Coal pillar-free continuous mining overburden strata separation grouting filling mining method

Abstract

The coal pillar-free continuous mining overburden separation grouting filling mining method comprises the following steps: S1, dividing the coal mining area into multiple coal mining faces; S2, arranging multiple grouting drill holes on each coal mining face, and the final hole of the grouting drill hole is located above the water flowing fractured zone; S3, dividing the multiple coal mining faces into several groups along the distribution direction of the coal mining face, and the coal mining faces in the same group are sequentially adjacent; S4, sequentially mining the coal mining faces in the same group, and the mined area forms a goaf, and during the mining process of the last coal mining face in the same group, the grouting drill hole in the goaf of the last coal mining face is extended to below the water flowing fractured zone to obtain a reinforcing drill hole, a grouting drill rod is lowered into the reinforcing drill hole, the reinforcing slurry is injected into the water flowing fractured zone and the caving zone through the grouting drill rod, and the water flowing fractured zone and the caving zone form a reinforced zone. The coal pillar-free continuous mining overburden separation grouting filling mining method does not need to leave an isolation coal pillar or the width of the isolation coal pillar is extremely small, and the coal recovery rate is improved.

Description

Technical Field

[0001] The invention relates to the technical field of coal mining, in particular to a method for continuous mining of overburden separation layer by grouting and filling without coal pillars. Background Art

[0002] Currently, grouting of overburden delaminations is mostly done using zoned isolation grouting. The basic principle is to determine the width of the coal mining face based on the maximum span allowed before the initial failure of the key stratum. Isolation pillars of a certain width are then left between two adjacent coal mining faces. This ensures that the key stratum remains stable and separate, closed delamination spaces are formed beneath the key stratum, thereby ensuring that the slurry can fully fill the overburden delamination area to form a filling body. It has been verified that the width of the isolation pillars is generally 40 to 80 meters. A coal pillar width less than 40 to 80 meters is prone to collapse, but a larger isolation pillar width results in a lower coal recovery rate. Summary of the Invention

[0003] In order to solve the problem of low coal recovery rate caused by leaving isolation coal pillars in the existing technology, the present invention provides a coal pillar-free continuous mining method of overburden stratum grouting and filling, which injects reinforcement slurry into the water-conducting fracture zone and the collapse zone in the goaf to form a reinforcement body for supporting the overburden stratum. There is no need to leave isolation coal pillars or the width of the isolation coal pillars is extremely small, thereby improving the coal recovery rate.

[0004] In order to achieve the above object, the specific scheme adopted by the present invention is: a coal mining method for continuous mining of overburden separation layer by grouting and filling without coal pillars, comprising the following steps:

[0005] S1, divide the coal mining area into multiple coal mining faces;

[0006] S2: Arrange multiple grouting holes on each coal mining face, with the final hole of the grouting hole located above the water-conducting fracture zone;

[0007] S3, dividing the multiple coal mining faces into several groups along the distribution direction of the coal mining faces, and the coal mining faces in the same group are adjacent to each other in sequence;

[0008] S4, the coal mining faces in the same group are mined in sequence, and the area after mining forms a goaf. During the mining process of the last coal mining face in the same group, the grouting borehole in the goaf of the last coal mining face is extended to the bottom of the water-conducting fracture zone to obtain a reinforced borehole, and a grouting drill rod is lowered into the reinforced borehole. Reinforcement slurry is injected into the water-conducting fracture zone and the caving zone through the grouting drill rod, so that the water-conducting fracture zone and the caving zone form a reinforced area.

[0009] This is a further optimization of the pillarless continuous mining overburden separation grouting filling coal mining method of the present invention: in S1, the width of the coal mining working face is 160 to 240 m.

[0010] This is a further optimization of the pillarless continuous mining overburden separation grouting filling coal mining method of the present invention: in S1, a windbreak is preset between two adjacent coal mining working faces, and the width of the windbreak is 2 to 3 meters.

