A coal mine end-mining working face rib spalling pre-treatment process

Abstract

The application provides a coal mine end-mining working face rib spalling pre-treatment process and relates to the technical field of mining engineering, which comprises the following steps: step one: selecting a drilling and grouting position in a coal body crack proliferation zone affected by an advanced working face support pressure and implementing high-pressure pouring; step two: uniformly arranging grouting holes in a single row at the coal wall waist line of the two gateways of the working face, drilling 2-3 m away from the bottom, spacing 3-10 m, and constructing near-horizontal angle drilling, with the final hole position close to the coal body transverse center surface and the coal seam roof, and the drilling of the two gateways being arranged at intervals; step three: arranging pipes in the coal body; the application adopts a method of high-pressure pouring of superfine particle size grouting material in the crack proliferation zone of the advanced working face, fills and bonds the coal body crack development in the early stage, realizes reinforcement and reinforcement of the coal body, prevents rib spalling of the coal wall during end-mining advancement of the working face, and adopts an early pre-grouting mode, which is small in construction amount, convenient in construction process, does not affect the mining of the working face, and has remarkable reinforcement treatment effect.

Description

Technical Field

[0001] The present invention relates to the technical field of mining engineering, in particular to a coal mine late mining face spalling pre-treatment process. Background Art

[0002] In coal mining projects, as the mining face reaches the final mining stage and approaches the support removal channel, the coal pillar becomes thinner, the mine pressure increases, and the self-stability of the coal wall at the working face deteriorates. Especially for working faces with large mining heights, rock spalling and associated roof falls often occur. Emergency response is difficult and has become a key link affecting mine production efficiency.

[0003] After the problem occurs, the polymer material grouting is mainly carried out within 10m of the working face. The coal cracks are fully developed, the grouting volume is large, the cost is high, and the grouting is carried out as the mining is carried out, which affects the mining efficiency. The ordinary cement slurry pre-grouting used in the chute has the problem of serious leakage in the shallow area affected by the support pressure, and the construction is difficult. The grouting volume is small in the deep area affected by the support pressure, and the reinforcement effect is not obvious. Therefore, the present invention proposes a pre-treatment process for the spalling of the coal mine working face at the end of mining to solve the problems existing in the prior art. Summary of the Invention

[0004] In response to the above problems, the present invention proposes a process for pre-treatment of coal wall spalling at the end-of-mining working face in a coal mine. The process can reinforce and strengthen the coal body, prevent the spalling problem of the coal wall during the advancement of the working face, and use pre-injection in advance. The construction amount is small, the construction process is convenient, and the mining of the working face is not affected, and the reinforcement and treatment effect is significant.

[0005] To achieve the purpose of the present invention, the present invention is implemented through the following technical solutions: a coal mine end-of-mining working face spalling pretreatment process, comprising the following steps:

[0006] Step 1: Select the drilling and grouting location in the coal body fissure proliferation area affected by the support pressure of the advanced working face and implement high-pressure grouting;

[0007] Step 2: Grouting holes are evenly arranged in a single row at the waistline of the coal wall of the two drifts of the working face. The holes are drilled 2-3m from the bottom and 3-10m apart. The holes are drilled at a nearly horizontal angle. The final hole position is close to the horizontal center plane of the coal body and the coal seam roof. The holes in the two drifts are arranged at intervals.

[0008] Step 3: Lay pipes inside the coal body, using 4-point plastic pipe threaded joints. Two parallel pipes are laid out, one throughout the borehole and the other within 10 meters of the borehole. Multiple jet holes are opened on the pipe bodies at the ends of both pipes.

[0009] Step 4: Place polyurethane quick-sealing bags at the position 0.3-0.6m and 8-12m from the hole mouth, respectively, to fill the gap between the pipeline and the drilled hole, dividing the entire grouting hole into two sections: shallow and deep.

[0010] Step 5: Use a two-component pressure-adjustable hydraulic grouting pump to connect the shallow grouting pipe, and use two-component rapid-setting grouting material to grout the shallow part of the coal body;

[0011] Step 6: Increase the pressure of the grouting pump, connect the deep grouting pipeline, and use single-component ultra-fine particle grouting material to fill and reinforce the deep cracks in the coal body.

[0012] Further improvements are as follows: the coal body fracture proliferation zone is 20-40m ahead of the working face, and it is judged through underground field measurements or analogy with the situation of nearby working faces with similar geological conditions.

[0013] A further improvement is that in step three, the pipes are laid using 2-3 meter 4-point plastic pipes with threaded splicing.

