Tendency strip filling method for super-long working face goaf

Abstract

This invention belongs to the field of coal mine goaf filling methods, specifically relating to a dip-strip filling method for goaf in ultra-long working faces. The invention proposes grouping multiple working faces together and setting up fracturing roadways outside all working faces. Through these fracturing roadways, fracturing and cutting zones are constructed along the dip in the basic roof, forming fracturing rock fragments on both sides of the strike, a cutting block in the middle, and collapsed rock masses adjacent to intact rock strata on both sides of the dip. Then, the cutting block is used as a diffusion surface for grouting, grouting the surrounding fracturing rock fragments to form several dip-stripped, highly supportive strips composed of rock fragments, cutting blocks, and grout; controlling the subsidence of the overlying sandstone group and preventing rockbursts. Subsequently, the remaining fracturing boreholes, cutting boreholes, and grouting boreholes are used to fill the goaf in subsequent working faces, thus solving the problem of large-scale long-bore drilling in ultra-long working faces.

Description

Technical Field

[0001] This invention belongs to the field of coal mine goaf filling methods, specifically relating to a method for filling diagonal strips in goaf areas of ultra-long working faces. Background Technology

[0002] Sandstone is a relatively hard rock stratum. If the coal seam is buried at a great depth and there are many sandstone layers in the strata, it is prone to mine tremors and even rockbursts. This is because the hardness of sandstone results in a large distance between the tops of the suspended layers, a large single fracture range, and a large amount of energy released. Generally, multiple adjacent sandstone layers tend to form sandstone clusters and fracture simultaneously. This makes the single fracture range of the sandstone cluster even larger, and the energy released is also greater, making it extremely easy to generate rockbursts. Fracturing sandstone clusters through hydraulic fracturing boreholes from the surface or underground to reduce the single fracture range and the energy released is an important means of preventing rockbursts. However, if there are many sandstone clusters in the strata, especially when they are thick, such as when a certain layer is more than 100 meters thick, hydraulic fracturing work is enormous, and it is very difficult to completely fracture extremely thick sandstone clusters.

[0003] For strata containing multiple sandstone groups, especially those with extremely thick sandstone groups exceeding 100 meters in thickness, goaf backfilling offers advantages in preventing rockbursts. This is because the large fracture distance of the sandstone groups and the long roof suspension time provide sufficient time for backfilling. In particular, existing technologies propose localized goaf backfilling techniques (such as forming backfill strips) to increase roof fracturing, which can reduce backfilling workload and costs. Specifically, increasing roof fracturing involves artificially fracturing the roof near the coal seam by drilling fracturing boreholes in the roadway. However, drilling fracturing boreholes in the roadway limits the drilling area and impacts working face production. The limitation of long-bore directional fracturing at the stop line or in a separate drilling site in the roadway is that long boreholes are generally more effective within a kilometer; excessive length makes it difficult to ensure fracturing pressure and control the fracturing location. Furthermore, it has poor adaptability for working faces with lengths of 3 kilometers or more. Therefore, how to efficiently carry out local backfilling of goaf areas in ultra-long working faces to prevent rockbursts has become a difficult problem to be solved in this field. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method for filling the dip strip of goaf in ultra-long working faces, comprising the following steps:

[0005] S1: Grouping multiple adjacent working faces together, constructing fracturing roadways along the strike outside the last working face;

[0006] S2: For each working face, several fracturing and top-cutting zones extending along the dip are set at intervals along the strike, and the fracturing and top-cutting zones of all working faces correspond one-to-one in the strike; the length of the fracturing and top-cutting zone of each working face is consistent with the dip width of the working face, and is located directly above it; the fracturing and top-cutting zone is located in the main roof, and its height is consistent with the height of the main roof; the fracturing and top-cutting zone includes the top-cutting zone located in the middle and the fracturing zones located on both sides of the top-cutting zone; top-cutting boreholes are drilled in the fracturing roadway in the top-cutting zone, and fracturing boreholes are drilled in the fracturing zone;

[0007] S3: Construction grouting boreholes, which include horizontal sections and branch sections. At least two branch sections shall be set in each cut-off zone of each working face.

[0008] S4: The first working face is back-mined, and the fracturing and top-cutting zone behind the suspended roof area is fracturing and top-cutting. The top-cutting dip section is located at the dip boundary of the first working face and the top-cutting dip section is a vertical plane; thus, the fracturing and top-cutting zone is constructed into a state where the two sides of the strike are fracturing rock fragments and the middle is a top-cutting block.

