Method for treating room-pillar type goaf through grouting and fully mechanized coal mining and coal pillar recovery

Abstract

The invention relates to the technical field of coal mining, in particular to a method for treating a room-and-pillar goaf through grouting and recycling coal pillars through fully mechanized mining, which comprises the following steps: forming a detection directional hole through a directional drilling technology, performing field detection on a distribution area of the room-and-pillar goaf, constructing a three-dimensional space model of the room-and-pillar goaf, and constructing a three-dimensional space model of the room-and-pillar goaf; gradually obtaining the range of the room-and-pillar goaf according to the boundary points of the room-and-pillar goaf detected by the plurality of detection directional holes; based on the range of the room-and-pillar goaf and the internal structure of the room-and-pillar goaf, the arrangement position, number and depth of drainage drill holes are obtained; based on the arrangement position, number and depth of the drainage drill holes, accumulated water in the goaf is introduced into a mine drainage system through a drainage pipe; grouting treatment is conducted on the room-pillar type goaf through the grouting drill holes; and after the working face is arranged according to the working face arrangement scheme, coal pillar recovery operation is carried out according to the formulated mining scheme.

Description

Technical Field

[0001] This invention relates to the field of coal mining technology, and in particular to a method for grouting to treat room-and-pillar goaf and recover coal pillars through fully mechanized mining. Background Technology

[0002] Currently, large-scale room-and-pillar goaf areas exist in coal bases. Due to their shallow burial depth, they are prone to spontaneous combustion, mine tremors, and other disasters, threatening surface and underground coal mine production and wasting coal resources. Existing technologies for treating room-and-pillar goaf areas mainly involve grouting through boreholes on the surface, but this method has several drawbacks: firstly, land acquisition is difficult; secondly, the complex terrain makes laying grout pipelines challenging; and thirdly, the grouting material is mostly paste, with a transport distance generally limited to within 10 km. Summary of the Invention

[0003] This invention provides a method for grouting treatment of room-and-pillar goaf and fully mechanized coal pillar recovery, addressing one of the shortcomings of existing technologies. By integrating geological data and directional drilling detection technology, the method achieves precise definition of the goaf's extent and internal structure, providing accurate spatial basis for subsequent operations. The use of underground directional drilling technology for water drainage and grouting operations avoids the difficulties in land acquisition and complex terrain leading to inconvenient grout pipeline laying encountered in surface treatment. Through gradient grouting treatment and a strict inspection and monitoring mechanism, the method ensures dense filling and stable cementation of the goaf, effectively mitigating potential hazards such as spontaneous combustion and mine vibration. The coal pillar recovery method balances mining efficiency, mechanization, and safety, achieving the dual goals of goaf disaster management and efficient coal resource recovery, solving a key issue urgently needing resolution in the industry, and reducing coal resource waste.

[0004] This invention provides a method for grouting to treat room-and-pillar goaf and recovering coal pillars through fully mechanized mining, comprising: The distribution area of ​​room-and-pillar goaf has been preliminarily determined; By forming directional drilling technology, the distribution area of ​​the room-and-pillar goaf is explored in the field, a three-dimensional spatial model of the room-and-pillar goaf is constructed, and the range of the room-and-pillar goaf is gradually obtained based on the boundary points of the room-and-pillar goaf detected by multiple directional drilling holes. Based on the three-dimensional spatial model of the room-and-pillar goaf, the internal structure of the room-and-pillar goaf is obtained. Based on the range of the room-and-pillar goaf and its internal structure, the location, number, and depth of the drainage boreholes are obtained. Based on the location, number, and depth of the drainage boreholes, the accumulated water in the goaf is introduced into the mine drainage system through drainage pipes; At least some of the aforementioned directional boreholes are selected as grouting boreholes, and the room-and-pillar goaf is treated by grouting through the grouting boreholes. Based on the scope of the treated room-and-pillar goaf, the distribution of coal pillars, and the mining technology conditions of the mining area, a working face layout plan is formulated. After the working face is arranged according to the working face layout plan, the coal pillar recovery operation is carried out in accordance with the established mining plan.

[0005] According to the present invention, a method for grouting treatment of room-and-pillar goaf and fully mechanized coal pillar recovery includes forming directional boreholes using directional drilling technology to conduct on-site exploration of the distribution area of ​​the room-and-pillar goaf and constructing a three-dimensional spatial model of the room-and-pillar goaf. Directional drilling proceeds along a first preset trajectory, and the geological conditions inside the borehole are obtained through real-time monitoring. By combining the geological conditions inside the borehole with the borehole trajectory data, a three-dimensional spatial model of the goaf is constructed.

[0006] According to the present invention, a method for grouting to treat room-and-pillar goaf and recovering coal pillars through fully mechanized mining includes, wherein constructing a three-dimensional spatial model of the goaf by combining the geological conditions within the borehole with borehole trajectory data includes: Based on the azimuth, dip angle, and elevation of the borehole, combined with depth measurement and trigonometric function calculations, the coordinates of the borehole in three-dimensional space are determined point by point, generating a three-dimensional spatial model of the goaf.

[0007] According to the present invention, a method for grouting to treat room-and-pillar goaf and recovering coal pillars through fully mechanized mining includes, in which, based on the arrangement, number, and depth of the drainage boreholes, water accumulated in the goaf is introduced into the mine drainage system through drainage pipes, the method comprising: Select areas within the goaf where water accumulation is relatively concentrated and water levels are high to arrange the aforementioned drainage boreholes; The directional drill advances along the second preset trajectory to the water accumulation area of ​​the goaf. After the drilling is completed, a drainage pipe is installed in the drainage hole, and the hole and the drainage pipe are sealed. Water accumulated in the goaf is introduced into the mine drainage system through drainage pipes.