[0014] A further improvement is that in step 4, the polyurethane quick-sealing bag is controlled to foam and solidify within 10 minutes, condense and fill the gap between the pipeline and the drilled hole to seal the hole and fix the pipe.

[0015] A further improvement is that in step 4, the shallow part of the grouting hole is less than 10 meters, and the deep part of the grouting hole is greater than 10 meters, thereby separating the grouting pipelines into two trips.

[0016] A further improvement is that in step five, the two-component rapid-setting grouting material consists of powdered material A and material B, wherein material A is composed of a homogeneous mixture of 92%-96% of sulphoaluminate cement and high-alumina cement, 2%-5% of a composite retarder of boric acid and tartaric acid, and 3%-6% of a naphthalene-based water reducer; and material B is composed of a mixture of 68%-85% of gypsum, 10%-25% of a pH regulator, and 2%-7% of a composite metal salt early strength agent. Water is added to the two materials separately and stirred, and then mixed by a grouting mixer.

[0017] A further improvement is that in step five, the grouting pressure is 5-10 MPa, the pressure is gradually increased during the grouting process, the final pressure is 10 MPa, and the pressure holding time is 10-15 minutes.

[0018] A further improvement is that in step six, the single-component ultrafine particle grouting material is an ultrafine homogeneous inorganic powder, which is composed of 88-92% ultrafine cement, mesh size >1200, 3-7% pre-dispersed silica fume, 5-9% finely ground fly ash, mesh size >1000, 0.5-0.8% epoxy-modified high-efficiency carboxylic acid water reducer, and 0.05-0.1% defoaming agent, with a water-cement ratio of 0.5-0.8.

[0019] A further improvement is that in step six, the grouting pressure is 10-15 MPa, the final pressure is 15 MPa, and the pressure holding time is 30-40 minutes.

[0020] The beneficial effects of the present invention are:

[0021] 1. The present invention adopts the method of high-pressure injection of ultra-fine particle size grouting materials in the fissure proliferation area of ​​the advance working face, which can fill and bond the coal body fissures in the early stage of development, realize the reinforcement of the coal body, and prevent the spalling problem of the coal wall in the late mining of the working face. The advance pre-injection method has a small construction volume, a convenient construction process, does not affect the mining of the working face, and has a significant reinforcement and treatment effect.

[0022] 2. The present invention effectively blocks shallow cracks in the coal body through a primary rapid-setting grouting material, thereby avoiding leakage of ultrafine slurry, creating conditions for secondary high-pressure grouting, and achieving effective grouting of incompletely developed cracks and their fine tips with slurry, thus ensuring its grouting effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the advance support pressure distribution of the present invention;

[0024] Figure 2 A top view schematic diagram of the drilling arrangement of the present invention;

[0025] Figure 3 Schematic diagram of the pipeline arrangement of the present invention. DETAILED DESCRIPTION

[0026] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to the examples. The examples are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0027] Example 1

[0028] according to Figure 1 、 2 As shown in FIG. 3 , this embodiment proposes a coal mine end-of-mining working face spalling pretreatment process, comprising the following steps:

[0029] Step 1: Select the drilling and grouting location in the coal body fissure proliferation area affected by the support pressure of the advanced working face and implement high-pressure grouting;

[0030] Step 2: Grouting holes are evenly arranged in a single row at the waistline of the coal wall of the two drifts of the working face. The holes are drilled 2-3m from the bottom and 3-10m apart. The holes are drilled at a nearly horizontal angle. The final hole position is close to the horizontal center plane of the coal body and the coal seam roof. The holes in the two drifts are arranged at intervals.

[0031] Step 3: Lay pipes inside the coal body, using 4-point plastic pipe threaded joints. Two parallel pipes are laid out, one throughout the borehole and the other within 10 meters of the borehole. Multiple jet holes are opened on the pipe bodies at the ends of both pipes.

[0032] Step 4: Place polyurethane quick-sealing bags at the position 0.3-0.6m and 8-12m from the hole mouth, respectively, to fill the gap between the pipeline and the drilled hole, dividing the entire grouting hole into two sections: shallow and deep.

[0033] Step 5: Use a two-component pressure-adjustable hydraulic grouting pump to connect the shallow grouting pipe, and use two-component rapid-setting grouting material to grout the shallow part of the coal body;

[0034] Step 6: Increase the pressure of the grouting pump, connect the deep grouting pipeline, and use single-component ultra-fine particle grouting material to fill and reinforce the deep cracks in the coal body.

[0035] The present invention adopts the method of high-pressure injection of ultra-fine particle size grouting material in the fissure proliferation area of ​​the advance working face, and specifically fills and bonds the coal body fissures in the early stage of development, thereby realizing the reinforcement of the coal body and preventing the spalling problem of the coal wall during the advancement of the working face at the end of mining. The advance pre-injection method has a small construction volume, a convenient construction process, does not affect the mining of the working face, and has a significant reinforcement and control effect.

