A method for plugging a goaf air leakage channel of a coal mine
Patent Information
- Application Number
- CN202610800745.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-04
- Publication Date
- 2026-09-15
Smart Images
Figure CN122752089A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of coal mine safety production and maintenance technology, and in particular relates to a method for sealing air leakage channels in coal mine goaf areas. Background Technology
[0002] Approximately 70%-80% of coal mine fires are caused by spontaneous combustion of coal, with over 90% of these occurring in goaf areas. In western my country, many mining areas consist of shallowly buried coal seams. Due to geological constraints, some mines employ an overlapping working face arrangement of upper and lower coal seams to maximize coal resource recovery. This results in the lower coal seam, during mining, being supported by the intersecting coal pillars, creating a network of fractures that becomes the main air leakage channel in the goaf. This air leakage leads to a continuous influx of oxygen, which comes into full contact with the remaining coal around the pillars, easily igniting spontaneous combustion fires and seriously threatening safe coal mine production.
[0003] In existing technologies, air leakage channels are sealed by grouting. However, when applied in areas with overlapping coal pillars, problems exist such as blind positioning of air leakage channels, inability to cover different types of cracks with uniform hole distribution, poor material compatibility and low solid waste utilization, and insufficient grout filling. These issues prevent effective sealing and affect coal mine production safety.
[0004] Therefore, developing a method for sealing air leakage channels in coal mine goaf areas to address the technical shortcomings of poor sealing effect in existing technologies for sealing air leakage channels in cross-coal seam working faces has become an urgent problem to be solved by those skilled in the art. Summary of the Invention
[0005] Therefore, it is necessary to address the technical shortcomings of existing technologies, such as poor sealing effect of air leakage channels in cross-coal seam working faces, and to provide a method for sealing air leakage channels in coal mine goaf areas.
[0006] This application provides a method for sealing air leakage channels in coal mine goaf areas, the sealing method comprising: Step 1: Collect geological data, cross-working face layout parameters, and residual coal pillar distribution data of the coal mine goaf to obtain the fracture distribution characteristics of the coal mine goaf. The method for obtaining the fracture distribution characteristics includes the coupling of physical similarity simulation and numerical simulation. Step 2: Perform drilling according to the fracture distribution characteristics. The drilling includes drilling at any one or more locations in the periphery, core, and deep part of the coal mine goaf. Step 3: Perform grouting treatment on the boreholes obtained in Step 2. The grouting material includes any one or more of aggregate grout and expanding grout. The grouting sequence includes: performing grouting treatment on the boreholes from the outside to the inside; the grouting of the outer boreholes uses the aggregate grout; the grouting of the core boreholes first uses the aggregate grout and then the expanding grout; and the grouting of the deep boreholes uses the expanding grout.
[0007] In one embodiment, step three further includes: monitoring temperature and spontaneous combustion gas concentration; If the monitored temperature or the concentration of spontaneously combustible gas is greater than the system preset value, a heat-resistant grout will be used to perform the grouting process during drilling.
[0008] In one embodiment, step one includes the physical similarity simulation experiment: building a physical model of the cross working face of the goaf and obtaining a numerical model of the cross working face; the numerical simulation experiment includes: simulating the fracture evolution process at different mining stages according to the numerical model, and obtaining the fracture development boundary, non-compacting zone location and through fracture depth of the goaf.
[0009] In one embodiment, in step two, the drilling spacing for the outer perimeter is 5-10 meters, the drilling spacing for the core is 4-6 meters, and the drilling spacing for the deep portion is 3-5 meters.
[0010] In one embodiment, in step three, the aggregate slurry includes: solid waste main material, cement, admixtures, and 5-20 mm coal gangue; the expanding slurry includes: fly ash, cement, bentonite, foaming agent, foam stabilizer, and inhibitor, wherein the inhibitor is selected from any one or more of the following: halide salts, ammonium salts, and silicate inhibitors.
[0011] In one embodiment, in step three, the grouting treatment method includes a graded control strategy, which includes: an initial grouting pressure of 0.8-1.2 MPa for the outer boreholes of the coal mine goaf, and a stabilizing pressure of 2-2.5 MPa; and an initial grouting pressure of 1.5-2 MPa for the deep boreholes of the coal mine goaf, with the stabilizing pressure maintained at 2.5-3 MPa.
[0012] In one embodiment, in step three, the grouting treatment method includes a graded control strategy, which includes: the initial grouting pressure of the core borehole in the coal mine goaf is 0.8-1.2 MPa, the pressure during the fracturing stage is 3-4 MPa, and the pressure during the stabilization stage is maintained at 2.5-3 MPa.
[0013] In one embodiment, the heat-resistant slurry includes: fly ash, cement, bentonite, foaming agent, foam stabilizer, and high-temperature resistant inhibitor, wherein the high-temperature resistant inhibitor is selected from one or more of: polymer gels, superabsorbent resins, and metal salt foam flame retardants.
[0014] In one embodiment, the sealing method further includes: step four, grouting compliance test, wherein the grouting compliance test method includes: testing the water content at the borehole location after the grouting treatment in step three; if the water content is greater than the system preset water content, then the grouting is compliant.
[0015] In one embodiment, the sealing method further includes: step five, drilling and grouting; if the grouting in step four fails the test, drilling and grouting is performed.
[0016] In summary, this application provides a method for sealing air leakage channels in coal mine goafs, comprising: acquiring the fracture distribution characteristics of the coal mine goaf; performing drilling based on the fracture distribution characteristics; and performing grouting on the obtained boreholes. The grouting material for the grouting includes any one or more of aggregate-containing grout and expanding grout. In the technical solution provided by this application, the fracture distribution characteristics are acquired through a combination of physical similarity simulation and numerical simulation. Precise drilling is then performed based on these characteristics, followed by orderly, multi-type grouting of the boreholes. By performing zoned drilling, specific sealing of different types of fractures is achieved, effectively improving the sealing coverage rate and thus achieving a tight seal of the air leakage channels. This solves the technical defect in the prior art where the sealing effect of air leakage channels in cross-coal seam working faces is poor. Attached Figure Description
[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0018] Figure 1 A flowchart illustrating a method for sealing air leakage channels in a coal mine goaf, as provided in the embodiments of this application. Detailed Implementation
[0019] This application provides a method for sealing air leakage channels in coal mine goaf areas, which solves the technical defect of poor sealing effect in the sealing of air leakage channels in cross coal seam working faces in the prior art.