[0008] According to the present invention, a method for grouting treatment of room-and-pillar goaf and fully mechanized coal pillar recovery includes selecting at least a portion of the directional boreholes as grouting boreholes and performing grouting treatment of the room-and-pillar goaf through the grouting boreholes, comprising: The first stage of grouting is performed on the room-and-column goaf using bottom material; After the first stage of grouting is completed, directional drilling is carried out to drain the oozing water; The second stage of grouting is performed on the room-column goaf after the first stage of grouting using top material.

[0009] According to the present invention, a method for grouting to treat room-and-pillar goaf and recover coal pillars through fully mechanized mining is provided, wherein the bottom material is a fly ash-based cementitious material, accounting for 90%-95% of the grouting volume; and the top material is a hydrophilic expansion composite material, accounting for 5%-10% of the grouting volume.

[0010] According to the method for grouting treatment of room-and-pillar goaf and fully mechanized coal pillar recovery provided by the present invention, the method further includes, between the step of grouting treatment of the room-and-pillar goaf based on at least a portion of the directional boreholes and the step of formulating a working face layout plan based on the extent of the treated room-and-pillar goaf, the distribution of coal pillars, and the mining technology conditions of the mining area, the following: Through inspection and continuous monitoring, we ensure that the grouting treatment effect meets the design requirements.

[0011] According to the present invention, a method for grouting treatment of room-and-pillar goaf and fully mechanized coal pillar recovery, wherein ensuring the grouting treatment effect meets design requirements through inspection and continuous monitoring includes: After the grout injected into the treatment area has completely solidified, detection boreholes are formed in the treatment area using directional drilling technology, and core sampling is carried out. The extracted grouting core was analyzed to determine the filling condition of the grouting material and its bonding state with the coal pillar and rock strata. Drilling inspection technology was used to observe the filling condition of the goaf inside the borehole and to detect the grouting filling rate. Rock mechanics tests were conducted on the extracted grout-bonded rock core to determine its compressive strength, shear strength, and other mechanical parameters, verifying whether the strength of the grout-bonded body met the design standards.

[0012] According to the present invention, a method for grouting to treat room-and-pillar goaf and recover coal pillars in fully mechanized mining, wherein the number of detection boreholes is 5% of the number of grouting boreholes, and the detection boreholes are arranged at equal intervals. After the goaf is treated, the roadway is delineated, and short holes are laid out using a conventional drilling rig to enhance the inspection effect. The spacing of the short holes is smaller than the spacing of the inspection boreholes.

[0013] According to the present invention, a method for grouting treatment of room-and-pillar goaf and fully mechanized coal pillar recovery is provided. During the treatment process and subsequent coal pillar recovery in the treated area, a microseismic monitoring system and a mine pressure monitoring system are used to monitor the treated area in real time. The microseismic monitoring and mine pressure monitoring data are comprehensively analyzed to provide a basis for safety early warning of coal pillar recovery in the treated area.

[0014] The method for grouting to treat room-and-pillar goaf and recovering coal pillars provided by this invention is applicable to large-scale room-and-pillar goafs in coal mines that are shallow in burial depth and prone to spontaneous combustion and mine earthquake disasters. First, based on existing geological data such as coal seam distribution, stratigraphic lithology and structure, burial depth, coal thickness, and dip angle, the potential distribution area of ​​the room-and-pillar goaf is initially identified, defining the scope for subsequent exploration work. Then, directional drilling technology is used to construct directional boreholes. This technology allows drilling along a preset trajectory, flexibly adjusting direction and depth, and effectively adapting to complex underground geological conditions. By real-time monitoring of changes in rock strata within the borehole and whether goafs are encountered, a three-dimensional spatial model of the goaf is constructed based on the borehole trajectory data. Then, the boundary points detected by multiple directional boreholes are integrated to accurately delineate the precise range of the goaf. After clarifying the internal structure of the goaf based on the constructed three-dimensional spatial model, the water distribution characteristics are analyzed in conjunction with the delineated goaf range to determine the optimal location, number, and depth of drainage boreholes, prioritizing those with concentrated water accumulation and high water levels. Area-specific borehole layout; construct drainage boreholes according to determined parameters, install drainage pipes and seal them to introduce accumulated water into the mine drainage system, ensuring full drainage; utilize some previously constructed exploratory directional boreholes as grouting boreholes to avoid repeated drilling operations and reduce construction costs; fill and treat the goaf through two-stage gradient grouting; after grouting is completed, inspect and continuously monitor to confirm that the treatment effect meets the standards; then, based on the treated goaf area, coal pillar distribution, and mining technology conditions, formulate a longwall fully mechanized mining face layout plan, rationally divide the recovery working face, determine parameters such as strike length, dip length, and mining height, and arrange the intake airway, return airway, and transport airway accordingly; after installing fully mechanized mining equipment such as coal mining machines, scraper conveyors, and hydraulic supports, carry out coal pillar recovery operations according to the mining plan, while continuously monitoring to ensure operational safety.

