Slurry for grouting in underground spaces of mines and method for its preparation

Abstract

The present application provides a kind of slurry for mine underground space grouting and its preparation method.The slurry is composed of grouting solid material, water and water reducing agent, the water-cement ratio of slurry is 0.5~1.2, and the dosage of water reducing agent is 0.1%~3.0% of the total mass of grouting solid material in terms of its solid phase mass;The grouting solid material includes coal gangue particles, and the particle size distribution of coal gangue particles is as follows:the mass proportion of particles with particle size d≥0.35 mm is 1%~10%, the mass proportion of particles with 0.35 mm>d≥0.20 mm is 40%~70%, the mass proportion of particles with 0.20 mm>d≥0.074 mm is 20%~50%, and the mass proportion of particles with d<0.074 mm is 1%~10%.The slurry of the present application effectively ensures the liquidity and diffusion radius of grouting slurry, significantly reduces water consumption, significantly increases the particle size of solid particles in slurry, significantly reduces the bleeding rate of slurry, reduces the energy consumption of slurry preparation, and enhances the coagulation strength and stability of slurry.

Description

Technical Field

[0001] This invention relates to the field of underground space grouting technology in mines, and in particular to a grout for underground space grouting in mines and its preparation method. Background Technology

[0002] Mine underground space grouting involves injecting slurry made from bulk solid waste such as fly ash and coal gangue into underground spaces. This process mitigates ground subsidence, increases foundation bearing capacity, and controls mine water inflow, while simultaneously enabling large-scale solid waste disposal. It holds significant practical importance for coal mining and environmental protection. Mine underground space grouting includes techniques such as primary fissure grouting, overburden isolation grouting, and goaf grouting and filling.

[0003] Currently, studies have been conducted on the preparation and performance testing of fly ash-based, coal gangue-based, and cement-based grouting materials. The results show that: (1) Fly ash-based grout has a water-to-solid ratio of 1.0-1.5 and a density of 1.3-1.4 g / cm³. 3 1. The funnel viscosity is good when it is 20-30 s, and it is suitable for spatial grouting such as primary fissures and overburden delamination; (2) Coal gangue-based grout has a solid particle size of less than 100 mesh (30-40 mesh for grouting in caving zones), a water-to-solid ratio of 1.3-2.1, and a density of 1.2-1.3 g / cm³. 3 At that time, the viscosity of the funnel was 16-20s, the final setting time was 25 days, and the performance was good. It is suitable for filling and grouting in areas such as overburden delamination, caving zone and goaf; (3) Cement-based materials are mostly used for sealing cracks in the top and bottom plates of coal seams. Depending on the degree of crack development and water flow conditions, pure cement slurry, cement-fly ash slurry, cement-water glass slurry or clay-cement slurry can be selected.

[0004] Overburden isolation grouting and filling technology is a green mining method for achieving reduced coal mining losses and solid waste emission reduction. This technology is based on the inhibitory effect of the cumulative expansion of overburden caused by mining on delamination. Before the critical layer breaks, high-pressure grouting and filling is carried out below the selected critical layer through surface drilling, generating a "pressurization and support" effect to form a compacted bearing structure that effectively supports the critical layer. Grout fluidity is a crucial factor affecting the efficiency, effectiveness, and safety of grouting and filling. The fluidity of the filling grout is affected by the water used in its preparation. If the water-cement ratio is too high, most of the water in the grout will seep out under formation pressure, easily leading to low filling efficiency, limited application in water-scarce mining areas in western China, and safety issues in fault zones and other structural areas.

[0005] Existing research has explored the mechanism and improvement methods of water-reducing agents on fly ash and coal gangue slurries in the field of overburden isolation grouting. By observing the microstructure of the slurries before and after modification, it was found that the filling slurries contain a large number of flocculated structures with significant volume. These structures bind 10%-30% of free water, reducing the slurry's fluidity. Adding water-reducing agents can break down these flocculated structures and increase the proportion of free water. Adding 1.2% polycarboxylate superplasticizer increased the fluidity of fly ash slurry by 90%, reduced viscosity by 54%, and achieved a water reduction rate of 25%; the fluidity of gangue powder slurry increased by 120%, and the water reduction rate was 35%; the water reduction rate of gangue powder-fly ash composite slurry was 53%. Simultaneously, the compaction bleeding rates of fly ash slurry, gangue powder slurry, and composite slurry decreased by 50%, 60%, and 76%, respectively. However, adding water-reducing agents does not change the water-solidification rate of the slurry. Under the action of formation pressure, the water-solidification rate of fly ash slurry is 50.7%, and that of gangue slurry is 15%.

