Coal mining method for controlling ground surface settlement through bottom plate isolation grouting filling

Abstract

The invention relates to the field of mining area subsidence reduction and filling mining, in particular to a coal mining method for controlling ground subsidence through bottom plate isolation grouting filling. Comprising the steps that a rock stratum with a certain thickness is selected below a bottom plate damage zone to serve as a bottom plate pressure-bearing protection layer, the bottom plate pressure-bearing protection layer arches upwards under the grouting pressure, but cracks for conducting the upper bottom plate damage zone are not generated; the bottom interface of the pressure-bearing protection layer of the bottom plate serves as a grouting layer, and grouting drill holes are constructed to communicate with the grouting layer; and when grouting filling can be carried out, filling grout is injected into the grouting layer position from the grouting drill hole. The filling slurry lifts a bottom plate grouting pressure-bearing layer and a bottom plate damage zone under the action of high pressure, and finally the whole goaf is filled, the fracture degree of a coal seam roof is reduced, the settlement amplitude of an overlying rock layer is controlled, and then the surface subsidence amplitude is reduced. The coal mining process and the grouting filling process are separated, the influence of grouting filling operation on working face stoping is avoided, and the method is particularly suitable for coal mine areas with dense buildings.

Description

Technical Field

[0001] This invention relates to the field of mining subsidence reduction and backfilling, specifically to a method for controlling surface subsidence in coal mining by bottom plate isolation grouting and backfilling. Background Technology

[0002] The problem of coal seam pressure beneath buildings has always been a major technical challenge in coal mining, especially in eastern mining areas. Due to the dense concentration of surface buildings in these regions, mining activities can easily cause subsidence and damage to these structures and surface facilities. Therefore, a safe and efficient mining method is urgently needed to minimize the impact on surface buildings. Against this backdrop, the development of backfill mining technology has provided an effective solution to the problem of coal seam pressure beneath buildings.

[0003] In recent years, backfilling technology in coal mining has gradually matured, resulting in various methods for filling goafs, including solid backfilling, paste backfilling, and high-water material backfilling. Solid backfilling typically utilizes solid waste such as mine waste rock and gangue to fill goafs, which not only reduces surface subsidence but also effectively utilizes mine waste resources. Paste backfilling uses finely ground mine tailings mixed with water and additives to form a paste slurry for filling, exhibiting high strength and good stability, making it suitable for coal mining in densely built-up areas. High-water material backfilling is a technology that uses high-water solidification materials such as cement to form a solid filler through chemical reaction, which can quickly fill goafs and create high load-bearing capacity, effectively supporting overlying strata and reducing surface subsidence.

[0004] While backfill mining offers significant advantages in mitigating coal seam pressure issues, its implementation also faces several technical and economic challenges. Among these, interference from face mining and the impact on extraction rates are major drawbacks of backfill mining.

[0005] First, the injection and solidification of backfill material requires a large amount of construction equipment and procedures, which directly interferes with the normal mining progress of the working face, leading to reduced production efficiency. For example, the laying and solidification of the backfill takes time, increasing the work cycle, and a certain isolation distance must be maintained between the coal face and the backfill to ensure safety, which limits the mining length and advancement speed of the working face. At the same time, the operation process of backfill mining is relatively complex, requires highly skilled personnel, and requires more manpower and material resources, increasing operating costs.

[0006] Secondly, backfilling mining affects the recovery rate. Because the backfill occupies a portion of the space, the coal seam recovery rate is difficult to reach the level of traditional mining methods, leading to a decrease in resource utilization. During the backfilling process, in order to ensure the strength and stability of the backfill, a portion of the coal seam is usually left unmined, which further reduces the economic benefits of the mine.

[0007] In addition, due to the addition of backfill materials and the need for filling operations, the cost of extracting coal per unit is relatively high, which poses a certain challenge to the economics of backfill mining. This is especially true when resources are scarce or coal prices fluctuate, making the cost-effectiveness of this method even less than ideal. Summary of the Invention

[0008] To address the problems existing in the prior art, this invention proposes a method for controlling surface subsidence in coal mining by bottom plate isolation grouting and backfilling. This method can separate the backfilling process from the working face mining, effectively avoid interference from backfilling operations on the working face mining, and improve the working face extraction rate. Specifically, it includes the following steps:

[0009] S1: Determine the extent of the failure zone of the floor below the coal seam, and select a rock layer of a certain thickness below the failure zone as the pressure-bearing protective layer of the floor. The pressure-bearing protective layer of the floor arches upward under the grouting pressure, but does not generate cracks that connect to the upper failure zone of the floor, or the generated cracks are not connected to the cracks of the failure zone of the floor.