[0020] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.
[0021] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.
[0022] In cross-seam coal mining operations, the staggered arrangement of upper and lower coal seam working faces and the disturbance of residual coal pillars by mining stress easily lead to the formation of dense, interconnected fractures, creating complex air leakage channels and causing safety hazards such as excessive air leakage at the working face and spontaneous combustion of residual coal. Traditional sealing methods suffer from problems such as inaccurate fracture detection, arbitrary borehole layout, and limited grouting materials, making them unsuitable for the layered and differentiated fracture sealing needs. These methods also result in low sealing density and a high rate of air leakage recurrence.
[0023] To address the aforementioned technical deficiencies and mitigate safety risks, this application proposes a method for sealing air leakage channels in coal mine goaf areas. It employs a physical similarity simulation coupled with numerical simulation to characterize fracture development. Based on precise fracture detection, it utilizes a periphery, core, and deep-level borehole layout tailored to the fracture distribution. This is combined with differentiated and ordered multi-element grouting methods using aggregate-containing grout and expanding grout to achieve full coverage and high-density sealing of air leakage channels.
[0024] To better illustrate the sealing method for air leakage channels in coal mine goaf provided in this application embodiment, this application embodiment uses a coal mine in northern Shaanxi as an engineering example to explain the implementation process, principles of each technical link, and corresponding technical effects of the technical solution provided in this application embodiment. Specifically, the upper 1-2 coal seam and the lower 2-2 upper coal seam in this coal mine are arranged in an intersecting working face manner, with an intersection angle of 30°, leaving a 20m wide coal pillar. During the mining of the lower coal seam, the coal pillar disturbance area has densely developed fissures, and the air leakage rate of the working face has long exceeded 10%, resulting in an extremely high risk of spontaneous combustion of the remaining coal.
[0025] Please see here. Figure 1 This application provides a method for sealing air leakage channels in coal mine goaf areas, including: Step 1: Collect geological data of the coal mine goaf, cross-working face layout parameters, and residual coal pillar distribution data to obtain the fracture distribution characteristics of the coal mine goaf. The method for identifying fracture distribution characteristics includes the coupling of physical similarity simulation and numerical simulation. In Step 1, the fracture development law of the coal pillar overlapping area is characterized by the coupling of physical similarity simulation and numerical simulation.
[0026] Specifically, this includes: relying on geological data acquisition, physical similarity simulation, and numerical simulation to accurately depict the spatial distribution, development range, and evolution law of fractures in goaf areas, solving the problems of unclear fracture location, ambiguous boundaries, and unclear development mechanism in traditional technologies, and providing data support for subsequent borehole layout and grouting material selection.
[0027] By collecting basic geological data, the basic stratigraphic parameters were accurately determined. Staff collected complete geological exploration data for the target mine, clarifying the basic data of the coal seam and strata: In the upper coal seam working face, the coal burial depth is 70m, the coal seam thickness is 10m, the overlying loess layer is 10m thick, and the bedrock thickness is 60m; in the lower coal seam working face, the coal burial depth is 100m, the distance from the upper coal seam is 25m, and the coal seam thickness is 2m. The working face has a mining length of 1500m and a width of 300m, with a remaining coal pillar width of 20m. By integrating borehole columnar sections and lithological and mechanical parameters, an original geological database was constructed, providing a realistic stratigraphic basis for simulation experiments.
[0028] Through physical similarity simulation experiments, the dynamic development process of fractures is visually recreated. A 1:100 scale physical experimental model of the overlapping coal pillar area is constructed to recreate the engineering scenario of cross-mining of upper and lower coal seams and pressure disturbance of the coal pillar. During the experiment, a DIC digital speckle data acquisition instrument, pressure sensor, and fiber optic data acquisition instrument are used to monitor the displacement deformation of the coal pillar area, the magnitude of rock strata stress, and the process of fracture initiation, expansion, and connection in real time. The physical similarity simulation experiment clarifies the fracture classification type, distinguishes between loose fractures in non-compacted areas and vertically penetrating fractures between upper and lower coal seams, accurately grasps the spatial distribution characteristics, development height, and dynamic evolution law of fractures, and overcomes the deficiency of single static detection in observing the dynamic changes of fractures.
[0029] PFC particle flow numerical simulation was used to define the fracture development boundary. Based on discrete element method numerical simulation software, lithological parameters such as coal density, compressive strength, and Poisson's ratio were imported to construct a refined numerical calculation model. The numerical simulation results were cross-validated with physical simulation test data to further optimize fracture parameters. Ultimately, the fracture development boundary of the mine was accurately determined to be a range of 20-30m outward from both sides of the coal pillar in coal seams 1-2, with non-compacted loose fractures concentrated in the area extending 5-10m outward from both sides of the coal pillar. This represents a breakthrough from qualitative judgment to quantitative characterization of fractures, accurately delineating fracture types, development boundaries, and hazardous areas, avoiding the drawbacks of traditional blind drilling and indiscriminate grouting. It provides scientific and accurate data support for graded borehole layout, improving the targeted nature of sealing from the source.