[0006] Furthermore, particle size has a significant impact on the diffusion performance of grout. Studies have shown that grout with a particle size of 0.335 mm exhibits slurry limiting diffusion under grouting pressures of 50-100 kPa, and the slurry limiting diffusion radius increases with increasing grouting pressure; the particle size of the grout material is negatively correlated with the slurry diffusion radius. The particle size range for maintaining the gangue powder particles in a suspended state is 0.27-0.33 mm (corresponding to 45-55 mesh); exceeding this range makes it difficult to form a stable suspension grout. When considering the injectability of granular media, the particle size of the soil and the particle size of the grout are mainly used as the judgment indicators; however, the judgment of the injectability of fractured media requires consideration of both the particle size of the grout material and the fracture aperture, and the coarsest particle size of the solid phase particles in the grout used should not exceed 1 / 3 of the fracture aperture.

[0007] However, existing grouting slurries still have the following shortcomings.

[0008] To ensure the fluidity of the grout, existing technologies typically employ a high water-cement ratio, which results in: (1) a large water requirement during grout preparation, high dewatering after compaction and bleeding, and low filling efficiency; (2) limited application in water-scarce mining areas in western my country; and (3) the compaction and bleeding of the grout will flow to the working face when special geological structures such as faults exist, affecting safe coal mine production.

[0009] To ensure the fluidity and effective diffusion radius of the grout, the solid phase particle size of the existing grout is relatively fine, generally below 80 mesh (less than 0.2 mm), which leads to: (1) high energy consumption for powdering. Under conventional industrial conditions, crushing to 0.35 mm reduces energy consumption by about 40% (±5%) compared to crushing to 0.20 mm; (2) the solid particles are too fine and easily migrate with groundwater, making it difficult to stay in the target space, resulting in poor grouting, water plugging, or filling effects; (3) weak interparticle bonding, low strength and high porosity after setting, making it impossible to form a stable isolation layer, which is prone to deformation or permeation in the long term; (4) slow settling and separation, high grout bleeding rate after grouting, which easily leads to stratification and segregation, affecting the uniformity of the grout body.

[0010] In view of this, the present invention is proposed. Summary of the Invention

[0011] The purpose of this invention is to provide a grout for underground space grouting in mines and its preparation method, thereby solving at least one of the problems mentioned in the background art.

[0012] In a first aspect, the present invention provides a grout for grouting underground spaces in mines, comprising a grouting solid, water, and a water-reducing agent, wherein the water-cement ratio of the grout is 0.5 to 1.2, and the amount of the water-reducing agent is 0.1% to 3.0% of the total mass of the grouting solid based on its solid phase mass; the grouting solid includes coal gangue particles, and the particle size distribution of the coal gangue particles is as follows: Particles with a diameter d ≥ 0.35 mm account for 1% to 10% of the total mass. Particles with a diameter of 0.35 mm and a depth of d ≥ 0.20 mm account for 40% to 70% of the total mass. Particles with a diameter of 0.20 mm and a depth of d ≥ 0.074 mm account for 20% to 50% of the total mass. Particles with d < 0.074 mm account for 1% to 10% of the total mass.

[0013] A second aspect of the present invention provides a method for preparing the above-mentioned slurry, comprising the following steps: The coal gangue is crushed to obtain coal gangue particles with a particle size of no more than 0.35 mm. The coal gangue particles are mixed with water and a water-reducing agent and stirred evenly to obtain the grouting slurry.

[0014] The present invention has at least the following beneficial effects: This invention relates to a grout for underground space grouting in mines and its preparation method. The method involves multi-stage crushing and grinding of solid waste such as coal gangue to small particles of 0.35 mm or less. A certain amount of high-efficiency water-reducing agent is added to significantly reduce the water-ash ratio. Water, the water-reducing agent, and a mixture of small coal gangue particles or fly ash and small coal gangue particles are mixed together by stirring to form the grout. This invention effectively ensures the fluidity and diffusion radius of the grout while significantly reducing water consumption, significantly increasing the particle size of solid particles in the grout, significantly reducing the bleeding rate of the grout, reducing grout preparation energy consumption, and enhancing the grout's setting strength and stability. This makes it suitable for mines with insufficient water supply. Simultaneously, it enhances the grout's setting strength and stability, rapidly forming effective support for the strata, preventing the upward development of water-conducting fracture zones, protecting the integrity of overlying strata and aquifers, and enhancing surface subsidence reduction. Attached Figure Description