[0015] By integrating geological data and directional drilling detection technology, the precise definition of the goaf's extent and internal structure was achieved, providing accurate spatial basis for subsequent operations. The use of underground directional drilling technology for water drainage and grouting operations avoided the difficulties in land acquisition and complex terrain that hindered grout pipeline laying in surface remediation. The selection of highly fluid coal-based solid waste slurry enabled long-distance transport exceeding 10 km, overcoming the limitations of traditional paste grouting. Gradient grouting and a rigorous inspection and monitoring mechanism ensured dense filling and stable cementation of the goaf, effectively mitigating potential hazards such as spontaneous combustion and mine tremors. The use of longwall fully mechanized mining to recover coal pillars balanced mining efficiency, mechanization, and safety, achieving the dual goals of goaf remediation and efficient coal resource recovery. This solved a critical issue urgently needing resolution within the industry and reduced coal resource waste. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in this invention 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 some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the directional exploration borehole for the method of grouting treatment of room-and-pillar goaf and fully mechanized coal pillar recovery provided in the embodiments of the present invention; Figure 2 This is a schematic diagram of a directional exploration borehole profile of the method for grouting treatment of room-and-pillar goaf and fully mechanized coal pillar recovery provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the directional water drainage borehole profile of the method for grouting treatment of room-and-pillar goaf and fully mechanized coal pillar recovery provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the directional grouting borehole for the method of grouting treatment of room-and-pillar goaf and fully mechanized coal pillar recovery provided in this embodiment of the invention; Figure 5 This is a schematic diagram of the directional grouting borehole for the method of grouting treatment of room-and-pillar goaf and fully mechanized coal pillar recovery provided in this embodiment of the invention; Figure 6 This is a schematic diagram of the grouting material used in the method of grouting treatment of room-and-pillar goaf and fully mechanized coal pillar recovery provided in this embodiment of the invention; Figure 7 This is a schematic diagram of the directional inspection borehole for the method of grouting treatment of room-and-pillar goaf and fully mechanized coal pillar recovery provided in this embodiment of the invention; Figure 8 This is a schematic diagram of the directional inspection borehole profile of the method for grouting treatment of room-and-pillar goaf and fully mechanized coal pillar recovery provided in an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0019] In the description of the embodiments of the present invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention 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. Therefore, they should not be construed as limitations on the embodiments of the present invention. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0020] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention based on the specific circumstances.

[0021] In embodiments of the present invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0022] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0023] like Figures 1 to 8 As shown in the embodiment of the present invention, the method for grouting to treat room-and-pillar goaf and recovering coal pillars through fully mechanized mining includes: The distribution area of ​​room-and-pillar goaf has been preliminarily determined; By forming directional drilling technology, the distribution area of ​​the room-and-pillar goaf is explored in the field, a three-dimensional spatial model of the room-and-pillar goaf is constructed, and the range of the room-and-pillar goaf is gradually obtained based on the boundary points of the room-and-pillar goaf detected by multiple directional drilling holes. Based on the three-dimensional spatial model of the room-and-pillar goaf, the internal structure of the room-and-pillar goaf is obtained. Based on the range of the room-and-pillar goaf and its internal structure, the location, number, and depth of the drainage boreholes are obtained. Based on the location, number, and depth of the drainage boreholes, the accumulated water in the goaf is introduced into the mine drainage system through drainage pipes; At least some of the aforementioned directional boreholes are selected as grouting boreholes, and the room-and-pillar goaf is treated by grouting through the grouting boreholes. Based on the scope of the treated room-and-pillar goaf, the distribution of coal pillars, and the mining technology conditions of the mining area, a working face layout plan is formulated. After the working face is arranged according to the working face layout plan, the coal pillar recovery operation is carried out in accordance with the established mining plan.

[0024] The grouting method for treating room-and-pillar goaf and recovering coal pillars according to embodiments of the present invention is applicable to large-scale room-and-pillar goafs in coal bases that are shallow in burial depth and prone to spontaneous combustion and mine earthquake disasters. First, based on existing geological data such as coal seam distribution, strata lithology and structure, burial depth, coal thickness, and dip angle, the potential distribution area of ​​the room-and-pillar goaf is initially identified, defining the scope for subsequent exploration work. Then, directional drilling technology is used to construct directional boreholes. This technology allows drilling along a preset trajectory, flexibly adjusting direction and depth, and effectively adapting to complex underground geological conditions. By real-time monitoring of changes in rock strata within the borehole and whether goafs are encountered, a three-dimensional spatial model of the goaf is constructed based on the borehole trajectory data. Then, the boundary points detected by multiple directional boreholes are integrated to accurately delineate the precise range of the goaf. After clarifying the internal structure of the goaf based on the constructed three-dimensional spatial model, the water distribution characteristics are analyzed in conjunction with the delineated goaf range to determine the optimal location, number, and depth of drainage boreholes, prioritizing those with concentrated water accumulation and high water levels. Area-specific borehole layout; construct drainage boreholes according to determined parameters, install drainage pipes and seal them to introduce accumulated water into the mine drainage system, ensuring full drainage; utilize some previously constructed exploratory directional boreholes as grouting boreholes to avoid repeated drilling operations and reduce construction costs; fill and treat the goaf through two-stage gradient grouting; after grouting is completed, inspect and continuously monitor to confirm that the treatment effect meets the standards; then, based on the treated goaf area, coal pillar distribution, and mining technology conditions, formulate a longwall fully mechanized mining face layout plan, rationally divide the recovery working face, determine parameters such as strike length, dip length, and mining height, and arrange the intake airway, return airway, and transport airway accordingly; after installing fully mechanized mining equipment such as coal mining machines, scraper conveyors, and hydraulic supports, carry out coal pillar recovery operations according to the mining plan, while continuously monitoring to ensure operational safety.

