Layered mining method for filling fully-mechanized coal gangue and caving top coal in super-thick coal seam

Abstract

The invention discloses an extra-thick coal seam fully-mechanized coal mining gangue filling top coal caving layered mining method. The method specifically comprises the following steps that an extra-thick coal seam is divided into an upper layer and a lower layer to be mined; the upper layer adopts a fully-mechanized coal mining gangue filling method, and a metal net is laid on a working face bottom plate along with advancing of the working face; the mining of the working face of the lower layer lags behind the mining of the upper layer, the lower layer adopts a top coal caving mining method, the working face of the upper layer and the working face of the lower layer can be aligned up and down or not aligned up and down, and the principle is that the mining of the lower layer cannot influence the working face being mined and the unmined area of the upper layer; the extra-thick coal seam is mined according to the mining method until all the working faces of all the upper layers and all the lower layers are mined, and gob-side entry retaining is adopted between the working faces of the upper layers and the working faces of the lower layers. According to the method, the characteristics of fully-mechanized coal mining gangue filling mining and top coal caving mining methods are fully utilized, the lapping technology is utilized, and safe and efficient disposal and high recovery rate of the gangue in the extra-thick coal seam are achieved.

Description

Technical Field

[0001] This invention relates to the field of extra-thick coal seam mining technology, and in particular to a method for layered mining of extra-thick coal seams using fully mechanized gangue backfilling and top coal caving. Background Technology

[0002] Under the condition of extra-thick coal seams with a thickness of ≥12m, the backfilling and disposal of coal-based solid waste such as gangue presents significant challenges.

[0003] There are generally two methods: one is to use layered fully mechanized gangue solid backfilling, which is suitable for coal seam thickness of 3-5m, and the hydraulic support of the working face adopts a special hydraulic support for fully mechanized gangue backfilling; the other is to use gangue slurry backfilling, which involves crushing gangue into fine particles (generally less than 3mm in diameter), mixing it with water to make a gangue slurry of a certain concentration (about 50%), and backfilling it in a borehole drilled at a certain distance (generally more than 50m) behind the working face on the ground or underground.

[0004] Of the two methods, Method 1, the capacity of a mining face using gangue backfilling is generally 500,000-700,000 tons per year. However, the conventional capacity of a typical mine under non-backfilling mining conditions can reach 1-3 million tons per year, so using this method would severely impact the mine's capacity. Method 2, due to the highly variable and difficult-to-observe roof collapse conditions in the goaf, results in uncertainty regarding the available backfill space, with the estimated gangue processing capacity between 100,000 and 400,000 tons per year. Furthermore, this method carries safety risks such as the gangue slurry potentially entering the working face and threatening production, and the possibility of the slurry collapsing into the lower coal seam working face during mining (if any). Therefore, neither of these two methods has been practically applied in the backfilling treatment of extra-thick coal seams.

[0005] In extra-thick coal seams (≥12m), fully mechanized longwall mining is commonly employed. However, the supports and processes used in fully mechanized longwall mining often fail to meet the requirements for backfilling gangue in the goaf. Therefore, implementing backfilling in extra-thick fully mechanized longwall faces currently presents significant technical challenges. Relevant patents related to backfilling in fully mechanized longwall faces are as follows: 1. The patent with application number 202510344205.X and patent title "A method for controlling the deformation of mining space by grouting and filling in shallow-buried deep fully mechanized longwall mining".

[0006] This invention belongs to the field of backfilling mining and discloses a method for controlling the deformation of the mining space through grouting and backfilling in shallow-buried deep fully mechanized longwall mining. The method includes: dividing the mining space into a main control auxiliary backfilling space and an auxiliary control main backfilling space; and arranging double-hole grouting and backfilling boreholes at intervals on the ground. The main control auxiliary backfilling space is filled with high-strength rapid-setting material and fly ash-based reinforcing material. These two materials bond with the fractured rock mass to form a cemented composite support structure, hindering the movement of the key layer and extending the existence time of the auxiliary control main backfilling space. The auxiliary control main backfilling space is filled with coal gangue slurry, supporting the cemented composite support structure and assisting in controlling the key layer. The two spaces work together to achieve high-volume solid waste disposal and surface subsidence protection in shallow-buried deep fully mechanized longwall mining. This method is the aforementioned Method Two, "gangue slurry backfilling." This method has a low gangue disposal capacity and, due to its proximity to the working face, poses a safety risk of gangue slurry entering the working face and potentially collapsing into the lower coal seam working face during mining.