[0015] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0016] Figure 1 This is a flowchart of a method for preparing grout for underground space grouting in mines, as described in this invention. Figure 2 This is a schematic diagram of the coal gangue slurry preparation system in an embodiment of the present invention; Figure 3 A schematic diagram of the coal gangue-fly ash mixed slurry preparation system in an embodiment of the present invention; Explanation of reference numerals in the attached figures: 1-Coal gangue stockpile; 2-Coal gangue hopper; 3-Iron separator; 4-Feeder and belt conveyor; 5-Jaw crusher; 6-High-strength compound crusher; 7-Iron separator; 8-Ball mill / vertical mill; 9-Drum screen; 10-Coal gangue bin; 11-Coal gangue weighing hopper; 12-Water storage tank; 13-Water scale; 14-Liquid water-reducing agent storage tank; 15-Water scale; 16-Mixing tank; 17-Grouting pipe; 18-Grouting pump; 19-Grouting pipe valve; 20-Orifice pressure gauge; 21-Flange; 22-Grouting hole; 23-Fly ash bin; 24-Fly ash weighing hopper. Detailed Implementation

[0017] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0018] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form includes the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0019] It should be noted that if the text uses terms such as "first" or "second", these terms are only used to distinguish similar objects and should not be interpreted as indicating or implying their relative importance, order of precedence, or implicitly indicating the number of technical features indicated. It should be understood that the data in the descriptions of "first" and "second" can be interchanged where appropriate.

[0020] Throughout the accompanying drawings, identical elements are represented by the same or similar reference numerals. Conventional structures or configurations may be omitted where they might cause confusion in understanding the invention. Furthermore, the shapes, dimensions, and positional relationships of the components in the drawings do not reflect actual size, scale, or actual positional relationships. Additionally, any reference symbols placed within parentheses in this invention should not be construed as limiting the scope of the invention.

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] One aspect of the present invention provides a grout for grouting underground spaces in mines, comprising a grouting solid, water, and a water-reducing agent. The water-cement ratio of the grout is 0.5 to 1.2, and the amount of water-reducing agent is 0.1% to 3.0% of the total mass of the grouting solid, based on its solid phase mass. The grouting solid includes coal gangue particles, and the particle size distribution of the coal gangue particles is as follows: The mass percentage of particles with a diameter d ≥ 0.35 mm is 1% to 10%, for example, 3%, 7%, 9%, etc. The mass percentage of particles with a diameter of 0.35 mm and a diameter of d ≥ 0.20 mm is 40% to 70%, for example, 43%, 47%, 55%, 62%, 69%, etc. The mass percentage of particles with a diameter of 0.20 mm and a diameter of d ≥ 0.074 mm is 20% to 50%, for example, 23%, 27%, 33%, 40%, 45%, etc. Particles with d < 0.074 mm account for 1% to 10% of the total mass, for example, 3%, 6%, 9%, etc.

[0023] 0.35 mm is equivalent to 45 mesh, 0.20 mm is equivalent to 75 mesh, and 0.074 mm is equivalent to 200 mesh.

[0024] This invention is based on existing underground grouting and filling technology for mines, and solves problems such as large water demand for grout preparation, low filling efficiency, limited application in some areas, impact on mine safety, easy loss of solid particles, insufficient grout setting strength, and poor grout stability. It also solves many problems such as poor grouting sedimentation reduction effect, grout running, leakage, and overflow.

[0025] Existing grouting slurries are made by mixing materials such as fly ash, gangue powder, or a mixture of the two with water. They generally adopt a high water-cement ratio of 1 or higher and fine particles of less than 80 mesh to effectively ensure the fluidity of the slurry, thereby ensuring the long-distance pipeline transportation of the slurry and the filling of underground spaces with the grouting slurry.

[0026] The slurry of this invention, through the synergistic effect of continuous coarse particle gradation (below 0.35mm, with 0.20~0.35mm coarse particles accounting for 40~70%) and polycarboxylate superplasticizer, reduces the water-cement ratio to 0.5~1.2. The mechanism is as follows: coarse particles form a skeleton, medium and fine particles fill the voids, achieving dense packing; the superplasticizer breaks the flocculation structure, releasing bound water, maintaining excellent fluidity even with low water consumption. Ultimately, this significantly reduces water consumption and bleeding rate (suitable for water-scarce mining areas and fault safety grouting), reduces powdering energy consumption by approximately 40%, increases particle retention rate, and results in low porosity and high strength in the aggregate, comprehensively solving the problems of high water consumption, high energy consumption, easy loss, and poor strength in traditional slurries.