[0011] This is a further optimization of the pillarless continuous mining overburden separation grouting filling coal mining method of the present invention: in S2, the coal mining working face is an inclined long-arm coal mining working face, and the inclined long-arm coal mining working face is provided with main grouting boreholes and auxiliary grouting boreholes on the cutting side.

[0012] To further optimize the pillarless continuous mining overburden separation grouting filling coal mining method of the present invention: the distance between the main grouting borehole 8 and the cut eye is not more than one-third of the cut eye length, and the distance between the main grouting borehole and the auxiliary grouting borehole is 50-70m.

[0013] This is a further optimization of the pillarless continuous mining overburden separation grouting filling coal mining method of the present invention: in S2, the distance between two adjacent grouting boreholes is 130-170m.

[0014] This is a further optimization of the pillarless continuous mining overburden separation grouting filling coal mining method of the present invention: in S4, when the minimum distance between the worker's working position in the coal mining face and the grouting borehole in the goaf is 500-600m, the grouting borehole is extended to obtain a reinforced borehole.

[0015] This is a further optimization of the pillarless continuous mining overburden separation grouting filling coal mining method of the present invention: in S4, the reinforcement slurry is a mixed slurry of fly ash and cement, wherein the cement content is 10% to 20%.

[0016] To further optimize the coal pillar-free continuous mining overburden separation grouting and filling coal mining method of the present invention: In S4, the grouting drill rod includes a main drill rod connected to an external drilling rig and an extension drill rod extending into the bottom of the grouting borehole, and a connecting pipe is provided between the main drill rod and the extension drill rod, the bottom end of the connecting pipe is fixedly connected to the top end of the extension drill rod, the top end of the connecting pipe and the bottom end of the main drill rod can be connected and separated, and when the main drill rod is separated from the connecting pipe, the bottom end of the main drill rod is in the connecting pipe, and a movable gap is formed between the main drill rod and the inner wall of the connecting pipe.

[0017] To further optimize the pillarless continuous mining overburden separation grouting filling coal mining method of the present invention: the connecting pipe includes a coaxially arranged upper pipe section and a lower pipe section, the inner diameter of the upper pipe section is larger than the outer diameter of the main drill rod, and the outer diameter of the lower pipe section is equal to the inner diameter of the extended drill rod.

[0018] Beneficial effects:

[0019] 1. The coal mining method with no coal pillar and continuous mining of overburden separation layer by grouting filling, which forms a reinforced zone by injecting reinforcing slurry into the water flowing fractured zone and caving zone of the mined-out area, and the reinforced zone replaces the isolated coal pillar to support the overburden separation layer, thereby improving the coal recovery rate.

[0020] 2. When the slurry is injected into the water flowing fractured zone and caving zone of the mined-out area, the grouting drill rod is inserted into the water flowing fractured zone, and the grouting drill rod is prone to breakage as the water flowing fractured zone moves. In the present application, before the grouting drill rod is lowered into the reinforced borehole, the main drill rod is connected to the extension drill rod through the connecting pipe; after the grouting drill rod is lowered into the reinforced borehole, the main drill rod is separated from the connecting pipe, but the main drill rod is still inserted into the connecting pipe, and the main drill rod and the inner wall of the connecting pipe form a movable gap. When the water flowing fractured zone moves, the extension drill rod moves with the water flowing fractured zone. Due to the existence of the movable gap, the extension drill rod is provided with a moving space, thereby avoiding the breakage of the grouting drill rod and ensuring the smooth grouting. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a schematic view of a coal mining face;

[0022] Figure 2 is a schematic view of the distribution of grouting boreholes;

[0023] Figure 3 is a schematic view of a cross section of a coal mining face;

[0024] Figure 4 is a schematic view of a first coal mining face after mining;

[0025] Figure 5 is a schematic view of a second coal mining face after mining;

[0026] Figure 6 is a schematic view of a third coal mining face after mining;

[0027] Figure 7 is a schematic view of a fourth coal mining face after mining;

[0028] Figure 8 is a schematic view of the grouting drill rod after being lowered into the reinforced borehole;

