Coal seam outburst prevention and dust reduction water injection process

Abstract

This invention discloses a coal seam anti-outburst and dust reduction water injection process, relating to the field of safe coal mining, including the following steps: S1, Three-dimensional water injection network construction: a three-dimensional water injection method combining strike-line short-hole water injection and dip-advance strike-line long-hole water injection; S2, Water injection slurry preparation: anionic polyacrylamide is added to the water for water injection, with a mass ratio of polyacrylamide to water of 3:1000, and the mixture is stirred to form a water injection slurry; S3, Water injection construction and parameter control: after sealing the water injection boreholes, the water injection slurry is injected at a pressure of not less than 8MPa, and the water injection sequence is staggered; this coal seam anti-outburst and dust reduction water injection process, through a continuous three-dimensional water injection network combining strike and dip directions, overcomes the limitations of single-direction water injection, achieving large-scale, three-dimensional wetting of the coal seam mining area of ​​the working face, with an average increase in coal seam moisture of over 68%.

Description

Technical Field

[0001] This invention relates to coal mine safety mining technology, specifically to a coal seam anti-outburst and dust reduction water injection process. Background Technology

[0002] Fully mechanized longwall mining is a highly efficient method for mining thick coal seams in my country, but it generally suffers from prominent problems such as high coal dust generation, abnormal gas outbursts, and easy coal face (wall) spalling during the mining process. Coal seam water injection is one of the fundamental measures to solve these problems.

[0003] Traditional coal seam water injection techniques typically involve drilling shallow holes (usually 4-8m) in the coal face to inject water at medium to high pressure. This traditional method has the following significant drawbacks:

[0004] 1) The water injection wetting range is limited and the moisture distribution is uneven, which is not effective for low-permeability coal seams;

[0005] 2) Water injection operations are usually carried out during the intervals between mining operations, which affects the normal production schedule;

[0006] 3) The water injection pressure is high (usually not less than 8MPa), which poses a safety hazard of sealer failure and injury from high-pressure pipelines;

[0007] 4) In working faces where a large number of pre-drainage boreholes have been constructed, water injection is prone to flow along the existing boreholes, resulting in poor wetting effect. Summary of the Invention

[0008] The present invention aims to overcome the shortcomings of the prior art and provide a coal seam anti-outburst and dust reduction water injection process. This process can achieve large-scale, uniform and efficient wetting of the coal seam, significantly reduce dust concentration and gas emission, enhance coal body stability, and does not affect the normal mining operation of the working face.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a coal seam anti-outburst and dust reduction water injection process, comprising the following steps:

[0010] S1. Construction of three-dimensional water injection network: a three-dimensional water injection method combining strike-parallel short-hole water injection and dip-advance strike-parallel long-hole water injection is adopted;

[0011] S2. Preparation of water injection slurry: Add anionic polyacrylamide to the water for water injection. The mass ratio of polyacrylamide to water is 3:1000. Stir to form water injection slurry.

[0012] S3. Water injection construction and parameter control: After sealing the water injection borehole, inject the water injection grout at a pressure of not less than 8MPa, and the water injection sequence adopts an alternating method.

[0013] S4. Effect monitoring and judgment: Monitor the water injection effect. Stop water injection when the increase in coal seam moisture exceeds 2% or when leakage occurs and cannot be sealed.

[0014] Furthermore, in step S1, the strike-following short holes are constructed on the coal wall of the working face cut, with a hole depth of not less than 10 meters and a hole spacing of not more than 3.0 meters; the dip-advancing strike-following long holes are constructed on the coal wall of the working face return airway, with a hole depth of not less than 15 meters and a hole spacing of 1.8 meters ± 0.1 meters.

[0015] Furthermore, the orifice of the short borehole in the direction of the coal seam is 0.5-2 meters away from the top beam, and its angle ensures that the bottom of the borehole is located near the top of the coal seam; the dip angle of the long borehole in the direction of the coal seam is consistent with the dip angle of the coal seam.

[0016] Furthermore, in step S2, the stirring time is no less than 20 minutes, and compressed air is used to assist stirring.