[0009] S5: Grout the space above the cut-off block through grouting drill holes;

[0010] S6: Repeat steps S4-S5 until the first working face is mined back to the stop line; the inclined fracturing and top cutting zone forms a support strip along the dip with strong support capacity, which is composed of crushed gangue, top cutting blocks and grout, through fracturing, top cutting and grouting.

[0011] S7: Referring to the first working face, use the remaining fracturing boreholes, top cutting boreholes and grouting boreholes to fill the goaf of the remaining working face in sequence.

[0012] Preferably, in step S1, a section coal pillar is set between adjacent working faces; the return airway of the subsequent working face is constructed using the goaf excavation process.

[0013] Preferably, in step S1, a fracturing roadway is excavated along the haulage main roadway, and a protective coal pillar is left between the fracturing roadway and the haulage roadway of the last working face; the fracturing roadway includes an uphill section and a straight section, the height of the straight section is at the middle height of the basic roof, the uphill section connects the straight section and the haulage main roadway, and the uphill section starts from the haulage main roadway.

[0014] Preferably, in step S3, a grouting borehole is constructed directly above the top-cutting area, with the horizontal section parallel to the top-cutting borehole, and the branch section constructed downwards from the horizontal section; the horizontal section is directly used as the grouting inlet near the end of the fracturing roadway; or, it also includes a vertical section connected to the horizontal section, which is connected to the ground surface, and grouting is carried out from the ground surface through the vertical section.

[0015] Preferably, in step S4, a suspended roof zone is formed at the basic top. Before each period of collapse at the basic top, the fracturing and roof-cutting zone behind the suspended roof zone is subjected to fracturing and roof-cutting; or, before the even-numbered period of collapse at the basic top, the fracturing and roof-cutting zone behind the suspended roof zone is subjected to fracturing and roof-cutting.

[0016] Preferably, in step S4, the dip fracturing and top-cutting range is located directly above the first working face; the fracturing rock fragments and the top-cutting block are located above the direct top rock fragments, the fracturing rock fragments are formed by fracturing the fracturing zone, the top-cutting block falls as a whole after top-cutting, the top-cutting block is surrounded by fracturing rock fragments on both sides of the dip direction, and the dip sides are complete overburden strata; the top-cutting block is lower in height than the fracturing rock fragments on both sides of the dip direction.

[0017] Preferably, in step S5, the small size of the fractured rock fragments has a certain grout-blocking function, and the area directly above the cut-off block is filled with pure grout to form a pure grout filling body.

[0018] The key technical means and beneficial effects of this invention are as follows: For ultra-long working faces under deep-buried sandstone strata conditions, this invention proposes grouping multiple adjacent working faces together, with a fracturing roadway set up outside the last working face. Through the fracturing roadway, a fracturing and cutting zone is constructed along the dip in the underlying roof. The fracturing and cutting zones of all working faces correspond perfectly in strike, and the length of the fracturing and cutting zone of each working face is consistent with its dip width. The fracturing and cutting zone is constructed such that the sides of the strike are fracturing rock fragments, the middle is a cutting block, and the sides of the dip are adjacent to collapsed rock masses of intact strata. In terms of height, the fracture and expansion characteristics of the fracturing rock fragments compensate for the space loss during coal seam mining, providing timely support to the overlying sandstone strata. Then, the cut-off blocks are used as the diffusion surface for grouting to improve the diffusion capacity of the grout, and grout is injected into the surrounding fracturing debris. The fracturing debris has a certain ability to block the grout, preventing ineffective filling in the circumferential direction. Ultimately, the dipping fracturing and cut-off zone is formed by fracturing, cut-off, and grouting to create a strong supporting strip along the dip, composed of debris, cut-off blocks, and grout. This controls the subsidence of the overlying sandstone group, preventing its destruction and thus preventing rockburst. Afterward, the remaining fracturing boreholes, cut-off boreholes, and grouting boreholes are used to fill the goaf in subsequent working faces, thereby solving the problem of large-scale long-bore drilling in ultra-long working faces and ensuring the pressure of fracturing, cut-off, and grouting. Attached Figure Description

[0019] Figure 1 This is a schematic plan view of the goaf sloping strip filling method of the present invention;

[0020] Figure 2 This is a schematic diagram of the strike profile of the coal seam before mining using the goaf-filling method of the present invention.

[0021] Figure 3This is a schematic diagram of the strike profile of the coal seam after mining using the goaf-dipping strip filling method of the present invention.

[0022] Figure 4 This is a schematic diagram of the dip profile of the coal seam before mining using the goaf dip strip filling method of the present invention;

[0023] Figure 5 This is a schematic diagram of the dip profile of the top-cutting borehole after coal seam mining in the goaf filling method of the present invention.