[0007] 2. Patent with application number 202411259182.4 and patent title "A fully mechanized backfilling mining method for high-gas thick coal seams".

[0008] This invention discloses a fully mechanized longwall mining method for high-gas, thick coal seams, involving the field of coal seam mining. It employs a gas extraction and filling roadway located in the overlying strata to simultaneously perform gas extraction and filling, achieving multi-purpose use of a single borehole. Specifically, gas is extracted through boreholes drilled at the working face, and filling is performed behind the working face via boreholes, enabling parallel operations of filling and mining, improving mining efficiency and solving the problem of filling restricting mining efficiency. First, gas is extracted through boreholes, reducing the gas concentration at the working face. Then, grouting is performed from top to bottom through the boreholes, improving filling efficiency and solving the problem of insufficient height of traditional filling supports. Simultaneously, the filling grout, after being injected into the goaf, forms a filling body, creating an integral support structure that can connect to the roof, exhibiting strong load-bearing capacity and controlling surface subsidence, thus solving the problem of large-scale subsidence caused by fully mechanized longwall mining. This method is the aforementioned Method Two, "gangue grout filling," and suffers from the same problems.

[0009] 3. The patent with application number CN202411259182.4 and patent title "A comprehensive mechanized top coal caving and backfilling method for coal mining".

[0010] A fully mechanized top-coal caving and backfilling mining method utilizes a coal mining machine, a front scraper conveyor, and a rear scraper conveyor in a cyclical operation to achieve coal mining, coal release, support, and backfilling under the conditions of fully mechanized top-coal caving and backfilling mining with protective coal pillars in thick coal seams. The method involves lowering the rear roof beam to release top coal at a low or mid-level position; a rear suspended backfilling mining conveyor transports backfilling materials, and backfilling is achieved through the rear roof beam and a pressing device. This method not only maintains the working space for normal coal mining through the hydraulic supports of fully mechanized top-coal caving and backfilling mining, but also allows for the simultaneous execution of various processes across different sections of the working face, including coal release by the coal mining machine, coal transport by the front scraper conveyor, operation of the hydraulic supports for fully mechanized top-coal caving and backfilling mining, coal release by the rear roof beam, coal transport by the rear scraper conveyor, transport of backfilling materials by the backfilling mining conveyor, and pressing of backfilling materials by the upper and lower pressing devices. These processes operate independently without interference, improving the efficiency of coal mining, coal release, and backfilling. The entire construction process is simple, highly operable, and yields excellent backfilling results. This method aims to achieve gangue filling in the fully mechanized coal mining face by developing a new type of fully mechanized coal mining gangue filling support. However, since coal mining requires significant mine pressure, and filling will reduce the mine pressure in the working face, it is unlikely to achieve the expected results.

[0011] Therefore, a fully mechanized mining method for top coal caving with gangue backing is proposed for ultra-thick coal seams. Summary of the Invention

[0012] This invention provides a method for layered mining of extra-thick coal seams using gangue backfilling and top coal caving, which can solve the problems of low production capacity and the safety risks of slurry in the backfilling method.

[0013] This invention provides a method for layered mining of extra-thick coal seams using gangue backing and top coal caving, specifically including the following steps: The extra-thick coal seam is mined in two layers, upper and lower. The upper layer adopts the fully mechanized gangue backfilling method, and as the working face advances, metal mesh is laid on the bottom plate of the working face; The goaf retention technique is used between the upper and lower working faces; The mining of the lower working face should lag behind the mining of the upper working face. The lower working face adopts the top coal caving mining method. The upper working face and the lower working face can be aligned vertically or not. The principle is that the mining of the lower working face should not affect the working face being mined in the upper working face or the unmined area. The extra-thick coal seam is mined using the above mining method until all working faces of the upper and lower layers are mined out. In this process, roadway retention is adopted between the working faces of the upper and lower layers.