[0017] Furthermore, in step S3, the water injection pressure is 8-10 MPa, the sealing depth is 2-4 meters, and the water injection time per hole is not less than 12 minutes.

[0018] Furthermore, in step S3, the staggered water injection method is as follows: water is injected into the strike-lined short holes with odd-numbered numbers on odd-numbered days, and water is injected into the strike-lined short holes with even-numbered numbers on even-numbered days.

[0019] Furthermore, in step S3, an expansion hose sealer is used to seal the hole.

[0020] Furthermore, it is suitable for fully mechanized longwall or fully mechanized mining faces in thick coal seams with coal and gas outbursts and low permeability.

[0021] Compared with the prior art, the coal seam anti-outburst and dust reduction water injection process provided by the present invention has the following beneficial effects:

[0022] By combining directional and dip-oriented three-dimensional water injection networks, the limitations of single-directional water injection are overcome, achieving large-scale, three-dimensional wetting of the coal seam in the working face, with an average increase in coal seam moisture of over 68%.

[0023] The added polyacrylamide significantly increases the cohesion between coal particles, improving dust suppression efficiency (reducing the average total dust concentration by more than 50%) and enhancing the integrity of the coal body, effectively preventing spalling. Simultaneously, water injection reduces the gas desorption rate and outburst intensity, improving regional outburst prevention indicators.

[0024] Optimized water injection parameters (such as pressure and sealing depth) and staggered water injection sequence reduce high pressure risk, reduce water flow between boreholes, and improve the safety of the process and its adaptability to different coal seam conditions (especially low-permeability, high-outburst coal seams).

[0025] The tendency to advance the construction of long boreholes allows for earlier construction and water injection, while water injection in short boreholes can be staggered with production shifts, minimizing the impact on the normal mining progress of the working face. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0027] Figure 1 This is a schematic diagram of borehole A provided in an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the side view structure of borehole B provided in an embodiment of the present invention;

[0029] Figure 3 This is a schematic diagram of the main view structure of borehole B provided in an embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram of the C-hole structure provided in an embodiment of the present invention.

[0031] Explanation of reference numerals in the attached figures: Detailed Implementation

[0032] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0033] As attached Figure 1 To be continued Figure 4 As shown:

[0034] Example 1:

[0035] This invention provides a coal seam dust suppression and anti-outburst water injection process, comprising the following steps:

[0036] S1. Construction of three-dimensional water injection network: a three-dimensional water injection method combining strike-parallel short-hole water injection and dip-advance strike-parallel long-hole water injection is adopted;

[0037] S1 constructs a three-dimensional water injection network that combines strike-parallel short holes and dip-advance-parallel long holes. This design interweaves in three-dimensional space to form infiltration channels, overcoming the technical bottlenecks of limited wetting range in a single direction and uneven distribution of coal moisture, and laying the structural foundation for achieving large-scale uniform wetting.

[0038] S2. Preparation of water injection slurry: Add anionic polyacrylamide to the water for water injection. The mass ratio of polyacrylamide to water is 3:1000. Stir to form water injection slurry.

[0039] In step S2, anionic polyacrylamide is added to the water for water injection at a specific mass ratio and stirred to form a water injection slurry. After the additive dissolves in water, it can significantly change the physicochemical properties of the slurry. Its long-chain molecular structure can effectively aggregate coal particles and enhance the cohesion between them during the subsequent infiltration process.

[0040] S3. Water Injection Construction and Parameter Control: After sealing the water injection borehole, inject water injection grout at a pressure of not less than 8MPa, and adopt an alternating water injection sequence.

[0041] In step S3, the water injection construction and parameter control stage, the prepared slurry is injected into the sealed borehole at a pressure of not less than 8MPa. This pressure ensures that the slurry can overcome the resistance of coal seam fractures and possible gas pressure to effectively penetrate. At the same time, the staggered water injection method is adopted to avoid the premature interconnection of adjacent boreholes, which would lead to pressure loss and wetting blind spots, thus ensuring the overall water injection efficiency and uniformity of the three-dimensional network.