[0029] Figure 9 is a schematic view of the structure of Example 2;

[0030] Figure 10 is a schematic view of the structure of Example 3;

[0031] Figure 11 is a schematic view of the structure of Example 4;

[0032] BRIEF DESCRIPTION OF DRAWINGS:1, main drill rod, 101, second outer screw, 102, drill rod cavity, 103, clamping block, 104, retaining ring, 2, connecting pipe, 201, upper pipe section, 202, annular block, 203, second inner screw, 204, transition section, 205, first outer screw, 206, lower pipe section, 207, limiting block, 3, extended drill rod, 301, first inner screw, 302, screen hole, 303, extended inner cavity, 4, gap, 5, coal mining face, 6, grouting borehole, 7, main grouting borehole, 8, auxiliary grouting borehole, 9, overburden separation, 10, water-conducting fractured zone, 11, coal seam, 12, caving zone, 13, wind-blocking zone, 14, reinforcing borehole, 15, reinforced zone. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0034] The coal pillar-free continuous mining overburden separation grouting and filling mining method comprises the following steps:

[0035] S1, divide the coal mining area into multiple coal mining faces 5, divide the coal mining area according to the geographical position and the construction site condition of the coal mining area, divide multiple coal mining faces 5 and label them in sequence along the distribution direction of the coal mining faces 5 as: first coal mining face, second coal mining face, third coal mining face, …… In this embodiment, as shown in the figure, four coal mining faces 5 in the coal mining area are selected and labeled in sequence as: first coal mining face, second coal mining face, third coal mining face, fourth coal mining face and fifth coal mining face, Figure 1 the distribution of the coal mining faces 5 is in the direction of the arrow, i.e. from left to right. The width of the coal mining face 5 is 160-240 m. In this embodiment, the width of the coal mining face 5 is 200 m. Figure 1

[0036] As shown in the figure, in this embodiment, the wind-blocking zone 13 is arranged at the position of the coal seam 11, i.e. a coal wall is preset between the adjacent two coal mining faces 5, the width of the coal wall is set to 2 m, which plays a role of isolation and wind blocking, avoiding underground fire. Figure 5

[0037] S2, arrange multiple grouting boreholes 6 on each coal mining face 5, the grouting boreholes 6 are evenly distributed along the length direction of the coal mining face 5, and the centers of all the grouting boreholes 6 are located on the same straight line. As shown in the figure, in this embodiment, the grouting boreholes 6 are arranged on the coal mining face 5 in the form of a row, and the centers of the grouting boreholes 6 are located on the same straight line.​​ Figure 2 As shown, when the coal mining face 5 is an inclined long-arm coal mining face, the first grouting boreholes 6 on the cut-eye side of the inclined long-arm coal mining face are arranged in pairs, that is, the inclined long-arm coal mining face is provided with a main grouting borehole 8 and an auxiliary grouting borehole 7 on the cut-eye side, and the auxiliary grouting borehole 7 is located to the lower right of the main grouting borehole 8; wherein, the distance between the main grouting borehole 8 and the cut-eye is not greater than one-third of the cut-eye length, and the distance between the main grouting borehole 8 and the auxiliary grouting borehole 7 is 50 to 70 m. In this embodiment, the distance between the main grouting borehole 8 and the auxiliary grouting borehole 7 is 60 m.

[0038] The distance between two adjacent grouting boreholes 6 is 130-170 m. In this embodiment, the distance between two adjacent grouting boreholes 6 is 150 m.

[0039] like Figure 3 As shown, the terminal hole of the grouting borehole 6 is located above the water-conducting fracture zone 10 and is at a distance of not less than 50 m from the upper surface of the water-conducting fracture zone 10 .

[0040] S3. Divide the multiple coal mining faces 5 into a plurality of groups along their distribution direction. The coal mining faces 5 within a group are adjacent to each other. The number of coal mining faces 5 within a group is affected by grouting pressure. The number of coal mining faces 5 within a group is determined by testing with existing grouting equipment. In this embodiment, three coal mining faces 5 form a group: the first, second, and third coal mining faces form the first group; the fourth, fifth, and fifth coal mining faces form the second group; and so on. The multiple coal mining faces 5 are divided into a plurality of groups.