[0025] By integrating geological data and directional drilling detection technology, the precise definition of the goaf's extent and internal structure was achieved, providing accurate spatial basis for subsequent operations. The use of underground directional drilling technology for water drainage and grouting operations avoided the difficulties in land acquisition and complex terrain that hindered grout pipeline laying in surface remediation. The selection of highly fluid coal-based solid waste slurry enabled long-distance transport exceeding 10 km, overcoming the limitations of traditional paste grouting. Gradient grouting and a rigorous inspection and monitoring mechanism ensured dense filling and stable cementation of the goaf, effectively mitigating potential hazards such as spontaneous combustion and mine tremors. The use of longwall fully mechanized mining to recover coal pillars balanced mining efficiency, mechanization, and safety, achieving the dual goals of goaf remediation and efficient coal resource recovery. This solved a critical issue urgently needing resolution within the industry and reduced coal resource waste.

[0026] According to an embodiment provided by the present invention, forming a detection directional hole through directional drilling technology, conducting on-site detection of the distribution area of the room-and-pillar goaf, and constructing a three-dimensional space model of the room-and-pillar goaf includes: The directional drill drills according to a first preset trajectory, and the geological conditions in the drill hole are obtained through real-time monitoring; Combining the geological conditions in the drill hole with the drill hole trajectory data, a three-dimensional space model of the goaf is constructed.

[0027] In this embodiment, the specific process of using directional drilling technology to form a detection directional hole to conduct on-site detection of the distribution area of the room-and-pillar goaf and construct a three-dimensional space model is as follows: First, combine the basic data such as coal seam burial depth, dip angle, and formation lithology in the mine geological data to plan a first preset trajectory for the directional drill. This trajectory needs to avoid known complex geological structures, ensure that the drill hole can cover the potentially distributed area of the initially determined goaf, and at the same time meet the detection accuracy requirements; start the directional drill equipment and conduct drilling operations according to the planned first preset trajectory. During the drilling process, through the real-time monitoring system supporting the directional drill, continuously collect the geological condition data in the drill hole, including key information such as changes in rock formation lithology, whether the goaf is contacted, and the preliminary shape of the goaf; synchronously record the drilling trajectory data of the directional drill, including parameters such as the real-time azimuth angle, dip angle, drilling depth (depth measurement), and elevation of the drill hole; associate and integrate the geological condition data in the drill hole obtained through real-time monitoring with the synchronously recorded drill hole trajectory data. Through data fusion technology, match each geological feature point with the corresponding spatial trajectory point, and then construct a three-dimensional space model that can truly reflect the spatial position, shape, size of the room-and-pillar goaf and its relationship with the surrounding rock formations and coal pillars.

[0028] By drilling according to the preset trajectory with a directional drill, it effectively overcomes the limitations of complex underground geological conditions and ensures the pertinence and effectiveness of the detection process; the combination of real-time monitoring of geological conditions and trajectory data avoids the limitations of single data collection, enabling the constructed three-dimensional space model to accurately restore the actual spatial state of the goaf; this three-dimensional space model provides an accurate spatial basis for subsequent operations such as the layout of water drainage boreholes, grouting scheme design, and working face planning, greatly improving the scientificity and rationality of the entire treatment and recovery process, and avoiding problems such as low efficiency, cost waste, or safety hazards caused by blind construction.

[0029] In this embodiment, the purpose of the first preset trajectory is to ensure that the directional hole can fully explore the range of the room-and-pillar goaf. The main basis conditions are as follows: 1) The original formation state is used to determine the different drilling difficulties that may be encountered during the directional drill drilling and to feedback the trajectory preset; 2) The original mining design or summary of the goaf, and the preliminary exploration range is delineated through existing artificial construction plans or construction records; 3) Geophysical exploration conclusions: Using geophysical exploration methods, the exploration range is preliminarily delineated, which can be cross-verified with the original mining design or summary of the goaf area; Leave a margin for drilling exploration. To ensure the accuracy of the exploration, the exploration range can be expanded by 30m beyond the initial delineation during the pre-set trajectory process.

[0030] During directional drilling, the direction is set by the guiding system (screw motor), and the position is fed back in real time by the measurement-while-drilling system. The tool face is adjusted according to the real-time position to achieve precise drilling along the preset trajectory.

[0031] According to an embodiment of the present invention, constructing a three-dimensional spatial model of the goaf by combining the geological conditions within the borehole with borehole trajectory data includes: Based on the azimuth, dip angle, and elevation of the borehole, combined with depth measurement and trigonometric function calculations, the coordinates of the borehole in three-dimensional space are determined point by point, generating a three-dimensional spatial model of the goaf.

[0032] In this embodiment, a precise calculation method based on key borehole parameters and trigonometric functions is used to construct the three-dimensional spatial model of the goaf. First, during directional drilling, professional measuring equipment is used to collect real-time data on the borehole azimuth, dip angle, elevation, and depth at each detection node. The azimuth determines the projection direction of the borehole onto the horizontal plane, the dip angle reflects the angle between the borehole and the horizontal plane, the elevation represents the vertical height of the node, and the depth is the drilling length from the borehole start point to the node. Then, using the unified coordinate system of the mining area as a reference, point-by-point coordinate calculations are performed using trigonometric relationships: based on the azimuth and depth, the X-axis and Y-axis coordinate components of the node on the horizontal plane are calculated using cosine functions, i.e., water... The distribution of the horizontal projection distance in the X and Y directions; combined with the dip angle and depth sounding, the change in vertical height of the node relative to the borehole starting end is calculated using a sine function, and then the Z-axis coordinate (vertical coordinate) of the node is determined by combining the elevation of the starting end; after calculating the X, Y, and Z three-dimensional coordinates of each detection node in sequence, the coordinates of each node are connected according to the drilling sequence. At the same time, combined with the geological data corresponding to each node (such as whether it is a goaf boundary, rock stratum interface, etc.), the data is processed and the model is rendered using 3D modeling software, and finally a complete and accurate 3D spatial model of the goaf is generated.