[0042] S4. Effect monitoring and judgment: Monitor the water injection effect. Stop water injection when the increase in coal seam moisture exceeds 2% or when leakage occurs and cannot be sealed.

[0043] The effect monitoring and judgment of step S4 involves real-time observation of whether there is slurry leakage on site. This serves as a scientific basis for dynamic feedback control of the water injection process. When the moisture increase is greater than 2%, it indicates that the expected basic wetting and strengthening effect has been achieved. Or, when there is slurry leakage that cannot be sealed, it indicates that the local area may be saturated or there is a major seepage channel. At this time, stopping water injection can optimize resource allocation and prevent ineffective loss of slurry. The entire process, through the organic connection and synergy of the above four steps, systematically improves the wettability, stability and compactness of the coal body, thereby simultaneously achieving the comprehensive prevention and control goals of inhibiting gas desorption and outburst, significantly reducing dust generation and enhancing the integrity of the coal wall.

[0044] In step S1, the strike-following short boreholes are constructed on the coal wall of the working face cut, with a depth of not less than 10 meters and a spacing of not more than 3.0 meters; the dip-advance-following long boreholes are constructed on the coal wall of the working face return airway, with a depth of not less than 15 meters and a spacing of 1.8 meters ± 0.1 meters.

[0045] By precisely quantifying the key geometric parameters of strike-parallel short boreholes and dip-advance long boreholes, the three-dimensional water injection network is ensured to efficiently and economically cover the target coal body. The strike-parallel short boreholes, constructed on the coal face cut-in wall with a depth of no less than 10 meters and a spacing of no more than 3.0 meters, ensure sufficient forward wetting depth and reasonable borehole density along the working face advance direction, allowing for pre-treatment of the coal body within a sufficient distance in front of the coal face. Simultaneously, the close borehole spacing avoids wetting blind spots. The dip-advance long boreholes, constructed on the coal face of the return airway with a depth of no less than 15 meters and a spacing of 1.8 meters ± 0.1 meters, utilize the space of the return airway. Deep water injection is carried out in the working face along the dip direction of the coal seam. The long hole depth allows the wetting effect to effectively extend into the deep coal body, complementing the depth of the short holes in the strike direction. The precisely controlled hole spacing is based on the investigation of the effective radius of influence of water injection in the coal seam, aiming to ensure that the wetting areas of adjacent boreholes in the dip direction can effectively overlap to form a continuous and uniform wetting strip. The two sets of parameterized borehole groups, the short holes in the strike direction and the long holes in the dip direction, are orthogonally or obliquely coupled in space, together forming a parameter-optimized, comprehensive water injection network skeleton that can realize three-dimensional and efficient wetting of the coal seam. This is the basic structural guarantee for realizing efficient water injection technology.

[0046] The orifice of the short boreholes along the coal seam is 0.5-2 meters from the top beam, and its angle ensures that the bottom of the borehole is near the top of the coal seam; the dip angle of the long boreholes along the coal seam is consistent with the dip angle of the coal seam.

[0047] By controlling the opening position and angle of the borehole, the migration path and final distribution area of ​​the injection grout in the coal seam are precisely guided. The borehole opening of the short borehole along the bedding is 0.5-2 meters away from the roof beam, and the borehole bottom is ensured to be near the coal seam roof by adjusting the borehole angle. This design guides the main seepage and diffusion process of the injection grout to the middle and upper part of the coal seam to the roof area after injection. This area is usually a key area prone to spalling and concentrated gas outbursts under the influence of mining. Targeted wetting can significantly enhance the cohesion and overall stability of the coal body in this area. The dip angle of the long borehole along the bedding is required to be consistent with the dip angle of the coal seam. The consistent working principle is to ensure that the extension trajectory of the borehole strictly conforms to the natural occurrence of the coal seam. In this way, when the slurry flows along the borehole axis and seeps radially, it can extend more smoothly along the path of least resistance, such as the primary weak surfaces of the coal seam, such as bedding and fractures. This reduces ineffective fracturing of the intact coal body, improves the slurry transport efficiency and the ability to be evenly distributed in the coal seam, thereby achieving effective wetting along the true thickness of the coal seam. The synergistic constraint of these two directional parameters ensures that the borehole trajectory and the target area of ​​the slurry in the entire three-dimensional water injection network are highly matched with the geological conditions of the coal seam and the key points of engineering protection, thus improving the pertinence and effectiveness of the process.