[0041] S4, the coal mining faces 5 in the same group are mined in sequence, and the mining sequence between the coal mining faces 5 is along the distribution direction of the coal mining faces 5, such as Figure 3 In the direction of the arrows in this embodiment, the mining sequence is: the first coal mining face, the second coal mining face, and the third coal mining face.

[0042] In this embodiment, Figure 4 As shown, the first coal mining face is mined first. The area where workers are working in the coal mining face 5 is the excavation face. When the excavation face is no more than 30 meters from the nearest grouting borehole 6, water is injected into the nearest grouting borehole 6 to observe the development of the overburden stratum 9. Fly ash slurry is then injected into the overburden stratum 9 through the nearest grouting borehole 6. This cycle is repeated until the first coal mining face is mined and a caving zone 12 is formed in the goaf. The second and third coal mining faces are mined using the same method.

[0043] like Figure 6 and Figure 7As shown, the area after the mining forms a goaf, and in the process of mining the last coal mining face 5 in the same group, the last coal mining face 5 in this embodiment is the third coal mining face, when the nearest distance between the heading face and the grouting borehole 6 in the goaf of the third coal mining face is 500 m, the grouting borehole 6 in the goaf of the third coal mining face is extended to below the water flowing fractured zone 10 to obtain a reinforced borehole 14, a grouting drill pipe is lowered into the reinforced borehole 14, and the grouting drill pipe is used to inject the reinforcing slurry into the water flowing fractured zone 10 and the caving zone 12, so that the water flowing fractured zone 10 and the caving zone 12 form a reinforced zone 15. In this embodiment, the third coal mining face mines while the reinforcing slurry is injected to form the reinforced zone 15, which saves time compared to reinforcing after the three coal mining faces 5 are completely mined, and ensures normal coal mining of the mine. The water flowing fractured zone 10 and the caving zone 12 of the third coal mining face form the reinforced zone 15, which replaces the original isolation coal pillar, is used to support the overburden separation 9, avoids collapse of the ground, and improves the coal recovery rate.

[0044] After the first coal mining face, the second coal mining face and the third coal mining face are mined and reinforced, the mining and reinforcement of the next group of coal mining faces 5 are continued.

[0045] Embodiment 2

[0046] In S4, the grouting drill pipe includes a main drill pipe 1 connected with an external drilling machine and an extension drill pipe 3 extending into the bottom of the reinforced borehole 14, and in this embodiment, the outer diameter of the main drill pipe 1 is the same as the outer diameter of the extension drill pipe 3, and the inner diameter of the main drill pipe 1 is equal to the inner diameter of the extension drill pipe 3; the main drill pipe 1 forms a drill pipe inner cavity 102, the extension drill pipe 3 forms an extension inner cavity 303, the drill pipe inner cavity 102 and the extension inner cavity 303 are communicated, the slurry flows through the drill pipe inner cavity 102 and the extension inner cavity 303 in sequence through external equipment, and then enters the reinforced borehole 14 and flows into the overburden separation zone to complete the grouting. A connecting pipe 2 is arranged between the main drill pipe 1 and the extension drill pipe 3, the connecting pipe 2 forms a connecting inner cavity, the connecting inner cavity communicates the drill pipe inner cavity 102 and the extension inner cavity 303, the bottom end of the connecting pipe 2 is fixedly connected with the top end of the extension drill pipe 3 in a same axis, the top end of the connecting pipe 2 can be connected with and separated from the bottom end of the main drill pipe 1, and when the main drill pipe 1 is separated from the connecting pipe 2, the bottom end of the main drill pipe 1 is located in the connecting pipe 2 and forms a movable gap 4 between the inner side wall of the connecting pipe 2 and the bottom end of the main drill pipe 1. Figure 9As shown, in the embodiment, before the main drill rod 1, the connecting pipe 2 and the extension drill rod 3 are lowered into the reinforced borehole 14, the top end of the connecting pipe 2 is connected with the bottom end of the main drill rod 1, the bottom end of the connecting pipe 2 is connected with the extension drill rod 3 to form a grouting drill rod; when the overburden separation grouting is performed, the grouting drill rod is lowered into the reinforced borehole 14 until the bottom end of the extension drill rod 3 contacts the bottom of the reinforced borehole 14, then the main drill rod 1 is separated from the connecting pipe 2, at this time, the bottom end of the main drill rod 1 is still in the connecting pipe 2 and forms a movable gap 4 between the inner side wall of the connecting pipe 2. When the rock stratum is displaced and the extension drill rod 3 is moved, the movable gap 4 provides a moving space for the extension drill rod 3, avoiding the grouting drill rod from being broken, and ensuring the smooth grouting. After the grouting is completed, the main drill rod 1 is connected with the connecting pipe 2, then the main drill rod 1, the connecting pipe 2 and the extension drill rod 3 are taken out from the reinforced borehole 14.