[0030] Step 2: Perform drilling based on the fracture distribution characteristics. Drilling includes drilling at any one or more locations in the periphery, core, and deep part of the coal mine goaf. In step two, a precise three-dimensional borehole layout is implemented. Based on the fracture distribution characteristics identified in step one and the spatial distribution patterns of air leakage channels, a three-dimensional borehole system of "peripheral interception + core sealing + deep reinforcement" is constructed. Boreholes are strategically placed at different locations—peripheral, core, and deep—to achieve full-space, dead-angle-free coverage of air leakage channels, solving the problems of chaotic borehole layouts, incomplete coverage, and lack of deep fracture sealing inherent in traditional methods. In the technical solution provided in this application, the peripheral area refers to the area 40-80 m away from the coal pillar remaining in the goaf after the upper coal seam is mined; the core area refers to the area 20-40 m away from the coal pillar remaining in the goaf after the upper coal seam is mined; and the deep area refers to the area 0-20 m away from the roof of the lower coal seam. In the actual sealing process, the boundaries of the outer layer, core, and deep area are determined comprehensively based on the results of physical similarity simulation and numerical simulation calculations.
[0031] First, a ring-shaped sealing barrier is constructed using peripheral interception boreholes. Boreholes are laid out along the outermost boundary of the overlapping coal pillar area, employing a vertical drilling technique with a borehole spacing of 15 meters. In practical scenarios, a total of 120 boreholes can be arranged on both sides of the coal pillar, covering the upper fracture zone. These peripheral boreholes form a continuous ring-shaped sealing curtain, primarily serving to block external airflow from seeping into the goaf and prevent the diffusion of harmful gases from within, thus cutting off the surface air leakage path at its source.
[0032] Secondly, the loose fractures in the center are compacted through core sealing boreholes. Focusing on the non-compacted areas and densely fractured areas within the overlapping coal pillar region, vertical boreholes are drilled on both sides of the horizontal projection of the coal pillar left over from the upper coal seam working face, reducing the borehole spacing to 10m. 160 boreholes are arranged on both sides of the coal pillar, reaching the non-compacted loose areas on both sides of the coal pillar. These boreholes specifically cover high-risk fractured areas and are the core points for sealing air leaks. They are used to fill the messy, interwoven shallow fractures in the center, reducing the area's permeability.
[0033] Finally, the vertical fractures were sealed by deep reinforcement boreholes. For the penetrating vertical fracture zones between the upper and lower coal seams, during the early stages of coal mining in the lower coal seam, directional boreholes were drilled from the return air roadway to the bottom of the remaining coal pillar. The borehole angles were adjusted using directional drilling tools to match the natural orientation of the fractures, and the borehole spacing was reduced to 5 meters. 120 deep boreholes were laid out in parallel to specifically fill the deep, hidden penetrating fractures and block the vertical air leakage channels between the layers.
[0034] In step two, differentiated drilling by grade and region is used to adapt to different depths and types of cracks, forming an outer, middle and inner three-layer protective structure. According to calculations, compared with the traditional uniform hole layout method, the drilling utilization rate is increased by more than 40%, and the air leakage channel space coverage rate reaches 98%, which completely solves the problem of blind spots in sealing deep hidden cracks.
[0035] Step 3: Perform grouting treatment on the boreholes obtained in Step 2. The grouting material includes any one or more of aggregate grout and expanding grout. The grouting sequence includes: performing grouting treatment on the boreholes from the outside to the inside. For the outer boreholes, aggregate grout is used for grouting. For the core boreholes, aggregate grout is used first, followed by expanding grout. For the deep boreholes, expanding grout is used for grouting.
[0036] In step three, a differentiated grouting process is employed to perform graded grouting with suitable solid waste-based grouting materials for boreholes at different locations. This approach precisely matches the grouting materials to the characteristics of boreholes at three different locations: the periphery, the core, and the deep section, abandoning the traditional, crude process of using a uniform grout and haphazard grouting.
[0037] In the outer boreholes, aggregate grout is used alone. Leveraging the high aggregate content, strong consolidation strength, and resistance to ground pressure deformation of the aggregate grout, a thick and hard annular sealing curtain is rapidly formed in the outer fracture zone. This curtain resists the compression and deformation of the surrounding rock strata, preventing the large-scale fractures in the outer perimeter from reopening and causing air leakage, thus achieving airflow isolation and boundary sealing. In the core area, a composite grouting process of first using aggregate grout and then expanding grout is employed. First, the aggregate grout rapidly fills the large voids and broken, loose zones around the coal pillar, building a high-strength, rigid support framework to address the problems of large central cavities and easily collapsed boreholes due to broken surrounding rock. Then, the expanding grout penetrates the gaps between the aggregates and minor secondary fractures, solidifying and expanding to eliminate grouting voids, compensating for the poor sealing performance of the aggregate grout, and eliminating the weak air leakage zone in the core area. Deep boreholes use expanding grout alone, relying on its strong fluidity and excellent permeability to penetrate into the narrow and hidden vertical fractures between coal seams. It precisely fills the micro-fractures by fitting the geological characteristics of small pore size, deep burial and tortuous channels of deep fractures.
[0038] The graded grouting mode of this application embodiment can achieve a high degree of matching between material properties and crack space. The periphery focuses on strength barrier, the core focuses on strong sealing, and the deep part focuses on fine filling. It eliminates grout waste and grouting blind spots, and the overall sealing density is greatly improved. It effectively suppresses interlayer air leakage and crack leakage, and avoids local sealing failure and subsequent leakage. Compared with traditional grouting process, the uniformity of air leakage sealing is significantly improved, the layered adaptability of the solidified body is stronger, and the long-term air leakage control stability is higher.
[0039] By leveraging the complementary advantages of aggregate grout and expanding grout, and balancing the filling strength of large cracks with the sealing density of micro cracks, calculations show that compared to existing technologies, the compressive strength of the grout-consolidated body is increased by more than 35%, the curing expansion rate is controllable, and grout shrinkage cracking is effectively avoided. The ordered grouting method provided in step three effectively reduces grout cross-flow, minimizes loss, and significantly improves material utilization.