[0033] By combining azimuth, dip, elevation, depth sounding, and trigonometric functions, the precise three-dimensional coordinates of each detection node were located, avoiding errors caused by spatial location estimation in traditional modeling methods. The point-by-point coordinate determination method ensured that the model could accurately reflect the boundary contour, internal structure, and spatial relationship with surrounding geological bodies of the goaf. The model accuracy met the design requirements for subsequent operations such as drainage, grouting, and working face layout. The accurate three-dimensional spatial model provided reliable support for the optimization of various operation plans, helping to reduce construction risks, improve operation efficiency, and enhance treatment quality.

[0034] According to an embodiment of the present invention, the method of introducing accumulated water in the goaf into the mine drainage system through drainage pipes based on the arrangement location, number, and depth of the drainage boreholes includes: Select areas within the goaf where water accumulation is relatively concentrated and water levels are high to arrange the aforementioned drainage boreholes; The directional drill advances along the second preset trajectory to the water accumulation area of ​​the goaf. After the drilling is completed, a drainage pipe is installed in the drainage hole, and the hole and the drainage pipe are sealed. Water accumulated in the goaf is introduced into the mine drainage system through drainage pipes.

[0035] In this embodiment, water drainage operations are carried out based on the scope and internal structure of the goaf. The specific steps are as follows: First, based on the three-dimensional spatial model of the goaf, the distribution pattern of water accumulation inside the goaf is analyzed. Areas with relatively concentrated water accumulation and high water levels are preferentially selected as the layout areas for water drainage boreholes. Specifically, these include low-lying areas of the goaf, areas with densely developed fissures that may be connected to water sources. These areas have large water storage capacity and high drainage efficiency, which can quickly reduce the overall water level of the goaf. Second, according to the selected layout areas, a second preset trajectory for directional drilling is planned to ensure that the trajectory can accurately drill to the core area of ​​water accumulation in the goaf. The directional drill follows the second preset trajectory until the preset depth is reached to complete the final hole operation. Third, after the borehole is completed, water is immediately drained. A matching drainage pipe is lowered into the drainage borehole. The length of the drainage pipe must cover the entire distance from the borehole opening to the water accumulation area to ensure effective water extraction. Next, the gap between the borehole and the drainage pipe is sealed using a special sealing material to prevent water leakage and ensure the sealing and stability of the drainage channel. Fourth, the other end of the drainage pipe is connected to the mine drainage system, and the drainage equipment is activated. Water from the goaf is continuously introduced into the mine drainage system through the drainage pipe. During the drainage process, the drainage volume and water level changes in the goaf are monitored in real time. Based on the monitoring data, the power of the drainage equipment or the drainage strategy is dynamically adjusted to ensure that the water in the goaf is fully discharged until the water level drops to a level that does not affect the safety of subsequent grouting treatment work.

[0036] By precisely selecting the locations for drainage boreholes, drainage efficiency was improved and the drainage operation cycle was shortened. Directional drilling along a pre-set trajectory ensured that the boreholes accurately reached the water-accumulated areas, avoiding ineffective drilling. Sealing between the boreholes and drainage pipes prevented leakage during drainage, guaranteeing effective drainage. Real-time monitoring of drainage volume and water level changes allowed for timely adjustments to the drainage strategy, ensuring sufficient drainage of accumulated water. This effectively addressed the impact of accumulated water on the subsequent grouting material's setting effect and grouting quality, while also eliminating the safety hazard of water inrush accidents during mining, creating a safe working environment for grouting treatment and subsequent coal pillar recovery operations.

[0037] In this embodiment, the second preset trajectory is a precise preset of the water drainage borehole trajectory in the low-lying area of ​​the goaf floor based on the contour lines of the coal seam floor and combined with hydrogeological conditions.

[0038] According to an embodiment of the present invention, selecting at least a portion of the directional boreholes for grouting, and performing grouting treatment on the room-and-pillar goaf through the grouting boreholes, includes: The first stage of grouting is performed on the room-and-column goaf using bottom material; After the first stage of grouting is completed, directional drilling is carried out to drain the oozing water; The second stage of grouting is performed on the room-column goaf after the first stage of grouting using top material.

[0039] In this embodiment, the grouting process is carried out in two orderly stages: The first stage of grouting mainly uses the bottom material. Grouting is performed at a surface grouting station. After the grout is prepared strictly according to the formula, it is pumped and transported to the grouting borehole using a surface and underground pipeline system. The bottom material is then injected into the bottom of the goaf and most of the space through the grouting borehole, achieving the main filling of the goaf. After the first stage of grouting is completed, water will be secreted during the solidification process of the grout. If this water is not drained in time, it will affect the density and strength of the grout body. Therefore, a special arrangement is needed. The oozing water is centrally drained from the borehole to ensure rapid discharge. After the oozing water is drained, the second stage of grouting is started. The preparation and transportation process of the top material in the second stage of grouting is as follows: Material A is prepared separately through the ground grouting station and pumped to the underground grout storage tank of the coal mine through the ground and underground pipeline system. In the grout storage tank, Material A is fully mixed with the pre-stored Material B through a three-way device. After uniform mixing, qualified top grout is formed and then transported to the grouting borehole. It is injected into the remaining space at the top of the goaf through the grouting borehole to achieve full filling of the goaf.