[0047] As shown in the figure, Figure 9 The connecting pipe 2 includes an upper pipe segment 201 and a lower pipe segment 206 which are coaxially arranged, the inner diameter of the upper pipe segment 201 is greater than the outer diameter of the main drill rod 1, and the outer diameter of the lower pipe segment 206 is equal to the inner diameter of the extension drill rod 3. In the embodiment, the upper pipe segment 201 is connected with and separated from the main drill rod 1, the lower pipe segment 206 is coaxially fixedly connected with the extension drill rod 3, and the inner diameter of the upper pipe segment 201 is greater than the inner diameter of the lower pipe segment 206. The upper pipe segment 201 and the lower pipe segment 206 are connected through a transition segment 204, the top end diameter of the transition segment 204 is the same as the diameter of the upper pipe segment 201, and the bottom end diameter of the transition segment 204 is the same as the diameter of the lower pipe segment 206. During the grouting process, the transition segment 204 can play a role of flow guide. In the embodiment, the upper pipe segment 201, the transition segment 204 and the lower pipe segment 206 are coaxially and integrally connected.

[0048] The connecting mode of the connecting pipe 2 and the extension drill rod 3 can be welding or screw thread connection, in the embodiment, the connecting mode of the two is screw thread connection, that is, the first outer screw thread 205 is arranged on the outer side wall of the connecting pipe 2, that is, the first outer screw thread 205 is arranged at the top of the lower pipe segment 206, and the first inner screw thread 301 which is matched with the first outer screw thread 205 is arranged on the inner side wall of the extension drill rod 3.

[0049] The connecting mode of the connecting pipe 2 and the main drill rod 1 is screw thread connection, the second inner screw thread 203 is arranged on the inner side wall of the connecting pipe 2, the second inner screw thread 203 is arranged at the bottom of the upper pipe segment 201, the second outer screw thread 101 which is matched with the second inner screw thread 203 is arranged on the main drill rod 1, and the second outer screw thread 101 is arranged at the bottom of the main drill rod 1. In the embodiment, as shown in the figure, Figure 9As shown, a retaining ring 104 is provided around the outer wall of the main drill pipe 1, and the retaining ring 104 is fixedly connected to the outer wall of the main drill pipe 1, and the connection method of the two is welding. The second outer screw buckle 101 is provided on the outer wall of the retaining ring 104; an annular block 202 is fixedly connected to the inner wall of the connecting pipe 2, and the annular block 202 is fixedly connected to the inner wall of the upper pipe section 201. The connection method of the two is welding, and the second inner screw buckle 203 is provided on the inner wall of the annular block 202. Before grouting, the main drill rod 1 is connected to the upper pipe section 201, that is, the second outer screw buckle 101 is screwed into the second inner screw buckle 203; during grouting, the grouting drill rod is lowered into the reinforcement borehole 14 until the bottom end of the extension drill rod 3 contacts the bottom of the reinforcement borehole 14, and then, the main drill rod 1 is rotated to make the second outer screw buckle 101 screw out of the second inner screw buckle 203, and then the main drill rod 1 is separated from the upper pipe section 201, and there is a gap between the second outer screw buckle 101 and the inner wall of the upper pipe section 201, providing space for the extension drill rod 3 to move; after the grouting is completed, the main drill rod 1 is rotated in the opposite direction to make the second outer screw buckle 101 screwed into the second inner screw buckle 203, the main drill rod 1 is connected to the extension drill rod 3, and the main drill rod 1, the connecting pipe 2 and the extension drill rod 3 are taken out from the reinforcement borehole 14.