[0010] S2: The bottom interface of the pressure-bearing protective layer of the base plate is used as the grouting layer, and the grouting borehole is connected to the grouting layer.

[0011] S3: When the working face is being mined, and grouting is possible, fill the grouting slurry into the grouting layer through the grouting borehole.

[0012] Preferably, in step S1, the rock stratum at the bottom of the pressure-bearing protective layer of the base plate has a low elastic modulus and good water-proof properties.

[0013] Preferably, in step S2, when the working face adopts a single-lane layout, the grouting boreholes are constructed in the horizontal lanes on both sides of the working face towards the grouting layer of the coal seam floor in advance of the working face mining position. The grouting boreholes are inclined in the direction of the cut in the plane. The grouting boreholes are constructed in pairs in the horizontal lanes on both sides of the working face at a certain distance from the cut in the working face advancing direction.

[0014] Preferably, in step S2, when both horizontal roadways on both sides of the working face adopt a double-roadway arrangement, grouting boreholes are constructed in the two outer horizontal roadways toward the grouting layer of the coal seam floor inside the working face. The grouting boreholes are inclined in the direction of the cut in the plane. The grouting boreholes are constructed in pairs in the horizontal roadways on both sides of the working face at a certain distance from the cut, along the working face advancement direction.

[0015] Preferably, in step S2, directional grouting boreholes are drilled from the ground outside the cut-out on the working face. The horizontal section of the directional grouting borehole is drilled close to the bottom interface of the pressure-bearing protective layer of the base plate, and the drilling extends at least to a certain range within the working face.

[0016] Preferably, in step S2, directional grouting boreholes are constructed from the ground outside the horizontal tunnel on one side of the working face. The horizontal section of the directional grouting borehole is constructed close to the bottom interface of the pressure-bearing protective layer of the bottom plate, and is constructed to at least a certain range within the working face. Several directional grouting boreholes are constructed at certain intervals along the working face advancing direction.

[0017] Preferably, in step S3, the filling slurry is made of fly ash slurry or gangue powder slurry.

[0018] Preferably, in step S3, when the working face adopts a single-lane layout, when the working face is backed up to above the final hole of a certain pair of grouting boreholes, trial grouting is started for the pair of grouting boreholes. When it is possible to inject, filling grout is injected into the grouting layer through the pair of grouting boreholes. When the working face is backed up to the position of the opening of the pair of grouting boreholes, grouting is stopped and the holes are sealed. Then, the next pair of grouting boreholes are grouted in the same way.

[0019] Preferably, in step S3, when both horizontal tunnels on both sides of the working face adopt a double-tunnel arrangement, when the working face is back-mined to above the final hole of a certain pair of grouting boreholes, trial grouting is started on the pair of grouting boreholes. When it is possible to inject, filling grout is injected into the grouting layer through the pair of grouting boreholes. When the pair of grouting boreholes cannot be injected due to high grouting pressure, grouting is stopped and the holes are sealed. Then, the next pair of grouting boreholes are grouted in the same way.

[0020] Preferably, in step S3, when drilling directional grouting holes from the ground outside the working face cut, when grouting can be carried out, filling grout is injected from the directional grouting hole into the grouting layer. When grouting cannot be injected due to high grouting pressure, grouting is stopped and the hole is sealed.

[0021] Preferably, in step S3, when directional grouting boreholes are drilled from the ground outside the horizontal tunnel on one side of the working face, for each directional grouting borehole, when grouting and filling can be carried out, filling grout is injected from the directional grouting borehole to the grouting layer. When a certain directional grouting borehole cannot be injected due to high grouting pressure, grouting through that directional grouting borehole is stopped and the borehole is sealed.