[0024] Figure 6 This is a schematic diagram of the dip profile along the fracturing borehole after coal seam recovery using the goaf dip strip filling method of the present invention.

[0025] In the diagram: 1-First working face; 2-Second working face; 3-Third working face; 11-Return airway; 12-Transport main roadway; 13-Return airway; 14-Gluing transport roadway; 15-Mining area; 16-Fracturing roadway; 21-Stop mining line; 22-Section coal pillar; 23-Overhanging roof area; 24-Goaf; 25-Protective coal pillar; 31-Fracturing borehole; 32-Vertical section; 33-Horizontal section; 34-Branch section; 35-Roof cutting borehole; 41-Coal seam; 42-Issued roof; 43-Main roof; 44-Ordinary strata; 45-Second sandstone group; 51-Fracturing zone; 52-Roof cutting zone; 53-Fracturing rock fragments; 54-Roof cutting block; 55-Issued roof rock fragments; 56-Pure slurry filling body; 57-Main roof fractured block; 58-Roof cutting dip section. Detailed Implementation

[0026] The following is in conjunction with the appendix Figure 1-6 Specific embodiments of the present invention will be described in detail below.

[0027] Yingpanhao Coal Mine is currently mining the 2-2 coal seam, with some working faces designed to be over 3,000 meters long. The 2-2 coal seam is buried at a depth of 680-720m, with a thickness of approximately 6.5m and a dip angle of 1-3°. Within a 150m range above the 2-2 coal seam, there are three sandstone groups, which are sub-critical layers. The first sandstone group forms the basic roof 43. The main critical layer is located approximately 300m above the 2-2 coal seam, consisting of a sandstone group with a thickness of approximately 300m. In view of the above geological conditions, this invention proposes a dip-strip filling method for the goaf of ultra-long working faces, including the following steps:

[0028] S1: As Figure 1 , Figure 2 , Figure 4As shown, three longwall mining faces are adjacent to each other along the dip, namely the first working face 1, the second working face 2, and the third working face 3. A section coal pillar 22 is set between adjacent working faces. Each working face includes a haulage roadway 14 and a return air roadway 13. The haulage roadway 14 is constructed along the strike and connects to the haulage main roadway 12 constructed along the dip. The return air roadway 13 is constructed along the strike and connects to the return air main roadway 11 constructed along the dip. This arrangement of the three longwall mining faces is well known in the art and will not be described in detail here. The return air roadway 13 of the latter working face is constructed using a goaf excavation technique to reduce the width of the section coal pillar 22. A fracturing roadway 16 is excavated from the outside of the third working face 3 along the direction of the main transport roadway 12. A protective coal pillar 25 is left between the fracturing roadway 16 and the haulage roadway 14 of the third working face 3. The fracturing roadway 16 includes an uphill section and a straight section. The height of the straight section is at the middle height of the basic roof 43. The uphill section connects the straight section and the main transport roadway 12 and starts from the main transport roadway 12.

[0029] S2: For each working face, several fracturing and top-cutting zones extending along the dip are set at intervals along the strike; the fracturing and top-cutting zones of all working faces correspond completely in the strike to save the construction workload of fracturing boreholes 31, top-cutting boreholes 35, and grouting boreholes. The length of the fracturing and top-cutting zone of each working face is consistent with the dip width of the working face and is located directly above it. The fracturing and top-cutting zone is located in the basic roof 43, and its height is consistent with the height of the basic roof 43. The fracturing and top-cutting zone includes a top-cutting zone 52 located in the middle and fracturing zones 51 located on both sides of the top-cutting zone 52; top-cutting boreholes 35 are constructed in the top-cutting zone 52 from the fracturing tunnel 16, and fracturing boreholes 31 are constructed in the fracturing zones 51. Depending on the size of the top-cutting zone 52, one or more top-cutting boreholes 35 can be constructed, and depending on the size of the fracturing zone 51, one or more fracturing boreholes 31 can be constructed. In this embodiment, one borehole is used as an example.

[0030] S3: Directly above the top-cutting zone 52, a grouting borehole is constructed. The grouting borehole includes at least a horizontal section 33 and a branch section 34. The horizontal section 33 is parallel to the top-cutting borehole 35. The branch section 34 is constructed downwards from the horizontal section 33, and at least two branch sections 34 are provided in each top-cutting zone 52 of each working face. The horizontal section 33 near the end of the fracturing roadway 16 can be directly used as a grouting inlet, and the construction roadway extends to this point as a grouting site; alternatively, it also includes a vertical section 32 connected to the horizontal section 33, which connects to the ground surface, allowing grouting to be performed from the ground surface through the vertical section 32.