[0050] The extended drill rod 3 forms an extended inner cavity 303. A plurality of sieve holes 302 are provided on the side wall of the extended drill rod 3 to connect the extended inner cavity 303 and the reinforced borehole 14. The slurry enters the reinforced borehole 14 from the extended inner cavity 303 through the sieve holes 302.

[0051] Example 3

[0052] This embodiment is an improvement on the basis of the embodiment 2. Its main structure is the same as that of the embodiment 2, and the improvements are as follows:

[0053] like Figure 10 As shown, a limit block 207 is fixedly connected to the inner wall of the connecting pipe 2. The limit block 207 is annular. The outer diameter of the limit block 207 is equal to the inner diameter of the upper pipe section 201. The inner diameter of the limit block 207 is larger than the outer diameter of the retaining ring 104. The limit block 207 is connected to the connecting pipe 2 by welding. There is a gap between the inner wall of the limit block 207 and the outer wall of the main drill pipe 1 to provide a movable space for the extended drill pipe 3. The limit block 207 cooperates with the retaining ring 104 to prevent the main drill pipe 1 from extending out of the connecting pipe 2.

[0054] Example 4

[0055] This embodiment is an improvement on the basis of embodiment 2. Its main structure is the same as that of embodiment 2. The improvement is as follows: Figure 11As shown, an annular block 202 is fixedly connected to the inner sidewall of the connecting tube 2. The annular block 202 is connected to the connecting tube 2 by welding. A second inner screw thread 203 is provided on the inner sidewall of the annular block 202, and a second outer screw thread 101 is provided at the bottom of the outer sidewall of the main drill pipe 1. A limit block 207 is fixedly connected to the inner sidewall of the connecting tube 2, with a gap between the inner sidewall of the limit block 207 and the outer sidewall of the main drill pipe 1. A clamping block 103 is fixedly connected to the outer sidewall of the main drill pipe 1, with a gap between the outer sidewall of the clamping block 103 and the inner sidewall of the connecting tube 2. In this embodiment, both the limit block 207 and the clamping block 103 are annular. The outer diameter of the limit block 207 is equal to the inner diameter of the upper pipe section 201, and the inner diameter of the limit block 207 is larger than the outer diameter of the clamping block 103. The limit block 207 is connected to the upper pipe section 201, and the clamping block 103 is connected to the main drill pipe 1 by welding. The limiting block 207 cooperates with the clamping block 103 to prevent the main drill rod 1 from extending out of the connecting pipe 2.