[0022] The inventive points and beneficial effects of this invention: This invention creatively proposes a method for controlling surface subsidence in coal mining through bottom plate isolation grouting and filling. During coal seam mining, filling grout is injected into the bottom interface of the bottom grouting pressure layer beneath the coal seam floor through grouting boreholes. Under high pressure, the filling grout lifts the bottom grouting pressure layer and the floor failure zone, ultimately filling the entire goaf, reducing the degree of roof fracture, controlling the subsidence of the overlying strata, and thus reducing the surface subsidence. In this invention, the coal mining and grouting processes are separated, avoiding the impact of grouting and filling operations on the working face recovery, making it particularly suitable for coal mining areas with dense buildings. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the single-lane straight hole arrangement for bottom plate isolation grouting filling in this invention;

[0024] Figure 2 This is a schematic diagram of the double-lane straight hole arrangement for bottom plate isolation grouting filling in this invention;

[0025] Figure 3 This is a schematic diagram of the ground drilling arrangement along the direction of the bottom plate isolation grouting filling in this invention;

[0026] Figure 4 This is a schematic diagram of the ground drilling holes arranged along the directional direction for the bottom plate isolation grouting filling in this invention;

[0027] In the diagram: grouting bearing layer-1, uniform fracture zone of the bottom plate-2, fracture expansion zone of the bottom plate-3, section coal pillar-4, horizontal roadway-5, caving zone-6, fissure zone-7, grouting borehole-8, filling slurry-9. Detailed Implementation

[0028] To better understand the technical content of this invention, specific embodiments are described below in conjunction with the accompanying drawings. Various aspects of this invention are described with reference to the accompanying drawings, which illustrate numerous illustrative embodiments. The embodiments of this invention are not limited to those shown in the drawings. It should be understood that this invention is implemented through any of the various concepts and embodiments described above, as well as the concepts and embodiments described in detail below, because the concepts and embodiments disclosed in this invention are not limited to any particular implementation. Furthermore, some aspects of this invention can be used alone or in any suitable combination with other aspects disclosed in this invention.

[0029] like Figure 1-4 As shown, this invention proposes a method for controlling surface subsidence in coal mining through bottom plate isolation grouting and filling, comprising the following steps: S1: Determine the range of the bottom plate failure zone below the coal seam. The bottom plate failure zone includes a bottom plate fracture expansion zone 3 and a bottom plate uniform fracture zone 2. In the bottom plate fracture expansion zone 3, the bottom plate rock strata are fractured in an irregular network pattern, and the fractured blocks are relatively small. Due to the gaps between the fractured blocks, they have a certain expansion characteristic. In the bottom plate uniform fracture zone 2, the bottom plate rock strata are fractured with regular longitudinal and transverse cracks, forming relatively large regular fractured blocks. The bottom plate failure zone can form water-conducting channels. Below the bottom plate failure zone, a rock stratum of a certain thickness (usually containing multiple rock strata) is selected as the bottom plate pressure-bearing protective layer 1. The bottom plate pressure-bearing protective layer 1 arches upward under grouting pressure, but does not generate cracks that connect to the upper bottom plate failure zone, or the generated cracks do not connect with the cracks in the bottom plate failure zone. The rock stratum at the bottom of the bottom plate pressure-bearing protective layer is preferably a rock stratum with low elastic modulus and good water-impermeability, such as mudstone.

[0030] S2: The bottom interface of the pressure-bearing protective layer 1 of the base plate is taken as the grouting layer, and the grouting borehole 8 is connected to the grouting layer.

[0031] There are several ways to arrange the grouting boreholes 8, such as:

[0032] S201: As Figure 1 As shown, the working face adopts a single-lane layout, that is, a return airway and a transport airway are arranged on both sides of the working face. The single-lane layout is a well-known layout in the field and will not be described in detail here. At the advance working face mining position, grouting boreholes 8 are constructed in the horizontal roadways 5 on both sides of the working face towards the grouting layer of the coal seam floor. The grouting boreholes 8 are inclined in the plane towards the cutting direction. The grouting boreholes 8 are constructed in pairs in the horizontal roadways 5 on both sides of the working face at a certain distance from the cutting direction along the working face advancement direction. The vertical depth, angle and plane inclination of each pair of grouting boreholes 8 are the same.