[0014] In the aforementioned method for fully mechanized mining of extra-thick coal seams with gangue backfilling and top coal caving, preferably, the upper layer has a mining thickness of 2-5m.

[0015] In the aforementioned method for fully mechanized mining of extra-thick coal seams with gangue backfilling and top coal caving, preferably, the thickness of the lower layer is 10-15m.

[0016] The method for layered mining of extra-thick coal seams using gangue backfilling and top coal caving, preferably, includes the following steps in the step "the mining of the lower layer should lag behind the mining of the upper layer": After the first working face of the upper layer is mined out, and the second working face of the upper layer is mined out for 100m, the first working face of the lower layer will be mined. After the second working face of the upper layer is mined out, the third working face of the upper layer is mined out until all working faces of the upper layer are mined out. At the same time, after the first working face of the lower layer is mined out, all working faces of the lower layer are mined out in sequence.

[0017] In the aforementioned method for layered mining of extra-thick coal seams using gangue backfilling and top coal caving, preferably, the metal mesh is made of medium-low carbon steel wire.

[0018] In the aforementioned method for layered mining of extra-thick coal seams using gangue backfilling and top coal caving, preferably, the wire diameter of the metal mesh is 4-6 mm, and the mesh opening diameter ranges from 5-80 mm.

[0019] In the aforementioned method for layered mining of extra-thick coal seams using gangue backfilling and top coal caving, the metal mesh is preferably made of Q195, Q235, or Q355 carbon structural steel.

[0020] In the aforementioned method for layered mining of extra-thick coal seams using gangue backing and top coal caving, preferably, the gangue used in the gangue backing technology has a particle size of less than 100mm.

[0021] The method for layered mining of extra-thick coal seams using fully mechanized gangue backing and top coal caving, preferably, includes the following steps: The prepared gangue backfill material is transported from the upper working face to the end of the working face by a belt conveyor, and then transferred by a gangue transfer machine to the bottom discharge scraper conveyor suspended under the tail beam of the upper layer special backfill hydraulic support. The gangue is released in the goaf by opening and closing the plate chute. The tamping mechanism installed on the base of the filling hydraulic support is used to tamp the gangue filling body to improve its density. The upper-layer gangue backfilling working face adopts a one-cut-one-fill method for cyclic coal mining and backfilling operations until the mining of multiple working faces in the upper layer is completed in sequence.

[0022] The method for layered mining of extra-thick coal seams using gangue backing and top coal caving, preferably, includes the following steps in the lower-layer top coal caving technique: In a fully mechanized longwall face with top coal caving arranged along the bottom of the coal seam, after the coal mining machine cuts the coal, the hydraulic support for top coal caving is promptly supported and moved to a new position; Move the front conveyor to the coal face, and then operate the special jacks for the rear conveyor to move the rear conveyor forward accordingly. After one to three cuts, the coal release window is opened to release the loosened coal, completing the coal mining in one working face of the next layer; Repeat the above process until all lower-level working faces have been mined in sequence.

[0023] The beneficial effects are: This invention utilizes a fully mechanized gangue backfilling face in the upper layer to dispose of gangue on a large scale, with a capacity of 700,000 to 1,000,000 tons per year, without any safety risks. The lower layer employs fully mechanized caving mining, with a production capacity of 1,000,000 to 3,000,000 tons per year. Due to the meshing between the upper and lower layers, compared with conventional full-layer fully mechanized caving mining, the recovery rate of the lower layer fully mechanized caving mining is increased by 5-10%, and the gangue content is reduced by 15-20%.

[0024] Both upper and lower working faces can implement goaf-keeping, reducing the tunneling rate and increasing the resource recovery rate. Extra-thick coal seams can be mined in two layers using two mining methods to achieve both large-scale and safe disposal of gangue, as well as high production and efficiency.