[0031] S4: As Figure 1 , Figure 3 , Figures 5-6As shown, the first working face 1 is mined, and the direct roof 42 collapses behind the stope 15 to form direct roof crushed rock 55. Due to the large strength and thickness of the basic roof 43, a suspended roof zone 23 will be formed. When the exposed length of the suspended roof zone 23 along the strike is large, before reaching the periodic collapse step distance of the basic roof 43, for example, when the strike length of the suspended roof zone 23 reaches 30-50m (the specific length is determined according to the strength, thickness and collapse step distance of the basic roof 43), fracturing and roof cutting are carried out in the fracturing and roof cutting zone behind the suspended roof zone 23. The diagonal fracturing and roof cutting range is located directly above the first working face 1. At this time, the number of fracturing and roof cutting zones is consistent with the number of collapses of the basic roof 43. Alternatively, before the even-numbered period of collapse of the basic roof 43, fracturing and cutting can be performed on the fracturing and cutting zone behind the suspended roof area 23. In this case, the number of fracturing and cutting zones is half the number of collapses of the basic roof 43. The specific number of fracturing and cutting zones can be adjusted to at least ensure that the second sandstone group 45 does not break. The basic roof 43 is the first sandstone group placed on the coal seam 41, and the second sandstone group 45 is the second sandstone group above the coal seam 41.

[0032] Specifically, the fracturing zones 51 on both sides of the strike are fracturing through fracturing borehole 31, and the top-cutting zone 52 (preferably also including the immediate roof 42 directly below the top-cutting zone 52) is cut through the top-cutting borehole 35. The top-cutting dip section 58 is located at the dip boundary of the first working face 1, and the top-cutting dip section 58 is a vertical plane. Thus, the fracturing and top-cutting zone is constructed into a state where the sides of the strike are fracturing rock fragments 53, and the middle is a top-cutting block 54. The fracturing rock fragments 53 and the top-cutting block 54 are located above the immediate roof rock fragments 55. The fracturing rock fragments 53 are formed by fracturing through the fracturing zones 51, and the top-cutting block 54 falls as a whole after top-cutting. The top-cutting block 54 is surrounded by fracturing rock fragments 53 on both sides of the strike, and the dip sides are intact overburden strata above the coal pillar. And because the rock has the characteristic of fragmentation and expansion after fracturing, the height of the top-cutting block 54 is lower than that of the fracturing rock fragments 53 on both sides of the dip. Furthermore, since the rock has the property of shuffling after being broken, it can fill the space created by the mining of coal seam 41, support the ordinary rock layer 44 between the upper second sandstone group 45, the basic roof 43, and the second sandstone group 45, and control the second sandstone group 45 and its overlying rock layer (not shown in the figure) from breaking.

[0033] S5: Grouting is performed on the space above the cut-off block 54 through grouting boreholes. The cut-off block 54 is surrounded by a rectangular trench formed by fracturing rock fragments 53 higher than it and the complete overburden strata (the top surface of the cut-off block 54 is the bottom, and the fracturing rock fragments 53 and the complete overburden strata above the coal pillar form the perimeter of the rectangular trench). The grout injected into the top surface of the cut-off block 54 from the branch section 34 can quickly expand to the fracturing rock fragments 53 on both sides of the cut-off block 54 and bond with the fracturing rock fragments 53 to form a filling body containing rock fragments, thereby improving the support performance of the fracturing rock fragments 53. Since the fracturing rock fragments 53 are artificially fractured, their small size has a certain grout-blocking function, which can reduce the circumferential flow range of the injected grout. Finally, the area directly above the cut-off block 54 is filled with pure grout to form a pure grout filling body 56.

[0034] S6: Repeat steps S4-S5 until the first working face 1 is mined back to the stop line 21; the inclined fracturing and cutting zone forms a support strip with strong support capacity along the dip through fracturing, cutting and grouting. It is composed of crushed rock, cutting blocks 54 and grout. The adjacent support strips along the strike are basic top-breaking blocks 57, which can provide certain lateral support for the support strip.

[0035] S7: Referring to the first working face 1, the remaining fracturing boreholes 31, top cutting boreholes 35 and grouting boreholes are used to fill the goaf 24 of the second working face 2 and the third working face 3 in sequence.

[0036] The fracturing method can be hydraulic fracturing or carbon dioxide fracturing, which are existing technologies in the field, and can be selected as needed.