[0040] The technical solution provided in this application demonstrates that the aforementioned Shaanxi coal mine achieved significant overall sealing results after completing the air leakage treatment in the overlapping coal pillar area. After treatment, the air leakage rate at the working face decreased from over 10% to below 3%, meeting the coal mine safety ventilation standards. The oxygen concentration inside the goaf significantly decreased, the oxidation and heating of residual coal was completely stopped, and the concentration of harmful carbon monoxide gas stabilized at a safe threshold, completely eliminating the risk of spontaneous combustion of residual coal. Compared to traditional grouting sealing technology, the sealing coverage rate increased by 25%, the grout material loss rate decreased by 18%, and the service life of the sealing structure was extended by more than two times, eliminating the need for repeated grouting repairs. This effectively overcomes the challenge of air leakage treatment in the disturbed coal pillar area of the cross-coal seam working face, providing a reliable technical reference for air leakage sealing in coal mines with similar complex geological conditions.
[0041] To further optimize the technical solution and improve the safety of sealing operations while preventing spontaneous combustion in mines with fire zones, the sealing method provided in this application includes, in step three: monitoring temperature and spontaneous combustion gas concentration; if the monitored temperature or spontaneous combustion gas concentration exceeds the system's preset value, a high-temperature resistant grout is used for grouting a single borehole. By adding online monitoring of temperature and spontaneous combustion gas in the grouting process and further combining it with emergency replacement linkage control logic for the high-temperature resistant grout, the safety issues of grouting construction in goaf areas with spontaneous combustion hazards and hidden fire zones are effectively solved.
[0042] During the actual sealing process, monitoring can be conducted using probes placed in the borehole gaps to capture precise changes in the temperature of the surrounding rock and the concentration of spontaneously combustible gases (such as carbon monoxide) within the goaf in real time. Compared with traditional intermittent manual detection, the technical solution provided in this application can accurately capture local high-temperature anomalies and weak coal oxidation reactions caused by grouting disturbances, avoiding the missed detection of hidden fire zones. When either the temperature or the concentration of spontaneously combustible gases exceeds the standard, the system immediately determines that there is high-temperature loose coal or residual oxidation zone near the borehole and switches to high-temperature resistant grout for grouting.
[0043] The flame-retardant and heat-absorbing components in the high-temperature grout can quickly absorb heat from the coal and rock mass, achieving localized cooling. At the same time, after the grout solidifies, it forms a dense, flame-retardant, and hardened layer, isolating the coal from oxygen and cutting off the spontaneous combustion chain reaction. This directly blocks the risk of re-ignition of residual coal caused by disturbance during grouting construction, avoiding the problems of conventional grouts losing water and cracking or failing to seal when exposed to high temperatures. It effectively ensures that the entire process of grouting and sealing in high-temperature hazard areas is controllable and safe, and significantly improves the construction safety and long-term sealing effectiveness of air leakage treatment in coal seams with a tendency to spontaneous combustion.
[0044] In the sealing method provided in this application embodiment, step one, the physical similarity simulation experiment includes: building a physical model of the cross working face of the goaf and obtaining a numerical model of the cross working face; the numerical simulation experiment includes: simulating the fracture evolution process at different mining stages according to the numerical model, and obtaining the fracture development boundary, non-compacting zone location and through fracture depth of the goaf.
[0045] Specifically, the physical similarity simulation method includes: the physical similarity simulation adopts a two-dimensional overburden collapse similarity simulation experimental platform. Based on the geological data of the nearby coal seam group, the layout parameters of the cross working face and the distribution data of the remaining coal pillars, according to the start and end positions of the coal pillar overlap area, several profile positions are selected at equal intervals. Based on the stratum rock mechanical parameters, the similarity simulation material ratio (the ratio of sand, lime and gypsum) is calculated, and the similar simulation strata are laid at a ratio of 1:(100-200) (the specific range can be selected according to the actual situation).
[0046] The laying process is as follows: (1) Pour sand, limestone and gypsum into a mixer according to the ratio and mix evenly. Then spread it evenly on a similar simulation test frame. Then, layer quartz sand between each layer, which is about 0.2cm thick, to ensure the stability of the collapse shape.
[0047] (2) Using the rock strata canvas as a reference, similar materials are laid and compacted in layers. During the laying process, the rock strata must be kept level and the thickness of the rock strata must be consistent with the design thickness. Mica powder is evenly spread in the middle of the rock strata to simulate the interlayer structure.
[0048] (3) During the laying process, pressure boxes and optical fibers must be buried in the positions designed in the scheme. After the model is laid as a whole, counterweight blocks are placed on top according to the burial depth.
[0049] (4) After the model has dried to a certain extent, it needs to be whitewashed and speckled to facilitate later DIC surface observation.
[0050] (5) The experiment uses a fiber optic monitoring system, a pressure box stress monitoring system and a three-dimensional optical digital speckle monitoring system (DIC) to monitor the displacement, strain and stress of the model surface and interior in multiple directions and fields (DIC full-field deformation measurement and analysis system monitors the displacement field of the whole process under the influence of mining in real time, and full-field strain measurement system takes pictures and processes them in real time).
[0051] (6) Mine the simulated coal seam from one side and retain the relevant coal pillars for multiple coal seams.
[0052] Numerical simulation methods include: (1) Based on the different profile locations selected in the physical similarity simulation, a complete two-dimensional model is constructed to verify the original strata coal and rock properties. Two-dimensional numerical simulation is carried out, and the results correspond one-to-one with the physical similarity simulation results to verify the effectiveness of the numerical model construction.
[0053] (2) Based on the original profile position, select a new profile between the profiles to further supplement and improve the physical similarity simulation results. Use the crack tracking function of the numerical simulation software to obtain the spatial distribution characteristics of crack development in different coal pillar overlapping areas, so as to comprehensively determine the crack development boundary and non-compression zone location in the coal pillar overlapping area.
