Pillarless mining method for ultra-long working faces with close proximity to coal seams

Abstract

This invention discloses a method for pillarless mining of ultra-long working faces in closely spaced coal seams. During the mining of the upper coal seam, the ultra-long working face reduces the number of roadways and coal pillars. A concrete wall is constructed within the first roadway as a side support, achieving pillarless roadway retention. This improves resource recovery rate, reduces roadway excavation rate, and optimizes mining continuity. After the working face is mined out, the concrete wall is subjected to controlled fracturing, eliminating the drawbacks of traditional structures being difficult to remove, affecting goaf management, and causing long-term stress concentration. During the mining of the lower coal seam, the vertical superposition of stress concentration zones is actively avoided, breaking the stress concentration hazard chain in closely spaced coal seams that affects the underlying coal seam, thus significantly improving the safety and efficiency of the overall mining of the coal seam group.

Description

Technical Field

[0001] This invention relates to the field of coal mining technology, specifically to a method for pillarless mining of ultra-long working faces with closely spaced coal seams. Background Technology

[0002] Coal mining technology has evolved from traditional to modern methods. The early "121" mining model adopted a layout of "one working face, two roadways, and one coal pillar," with the coal pillar used for section isolation and roadway protection. Although this method was simple and easy to implement, it had significant drawbacks: coal pillar loss resulted in a large waste of resources (reducing the extraction rate by about 10%-15%), the roadway maintenance workload was high, and when mining close-range coal seams, the remaining coal pillars could easily form stress concentration zones in the underlying coal seams, inducing disasters such as rock bursts, gas outbursts, or floor water inrushes, seriously restricting the safe and efficient mining of the mine.

[0003] To overcome the aforementioned problems, pillarless mining technology has emerged, with the "110" model ("1 working face, 1 roadway, 0 coal pillars") becoming an important development direction. This model replaces solid coal pillars with roadway-side structures (such as flexible concrete walls, paste-filled structures, and automatic roadway formation with roof cutting and pressure relief), allowing the retained and reused mining roadways, thus achieving mining with one less roadway and "zero" coal pillars. This method effectively improves resource recovery rate, reduces roadway excavation rate, improves roadway maintenance, and alleviates the conflict between mining and excavation continuity.

[0004] In recent years, with the advancement of fully mechanized mining technology and equipment, ultra-long working face technology (working face length of 400 meters and above) has developed rapidly. Compared with conventional working faces, ultra-long working faces have the following advantages: increased coal mining machine operating rate and average coal cutting speed, reduced end-feed time, and significantly improved mining efficiency; reduced number of working faces and isolation coal pillars in the mining area or panel, increasing extraction rate; reduced roadway excavation work, and optimized mining system. Several mines both domestically and internationally have successfully applied 400-450 meter ultra-long working face technology.

[0005] However, significant limitations still exist in the relevant technologies. Under conditions of close-range coal seam mining, stress concentration zones formed by leftover coal pillars or roadway-side structures can still pose a threat to the mining of underlying coal seams. On the other hand, in existing pillarless roadway retention technologies, roadway-side structures (such as flexible concrete walls) are difficult to break down after mining, failing to eliminate stress concentrations. This not only affects goaf management but may also create stress concentrations in subsequent coal seams. Summary of the Invention

[0006] The present invention aims to at least partially solve one of the technical problems in the related art.

[0007] Therefore, embodiments of the present invention propose a method for pillarless mining of ultra-long working faces in close-range coal seam groups.

[0008] The method for pillarless mining of ultra-long working faces with closely spaced coal seams according to an embodiment of the present invention includes the following steps:

[0009] S1: For the upper coal seam in a closely spaced coal seam group, arrange at least two ultra-long working faces; S2: Two adjacent ultra-long working faces include a first working face and a second working face. A common first roadway is arranged between the first working face and the second working face. A second roadway is arranged on the other side of the first working face, and a third roadway is arranged on the other side of the second working face. S3: During the mining process of the first working face, the first roadway is retained and a concrete wall extending along the length of the first roadway is constructed in the first roadway. The top of the concrete wall abuts against the top plate of the first roadway and the bottom of the concrete wall abuts against the bottom plate of the first roadway. S4: After all the long working face has been mined, the concrete wall is subjected to controlled pyrolysis.