[0048] In step S2, the stirring time shall be no less than 20 minutes, and compressed air shall be used to assist in stirring.

[0049] Sufficient mechanical stirring and sufficient time are essential to completely break down the agglomeration forces between polyacrylamide particles, ensuring their full dissolution and uniform dispersion in the water. This prevents the formation of undissolved, fish-eye-like clumps, which not only clog pumps and pipelines but also prevent them from effectively thickening, flocculating, and binding coal particles during water injection. Introducing compressed air-assisted stirring generates strong turbulence and circulating convection by injecting compressed air into the bottom of the liquid. This dynamic stirring method is more effective than simple mechanical stirring in lifting lightweight particles and promoting uniform mixing throughout the tank, especially preventing particle deposition in corners or at the bottom. This ensures the prepared water injection slurry has a uniform concentration and stable performance. Only through such thorough and efficient stirring can a polyacrylamide solution with uniform properties and fully expanded active molecules be prepared. This allows for effective bridging and adsorption of coal and rock particles through its long polymer chains after subsequent high-pressure injection into the coal seam, significantly increasing the cohesion between coal particles. This is a crucial material science prerequisite for achieving dust suppression and anti-scraping functions.

[0050] In step S3, the water injection pressure is 8-10 MPa, the sealing depth is 2-4 meters, and the water injection time for a single hole is not less than 12 minutes.

[0051] The water injection pressure is set at 8-10 MPa to overcome capillary resistance and drive the slurry into the tiny fractures and pores of the coal seam. This pressure is controlled within a reasonable upper limit, effectively fracturing and connecting some of the original fractures to expand the wetting range, while avoiding excessive pressure that could lead to overall instability of the coal wall or the creation of new through fractures causing slurry short-circuiting and loss. The sealing depth is required to be 2 to 4 meters. Its working principle is to ensure that the sealing section can pass through the pressure-relief fracture zone around the roadway, anchoring the water injection point in a relatively intact original rock stress zone. This establishes an effective pressure-bearing seal at the borehole opening, preventing premature leakage of high-pressure slurry along the fractured borehole wall and ensuring that the water injection pressure can fully act on the coal seam to be wetted. The requirement of a single-hole water injection time of no less than 12 minutes is based on experimental investigations of the slurry's seepage velocity and diffusion radius under specific coal seam conditions. This ensures sufficient time for the designed slurry volume to fully penetrate the coal seam under pressure, allowing the polyacrylamide solution to undergo sufficient physicochemical interaction with the coal particles, achieving a stable and deep wetting effect.

[0052] In step S3, the staggered water injection method is as follows: on odd-numbered days, water is injected into the strike-lined short holes with odd-numbered numbers, and on even-numbered days, water is injected into the strike-lined short holes with even-numbered numbers.

[0053] The alternating water injection mechanism, based on the odd-even date system, effectively isolates the water injection activities of adjacent or spatially close boreholes. This creates sufficient time windows for pressure build-up, slurry penetration, and moisture solidification for each injection operation. It avoids the superposition and competition of water injection pressure fields caused by simultaneous or continuous high-pressure water injection in adjacent boreholes, or the premature formation of hydraulic communication channels. This prevents the slurry from flowing into neighboring borehole areas or leaking directly through already penetrated fractures before fully wetting the target coal body of the borehole. This method ensures that each borehole can operate under its own optimal hydraulic conditions, promoting a more uniform radial diffusion of the slurry from the borehole center. Ultimately, it ensures that the water injection sub-network composed of all strike-and-bedding short holes can form a coherent, uniform, and weak-spot-free coal seam wetting zone, greatly improving the overall reliability and stability of the strike-and-bedding water injection system.

[0054] In step S3, an expansion hose sealer is used to seal the hole.