[0040] This embodiment utilizes directional boreholes for grouting, reducing drilling volume and saving construction costs and time. The two-stage grouting combined with water drainage effectively solves problems such as incomplete filling and water seepage affecting grouting quality that may occur with a single grouting method. The first stage of grouting fills the main space of the goaf, while the second stage precisely fills the remaining space at the top, ensuring the overall filling effect of the goaf, improving the reliability and stability of grouting treatment, and providing a solid geological guarantee for subsequent coal pillar recovery operations.

[0041] According to one embodiment of the present invention, the bottom material is a fly ash-based cementitious material, accounting for 90%-95% of the grouting volume; the top material is a hydrophilic expansion composite material, accounting for 5%-10% of the grouting volume.

[0042] In this embodiment, the two materials used in the grouting treatment are precisely proportioned and designed to meet the different needs of goaf filling: the bottom material is a fly ash-based cementitious material, which is mainly composed of fly ash, accounting for more than 80% and cementitious material accounting for 20%, with the slurry concentration controlled at 50%-55%. Its usage accounts for 90%-95% of the total grouting volume, which can fully fill the bottom of the goaf and most of the main space. This material has good fluidity and can achieve long-distance transportation of more than 10 km, solving the problem of limited transportation distance of traditional paste grouting. At the same time, it uses industrial solid waste fly ash as the main raw material, which is both environmentally friendly and economical. The top material is a hydrophilic expansion composite material with a slurry concentration of 50%-70% and a usage accounting for 5%-10% of the total grouting volume. It is specifically used to fill the remaining space at the top of the goaf. This material has hydrophilic properties and can absorb the residual seepage water that was not drained after the first stage of grouting. At the same time, it undergoes micro-expansion to achieve a tight fit (top connection) with the top plate of the goaf, avoiding the appearance of top gaps.

[0043] Fly ash-based cementitious materials are characterized by large dosage, good fluidity, and low cost, enabling efficient filling of the main structure of goaf areas. Their long-distance transport characteristics are suitable for complex terrain and long-distance operations, reducing the difficulty of pipeline laying. Hydrophilic expandable composite materials, while requiring less dosage, are highly targeted. Through water absorption and expansion, they achieve a tight connection to the roof, solving the problem of insufficient compaction at the top of the goaf and ensuring a void-free filling of the entire goaf. The proportions and performance design of the two materials complement each other, and their synergistic effect significantly improves the overall density and stability of the grout, enhances the bearing capacity of the surrounding rock in the goaf, and provides a safe and stable geological environment for subsequent coal pillar recovery operations. Furthermore, the large-scale utilization of fly ash realizes the resource recovery of industrial solid waste, aligning with the concept of green mining.

[0044] According to an embodiment of the present invention, between the step of grouting treatment of the room-and-pillar goaf based on at least a portion of the directional boreholes and the step of formulating a working face layout plan based on the extent of the treated room-and-pillar goaf, the distribution of coal pillars, and the mining technology conditions of the mining area, the following method is further included: Through inspection and continuous monitoring, we ensure that the grouting treatment effect meets the design requirements.

[0045] In this embodiment, the added inspection and continuous monitoring steps establish a dual guarantee system of post-inspection and full-process monitoring, effectively avoiding the safety risks of proceeding to subsequent operations before the grouting treatment effect meets the standards. The inspection step can comprehensively and accurately assess the grouting filling quality and mechanical properties, ensuring that the grout body meets the load-bearing and stability requirements. The continuous monitoring step can capture real-time geological dynamic changes in the treatment area and during the recovery process, promptly identifying potential risks such as rock mass instability and providing a basis for safety early warning. This significantly improves the safety and reliability of coal pillar recovery operations, avoids disasters caused by inadequate grouting treatment, and ensures the safety and controllability of the entire mining process.

[0046] According to one embodiment of the present invention, ensuring that the grouting treatment effect meets the design requirements through inspection and continuous monitoring includes: After the grout injected into the treatment area has completely solidified, detection boreholes are formed in the treatment area using directional drilling technology, and core sampling is carried out. The extracted grouting core was analyzed to determine the filling condition of the grouting material and its bonding state with the coal pillar and rock strata. Drilling inspection technology was used to observe the filling condition of the goaf inside the borehole and to detect the grouting filling rate. Rock mechanics tests were conducted on the extracted grout-bonded rock core to determine its compressive strength, shear strength, and other mechanical parameters, verifying whether the strength of the grout-bonded body met the design standards.

[0047] In this embodiment, the specific operation for verifying the grouting treatment effect is as follows: First, the grout injected into the treatment area is completely solidified. The solidification time is determined according to the characteristics of the grouting material (fly ash-based cementitious material and hydrophilic expansion composite material) and the geological conditions of the mining area, usually 7-14 days, to ensure that the grout fully solidifies to form a stable grouting cement body. Subsequently, detection boreholes are drilled in the treatment area using directional drilling technology. The layout of the detection boreholes needs to cover the entire treatment area to ensure comprehensiveness of the inspection. Core sampling is performed through the detection boreholes to obtain core samples of the grouting cement body. The extracted core samples are visually observed and analyzed, with a focus on determining the uniformity of the grouting material filling in the goaf. The study assesses the presence of unfilled voids and the tightness of the bonding between the grouting cementitious body and the coal pillar and surrounding rock strata to evaluate the quality of the interface bonding. Simultaneously, borehole inspection technology is employed, extending inspection equipment into the goaf through a detection borehole to transmit internal images in real time, allowing for a direct observation of the overall filling status of the goaf and precise detection of the grouting filling rate to determine if the design filling standard has been met. Furthermore, some core samples are sent to a specialized laboratory for rock mechanics testing. Dedicated testing equipment is used to determine key mechanical parameters such as the compressive strength and shear strength of the grouting cementitious body. The test results are compared with design standards to verify whether the strength of the grouting cementitious body meets the requirements for surrounding rock stability during subsequent coal pillar recovery operations.