[0027] In some embodiments, the particle size distribution of the coal gangue particles is as follows: Particles with a diameter d ≥ 0.35 mm account for 3% to 7% of the total mass. Particles with a diameter of 0.35 mm and a depth of d ≥ 0.20 mm account for 55% to 65% of the total mass. Particles with a diameter of 0.20 mm and a depth of d ≥ 0.074 mm account for 25% to 40% of the total mass. Particles with d < 0.074 mm account for 3% to 8% of the total mass.

[0028] In some embodiments, the mass percentages of grouting solids, water, and water-reducing agent in the grout are 50%–70%, for example, 55%, 60%, 64%, 69%, etc.; 30%–50%, for example, 34%, 38%, 45%, 48%, etc.; and 1%–10%, for example, 2%, 5%, 8%, etc. In this composition, the grouting solids account for 50%–70%, ensuring that the grout has sufficient solid content to form a dense filling body; water accounts for 30%–50%, which, combined with the water-reducing agent, maintains good fluidity with low water consumption; and the water-reducing agent accounts for 1%–10%, which is sufficient to play a dispersing and deflocculating role. The grout with this composition has moderate viscosity, low bleeding rate, high strength of the aggregate, and controllable material costs, taking into account both grouting performance and filling quality.

[0029] In some preferred embodiments, particles with a diameter ≥ 0.35 mm account for 5%, particles with a diameter between 0.20 mm and 0.35 mm account for 60%, particles with a diameter between 0.074 mm and 0.20 mm account for 30%, and particles with a diameter < 0.074 mm account for 5%.

[0030] The two preferred schemes described above further optimized the gradation ratio of coarse, medium, and fine particles, resulting in a denser skeleton-filler structure and a significant reduction in porosity. The optimal ratio (5%:60%:30%:5%) maximizes the solid-phase bulk density while ensuring grout fluidity, thereby achieving the highest stone strength and lowest bleeding rate with the lowest water consumption and water-reducing agent dosage. Simultaneously, this gradation further reduces pulverization energy consumption, enhances particle retention in fissures, and improves grouting and filling effects.

[0031] In some embodiments, the water-reducing agent is a polycarboxylate superplasticizer. Compared to traditional naphthalene-based or lignin-based superplasticizers, polycarboxylate superplasticizers have stronger steric hindrance and electrostatic repulsion effects. They can efficiently break down the flocculated structure of slurry with extremely low dosage, releasing bound free water, significantly improving slurry fluidity and reducing the water-cement ratio. Simultaneously, they have minimal impact on slurry setting time, resulting in good strength development of the aggregate.

[0032] In some embodiments, the polycarboxylate superplasticizer is a liquid agent with a solids content of 10% to 50%, such as 13%, 17%, 22%, 28%, 35%, 42%, 48%, etc., preferably 15% to 30%. The dosage is 1% to 2% of the total mass of the pulp solids based on its solid phase mass, such as 1.3%, 1.5%, 1.8%, etc. Using a liquid agent facilitates accurate measurement and uniform dispersion, and a solids content of 15% to 50% can balance storage stability and transportation costs. A dosage of 1% to 2% can ensure stable water-reducing effect and avoid segregation or retardation caused by over-doping.

[0033] In some preferred embodiments, the polycarboxylate superplasticizer has a solids content of 20% and is added at a dosage of 1.2% of the total mass of the pulp solids, achieving the best cost-effectiveness in engineering practice.

[0034] In order to significantly reduce the bleeding rate of the slurry, decrease the porosity of the filling body, and increase the strength of the stone body, in some embodiments, the water-cement ratio is 0.5~1.0, preferably 0.7, to achieve the best balance between fluidity and strength, and is suitable for water-scarce mining areas in the west.

[0035] In some embodiments, the slurry solids also include fly ash, with a mass ratio of coal gangue to fly ash of 0.3 to 3, for example, 0.4, 0.8, 1.2, 1.6, 2.2, 2.7, etc., preferably 0.5 to 2, and most preferably 1. The micro-aggregate effect of fly ash can further fill the tiny voids between particles, and its pozzolanic activity can undergo secondary hydration with the active components in coal gangue. A mass ratio of 0.3 to 3 of coal gangue to fly ash improves the workability of the slurry, reduces the bleeding rate, and significantly enhances the later-stage strength of the aggregate; it also enables the synergistic treatment of two bulk solid wastes, reducing material costs. The optimal ratio of 1:1 yields the best overall performance.