[0036] Example 2

[0037] according to Figure 1 、 2 As shown in FIG. 3 , this embodiment proposes a coal mine end-of-mining working face spalling pretreatment process, comprising the following steps:

[0038] The drilling and grouting location is selected in the crack growth area affected by the advance support pressure of the working face. Figure 1 Generally, the advance working face is about 20-40m, which can be measured in the field underground or compared with the working face with similar geological conditions nearby, rather than the fully developed fracture area (advance working face is about <20m) for conventional emergency treatment.

[0039] The drilling and grouting holes are evenly arranged in a single row on the coal wall side of the two chute of the working face, 2-3 meters from the bottom. The drilling spacing is 3-10m, which is determined according to the degree of development of the internal cracks of the coal body. The hole is constructed at a near-horizontal angle, and the final hole position is close to the horizontal center plane of the coal body and the coal seam roof. Due to the diffusion radius of the ultra-fine grouting material of 4-6m, the slurry can cover the entire coal body. The drilling holes of the two chute are arranged at intervals (1-4#) Figure 2 .

[0040] In order to avoid damaging the coal mining machine picks, the pipes are laid inside the coal body using 2-3 meter 4-point plastic pipes with threaded splicing. Two pipes are arranged in parallel, one throughout the borehole and the other within 10 meters of the hole mouth. Multiple jet holes are opened on the pipe bodies at the ends of both pipelines.

[0041] Polyurethane quick-sealing bags were placed at 0.5m and 10m from the borehole, respectively. These bags rapidly foamed, solidified, and solidified within 10 minutes, filling the gap between the plastic pipe and the borehole. This ensured rapid sealing and pipe consolidation, dividing the borehole into shallow (less than 10m) and deep (greater than 10m) sections and separating the two grouting lines. The grouting pipes were short plastic sections connected by plastic threads, and the polyurethane sealing bags were used for both consolidation and segmentation, ensuring no interference with shearer cutting.

[0042] The primary grouting process uses a pressure-adjustable two-component hydraulic grouting pump connected to a shallow grouting pipe. This allows for sequential injection of two-component and single-component slurries at varying pressures. Two-component rapid inorganic grouting materials are used for grouting within a 10-meter radius of the shallow coal body, rapidly sealing shallow cracks. The primary grouting material used is a two-component rapid-setting material consisting of powdered material A and material B. Material A comprises a homogeneous mixture of 92% to 96% sulfoaluminate cement and high-alumina cement, 2% to 5% boric acid and tartaric acid composite retarder, and 3% to 6% naphthalene-based water reducer. Material B comprises 68% to 85% gypsum, 10% to 25% pH regulator, and 2% to 7% composite metal salt early strength agent. The two materials are stirred separately with water and mixed in a grouting mixer. After mixing, they lose fluidity in 1 to 5 minutes and fully solidify in 5 to 10 minutes. Grouting is done once with a grouting pressure of 5-10 MPa. The pressure increases gradually during the grouting process, with a final pressure of 10 MPa and a pressure holding time of 10-15 minutes.

[0043] Secondary grouting increases the grouting pump pressure and connects to the deep grouting pipeline. Both components use ultrafine grouting materials to fill and reinforce the deep cracks in the coal body in the advanced support pressure zone of the working face. No equipment needs to be replaced during the two grouting operations, making construction quick. The secondary grouting material used is a single-component ultrafine particle size material. This material is an ultrafine homogeneous inorganic powder with an adjustable water-cement ratio of 0.5-0.8. It has an initial setting time of 45-60 minutes and a curing time of 6-8 hours, achieving a 3d compressive strength of 20-35MPa. It is mainly composed of 88-92% ultrafine cement (mesh number > 1200), 3-7% pre-dispersed silica fume, 5-9% finely ground fly ash (mesh number > 1000), 0.5-0.8% epoxy-modified high-efficiency carboxylic acid water reducer, and 0.05-0.1% defoamer. The use of ultrafine-grained materials for high-pressure pre-injection in the fractured growth zone under the influence of support stress at the advanced working face prevents and manages the spalling problem at the end of the working face. Grouting is performed twice per hole. The first shallow, low-pressure injection seals the fractures, paving the way for the second, deeper, high-pressure injection. The second injection is performed at a pressure of 10-15 MPa, a final pressure of 15 MPa, and a holding time of 30-40 minutes.