[0048] Through multi-dimensional inspection methods, a comprehensive and accurate assessment of the grouting treatment effect was achieved: core analysis and borehole inspection technology can intuitively reflect the filling condition and cementation status, and promptly detect problems such as incomplete filling and poor cementation; rock mechanics testing can quantify the mechanical properties of the grout cemented body to ensure that its strength meets the load-bearing requirements; the entire inspection process is scientific and rigorous, avoiding the limitations of a single inspection method, and ensuring that subsequent operations only proceed after the grouting treatment effect fully meets the design requirements, effectively avoiding safety risks caused by substandard treatment and ensuring the smooth progress of coal pillar recovery operations.

[0049] According to one embodiment of the present invention, the number of detection boreholes is 5% of the number of grouting boreholes, and the detection boreholes are arranged at equal intervals; After the goaf is treated, the roadway is delineated, and short holes are laid out using a conventional drilling rig to enhance the inspection effect. The spacing of the short holes is smaller than the spacing of the inspection boreholes.

[0050] This embodiment optimizes the borehole layout for the inspection process, improving the accuracy and comprehensiveness of the inspection: First, a standard for the number of inspection boreholes is determined, setting the number of inspection boreholes at 5% of the number of grouting boreholes. This proportion ensures the representativeness of the inspection samples while avoiding cost waste and damage to the grouting body caused by excessive drilling. The inspection boreholes are arranged at equal intervals, evenly distributed throughout the entire treatment area according to its shape and size, ensuring that each area can be effectively inspected and avoiding blind spots. After grouting treatment is completed, the location of the roadway is delineated within the treatment area. As an important passage for subsequent mining operations, the stability of the surrounding area of ​​the roadway is crucial. Therefore, short holes are arranged around the roadway using a conventional drilling rig for enhanced inspection. The spacing of the short holes is smaller than that of the inspection boreholes, allowing for more dense collection of inspection data. The focus is on checking the grouting filling quality and cementation state of the area around the roadway, ensuring that the stability of the roadway and its surrounding area meets the requirements of mining operations.

[0051] By scientifically setting the number and arrangement of inspection boreholes, the representativeness and comprehensiveness of the inspection results were ensured, avoiding inspection deviations caused by insufficient number of boreholes or unreasonable arrangement. The dense inspection design of short holes around the roadway specifically strengthened the inspection efforts in key areas, ensuring the safety and stability of the subsequent mining operation channel. This borehole arrangement scheme, while ensuring the inspection effect, also takes into account economy and practicality, effectively identifying potential hazards in the grouting treatment process and providing a more reliable guarantee for the safe conduct of subsequent operations.

[0052] According to one embodiment of the present invention, during the treatment process and subsequent coal pillar recovery in the treatment area, a microseismic monitoring system and a mine pressure monitoring system are used to monitor the treatment area in real time; the microseismic monitoring and mine pressure monitoring data are comprehensively analyzed to provide a basis for safety early warning of coal pillar recovery in the treatment area.

[0053] In this embodiment, a dual-system collaborative monitoring mechanism was established throughout the entire treatment process and subsequent coal pillar recovery: On the one hand, a microseismic monitoring system was deployed. This system, by arranging multiple microseismic sensors in and around the treatment area, can sensitively capture microseismic signals generated by rock mass fracturing, displacement, and other activities within the treatment area. It collects and analyzes parameters such as the location, energy magnitude, and frequency of microseismic events in real time, and identifies the stability status of the coal pillar and overlying strata through signal feature identification, thereby promptly detecting potential risks such as rock mass instability and collapse. On the other hand, a mine pressure monitoring system was installed. Pressure sensors were set up in key locations such as roadways and working face supports to monitor data such as surrounding rock pressure and support working resistance in real time. By analyzing these data, the distribution pattern and trend of mine pressure during mining were understood, and the support effect of the supports on the roof and the bearing capacity of the surrounding rock were evaluated. By comprehensively summarizing and cross-analyzing the data collected by the microseismic monitoring system and the mine pressure monitoring system, a data correlation model is established. Through the collaborative interpretation of the two types of data, the geological dynamic changes in the treatment area can be comprehensively and accurately judged, providing real-time and reliable safety early warning basis for coal pillar recovery operations in the treatment area. When abnormal monitoring data occurs, early warning signals are issued in a timely manner to guide on-site operators to take emergency measures.