[0025] This invention fully utilizes the characteristics of fully mechanized gangue backfilling mining, fully mechanized caving mining, and extra-thick coal seams. By employing mesh laying technology, it combines the advantages of fully mechanized caving mining and fully mechanized solid backfilling to propose an extra-thick coal seam gangue backfilling technology with upper-layer fully mechanized gangue backfilling and lower-layer fully mechanized caving mining. This technology can handle 500,000-700,000 tons / year of gangue while ensuring safety, and can also guarantee a production capacity of 1-3 million tons / year using fully mechanized caving mining. Due to the mesh laying between the upper and lower layers, the gangue in the upper layer is blocked, and the gangue in the lower layer is fully mechanized caving mining, which can achieve a high recovery rate and a low gangue content, achieving multiple benefits and significant economic advantages. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the upper and lower layer construction of the present invention; Figure 2 This is a schematic diagram of the upper and lower layered working surfaces; Figure 3 A schematic diagram of fully mechanized gangue backfilling technology; Figure 4 This is a cross-sectional view of AA. Figure 5 A schematic diagram of gangue backfilling in a fully mechanized mining face; Figure 6 This is a schematic diagram of the longwall top coal caving mining technology. Figure 7 This is a cross-sectional view of plane II.

[0027] 1. Upper layer; 1-1. First working surface of the upper layer; 1-2. Second working surface of the upper layer; 1-3. Third working surface of the upper layer; 2. Lower layer; 2-1. First working surface of the lower layer; 3. Leave a roadway along the goaf; 4. Upper roadway; 5. Metal mesh; 6. Gangue; 7. Gangue transfer machine; 8. Upper layer special filling hydraulic support; 9. Rear tail beam of hydraulic support; 10. Bottom-discharge scraper conveyor; 11. Compaction mechanism; 12. Front scraper conveyor; 13. Drawer chute; 14. Coal mining machine; 15. Front conveyor; 16. Lower layer hydraulic support; 17. Rear conveyor. Detailed Implementation

[0028] 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.

[0029] In the description of this invention, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the system or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the use of terms such as "first," "second," etc., to define components is merely for the convenience of distinguishing the aforementioned components; unless otherwise stated, these terms have no special meaning and should not be construed as indicating or implying relative importance.

[0030] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "setting," and "connection" 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0031] This invention provides a method for layered mining of extra-thick coal seams using fully mechanized gangue backing and top coal caving, specifically including the following steps: dividing the extra-thick coal seam into upper and lower layers for mining; the upper layer employs fully mechanized gangue backing, and as the working face advances, a metal mesh is laid on the floor of the working face; the lower layer employs top coal caving; both upper and lower working faces use gob-side entry; the mining of the lower layer should lag behind the mining of the upper layer, wherein the upper and lower working faces can be aligned vertically or not, the principle being that the mining of the lower layer should not affect the upper layer's currently being mined working face or unmined areas; the extra-thick coal seam is mined according to the above mining method until all upper and lower layers are mined. This invention fully utilizes the characteristics of fully mechanized gangue backing mining and top coal caving methods, and utilizes mesh laying technology to achieve safe and efficient disposal and high recovery rate of gangue from extra-thick coal seams.

[0032] The following section uses a fully mechanized mining method for top coal caving with gangue backing in extra-thick coal seams as an example to illustrate the entire technical process in detail.

[0033] Example 1 like Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown, a method for layered mining of extra-thick coal seams using gangue backing and top coal caving in fully mechanized mining specifically includes the following steps: S1: Divide the extra-thick coal seam into upper layer 1 and lower layer 2 for mining.

[0034] S2: The upper layer 1 adopts the fully mechanized gangue filling method, and as the working face advances, the bottom plate of the working face is laid with metal mesh 5.

[0035] S3: The mining of the lower layer 2 working face should lag behind the mining of the upper layer 1. The lower layer 2 adopts the top coal caving mining method. The working faces of the upper layer 1 and the lower layer 2 can be aligned vertically or not. The principle is that the mining of the lower layer 2 should not affect the working face of the upper layer 1 that is being mined or the unmined area.

[0036] like Figure 2 As shown, the working surfaces of the upper layer 1 and the lower layer 2 are not aligned vertically.

[0037] S4: Mining of the extra-thick coal seam is carried out according to the mining methods of steps S2 to S3 until all working faces of upper layer 1 and lower layer 2 are mined.