[0010] In some embodiments, when the first working face is being mined, the first roadway serves as the transport roadway of the first working face, and the second roadway serves as the return air roadway of the first working face. When the second working face is being mined, the third roadway serves as the transport roadway of the second working face, and the first roadway serves as the return air roadway of the second working face.

[0011] In some embodiments, when the first working face is being mined, the first roadway and the third roadway are connected and simultaneously ventilate the first working face, and return air is carried out through the first roadway.

[0012] In some embodiments, the concrete wall is a flexible molded concrete wall formed by on-site casting using a flexible mold.

[0013] In some embodiments, the concrete wall has a plurality of spaced-apart fracturing holes on at least one side in its thickness direction. The controlled pyrolysis of the concrete wall is carried out using a silent static expansion agent. The slurry formed by mixing the silent static expansion agent with water is injected into the fracturing holes, and the expansion pressure generated by its slow chemical reaction causes the concrete wall to pyrolyze and break.

[0014] In some embodiments, the fracturing holes are arranged in a rectangular array.

[0015] In some embodiments, the plurality of fracturing holes include a plurality of fracturing groups, the plurality of fracturing groups being arranged at intervals in the height direction of the concrete wall, the fracturing group including a plurality of fracturing holes arranged at intervals along the extension direction of the concrete wall, wherein the fracturing holes in two adjacent fracturing groups are staggered in the height direction of the concrete wall.

[0016] In some embodiments, a stress monitoring device is provided inside the fracturing hole.

[0017] In some embodiments, the length of the extra-long working surface is greater than 400m.

[0018] The method for pillarless roadway mining of ultra-long working faces in close-range coal seam groups according to embodiments of the present invention reduces the number of roadways and coal pillars during the mining of the upper coal seam by utilizing the ultra-long working face. A concrete wall is constructed in the first roadway as a roadway-side support, achieving pillarless roadway retention. This improves resource recovery rate, reduces roadway excavation rate, and optimizes mining continuity. After the working face is mined out, the concrete wall is subjected to controlled pyrolysis, eliminating the drawbacks of traditional structures being difficult to remove, affecting goaf management, and causing long-term stress concentration. During the mining of the lower coal seam, the vertical superposition of stress concentration zones is actively avoided, breaking the stress concentration hazard chain caused to the underlying coal seam in the close-range coal seam group, thereby significantly improving the safety and efficiency of the overall mining of the coal seam group. Attached Figure Description

[0019] Figure 1 This is a schematic flowchart of the method for pillarless mining of ultra-long working faces in close-range coal seam groups according to an embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram of the mining operations of the first and second working faces according to an embodiment of the present invention.

[0021] Figure 3 This is a cross-sectional schematic diagram of the first and second working surfaces according to an embodiment of the present invention.

[0022] Figure 4 This is a schematic diagram of the concrete walls and stress distribution of the upper and lower coal seams in an embodiment of the present invention.

[0023] Figure 5 This is a structural schematic diagram of the concrete wall according to the first embodiment of the present invention.

[0024] Figure 6 This is a structural schematic diagram of a concrete wall according to the second embodiment of the present invention.

[0025] Figure 7 This is a schematic diagram of the concrete wall before it cracks according to an embodiment of the present invention.

[0026] Figure 8This is a schematic diagram of the structure of a concrete wall after cracking according to an embodiment of the present invention.