[0033] S202: As Figure 2 As shown, both horizontal roadways 5 on both sides of the working face adopt a double-roadway layout. A section coal pillar 4 is left between the two horizontal roadways 5 on the same side. Grouting boreholes 8 are constructed in the two outer horizontal roadways 5 towards the grouting layer of the coal seam floor inside the working face. The grouting boreholes 8 are inclined in the plane towards the cutting direction. The grouting boreholes 8 are constructed in pairs in the horizontal roadways 5 on both sides of the working face along the working face advancement direction, starting from the cutting direction and spaced at a certain distance. The vertical depth, angle and plane inclination of each pair of grouting boreholes 8 are the same.

[0034] S203: As Figure 3 As shown, directional grouting borehole 8 is constructed from the ground outside the cut-out on the working face. The horizontal section of the directional grouting borehole 8 is constructed close to the bottom interface of the pressure-bearing protective layer 1 of the bottom plate, and is constructed to at least a certain range within the working face.

[0035] S204: As Figure 4 As shown, directional grouting boreholes 8 are constructed from the ground outside the horizontal tunnel 5 on one side of the working face. The horizontal section of the directional grouting boreholes 8 is constructed close to the bottom interface of the pressure-bearing protective layer 1 of the bottom plate, and is constructed at least to a certain range within the working face. Several directional grouting boreholes 8 are constructed at certain intervals along the working face advancing direction (i.e., direction).

[0036] S3: When the working face is being mined and grouting is possible, filling grout 9 is injected into the grouting layer from the grouting borehole. Filling grout 9 is preferably made of coal-based solid waste materials such as fly ash grout or gangue grout. The injected high-pressure grout 9 gradually lifts the pressure-bearing protective layer 1 of the bottom plate and the uniform fracture zone 2 and the fracture expansion zone 3 of the bottom plate above it. Under the action of grouting, the uniform fracture zone 2 and the fracture expansion zone 3 of the bottom plate will increase the damage range, and the looseness of the irregular rock blocks in the fracture expansion zone 3, i.e. the degree of fragmentation, will also increase, further filling the goaf space. Together with the filling grout 9, it offsets part of the space formed by coal seam mining, thereby reducing the equivalent mining height of the coal seam, thereby reducing the subsidence of the overlying strata and reducing surface subsidence.

[0037] The matching relationship between grouting and coal mining is as follows, depending on the different arrangements of the grouting boreholes 8:

[0038] S301: As Figure 1 As shown, when the working face adopts a single-lane layout, when the working face is backed up to above the final hole of a pair of grouting boreholes 8, trial grouting of the pair of grouting boreholes 8 is started. When it is possible to inject, filling grout 9 is injected into the grouting layer through the pair of grouting boreholes 8. When the working face is backed up to the position of the opening of the pair of grouting boreholes 8, grouting is stopped and the hole is sealed. Then, the next pair of grouting boreholes is grouted in the same way.

[0039] S302: As Figure 2 As shown, when both horizontal tunnels 5 on both sides of the working face adopt a double-tunnel layout, when the working face is back-mined to above the final hole of a certain pair of grouting boreholes 8, trial grouting is started on the pair of grouting boreholes 8. When it is possible to inject, filling grout 9 is injected into the grouting layer through the pair of grouting boreholes 8. When the pair of grouting boreholes 8 cannot be injected due to high grouting pressure, grouting is stopped and the holes are sealed. Then, the next pair of grouting boreholes 8 is grouted in the same way.

[0040] S203: As Figure 3 As shown, when directional grouting borehole 8 is drilled from the ground outside the working face cut, when grouting can be carried out, filling grout 9 is injected from directional grouting borehole 8 into the grouting layer. When grouting cannot be injected due to high grouting pressure, grouting is stopped and the borehole is sealed.

[0041] S204: As Figure 4 As shown, when directional grouting boreholes 8 are drilled from the ground outside the horizontal tunnel 5 on one side of the working face, for each directional grouting borehole 8, when grouting and filling can be carried out, filling grout 9 is injected from the directional grouting borehole 8 into the grouting layer. When a certain directional grouting borehole 8 cannot be injected due to high grouting pressure, grouting through that directional grouting borehole is stopped and the borehole is sealed.