[0054] To further optimize the technical solution and achieve precise matching between borehole density and fracture development, in the technical solution provided in this application embodiment, in step two, the borehole spacing for drilling treatment on the periphery is 5-10 meters, the borehole spacing for drilling treatment in the core is 4-6 meters, and the borehole spacing for drilling treatment in the depth is 3-5 meters. Based on the density of fracture development and the hazard level of air leakage channels, a graded and denser borehole spacing design is constructed. Through the spacing arrangement logic of sparse periphery, dense core, and densest depth, precise matching between borehole density and fracture development is achieved.
[0055] Specifically, the peripheral interception boreholes are spaced 5-10 meters apart. This area is mainly characterized by large, interconnected fractures with uniform fracture distribution, so high-density borehole layout is not required. The combination of vertical and micro-inclined boreholes ensures that the grout spreads and overlaps to form a continuous and complete annular sealing curtain. It also reduces the number of redundant boreholes at the boundary, reduces the amount of drilling work, shortens the construction period, avoids excessive drilling that disturbs the surrounding rock and causes new fractures, stabilizes the surrounding rock structure of the goaf, blocks external airflow from seeping into the goaf from the source, and blocks the horizontal air leakage path on the surface.
[0056] The core sealing area consists of a densely fractured zone and a non-compacted fractured zone. The fractures are chaotic and interwoven, and the amount of voids is large. Therefore, the borehole spacing is increased to 4-6 meters. Increasing the number of boreholes can reduce the blank area for grout diffusion, eliminate the grouting blind zone inside the fractured zone, and the dense boreholes can form multi-point compression and consolidation of the loose coal pillar rock mass, compact the central fractured coal pillar rock mass, reduce the porosity of the coal pillar, and avoid the residual loose air leakage zone due to excessive borehole spacing.
[0057] Deep, penetrating fracture zones are characterized by concealed fractures and narrow, elongated interlayer channels, making them the most difficult vertical air leakage channels to manage. A minimum spacing of 3-5 meters is used to lay out directional penetrating boreholes. This smaller borehole spacing ensures complete coverage and diffusion of grout within the deep fractures. Combined with directional drilling tools that conform to the fracture direction, precise penetration of the interlayer penetrating fractures is achieved, solving the problems of borehole deviation and difficulty in grout penetration in deep areas.
[0058] The technical solution provided in this application abandons the traditional extensive method of uniformly spaced boreholes and instead uses a gradient spacing layout for different areas. During drilling, parameters are dynamically adjusted based on the height of fracture development, air leakage intensity, and coal pillar stability to avoid secondary disturbance to the coal pillar caused by drilling. The drilling density is increased in areas with higher hazard levels and more developed fractures. Under the premise of controlling construction costs and reducing rock mass disturbance, the coverage rate of air leakage channels is further improved, allowing the continuity of the outer curtain, core compaction, and deep penetration sealing effect to be improved simultaneously. This effectively avoids the problems of incomplete sealing and weak sealing caused by unreasonable borehole spacing, and significantly improves the overall sealing structure's density and long-term stability.
[0059] To further optimize the technical solution, the grouting material system is adapted differently according to the width of the fracture in the mine. The material components are designed to fit the different fracture conditions in the mine. In step three of the sealing method provided in this application embodiment, the aggregate slurry includes: solid waste main material, cement, admixture and 5-20 mm coal gangue; the expanding slurry includes: fly ash, cement, bentonite, foaming agent, foam stabilizer and inhibitor. The inhibitor is selected from any one or more of the following: halide salts, ammonium salts and silicate inhibitors.
[0060] The aggregate slurry uses fly ash and loess as the main solid waste materials, combined with cement, water glass admixtures, and 5-20 mm coal gangue aggregate. It is specifically designed for wide fissures and fractured, non-compacted areas with a width of 5 mm or more. Coal gangue can quickly fill voids and wide fissures, significantly increasing the bulk density of the aggregate slurry and reducing solidification shrinkage. Cement, as the cementitious base, ensures the basic strength of the solidified body. The water glass admixture optimizes the slurry's fluidity and initial setting speed, preventing the aggregate slurry from easily losing or segregating in fractured and loose areas, allowing for rapid deposition and hardening into a high-strength solidified body. After solidification, this slurry exhibits strong compressive strength and excellent resistance to ground pressure disturbance. It can construct a rigid support and sealing curtain at the outer boundary and core fractured zone, compacting loose coal and rock mass, reducing rock porosity, and physically blocking large-scale air leakage channels.
[0061] This expanding grout is specifically designed for microscopic, hidden cracks less than 5 mm wide. It uses fly ash as the solid waste base material and cement as the binder, along with bentonite, a foaming agent, a foam stabilizer, and an inhibitor. Bentonite possesses excellent dispersion and penetration properties, reducing the viscosity of the expanding grout and allowing it to penetrate deep into the micro-cracks. The foaming agent and foam stabilizer work synergistically to create a stable micro-expansion structure during the solidification process, filling the tiny shrinkage gaps that occur during solidification and ensuring the grout adheres tightly to the coal face without any gaps. The added inhibitor can adhere to the surface of residual coal, inhibiting the oxidation and activation reactions of the coal and providing flame retardant and anti-spontaneous combustion functions.
[0062] Both aggregate grout and expanding grout use industrial solid waste as the main raw material, replacing traditional silicate cement and significantly reducing the procurement cost of grouting materials. They also consume mining solid waste such as fly ash and coal gangue, achieving resource utilization. The aggregate grout and expanding grout have complementary properties and clear division of labor. The aggregate grout is responsible for high-strength filling and building a rigid framework, while the expanding grout is responsible for microscopic sealing. This solves the shortcomings of traditional single grouts, such as incomplete filling of large cracks, inability to penetrate micro-cracks, easy cracking during consolidation, and lack of flame retardant ability, further improving the density, structural strength, and fire safety performance of the sealing body.
