risk of water inrush disaster, advanced long borehole fracturing and drainage treatment is carried out. From the bottom corner of the roadway near the coal mine working face (9) on both sides of the coal mine working face (9), advanced long-distance drainage holes (4) are drilled towards the aquifer below the coal mine working face (9). The drainage holes (4) extend to the lower part of the water-rich floor (11). Hydraulic jet fracturing and hydraulic fracturing operations are carried out on the water-rich floor (11) section of the drainage holes (4). After fracturing, the hydraulic fracturing effect is checked by monitoring instruments. Additional drainage holes (4) are set up in the key treatment area (8) of floor water inrush for key drainage treatment. Insert a submersible pump into the bottom of the drainage hole (4) to drain the water flowing into the drainage hole (4) until the drainage volume of a single hole is less than the preset value, then the drainage work of the water-rich bottom plate (11) is completed. The TSP method and transient electromagnetic method were used to test the water drainage effect in the roadways on both sides of the coal mining face (9). Based on the results of the geophysical exploration method, supplementary local long borehole fracturing water drainage treatment was carried out in the test abnormal area. After all the drainage work is completed, random drainage effect verification holes are drilled on the coal mining face (9); Among them, the number n of the pre-drilled long borehole fracturing drainage holes (4) is evenly distributed on both sides of the roadway of the coal mining face (9), and is calculated according to the following formula: ； in, The inflow rate of the water-rich bottom plate (11) The amount of water flowing from the borehole for drainage.

8. The method for controlling delayed water inrush disasters in goaf areas of water-rich bottom rock strata according to claim 7, characterized in that, In step S6, after the bottom rock strata of the coal mining face (9) are drained, drainage effect verification holes are randomly drilled on the bottom of the coal mining face (9). The verification holes are arranged in groups, and the number of groups of verification holes is 5% to 10% of the number of drainage holes. 5% to 10% of the drainage holes (4) in the side roadways are randomly sampled, and verification holes are drilled in the roadway sidewall area 1 to 3m around the sampled drainage holes (4); verification holes account for 30% to 40% of the total number of verification holes in the key treatment area (8) of floor water inrush, and verification holes account for 60% to 70% of the total number of verification holes in the remaining areas of the floor of the coal mine working face (9); The water inflow and water head height of the verification borehole are measured. When the water inflow of the borehole is less than 1 m³ / h and the water head height is lower than the bottom rock strata of the goaf, the water content of the bottom rock strata is identified as the dewatering state. The advanced long borehole fracturing and drainage treatment is specifically carried out by uniformly drilling drainage long boreholes on both sides of the coal mining face (9) before the formal mining. The drainage holes (4) are drilled at an angle of 15° to 45° with the horizontal plane along the normal direction of the roadway side until the bottom of the water-rich bottom plate (11). The diameter of the drainage borehole is 150mm to 300mm, and the horizontal position of the end of the borehole is close to one-third of the advancing direction of the coal mining face (9).

9. The method for controlling delayed water inrush disasters in goaf areas of water-rich bottom rock strata according to claim 7, characterized in that, In step S6, hydraulic jet fracturing and hydraulic pressure fracturing operations are performed on the water-rich base plate (11) section of the drainage hole (4) to fracture the water-rich base plate (11), expand the cracks in the water-rich base plate (11), and make the artificially fracturing cracks and natural joint cracks connect. Using the crack network of the water-rich base plate (11) under natural pressure difference, the water existing in the rock layer seeps into the drainage hole, and the submersible pump at the bottom of the drainage hole discharges the water in the drainage hole (4) into the drainage channel on both sides of the trench, forming a natural pressure difference again and enriching the water in the water-rich base plate (11). The operation is repeated until the rock layer is quickly drained. The installation, fixing, and operation steps of the submersible pump are as follows: The submersible pump is connected to a plastic drain pipe and suspended by a steel rope. It is lowered to the bottom of the drainage borehole. The drain pipe is fixed to the wire mesh on both sides of the trough. The drain outlet faces the drainage ditch. The steel rope is connected to the anchor bolts of the adjacent side. Turn on the submersible pump to discharge the water flowing into the drainage channel from the drainage hole (4). The fissure water continues to accumulate at the bottom of the hole under the natural pressure difference. The working cycle of the submersible pump is 1 to 4 hours. The working cycle is positively correlated with the water flow rate of a single hole. After the water-rich bottom plate (11) reaches the drainage state, the submersible pump is stopped and retrieved. The outer diameter of the submersible pump is smaller than the inner diameter of the drainage hole (4) and has a margin. The drainage head is greater than the vertical depth of the drainage hole (4).

10. The method for controlling delayed water inrush disasters in goaf areas of water-rich bottom rock strata according to claim 1, characterized in that, In step S7, the specific operation of grouting reinforcement is as follows: several sets of grouting holes (7) are evenly distributed on both sides of the roadway of the coal mining face (9). Each set of grouting holes (7) consists of a grouting distal hole (6) and a grouting proximal hole (5). The grouting distal hole (6) extends to the middle of the rock stratum of the direct bottom plate (10) over the water-rich bottom plate (11), and the horizontal position of the end of the grouting distal hole (6) is close to three-eighths of the position of the coal mining face (9). The grouting proximal hole (5) extends to the middle of the rock stratum of the direct bottom plate (10) over the water-rich bottom plate (11), and the horizontal position of the end of the grouting proximal hole (5) is close to one-sixth of the position of the coal mining face (9). The direction of the grouting hole (7) is 20° to 30° with the normal direction of the side wall. The grouting distal hole (6) and the grouting proximal hole (5) are arranged in opposite directions. The grouting uses single-liquid cement grout and CS double-liquid grout. The specific operation of thin-layer backfilling is as follows: during the mining advance of the coal mining face (9), the lagging coal mining face (9) sprays high water and quick-setting material slurry evenly into the goaf; the high water and quick-setting material is made of material A and material B in equal proportions; according to the division of the risk area of ​​water inrush in the bottom plate, full-area backfilling or partial backfilling is selected, and the backfilling thickness is 5cm to 10cm.

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