[0055] The expandable hose sealing device consists of an expandable hose made of high-strength rubber or composite materials, an internal core tube, and connecting components. When high-pressure injection slurry enters the sealing device through the core tube, hydraulic pressure acts on the inner wall of the hose, forcing the flexible hose to expand elastically in the radial direction, thereby tightly squeezing the borehole wall. As the pressure increases, the hose continues to expand and deform until it achieves a mechanical seal that fully conforms to the irregular borehole wall. This sealing method has the characteristic of adapting to the borehole shape, effectively sealing borehole wall cracks, and the sealing effect increases with the increase of injection pressure, showing a positive correlation with the injection process. This establishes a reliable pressure barrier in the sealing section of the borehole, ensuring that the high-pressure slurry is guided to the predetermined coal body area deep within the borehole for penetration, rather than leaking from near the borehole opening. The use of expandable hose sealing devices is one of the key technical guarantees for the safety and efficiency of high-pressure water injection processes.

[0056] It is suitable for fully mechanized longwall or fully mechanized mining faces in thick coal seams with coal and gas outbursts and low permeability.

[0057] This process, through synergistic optimization of various technical characteristics, can specifically address the core challenges of coal and gas outbursts and low-permeability thick coal seams in fully mechanized longwall or longwall mining. For coal and gas outburst-prone seams, this process uses a three-dimensional network to extensively wet the coal body, combined with polyacrylamide to enhance coal plasticity, effectively reducing the elastic potential of the coal and the gas desorption rate, thereby weakening the mechanical and gas conditions for outbursts. For low-permeability coal seams, an injection pressure of 8-10 MPa can partially fracture and connect the original fractures in the coal body, and combined with long-term water injection to promote the slow infiltration of slurry, thereby improving local permeability and providing... Favorable conditions are created for gas migration. For fully mechanized longwall or longwall mining faces in thick coal seams, the three-dimensional water injection method combining short strike holes and long dip holes can effectively cover the full thickness or mineable thickness of the thick coal seam. In particular, by controlling the angle of the short strike holes, the wetted area can reach near the roof, which is crucial for preventing coal wall spalling caused by top coal caving or high mining height. Therefore, the integrated features of this process, such as three-dimensional water injection, additive enhancement, parameterized control, and staggered operation, together constitute a comprehensive solution that is particularly suitable for the safe and efficient mining of complex thick coal seams with high stress, high gas content, and low permeability.

[0058] Example 2:

[0059] Taking the application of the process of this invention in the 1607 fully mechanized longwall face of a certain mine as an example.

[0060] 1. Overview of the working face: This working face mines the No. 2-1 coal seam, with an average thickness of approximately 7m. It is a low-permeability coal seam prone to gas outbursts. Traditional mining methods face problems such as high levels of coal dust, roof spalling, and abnormal gas emissions.

[0061] 2. Process Implementation:

[0062] (1) Drilling layout:

[0063] Water injection holes are arranged along the dip direction of the cut coal face. ZQS-50 type pneumatic coal drill with φ42mm drill bit is used for construction. The hole depth is 10-12m, the hole spacing is 2.5m, and the hole is opened about 1m above the top beam. The elevation angle is adjusted according to the coal seam thickness so that the bottom of the hole reaches the top plate of the coal seam.

[0064] In the 1607 return airway, water injection holes were constructed on the lower coal face, with a depth of 15m, a spacing of 1.8m, an inclination angle of approximately 12° (consistent with the coal seam inclination angle), and the hole openings were 1.2-1.5m from the bottom plate.

[0065] (2) Grout preparation: Fill the water injection pump box (volume 2500L) located in the 16061 yard with water, and evenly sprinkle in 7.5kg of anionic polyacrylamide (with a water-to-material ratio of 1000:3). Connect the compressed air pipe and blow air at the bottom of the box for more than 20 minutes to ensure uniform dissolution. During the grouting process, add about 1kg of polyacrylamide evenly every 70 seconds.

[0066] (3) Water injection construction:

[0067] Use an FKSY-20 / 38 type expansion hose sealer to seal the hole to a depth of approximately 3m. Seal the area behind the sealer with yellow mud for at least 0.3m.