[0044] This coal mine's final working face spalling pre-treatment process uses high-pressure injection of ultrafine grouting materials into the fissure proliferation zone of the advanced working face. This targeted filling and bonding of coal body fissures in the early stages of coal body development reinforces the coal body and prevents spalling of the coal wall during the final mining phase of the working face. This pre-injection method reduces the construction workload, facilitates the construction process, does not affect the recovery of the working face, and achieves significant reinforcement and treatment effects. Furthermore, the present invention effectively blocks shallow coal body fissures through a single rapid-setting grouting material, preventing leakage of ultrafine slurry, creating conditions for secondary high-pressure grouting, and effectively injecting slurry into incompletely developed fissures and their fine tips, ensuring the grouting effect.

[0045] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A coal mine end-of-mining working face spalling pretreatment process, characterized in that: The following steps are involved: Step 1: Select the drilling and grouting location in the coal body fracture proliferation zone affected by the support pressure of the advanced working face, and implement high-pressure grouting. The coal body fracture proliferation zone is 20-40m away from the advanced working face. The judgment is made through underground field measurement or analogy with the situation of nearby working faces with similar geological conditions; Step 2: Grouting holes are evenly arranged in a single row at the waistline of the coal wall of the two drifts of the working face. The holes are drilled 2-3m from the bottom and 3-10m apart. The holes are drilled at a nearly horizontal angle. The final hole position is close to the horizontal center plane of the coal body and the coal seam roof. The holes in the two drifts are arranged at intervals. Step 3: Lay pipes inside the coal body, using 4-point plastic pipe threaded joints. Two parallel pipes are laid out, one throughout the borehole and the other within 10 meters of the borehole. Multiple jet holes are opened on the pipe bodies at the ends of both pipes. Step 4: Place polyurethane quick-sealing bags at the position 0.3-0.6m and 8-12m from the hole mouth, respectively, to fill the gap between the pipeline and the drilled hole, dividing the entire grouting hole into two sections: shallow and deep. Step 5: Use a two-component pressure-adjustable hydraulic grouting pump to connect the shallow grouting pipe, and use two-component rapid-setting grouting material to grout the shallow part of the coal body; Step 6: Increase the pressure of the grouting pump, connect the deep grouting pipeline, and use single-component ultra-fine particle grouting material to fill and reinforce the deep cracks in the coal body.

2. A coal mine late mining face spalling pretreatment process according to claim 1, characterized in that: In the step three, the pipes are laid by splicing 2-3 meters of 4-point plastic pipes with threaded connections.

3. A coal mine late mining face spalling pretreatment process according to claim 2, characterized in that: In the step 4, the polyurethane quick-sealing bag is controlled to foam and solidify within 10 minutes, condense and fill the gap between the pipeline and the drilled hole, thereby sealing the hole and fixing the pipe.

4. A coal mine late mining face spalling pretreatment process according to claim 3, characterized in that: In the step 4, the shallow part of the grouting hole is less than 10 meters, and the deep part of the grouting hole is greater than 10 meters, thereby dividing the grouting pipeline into two trips.

5. A coal mine late mining face spalling pretreatment process according to claim 4, characterized in that: In the step 5, the two-component rapid-setting grouting material is composed of powdered material A and material B, wherein material A is composed of a homogeneous mixture of 92%-96% of sulfoaluminate cement and high-alumina cement, 2%-5% of a composite retarder of boric acid and tartaric acid, and 3%-6% of a naphthalene-based water reducer; and material B is composed of a mixture of 68%-85% of gypsum, 10%-25% of a pH regulator, and 2%-7% of a composite metal salt early strength agent. Water is added to the two materials separately, stirred, and mixed in a grouting mixer.

6. A coal mine late mining face spalling pretreatment process according to claim 5, characterized in that: In the step 5, the grouting pressure is 5-10 MPa, the pressure is gradually increased during the grouting process, the final pressure is 10 MPa, and the pressure holding time is 10-15 minutes.

7. A coal mine late mining face spalling pretreatment process according to claim 6, characterized in that: In step six, the single-component ultrafine particle grouting material is an ultrafine homogeneous inorganic powder, which is composed of 88-92% ultrafine cement with a mesh size of >1200, 3-7% pre-dispersed silica fume, 5-9% finely ground fly ash with a mesh size of >1000, 0.5-0.8% epoxy-modified high-efficiency carboxylic acid water reducer, and 0.05-0.1% defoaming agent, with a water-cement ratio of 0.5-0.

8.

8. A coal mine late mining face spalling pretreatment process according to claim 7, characterized in that: In step six, the grouting pressure is 10-15 MPa, the final pressure is 15 MPa, and the pressure holding time is 30-40 min.

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