[0038] In particular, the goaf retention technique is used between the working faces of the upper layer 1 and the lower layer 2.

[0039] The upper layer 1 has a mining thickness of 2-5m, and the lower layer 2 has a mining thickness of 10-15m.

[0040] In the fully mechanized gangue backfilling technology, the gangue used has a particle size of less than 100mm.

[0041] In step S3, the metal mesh 5 is made of medium-low carbon steel wire, with a wire diameter of 4-6 mm and a mesh size range of 5-80 mm.

[0042] Furthermore, the metal mesh is made of Q195, Q235, or Q355 carbon structural steel, cold-drawn into steel wire. The metal mesh comes in two structural types: woven and welded. Common specifications are 40×40mm and 70×70mm, with a permissible deviation of ±5° for the mesh angle (diamond mesh). Welded mesh requires the weld joint shear strength to reach 1.5 times the nominal tensile strength of the steel wire, and the weld detachment rate to not exceed 3 points / piece.

[0043] The allowable deviation for the length of the metal mesh is 0 to +25 mm, the allowable deviation for the width is 0 to one mesh length, and the flatness of the mesh shall not exceed 20 mm.

[0044] Among these requirements, the mechanical properties must meet the minimum values ​​specified in the standard, which depend on the material: Q195 material: tensile strength 315-455MPa, yield strength >195MPa, net strength 30kN (nominal diameter 5mm).

[0045] Q235 material: tensile strength 375-500MPa, yield strength >235MPa, mesh strength >35KN (nominal diameter 5mm).

[0046] Q355 material: tensile strength 355-455MPa, yield strength >355MPa, mesh strength >60kN (nominal diameter 5mm).

[0047] like Figure 6 and Figure 7 As shown, the fully mechanized gangue backfilling technology specifically includes the following steps: S31: The prepared gangue backfill material is transported from the upper roadway 4 to the end of the working face by a belt conveyor, and then transferred by the gangue transfer machine 7 to the bottom discharge scraper conveyor 10 suspended under the tail beam 9 of the upper layer special backfill hydraulic support 8. The gangue 6 is discharged by opening and closing the pull plate chute 13.

[0048] S32: The tamping mechanism 11 installed on the upper layer hydraulic support base is used to tamp the gangue 6 to improve the density of the gangue 6 filling body.

[0049] S33: After the gangue is released, a one-cut (advance of about 0.8m) and one-charge method is used for cyclic coal mining operations until the mining of multiple working faces of the upper layer 2 is completed in sequence.

[0050] like Figure 4 As shown, the fully mechanized longwall top coal caving technology specifically includes the following steps: S41: In a fully mechanized mining face arranged along the bottom of a coal seam or section, after the coal mining machine 14 cuts the coal, the lower layer hydraulic support 16 promptly supports the coal and moves it to a new position.

[0051] S42: Move the front conveyor 15 to the coal face, and then operate the special jack of the rear conveyor 17 to move the rear conveyor 17 forward accordingly.

[0052] S43: After 1 to 3 cuts, open the coal venting window to release the loosened coal. Once the gangue content in the released coal exceeds the limit, close the coal venting window in time to complete the coal mining in one working face of the next layer.

[0053] S44: Repeat steps S1 to S43 until all lower-level working faces are mined in sequence.

[0054] Example 2 like Figure 1 and Figure 2 As shown, a method for layered mining of extra-thick coal seams using gangue backing and top coal caving in fully mechanized mining specifically includes the following steps: S1: Divide the extra-thick coal seam into upper layer 1 and lower layer 2 for mining.

[0055] S2: The first working face 1-1 of the upper layer is mined using the fully mechanized gangue backfilling method, and as the working face advances, a metal mesh 5 is laid on the bottom plate of the working face.

[0056] S3: After the mining of the first working face 1-1 of the upper layer is completed, the mining of the second working face 1-2 of the upper layer will begin. After the second working face 1-2 of the upper layer has been mined for 100m, the first working face 2-1 of the lower layer will be mined using the top coal caving method. This is to ensure that the mining of the lower layer working face lags behind the mining of the upper layer working face. The working face of the upper layer 2 and the working face of the lower layer 1 can be aligned vertically or not. The principle is that the mining of the lower layer should not affect the working face being mined in the upper layer or the unmined area.