[0027] 100. Upper coal seam; 200. Lower coal seam; 1. First working face; 2. Second working face; 3. First roadway; 4. Second roadway; 5. Third roadway; 6. Concrete wall; 601. Fracturing hole. Detailed Implementation

[0028] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0029] like Figures 1 to 8 As shown, the method for pillarless mining of ultra-long working faces with closely spaced coal seams according to an embodiment of the present invention includes the following steps: S1: For the upper coal seam 100 in a closely spaced coal seam group, at least two ultra-long working faces shall be arranged. S2: Two adjacent ultra-long working faces include a first working face 1 and a second working face 2. A shared first roadway 3 is arranged between the first working face 1 and the second working face 2. A second roadway 4 is arranged on the other side of the first working face 1, and a third roadway 5 is arranged on the other side of the second working face 2. S3: During the mining process of the first working face 1, the first roadway 3 is retained and a concrete wall 6 extending along the length of the first roadway 3 is constructed in the first roadway 3. The top of the concrete wall 6 abuts against the top plate of the first roadway 3 and the bottom of the concrete wall 6 abuts against the bottom plate of the first roadway 3. S4: After all the long working face has been mined, the concrete wall 6 is subjected to controlled pyrolysis.

[0030] The method for pillarless roadway mining in a near-distance coal seam group using an ultra-long working face in this invention reduces the number of roadways and coal pillars during the mining of the upper coal seam 100. A concrete wall 6 is constructed within the first roadway 3 as a roadway-side support, achieving pillarless roadway retention. This improves resource recovery rate, reduces roadway excavation rate, and optimizes mining continuity. After the working face is mined out, the concrete wall 6 is subjected to controlled pyrolysis, eliminating the drawbacks of traditional structures being difficult to remove, affecting goaf management, and causing long-term stress concentration. During the mining of the lower coal seam 200, the method actively avoids the vertical superposition of stress concentration zones, breaking the stress concentration hazard chain in the near-distance coal seam group that affects the underlying coal seam, thereby significantly improving the safety and efficiency of the overall mining of the coal seam group.

[0031] In some embodiments, when mining the first working face 1, the first roadway 3 serves as the transport roadway of the first working face 1, and the second roadway 4 serves as the return air roadway of the first working face 1. When mining the second working face 2, the third roadway 5 serves as the transport roadway of the second working face 2, and the first roadway 3 serves as the return air roadway of the second working face 2.

[0032] like Figure 2 and Figure 3 As shown, during the mining of the first working face 1, the first roadway 3 serves as the transport roadway for that working face, and the second roadway 4 serves as its return airway. During the mining of the adjacent second working face 2, the third roadway 5 serves as the transport roadway for the second working face 2, while the previously retained first roadway 3, for which a concrete wall 6 has been constructed, is reused as the return airway for the second working face 2. This design enables the reuse of a single roadway (the first roadway 3) during the mining of two adjacent working faces, fully demonstrating the core advantage of "fewer roadway excavations" in pillarless mining. It also clarifies the conversion path of the ventilation system during the working face advancement, providing a clear technological arrangement for the safe and efficient mining of ultra-long working faces.

[0033] In some embodiments, when the first working face 1 is being mined, the first roadway 3 and the third roadway 5 are connected and simultaneously ventilate the first working face 1, and return air is carried out through the first roadway 3.

[0034] During the mining of the first working face 1, not only is the first roadway 3 used as a transport roadway, but the first roadway 3 is also connected in advance to the third roadway 5 (i.e., the transport roadway for the future second working face 2) to form a parallel ventilation path, which supplies air to the first working face 1 and ultimately returns through the first roadway 3. This design makes full use of the excavated roadways and adopts a two-in-one-out "Y" shaped ventilation method, which can build a smoother and more efficient ventilation network in the early stage of mining of ultra-long working faces. It effectively solves the potential problems of long ventilation distance and high ventilation resistance in ultra-long working faces, provides a guarantee for safe and efficient production of the working face, and also reflects the synergy of the overall planning of the mining system.

[0035] In some embodiments, the concrete wall 6 is a flexible-mold concrete wall 6 formed by on-site casting using flexible molds. This wall construction technology is mature, enabling it to closely conform to the roof and floor slabs of the roadway, providing timely and effective roadway-side support, and ensuring the stability of the roadway under mining influences. Simultaneously, as a later-stage structure, the material and structural characteristics of the flexible-mold concrete facilitate the subsequent implementation of "controlled pyrolysis" in step S4, providing a feasible engineering basis for achieving the goal of actively eliminating stress concentration.