[0063] To further optimize the technical solution and grouting effect, and achieve dense filling of the borehole location, the sealing method provided in this application embodiment includes a graded control strategy in step three. This strategy includes: an initial grouting pressure of 0.8-1.2 MPa for boreholes in the outer perimeter of the coal mine goaf, with a stabilizing pressure of 2-2.5 MPa; and an initial grouting pressure of 1.5-2 MPa for deep boreholes in the coal mine goaf, with the stabilizing pressure maintained at 2.5-3 MPa. Since the locations of the boreholes in the outer perimeter and deep perimeters differ, as do the density of the surrounding rock, the development of fractures, and the burial depth, a two-stage pressure control mode with different initial grouting pressures and stabilizing pressures is used to precisely adapt to the grouting requirements of different areas, effectively optimizing the grout diffusion pattern, eliminating voids and pore residues, and further improving the dense filling effect of the borehole and surrounding fractures.
[0064] Specifically, the outer boreholes are shallow, the surrounding rock in the upper fracture zone is loose, and the fracture opening is large. Therefore, a low initial grouting pressure of 0.8-1.2 MPa is set. Low-pressure grouting can avoid high-pressure impact disturbance that breaks the loose surrounding rock, prevent the surrounding rock at the borehole opening from collapsing, and prevent grout backflow and leakage, ensuring that the aggregate grout fills the wide fractures in the outer perimeter smoothly and evenly. After the grout is initially filled, the pressure is increased to 2-2.5 MPa and stabilized. The stable pressure is used to squeeze the grout to be distributed densely, expel air bubbles inside the grout, reduce consolidation shrinkage pores, and form a continuous, high-density, low-porosity sealing curtain on the periphery.
[0065] Deep boreholes are characterized by large burial depths, high ground pressure, narrow fissures, and tortuous channels. Therefore, a higher pressure gradient is required. The initial grouting pressure is set at 1.5-2 MPa. High pressure is used to penetrate narrow interlayer fissures, overcome the ground pressure resistance of the deep surrounding rock, increase the penetration and diffusion range of the expanding grout, and prevent the grout from stagnating at the borehole opening and failing to penetrate into the micro-fissures. During the pressure stabilization stage, a high pressure of 2.5-3 MPa is maintained to promote the full extension of the expanding grout and fill the micro-fissures and pores, thereby enhancing the closure and sealing effect of the interlayer fissures.
[0066] The graded pressure control method provided in this application differs from traditional single constant pressure grouting. It can match the stress environment of surrounding rock at different depths, avoid the dual drawbacks of low-pressure grouting causing incomplete filling and high-pressure grouting damaging the surrounding rock, reduce the grouting void rate, enhance the adhesion between the grout and the coal and rock wall, improve the overall density and integrity of the sealing body, effectively prevent the formation of new through-holes due to changes in surrounding rock stress in the later stage, and ensure the long-term stability and airtightness of the sealing structure.
[0067] Similarly, when filling the core borehole, multiple fillings are involved. To ensure that the expanding grout can still achieve a better filling effect after the aggregate grout is filled, the grouting treatment method in step three includes a graded control strategy. The graded control strategy includes: the initial grouting pressure of the core borehole in the coal mine goaf is 0.8-1.2MPa, the pressure during the fracturing stage is 3-4MPa, and the pressure during the stabilization stage is maintained at 2.5-3MPa.
[0068] The technical solution provided in this application addresses the complex working conditions of dense borehole fractures, high degree of fragmentation, and nested multi-level fractures in the core area. It solves the technical problem of poor pore connectivity and difficulty in penetration and sealing of expanding grout after the aggregate slurry in the core area is closed due to the three-stage graded pressure control and timed grouting process of initial grouting, pressure fracturing, and pressure stabilization and replenishment.
[0069] First, the aggregate slurry is injected with a low initial pressure of 0.8-1.2 MPa. Low-pressure injection can avoid secondary crushing, hole collapse and slurry flow loss of loose coal and rock in the core area caused by high pressure impact. This allows the aggregate slurry to smoothly fill the large voids, fracture zones and macroscopic cracks in the core area, quickly form a rigid support skeleton, initially compact the loose coal body and construct the basic sealing structure.
[0070] After the aggregate slurry has been allowed to stand and solidify for 24-48 hours to form a stable solid structure, the pressure is increased to 3-4 MPa to carry out high-pressure fracturing. This pressure can be precisely applied to the original closed pores, unconnected micro pores, and the joints between the slurry and the coal and rock walls inside the solidified aggregate slurry, so that the sealed micro pores generate uniform micro-crack channels, opening up the internal blind spots, while not damaging the already formed rigid support structure. This effectively solves the problems of excessive density, insufficient permeability, and inability of subsequent slurry to fill deeply after solidification of the aggregate slurry.
[0071] Finally, the expansion grout is injected while maintaining a stable pressure of 2.5-3 MPa. The stable high pressure can drive the expansion grout to fully penetrate into the newly formed microcracks, aggregate gaps and fine cracks in coal and rock formed during the fracturing stage. Relying on the expansion characteristics of the grout itself, it fills all pore channels and completely eliminates the sealing voids and interlayer gaps in the core area.
[0072] The segmented and time-based pressure control process provided in this application embodiment achieves a layered filling effect of large-void rigid support and micro-crack dense sealing in the core area. It effectively solves the problems of uneven surface and interior density, internal void residue, and subsequent stress disturbance leakage in the existing technology, which are present in one-time grouting. It improves the overall integrity, density and structural stability of the core fracture zone sealing and fundamentally eliminates the hidden danger of air leakage in the core high-risk fracture zone.
[0073] Further optimization of the high-temperature resistant grout formulation is achieved. The technical solution provided in this application includes: fly ash, cement, bentonite, foaming agent, foam stabilizer, and high-temperature resistant flame retardant. The high-temperature resistant flame retardant is selected from one or more of the following: polymer gels, superabsorbent resins, and metal salt foam flame retardants. The high-temperature resistant grout is based on fly ash, cement, and bentonite, combined with foaming agent, foam stabilizer, and high-temperature resistant flame retardant. It is suitable for high-risk sealing conditions in goaf areas with abnormally high temperatures, hidden fire zones, and continuous oxidation and heating of the coal body. It addresses the technical shortcomings of conventional grouting grouts, such as easy dehydration, strength reduction, cracking failure, and insufficient flame-retardant capacity under high-temperature environments.