[0037] Of course, the above description is only a preferred embodiment of the present invention. The present invention is not limited to the above-described embodiments. It should be noted that any equivalent substitutions or obvious modifications made by those skilled in the art under the guidance of this specification fall within the scope of this specification and should be protected by the present invention.

Claims

1. A method for filling diagonal strips in the goaf of an ultra-long working face, characterized in that, Includes the following steps: S1: Grouping multiple adjacent working faces together, constructing fracturing roadways along the strike outside the last working face; S2: For each working face, several fracturing and top-cutting zones extending along the dip are set at intervals along the strike, and the fracturing and top-cutting zones of all working faces correspond one-to-one in the strike; the length of the fracturing and top-cutting zone of each working face is consistent with the dip width of the working face, and is located directly above it; the fracturing and top-cutting zone is located in the main roof, and its height is consistent with the height of the main roof; the fracturing and top-cutting zone includes the top-cutting zone located in the middle and the fracturing zones located on both sides of the top-cutting zone; top-cutting boreholes are drilled in the fracturing roadway in the top-cutting zone, and fracturing boreholes are drilled in the fracturing zone; S3: Construction grouting boreholes, which include horizontal sections and branch sections. At least two branch sections shall be set in each cut-off zone of each working face. S4: The first working face is back-mined, and the fracturing and top-cutting zone behind the suspended roof area is fracturing and top-cutting. The top-cutting dip section is located at the dip boundary of the first working face and the top-cutting dip section is a vertical plane; thus, the fracturing and top-cutting zone is constructed into a state where the two sides of the strike are fracturing rock fragments and the middle is a top-cutting block. S5: Grout the space above the cut-off block through grouting drill holes; S6: Repeat steps S4-S5 until the first working face is mined back to the stop line; the inclined fracturing and top cutting zone forms a support strip along the dip with strong support capacity, which is composed of crushed gangue, top cutting blocks and grout, through fracturing, top cutting and grouting. S7: Referring to the first working face, use the remaining fracturing boreholes, top cutting boreholes and grouting boreholes to fill the goaf of the remaining working face in sequence.

2. The method for filling the goaf in an ultra-long working face with diagonal strips according to claim 1, characterized in that, In step S1, a section coal pillar is set between adjacent working faces; the return airway of the next working face is constructed using the goaf excavation process.

3. The method for filling the goaf in an ultra-long working face with diagonal strips according to claim 2, characterized in that, In step S1, a fracturing roadway is excavated along the haulage main roadway. A protective coal pillar is left between the fracturing roadway and the haulage roadway of the last working face. The fracturing roadway includes an uphill section and a straight section. The height of the straight section is at the middle height of the basic roof. The uphill section connects the straight section and the haulage main roadway and starts from the haulage main roadway.

4. The method for filling the goaf in an ultra-long working face with diagonal strips according to claim 1, characterized in that, In step S3, a grouting borehole is constructed directly above the top-cutting area. The horizontal section is parallel to the top-cutting borehole, and the branch section is constructed downward from the horizontal section. The horizontal section near the end of the fracturing roadway serves directly as the grouting inlet. Alternatively, it also includes a vertical section connected to the horizontal section, which connects to the ground surface, and grouting is carried out from the ground surface through the vertical section.

5. The method for filling the goaf of an ultra-long working face with diagonal strips according to claim 1 or 4, characterized in that, In step S4, a suspended roof zone will be formed at the basic top. Before each period of collapse at the basic top, the fracturing and roof cutting zone behind the suspended roof zone will be fracturing and roof cutting will be performed; or, before the even-numbered period of collapse at the basic top, the fracturing and roof cutting zone behind the suspended roof zone will be fracturing and roof cutting will be performed.

6. The method for filling the goaf in an ultra-long working face with diagonal strips according to claim 5, characterized in that, In step S4, the dip fracturing and top cutting range is located directly above the first working face; the fracturing rock fragments and top cutting blocks are located above the direct top rock fragments. The fracturing rock fragments are formed by fracturing the fracturing zone, and the top cutting blocks fall as a whole after top cutting. The top cutting blocks are surrounded by fracturing rock fragments on both sides of the dip direction, and are adjacent to complete overburden strata on both sides of the dip direction. The height of the top cutting blocks is lower than that of the fracturing rock fragments on both sides of the dip direction.

7. The method for filling the goaf in an ultra-long working face with diagonal strips according to claim 6, characterized in that, In step S5, the small size of the fracturing rock fragments has a certain grout-blocking function, and the area directly above the cut-off block is filled with pure grout to form a pure grout filling body.

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