[0036] In some embodiments, the concrete wall 6 has a plurality of spaced-apart fracturing holes 601 on at least one side in its thickness direction. The controlled pyrolysis of the concrete wall 6 is carried out using a silent static expansion agent. The slurry formed by mixing the silent static expansion agent with water is injected into the fracturing holes 601, and the expansion pressure generated by its slow chemical reaction causes the concrete wall 6 to pyrolyze and break.

[0037] It should be noted that the specific location and arrangement of the fracturing holes 601 can be determined based on the mining conditions and the strength and size of the concrete wall 6. In this embodiment of the invention, the fracturing holes 601 are pre-reserved during the pouring of the concrete wall 6 to avoid the problems of complex construction procedures and high construction costs caused by separately processing the fracturing holes 601 on the concrete wall 6 later.

[0038] To ensure the safety, efficiency, and controllability of the concrete wall 6, multiple spaced fracturing holes 601 are pre-installed on at least one side of the concrete wall 6 along its thickness direction. During the fracturing process, a silent static expanding agent is mixed with water to form a slurry, which is then injected into these fracturing holes 601. The slurry undergoes a slow chemical reaction within the holes, generating continuous and enormous expansion pressure. This pressure, applied from within the wall, causes the concrete wall 6 to fracture and break into smaller pieces in a predetermined direction. This method avoids the vibration, flyrock, and dust hazards of traditional blasting, offering high operational safety, controllable fracturing process, and enabling the clearing of structures along the goaf roadway, eliminating their concentrated stress on the underlying coal seam.

[0039] In some embodiments, such as Figure 5 As shown, the fracturing holes 601 are arranged in a rectangular array. The fracturing holes 601 are arranged in a rectangular array within the concrete wall 6. This regular array arrangement allows the expansion pressure generated by the silent static expansion agent to be distributed more evenly and controllably within the wall, guiding the concrete wall 6 to fracture in an orderly manner along the predetermined fracture surface with relatively uniform block size. This improves the efficiency and controllability of the operation, facilitates subsequent debris removal, and further ensures the safety and reliability of the process.

[0040] In some embodiments, such as Figure 6 As shown, the multiple fracturing holes 601 include multiple fracturing groups, which are arranged at intervals along the height direction of the concrete wall 6. Each fracturing group includes multiple fracturing holes 601 arranged at intervals along the extension direction of the concrete wall 6, wherein the fracturing holes 601 in two adjacent fracturing groups are staggered in the height direction of the concrete wall 6.

[0041] Multiple fracturing holes 601 are divided into several fracturing groups arranged at intervals along the height of the concrete wall 6. Each fracturing group contains multiple fracturing holes 601 arranged at intervals along the wall's extension direction. The fracturing holes 601 in adjacent fracturing groups are staggered along the wall's height. This three-dimensional staggered array can guide the expansion pressure to form a more complex and dispersed stress network within the wall, effectively avoiding excessively large through cracks or overall collapse, and promoting more uniform fragmentation of the concrete wall 6 into smaller blocks, creating more favorable conditions for the subsequent stress environment in the goaf.

[0042] In some embodiments, a stress monitoring device is provided within the fracturing hole 601. To further enhance the controllability and safety of the fracturing process, a stress monitoring device is installed within the fracturing hole 601. This device can monitor in real time the changes and distribution of internal stress in the concrete surrounding the hole wall after the injection of the silent static expansion agent. Through the monitoring data, the timing of fracturing, the pattern of crack propagation, and the uniformity of pressure release can be accurately determined, thereby achieving dynamic feedback and precise control of the fracturing failure process. This not only ensures that the concrete wall 6 can be safely and completely fractured according to the predetermined plan, but also provides important data support for evaluating the effect and optimizing subsequent similar process parameters.