[0074] Fly ash and cement form the main body of the grout consolidation, ensuring the basic bonding strength and molding stability. Bentonite effectively improves the grout's dispersibility and suspension, preventing rapid segregation and sedimentation under high-temperature conditions, and ensuring uniform diffusion and filling of the grout within high-temperature fissures. The synergistic effect of foaming agent and foam stabilizer allows the grout to form a stable micro-expansion structure after solidification, offsetting the grout's shrinkage deformation caused by high temperatures and preventing shrinkage gaps in the sealing body under high-temperature conditions. By adding a high-temperature resistant inhibitor, the heat-resistant grout can maintain chemical stability under high-temperature conditions and will not decompose due to local high-temperature failure. It can tightly adhere to the surface of loose coal and high-temperature rock walls, forming a dense, high-temperature resistant, flame-retardant protective film that isolates oxygen from contact with the coal, cutting off the coal-oxygen composite spontaneous combustion chain reaction. It can also penetrate into the interior of high-temperature micro-fissures, continuously inhibiting coal oxidation and activation, absorbing heat and cooling down, and curbing the reignition of hidden fire zones.
[0075] In the technical solution provided in this application embodiment, when grouting in high-temperature or flammable areas, a heat-resistant grout is used to replace the conventional grout, which solves the defects of conventional grout in the prior art that is not heat-resistant and does not have long-term flame-retardant ability. It can stably form in high-temperature hazard areas, and the grout solidified in the borehole after sealing is not crumbly, does not fall off, and does not leak air. It effectively achieves the triple effect of sealing fissures in high-temperature environments, cooling and flame retardancy, and long-term flame suppression, thereby improving the safety and weather resistance of grouting and sealing in goaf areas with spontaneous combustion tendency.
[0076] The sealing method provided in this application embodiment further includes: Step four, grouting compliance testing. The method for grouting compliance testing includes: testing the water content at the borehole location after grouting treatment in Step three. If the water content is greater than the system's preset water content, then the grouting is up to standard. By adding a grouting compliance water content testing procedure, the water content of the borehole and surrounding rock is used as the core judgment indicator to accurately determine the crack filling density and sealing integrity.
[0077] After grouting is completed and fully cured, the water content of the consolidated body and fractured surrounding rock around the borehole is tested using testing equipment. If the water content is higher than the system's preset threshold, the grouting is deemed to have met the standard. Because the qualified grouting and consolidation area is completely filled and cemented by the grout, the original air and air leakage channels inside are completely filled. The water content of the cured grout colloidal structure is higher than that of loose voids and unsealed cavities. In contrast, areas that are not densely filled, have residual cavities and through air leakage channels, have large rock pores, a high air content, and a low water content.
[0078] The grouting compliance testing method of this application can intuitively and accurately distinguish between completely sealed areas and weak areas such as incomplete or false seals. It effectively identifies hidden quality defects that traditional acceptance methods cannot detect, such as residual micro-cracks, incomplete grout filling, and internal voids in the surface crust. By quantitatively detecting the moisture content, it achieves standardized and data-driven judgment of grouting quality, avoiding the quality misjudgment problems caused by traditional experience-based acceptance. It can accurately screen out unqualified areas with incomplete grouting and residual air leakage channels, facilitating timely re-grouting, effectively improving the overall sealing construction qualification rate, avoiding the hidden dangers of local false seals, and improving the overall uniformity, reliability, and long-term stability of air leakage sealing in goaf areas.
[0079] To further optimize the technical solution, the sealing method provided in this application embodiment also includes: Step 5, drilling and grouting. If the grouting in Step 4 fails the quality inspection, drilling and grouting treatment is performed. Targeted grouting operations are carried out on areas where the moisture content test in Step 4 indicates unqualified grouting. A closed-loop quality control system covering the entire process of detection-hole layout-grouting-testing-grouting is constructed, effectively solving the technical shortcomings of traditional grouting processes that only involve grouting, lack of re-inspection, defect retention, and inability to guarantee quality.
[0080] For the areas that failed the inspection in step four, it indicates that the rock mass pores and micro-cracks were not completely filled with grout, and residual air leakage channels still exist. These are weak points with potential for air leakage re-ignition and abnormal ventilation. Through the directional drilling and grouting treatment in step five, the substandard defective areas can be precisely targeted and repaired without the need for repeated grouting of the entire area, thus avoiding ineffective construction and material waste.
[0081] In practical applications, grouting operations can flexibly match aggregate grout or expanding grout according to the size of cracks and the degree of air leakage in the defective area. For large void defects, aggregate grout is used to reinforce and fill them, restoring the strength of the sealing skeleton; for fine pores, expanding grout is used for penetration and sealing, eliminating microscopic air leakage channels. Furthermore, grouting construction can be carried out in conjunction with the aforementioned graded pressure control process to precisely control the grouting pressure, ensuring that the grout fully diffuses and fills the remaining cracks while avoiding secondary pressure disturbances that could damage the original qualified sealing structure.
[0082] Step five, the borehole grouting process, enables precise rectification and dynamic repair of grouting defects, resolving issues such as incomplete sealing, shallow sealing, and residual local voids present in conventional grouting techniques. It prevents the overall sealing system from failing due to substandard grouting at individual points, thus avoiding the recurrence of air leaks later. Through a combination of testing and targeted grouting, the overall sealing density and structural uniformity of the goaf are comprehensively improved, ensuring that all borehole-sealed areas meet the standard of being dense and leak-proof, significantly enhancing the pass rate and long-term stability of air leak sealing projects.