[0068] Connect the grouting pipeline, gradually open the valves, stabilize the pressure at 8-10MPa, and begin grouting.

[0069] Staggered water injection is implemented: water is injected into the strike holes corresponding to odd-numbered frames on odd-numbered days, and into the strike holes corresponding to even-numbered frames on even-numbered days. The return airway dip holes serve as long-term water injection holes for continuous water injection.

[0070] When water is injected until the coal face is noticeably wet or leakage points appear, close the valve, release the pressure through the tee, and then remove the sealing device.

[0071] (4) Effect monitoring:

[0072] Coal samples were periodically taken from the water injection area to determine moisture content. Data showed that the average moisture content of the working face was 3.51% when no polyacrylamide was added; after adopting this process, the average moisture content rose to 5.93%, with a maximum of 10.8%.

[0073] Dust monitoring shows that the average dust concentration at the face cut and downwind side decreases by about 50% during coal mining.

[0074] The methane concentration in the return airflow of the working face remained stable at around 0.2%, and the absolute methane emission rate was about 2 m³ / min. The regional verification indicators (Δh2, Smax, q, etc.) did not exceed the standards, and the outburst prevention effect was significant.

[0075] 3. Summary of Results: This embodiment shows that the process of the present invention effectively solves the problems of "dust prevention, anti-outburst, and anti-scraping" of the high-protrusion working surface, improves production efficiency while ensuring safety, and has significant practical value and promotion prospects.

[0076] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A coal seam anti-outburst and dust reduction water injection process, characterized in that, Includes the following steps: S1. Construction of three-dimensional water injection network: a three-dimensional water injection method combining strike-parallel short-hole water injection and dip-advance strike-parallel long-hole water injection is adopted; S2. Preparation of water injection slurry: Add anionic polyacrylamide to the water for water injection. The mass ratio of polyacrylamide to water is 3:1000. Stir to form water injection slurry. S3. Water injection construction and parameter control: After sealing the water injection borehole, inject the water injection grout at a pressure of not less than 8MPa, and the water injection sequence adopts an alternating method. S4. Effect monitoring and judgment: Monitor the water injection effect. Stop water injection when the increase in coal seam moisture exceeds 2% or when leakage occurs and cannot be sealed.

2. The coal seam anti-outburst and dust reduction water injection process according to claim 1, characterized in that, In step S1, the strike-following short holes are constructed on the coal wall of the working face cut, with a hole depth of not less than 10 meters and a hole spacing of not more than 3.0 meters; the dip-advancing strike-following long holes are constructed on the coal wall of the working face return airway, with a hole depth of not less than 15 meters and a hole spacing of 1.8 meters ± 0.1 meters.

3. The coal seam anti-outburst and dust reduction water injection process according to claim 2, characterized in that, The orifice of the short borehole in the direction of the coal seam is 0.5-2 meters away from the top beam, and its angle ensures that the bottom of the orifice is located near the top of the coal seam; the dip angle of the long borehole in the direction of the coal seam is consistent with the dip angle of the coal seam.

4. The coal seam anti-outburst and dust reduction water injection process according to claim 1, characterized in that, In step S2, the stirring time is no less than 20 minutes, and compressed air is used to assist stirring.

5. The coal seam anti-outburst and dust reduction water injection process according to claim 1, characterized in that, In step S3, the water injection pressure is 8-10 MPa, the sealing depth is 2-4 meters, and the water injection time for a single hole is not less than 12 minutes.

6. The coal seam anti-outburst and dust reduction water injection process according to claim 1, characterized in that, In step S3, the staggered water injection method is as follows: on odd-numbered days, water is injected into the strike-lined short holes with odd-numbered numbers, and on even-numbered days, water is injected into the strike-lined short holes with even-numbered numbers.

7. The coal seam anti-outburst and dust reduction water injection process according to claim 1, characterized in that, In step S3, an expansion hose sealer is used to seal the hole.

8. The coal seam anti-outburst and dust reduction water injection process according to claim 1, characterized in that, It is suitable for fully mechanized longwall or fully mechanized mining faces in thick coal seams with coal and gas outbursts and low permeability.

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