[0043] In some embodiments, the length of the ultra-long working face exceeds 400m. Compared to conventional working faces, this length significantly increases the operating rate of the coal mining machine and the average coal cutting speed, while reducing the proportion of non-productive time such as end-feeding. Simultaneously, it drastically reduces the number of working faces required within the mining area or panel, as well as the number of associated isolation coal pillars, thereby reducing resource losses (approximately 10%-15%) and stress concentration risks caused by residual coal pillars at the source. In the context of close-range coal seam mining, using working faces within this length range, combined with the aforementioned pillarless roadway and controlled pyrolysis technology for structures, allows for more effective planning of the mining sequence and spatial layout, thus systematically solving the problems of stress transmission and concentration, and achieving a synergistic improvement in safety and efficiency.

[0044] In the description of this invention, 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," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0045] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0046] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0047] In this 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," "over," and "on top" of 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.

[0048] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the 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.

[0049] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for pillarless mining of ultra-long working faces in close-range coal seams, characterized in that, Includes the following steps: S1: For the upper coal seam (100) in a closely spaced coal seam group, arrange at least two ultra-long working faces; S2: The two adjacent ultra-long working faces include a first working face (1) and a second working face (2). A common first roadway (3) is arranged between the first working face (1) and the second working face (2). A second roadway (4) is arranged on the other side of the first working face (1), and a third roadway (5) is arranged on the other side of the second working face (2). S3: During the mining process of the first working face (1), the first roadway (3) is retained and a concrete wall (6) extending along the length of the first roadway (3) is constructed in the first roadway (3). The top of the concrete wall (6) abuts against the top plate of the first roadway (3) and the bottom of the concrete wall (6) abuts against the bottom plate of the first roadway (3). S4: After all the long working face has been mined, the concrete wall (6) is subjected to controlled pyrolysis.

2. The method for pillarless mining of ultra-long working faces with closely spaced coal seams according to claim 1, characterized in that, When mining the first working face (1), the first roadway (3) serves as the transport roadway of the first working face (1), and the second roadway (4) serves as the return air roadway of the first working face (1). When mining the second working face (2), the third roadway (5) serves as the transport roadway of the second working face (2), and the first roadway (3) serves as the return air roadway of the second working face (2).

3. The method for pillarless mining of ultra-long working faces with closely spaced coal seams according to claim 2, characterized in that, When the first working face (1) is being mined, the first roadway (3) and the third roadway (5) are connected and simultaneously ventilate the first working face (1), and return air is carried out through the first roadway (3).

4. The method for pillarless mining of ultra-long working faces with closely spaced coal seams according to claim 1, characterized in that, The concrete wall (6) is a flexible mold concrete wall (6) formed by on-site casting using a flexible mold.

5. The method for pillarless mining of ultra-long working faces with closely spaced coal seams according to claim 1, characterized in that, The concrete wall (6) has a plurality of spaced-apart fracturing holes (601) on at least one side in its thickness direction. The concrete wall (6) is subjected to controlled pyrolysis using a silent static expansion agent. The slurry formed by mixing the silent static expansion agent with water is injected into the fracturing holes (601), and the expansion pressure generated by its slow chemical reaction causes the concrete wall (6) to pyrolyze and break.

6. The method for pillarless mining of ultra-long working faces with closely spaced coal seams according to claim 5, characterized in that, The fracturing holes (601) are arranged in a rectangular array.

7. The method for pillarless mining of ultra-long working faces with closely spaced coal seams according to claim 5, characterized in that, The plurality of fracturing holes (601) include a plurality of fracturing groups, which are spaced apart in the height direction of the concrete wall (6). Each fracturing group includes a plurality of fracturing holes (601) spaced apart along the extension direction of the concrete wall (6), wherein the fracturing holes (601) in two adjacent fracturing groups are staggered in the height direction of the concrete wall (6).

8. The method for pillarless mining of ultra-long working faces with closely spaced coal seams according to claim 5, characterized in that, A stress monitoring device is installed inside the fracturing hole (601).

9. The method for pillarless mining of ultra-long working faces with closely spaced coal seams according to claim 1, characterized in that, The length of the ultra-long working face is greater than 400m.

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