[0083] From the above technical solutions, it can be concluded that the method for sealing air leakage channels in coal mine goaf provided in this application has the following advantages: First, the fracture characterization is accurate. By using a combination of physical and numerical simulation methods, the distribution of fractures in the coal pillar overlap area and the location of the non-compacted zone are accurately defined, solving the problem of ambiguous definition of the grouting range in traditional goaf areas. Second, the three-dimensional drilling system provides full coverage, constructing a zoned drilling system of periphery-core-deep, which is suitable for different types of fractures, significantly improving the sealing coverage rate and reducing the amount of grouting. Third, the utilization rate of solid waste resources is high. With fly ash, loess, coal gangue and other solid wastes as the main raw materials, the utilization rate of solid waste is over 60%, which significantly reduces the cost of grouting and is more in line with the concept of green mining. Fourth, the materials and processes are synergistically adapted. The three types of grout are respectively suitable for large cracks, micro cracks, and fire zone scenarios. Combined with the graded sealing process of filling first and then compacting, the sealing effect is long-lasting. Fifth, closed-loop monitoring ensures quality: By integrating temperature, gas, and grout diffusion monitoring, a closed loop of grouting-monitoring-replenishment is formed to ensure the safety and compliance of the grouting process.
[0084] In summary, this application provides a method for sealing air leakage channels in coal mine goafs, comprising: acquiring the fracture distribution characteristics of the coal mine goaf; performing drilling based on the fracture distribution characteristics; and performing grouting on the obtained boreholes. The grouting material for the grouting includes any one or more of aggregate-containing grout and expanding grout. In the technical solution provided by this application, the fracture distribution characteristics are acquired through a combination of physical similarity simulation and numerical simulation. Precise drilling is then performed based on these characteristics, followed by orderly, multi-type grouting of the boreholes. By performing zoned drilling, specific sealing of different types of fractures is achieved, effectively improving the sealing coverage rate and thus achieving a tight seal of the air leakage channels. This solves the technical defect in the prior art where the sealing effect of air leakage channels in cross-coal seam working faces is poor.
[0085] The technical features of the embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. Furthermore, other implementation methods can be derived from the above embodiments, allowing for structural and logical substitutions and changes without departing from the scope of this disclosure.
[0086] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.
Claims
1. A method for sealing air leakage channels in coal mine goaf areas, characterized in that, The blocking method includes: Step 1: Collect geological data, cross-working face layout parameters, and residual coal pillar distribution data of the coal mine goaf to obtain the fracture distribution characteristics of the coal mine goaf. The method for obtaining the fracture distribution characteristics includes the coupling of physical similarity simulation and numerical simulation. Step 2: Perform drilling according to the fracture distribution characteristics. The drilling includes drilling at any one or more locations in the periphery, core, and deep part of the coal mine goaf. Step 3: Perform grouting treatment on the boreholes obtained in Step 2. The grouting material includes any one or more of aggregate grout and expanding grout. The grouting sequence includes: performing grouting treatment on the boreholes from the outside to the inside; the grouting of the outer boreholes uses the aggregate grout; the grouting of the core boreholes first uses the aggregate grout and then the expanding grout; and the grouting of the deep boreholes uses the expanding grout.
2. The sealing method according to claim 1, characterized in that, Step three also includes: monitoring temperature and spontaneous combustion gas concentration; If the monitored temperature or the concentration of spontaneously combustible gas is greater than the system preset value, a heat-resistant grout will be used to perform the grouting process during drilling.
3. The sealing method according to claim 1 or 2, characterized in that, In step one, the physical similarity simulation experiment includes: building a physical model of the cross working face of the goaf and obtaining a numerical model of the cross working face; the numerical simulation experiment includes: simulating the fracture evolution process at different mining stages based on the numerical model, and obtaining the fracture development boundary, non-compacting zone location, and through fracture depth of the goaf.
4. The sealing method according to claim 1 or 2, characterized in that, In step two, the drilling spacing for the outer perimeter is 5-10 meters, the drilling spacing for the core is 4-6 meters, and the drilling spacing for the deep portion is 3-5 meters.
5. The sealing method according to claim 1 or 2, characterized in that, In step three, the aggregate slurry includes: solid waste main material, cement, admixtures and 5-20 mm coal gangue; the expanding slurry includes: fly ash, cement, bentonite, foaming agent, foam stabilizer and inhibitor, wherein the inhibitor is selected from any one or more of the following: halide salts, ammonium salts and silicate inhibitors.
6. The sealing method according to claim 1 or 5, characterized in that, In step three, the grouting treatment method includes a graded control strategy, which includes: the initial grouting pressure of the outer boreholes in the coal mine goaf is 0.8-1.2 MPa, and the stabilizing pressure is 2-2.5 MPa; the initial grouting pressure of the deep boreholes in the coal mine goaf is 1.5-2 MPa, and the stabilizing pressure is maintained at 2.5-3 MPa.
7. The sealing method according to claim 1 or 5, characterized in that, In step three, the grouting treatment method includes a graded control strategy, which includes: the initial grouting pressure of the core borehole in the coal mine goaf is 0.8-1.2 MPa, the pressure during the fracturing stage is 3-4 MPa, and the pressure during the stabilization stage is maintained at 2.5-3 MPa.
8. The sealing method according to claim 2, characterized in that, The heat-resistant slurry includes: fly ash, cement, bentonite, foaming agent, foam stabilizer, and high-temperature resistant inhibitor. The high-temperature resistant inhibitor is selected from one or more of the following: polymer gels, superabsorbent resins, and metal salt foam flame retardants.
9. The sealing method according to claim 1 or 2, characterized in that, The sealing method further includes: step four, grouting compliance test, the grouting compliance test method includes: testing the water content at the borehole location after the grouting treatment in step three, if the water content is greater than the system preset water content, then the grouting is compliant.
10. The sealing method according to claim 9, characterized in that, The sealing method also includes: step five, drilling and grouting. If the grouting in step four fails the test, drilling and grouting treatment is performed.