[0054] The synergistic application of microseismic monitoring and mine pressure monitoring systems enables comprehensive, real-time monitoring of the treatment area and recovery process, overcoming the limitations of single monitoring systems. Microseismic monitoring can provide early warnings of potential instability risks deep within the rock mass, while mine pressure monitoring can reflect the stress state around the working face in real time. The comprehensive analysis of these two types of data improves the accuracy and timeliness of safety warnings. This monitoring mechanism provides dynamic safety assurance for coal pillar recovery operations, ensuring that workers can promptly grasp changes in the geological environment, avoid risks in advance, ensure the safety and controllability of the entire mining process, and significantly reduce the probability of disasters and accidents.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for grouting to treat room-and-pillar goaf and recovering coal pillars in fully mechanized mining, characterized in that, include: The distribution area of ​​room-and-pillar goaf has been preliminarily determined; By forming directional drilling technology, the distribution area of ​​the room-and-pillar goaf is explored in the field, a three-dimensional spatial model of the room-and-pillar goaf is constructed, and the range of the room-and-pillar goaf is gradually obtained based on the boundary points of the room-and-pillar goaf detected by multiple directional drilling holes. Based on the three-dimensional spatial model of the room-and-pillar goaf, the internal structure of the room-and-pillar goaf is obtained. Based on the range of the room-and-pillar goaf and its internal structure, the location, number, and depth of the drainage boreholes are obtained. Based on the location, number, and depth of the drainage boreholes, the accumulated water in the goaf is introduced into the mine drainage system through drainage pipes; At least some of the aforementioned directional boreholes are selected as grouting boreholes, and the room-and-pillar goaf is treated by grouting through the grouting boreholes. Based on the scope of the treated room-and-pillar goaf, the distribution of coal pillars, and the mining technology conditions of the mining area, a working face layout plan is formulated. After the working face is arranged according to the working face layout plan, the coal pillar recovery operation is carried out in accordance with the established mining plan.

2. The method for grouting and treating room-and-pillar goaf and recovering coal pillars according to claim 1, characterized in that, The process of forming directional boreholes using directional drilling technology to conduct on-site surveys of the distribution area of ​​the room-and-pillar goaf, and constructing a three-dimensional spatial model of the room-and-pillar goaf, includes: Directional drilling proceeds along a first preset trajectory, and the geological conditions inside the borehole are obtained through real-time monitoring. By combining the geological conditions inside the borehole with the borehole trajectory data, a three-dimensional spatial model of the goaf is constructed.

3. The method for grouting to treat room-and-pillar goaf and recovering coal pillars according to claim 2, characterized in that, The construction of a three-dimensional spatial model of the goaf by combining the geological conditions within the borehole with the borehole trajectory data includes: Based on the azimuth, dip angle, and elevation of the borehole, combined with depth measurement and trigonometric function calculations, the coordinates of the borehole in three-dimensional space are determined point by point, generating a three-dimensional spatial model of the goaf.

4. The method for grouting and treating room-and-pillar goaf and recovering coal pillars according to claim 1, characterized in that, The method of introducing accumulated water in the goaf into the mine drainage system through drainage pipes, based on the arrangement, number, and depth of the drainage boreholes, includes: Select areas within the goaf where water accumulation is relatively concentrated and water levels are high to arrange the aforementioned drainage boreholes; The directional drill advances along the second preset trajectory to the water accumulation area of ​​the goaf. After the drilling is completed, a drainage pipe is installed in the drainage hole, and the hole and the drainage pipe are sealed. Water accumulated in the goaf is introduced into the mine drainage system through drainage pipes.

5. The method for grouting and treating room-and-pillar goaf and recovering coal pillars according to claim 1, characterized in that, The step of selecting at least a portion of the directional boreholes for grouting, and performing grouting treatment on the room-and-pillar goaf through the grouting boreholes, includes: The first stage of grouting is performed on the room-and-column goaf using bottom material; After the first stage of grouting is completed, directional drilling is carried out to drain the oozing water; The second stage of grouting is performed on the room-column goaf after the first stage of grouting using top material.

6. The method for grouting and treating room-and-pillar goaf and recovering coal pillars according to claim 5, characterized in that, The bottom material is a fly ash-based cementitious material, accounting for 90%-95% of the grouting volume; the top material is a hydrophilic expansion composite material, accounting for 5%-10% of the grouting volume.

7. The method for grouting to treat room-and-pillar goaf and recovering coal pillars according to claim 1, characterized in that, Between the grouting treatment of the room-and-pillar goaf based on at least a portion of the directional boreholes and the formulation of a working face layout plan based on the extent of the treated room-and-pillar goaf, the distribution of coal pillars, and the mining technology conditions of the mining area, the following further includes: Through inspection and continuous monitoring, we ensure that the grouting treatment effect meets the design requirements.

8. The method for grouting and treating room-and-pillar goaf and recovering coal pillars according to claim 7, characterized in that, Ensuring that the grouting treatment meets design requirements through inspection and continuous monitoring includes: After the grout injected into the treatment area has completely solidified, detection boreholes are formed in the treatment area using directional drilling technology, and core sampling is carried out. The extracted grouting core was analyzed to determine the filling condition of the grouting material and its bonding state with the coal pillar and rock strata. Drilling inspection technology was used to observe the filling condition of the goaf inside the borehole and to detect the grouting filling rate. Rock mechanics tests were conducted on the extracted grout-bonded rock core to determine its compressive strength, shear strength, and other mechanical parameters, verifying whether the strength of the grout-bonded body met the design standards.

9. The method for grouting to treat room-and-pillar goaf and recovering coal pillars in fully mechanized mining according to claim 8, characterized in that, The number of the inspection boreholes is 5% of the number of the grouting boreholes, and the inspection boreholes are arranged at equal intervals. After the goaf is treated, the roadway is delineated, and short holes are laid out using a conventional drilling rig to enhance the inspection effect. The spacing between the short holes is smaller than the spacing between the inspection boreholes.

10. The method for grouting and treating room-and-pillar goaf and recovering coal pillars according to any one of claims 1 to 9, characterized in that, During the treatment process and subsequent coal pillar recovery in the treated area, the treatment area is monitored in real time using a microseismic monitoring system and a mine pressure monitoring system. The microseismic monitoring and mine pressure monitoring data are comprehensively analyzed to provide a basis for safety early warning of coal pillar recovery in the treated area.

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