[0042] This invention is not limited to the preferred embodiments described above. Anyone can derive other methods in various forms under the guidance of this invention. Any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A method for coal mining by controlling ground subsidence by grouting and filling with floor isolation, characterized in that: The following steps are involved: S1: Determine the scope of the floor damage zone below the coal seam, select a rock layer of a certain thickness below the floor damage zone as the floor pressure-bearing protective layer, the floor pressure-bearing protective layer arches up under the grouting pressure, but does not generate cracks that connect to the upper floor damage zone, or the generated cracks are not connected to the cracks in the floor damage zone; S2: The bottom interface of the bottom plate pressure protection layer is used as the grouting layer, and the grouting drilling holes are constructed to connect the grouting layers; S3: Carry out mining on the working face. When grouting filling is possible, inject filling slurry into the grouting layer from the grouting borehole.

2. The coal mining method according to claim 1, characterized in that: In step S1, the rock layer at the bottom of the bottom plate pressure-bearing protective layer has a low elastic modulus and good water-proof properties.

3. The coal mining method according to claim 1, characterized in that: In step S2, when the working face adopts a single-tunnel layout, the working face mining position is advanced, and grouting holes are constructed in the horizontal tunnels on both sides of the working face toward the grouting layer of the coal seam bottom plate in the working face, and the grouting holes are inclined toward the cutting direction on the plane; the grouting holes are constructed in pairs in the horizontal tunnels on both sides of the working face at a certain distance from the cutting direction along the advancement direction of the working face.

4. The coal mining method according to claim 3, characterized in that: In step S3, when the working face is mined above the end hole of a pair of grouting boreholes, trial grouting of the pair of grouting boreholes is started, and when injection is possible, filling slurry is injected into the grouting layer through the pair of grouting boreholes. When the working face is mined to the position of the hole mouths of the pair of grouting boreholes, the grouting is stopped and the holes are sealed; then, the next pair of grouting boreholes are grouted in the above manner.

5. The coal mining method according to claim 1, characterized in that: In step S2, when the horizontal tunnels on both sides of the working face adopt a double tunnel layout, grouting holes are constructed in the two outer horizontal tunnels toward the grouting layer of the coal seam bottom plate in the working face, and the grouting holes are inclined toward the cutting direction on the plane; the grouting holes are constructed in pairs in the horizontal tunnels on both sides of the working face at a certain distance from the cutting direction along the advancement direction of the working face.

6. The coal mining method according to claim 5, characterized in that: In step S3, when the working face is mined above the end hole of a pair of grouting boreholes, trial grouting is started for the pair of grouting boreholes. When injection is possible, filling slurry is injected into the grouting layer through the pair of grouting boreholes. When the pair of grouting boreholes cannot be injected due to high grouting pressure, grouting is stopped and the holes are sealed; then grouting is performed on the next pair of grouting boreholes in the above manner.

7. The coal mining method according to claim 1, characterized in that: In step S2, a directional grouting drill hole is constructed from the ground outside the cut eye of the working face, and the horizontal section of the directional grouting drill hole is constructed closely to the bottom interface of the bottom plate pressure protection layer and is constructed at least to a certain range within the working face.

8. The coal mining method according to claim 7, characterized in that: In step S3, when a directional grouting drill hole is constructed from the ground outside the cut eye of the working face, when grouting filling can be carried out, the filling slurry is injected into the grouting layer from the directional grouting drill hole. When the grouting pressure cannot be injected due to high pressure, the grouting is stopped and the hole is sealed.

9. The coal mining method according to claim 1, characterized in that: In step S2, directional grouting holes are constructed from the ground outside the horizontal tunnel on one side of the working face. The horizontal section of the directional grouting holes is constructed close to the bottom interface of the bottom plate pressure protection layer and is constructed at least to a certain range within the working face. A number of directional grouting holes are constructed at a certain distance along the advancement direction of the working face.

10. The coal mining method according to claim 1, characterized in that: In step S3, when directional grouting drilling is constructed from the ground outside the horizontal tunnel on one side of the working face, for each directional grouting drilling hole, when grouting filling can be carried out, filling slurry is injected from the directional grouting drilling hole to the grouting layer. When a certain directional grouting drilling hole cannot be injected due to high grouting pressure, grouting through the directional grouting drilling hole is stopped and the hole is sealed.

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