[0056] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for continuous mining of overburden separation layer by grouting and filling without coal pillars, characterized in that: The following steps are involved: S1, dividing the coal mining area into multiple coal mining working faces (5); S2, arranging a plurality of grouting boreholes (6) on each coal mining working face (5), wherein the terminal holes of the grouting boreholes (6) are located above the water-conducting fracture zone (10); S3, dividing the plurality of coal mining working faces (5) into a plurality of groups along the distribution direction of the coal mining working faces (5), wherein the coal mining working faces (5) in the same group are adjacent to each other in sequence; S4, mining the coal mining working faces (5) in the same group in sequence, and the area after mining forms a goaf area. During the mining process of the last coal mining working face (5) in the same group, the grouting borehole (6) in the goaf area of ​​the last coal mining working face (5) is extended to the bottom of the water-conducting fracture zone (10) to obtain a reinforcement borehole (14). A grouting drill rod is lowered into the reinforcement borehole (14), and reinforcement slurry is injected into the water-conducting fracture zone (10) and the caving zone (12) through the grouting drill rod, so that the water-conducting fracture zone (10) and the caving zone (12) form a reinforcement area (15); The grouting drill rod comprises a main drill rod (1) connected to an external drilling rig and an extension drill rod (3) extending into the bottom of the reinforced drill hole (14); a connecting pipe (2) is provided between the main drill rod (1) and the extension drill rod (3); the bottom end of the connecting pipe (2) is fixedly connected to the top end of the extension drill rod (3); the top end of the connecting pipe (2) and the bottom end of the main drill rod (1) can be connected and separated; and when the main drill rod (1) is separated from the connecting pipe (2), the bottom end of the main drill rod (1) is located in the connecting pipe (2) and forms a movable gap (4) with the inner wall of the connecting pipe (2); The connecting pipe (2) comprises an upper pipe section (201) and a lower pipe section (206) which are coaxially arranged, wherein the inner diameter of the upper pipe section (201) is larger than the outer diameter of the main drill rod (1), and the outer diameter of the lower pipe section (206) is equal to the inner diameter of the extension drill rod (3); Before the main drill rod (1), the connecting pipe (2) and the extension drill rod (3) are lowered into the reinforcement borehole (14), the top end of the connecting pipe (2) is connected to the bottom end of the main drill rod (1), and the bottom end of the connecting pipe (2) is connected to the extension drill rod (3) to form a grouting drill rod; when grouting the overburden separation layer, the grouting drill rod is lowered into the reinforcement borehole (14) until the bottom end of the extension drill rod (3) contacts the bottom of the reinforcement borehole (14), and then the main drill rod (1) is separated from the connecting pipe (2), and the bottom end of the main drill rod (1) is still in the connecting pipe (2), and a movable gap (4) is formed between the main drill rod (1) and the inner wall of the connecting pipe (2); when the rock layer is displaced and the extension drill rod (3) is driven to move, the movable gap (4) provides a movable space for the extension drill rod (3).

2. The method for continuous mining of overburden separation layer by grouting and filling without coal pillars according to claim 1, characterized in that: In S1, the width of the coal mining face (5) is 160 to 240 m.

3. The method for continuous mining of overburden separation layer by grouting and filling without coal pillars according to claim 1, characterized in that: In S1, a windbreak (13) is preset between two adjacent coal mining working faces (5), and the width of the windbreak (13) is 2 to 3 meters.

4. The method for continuous mining of overburden separation layer by grouting and filling without coal pillars according to claim 1, characterized in that: In S2, the coal mining working face (5) is an inclined long-arm coal mining working face, and the inclined long-arm coal mining working face is provided with a main grouting borehole (8) and an auxiliary grouting borehole (7) on the cutting side.

5. The method for continuous mining of overburden separation layer by grouting and filling without coal pillars according to claim 4, characterized in that: The distance between the main grouting borehole (8) and the cut eye is no more than one-third of the cut eye length, and the distance between the main grouting borehole (8) and the auxiliary grouting borehole (7) is 50 to 70 m.

6. The method for continuous mining of overburden separation layer by grouting and filling without coal pillars according to claim 1, characterized in that: In S2, the distance between two adjacent grouting boreholes (6) is 130 to 170 m.

7. The method for continuous mining of overburden separation layer by grouting and filling without coal pillars according to claim 1, characterized in that: In S4, when the minimum distance between the worker's working position in the coal mining face (5) and the grouting borehole (6) in the goaf is 500-600m, the grouting borehole (6) is extended to obtain a reinforced borehole (14).

8. The method for continuous mining of overburden separation layer by grouting and filling without coal pillars according to claim 1, characterized in that: In S4, the reinforcement slurry is a mixed slurry of fly ash and cement, wherein the content of cement is 10% to 20%.

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