[0057] Step S4: Mining the extra-thick coal seam according to the above mining method until all working faces of upper layer 1 and lower layer 2 are mined out.

[0058] 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 layered mining of extra-thick coal seams using gangue backing and top coal caving, characterized in that, Specifically, the steps include the following: The extra-thick coal seam is mined in two layers, upper and lower. The upper layer adopts the fully mechanized gangue backfilling method, and as the working face advances, metal mesh is laid on the bottom plate of the working face; Both the upper and lower working faces use goaf-side roadway retention; The mining of the lower working face should lag behind the mining of the upper working face. The lower working face adopts the top coal caving mining method. The upper working face and the lower working face can be aligned vertically or not. The principle is that the mining of the lower working face should not affect the working face being mined in the upper working face or the unmined area. The extra-thick coal seam is mined using the above mining method until all working faces of the upper and lower layers are mined out. In this process, the goaf retention technique is used between the upper and lower working faces.

2. The method for layered mining of extra-thick coal seams using gangue backing and top coal caving according to claim 1, characterized in that, The thickness of the upper layer is 2-5m.

3. The method for layered mining of extra-thick coal seams using gangue backing and top coal caving according to claim 2, characterized in that, The thickness of the lower layer is 10-15m.

4. The method for layered mining of extra-thick coal seams using gangue backing and top coal caving according to claim 3, characterized in that, The method for the step "mining of the lower working face should lag behind mining of the upper working face" specifically includes the following steps: After the first working face of the upper layer is mined out, the first working face of the lower layer will be mined after the second working face of the upper layer has been mined for 100m. After the second working face of the upper layer is mined out, the third working face of the upper layer is mined out until all working faces of the upper layer are mined out. At the same time, after the first working face of the lower layer is mined out, all working faces of the lower layer are mined out in sequence.

5. The method for layered mining of extra-thick coal seams using gangue backing and top coal caving according to any one of claims 1 to 4, characterized in that, The metal mesh is made of medium-low carbon steel wire.

6. The method for layered mining of extra-thick coal seams using gangue backing and top coal caving according to claim 5, characterized in that, The wire diameter of the metal mesh is 4-6 mm, and the mesh aperture ranges from 5-80 mm.

7. The method for layered mining of extra-thick coal seams using gangue backing and top coal caving according to claim 6, characterized in that, The metal mesh is made of Q195, Q235 or Q355 carbon structural steel.

8. The method for layered mining of extra-thick coal seams using gangue backing and top coal caving according to claim 7, characterized in that, In the fully mechanized gangue backfilling technology, the gangue used has a particle size of less than 100mm.

9. The method for layered mining of extra-thick coal seams using gangue backing and top coal caving according to claim 8, characterized in that, The fully mechanized gangue backfilling method specifically includes the following steps: The prepared gangue backfill material is transported from the upper working face to the end of the working face by a belt conveyor, and then transferred by a gangue transfer machine to the bottom discharge scraper conveyor suspended under the tail beam of the upper layer special backfill hydraulic support. The gangue is released in the goaf by opening and closing the plate chute. The tamping mechanism installed on the base of the filling hydraulic support is used to tamp the gangue filling body to improve its density. The upper-layer gangue backfilling working face adopts a one-cut-one-fill method for cyclic coal mining and backfilling operations until the mining of multiple working faces in the upper layer is completed in sequence.

10. The method for layered mining of extra-thick coal seams using gangue backing and top coal caving according to claim 9, characterized in that, The lower-layer top coal caving technology specifically includes the following steps: In a fully mechanized longwall face with top coal caving arranged along the bottom of the coal seam, after the coal mining machine cuts the coal, the hydraulic support for top coal caving is promptly supported and moved to a new position; Move the front conveyor to the coal face, and then operate the special jacks for the rear conveyor to move the rear conveyor forward accordingly. After one to three cuts, the coal release window is opened to release the loosened coal, completing the coal mining in one working face of the next layer; Repeat the above process until all lower-level working faces have been mined in sequence.

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