[0036] Another aspect of the present invention provides a method for preparing the above-mentioned grout for underground space grouting in mines, comprising the following steps: The coal gangue is crushed to obtain coal gangue particles with a particle size of no more than 0.35 mm. Coal gangue particles are mixed with water and water-reducing agent, and stirred evenly to prepare grouting slurry.

[0037] The preparation method of the present invention uses multi-stage crushing and grinding to process coal gangue into fine particles no larger than or smaller than 0.35 mm. By adding a certain amount of high-efficiency water-reducing agent, the water-ash ratio is significantly reduced. By stirring, water, water-reducing agent, and a mixture of fine coal gangue particles or fly ash and fine coal gangue particles are mixed together to form a grouting slurry. While effectively ensuring the fluidity and diffusion radius of the grouting slurry, it significantly reduces water consumption, significantly increases the particle size of solid particles in the slurry, significantly reduces slurry bleeding rate, reduces slurry preparation energy consumption, and enhances the slurry's setting strength and stability to adapt to mines with insufficient water supply. At the same time, it enhances the setting strength and stability of the slurry, quickly forms effective support for the strata, prevents the upward development of water-conducting fracture zones, protects the integrity of overburden and aquifers, and enhances the surface subsidence reduction effect.

[0038] In some embodiments, the coal gangue is crushed, specifically including: Iron removal treatment is performed on coal gangue to remove iron pieces mixed in with the coal gangue; The iron-removed coal gangue is then subjected to coarse and fine crushing in sequence to obtain finely crushed material; Grind the finely crushed materials; The ground material is sieved, and the material that passes through the sieve is returned to the grinding step, while the material that passes through the sieve is coal gangue particles.

[0039] This process, through a closed-loop design of "multi-stage crushing + grinding + screening," can precisely control the particle size distribution of coal gangue, meeting the specific gradation requirements of this invention (maximum particle size ≤ 0.35mm). The iron removal step effectively removes metallic impurities, protecting subsequent crushing and grinding equipment and extending its service life. Circulating grinding avoids over-grinding, reducing energy consumption by approximately 40% while ensuring product fineness.

[0040] In some embodiments, coarse crushing is performed to a particle size of 20-90 mm, preferably ≤50 mm; fine crushing is performed to a particle size of 3-5 mm, preferably ≤4 mm. The two-stage crushing reduces the particle size of the material entering the mill from 250 mm to below 5 mm, thereby improving grinding efficiency and significantly reducing the power consumption per unit product.

[0041] In some embodiments, a jaw crusher is used for primary crushing. Jaw crushers have strong impact resistance and are suitable for the primary crushing of large coal gangue, providing a stable feed for subsequent processes.

[0042] In some embodiments, fine crushing employs impact crushers, cone crushers, or high-intensity compound crushers, with high-intensity compound crushers being preferred. Impact crushers or cone crushers produce finer output particles and a higher proportion of fine particles, significantly reducing the subsequent grinding load and resulting in lower overall energy consumption for powder production. High-intensity compound crushers primarily utilize centrifugal impact crushing, resulting in a large crushing ratio and fine output particle size (≤4mm), which can significantly reduce the load on grinding equipment.

[0043] In some embodiments, the finely crushed material undergoes secondary iron removal before grinding. Adding secondary iron removal before grinding further removes iron blocks missed in the primary iron removal process, as well as trace amounts of iron-containing particles newly exposed or generated during the crushing process. This effectively protects the liners and grinding media of the ball mill or vertical mill, reducing equipment wear and maintenance costs. Simultaneously, reducing the mixing of iron impurities into the final coal gangue particles helps improve the purity and stability of the slurry, preventing iron ions from adversely affecting the slurry's hydration properties and the grouting pipeline.

[0044] In some embodiments, grinding is performed using a ball mill or a vertical mill; screening is performed using a drum screen with a screen aperture size of 0.35 mm. Ball mills or vertical mills offer high grinding efficiency, capable of grinding materials to below 0.35 mm, and operate reliably. The drum screen's aperture is precisely controlled at 0.35 mm, effectively separating coarse particles (≥0.35 mm) and returning them to the grinding mill for reprocessing, forming a closed-loop cycle. This combination ensures controllable maximum particle size and stable, controllable gradation of the final product, meeting the particle size distribution requirements of grouting slurries.

[0045] The technical solution of the present invention will be described in detail below through specific embodiments, but the present invention is not limited to the following embodiments.

[0046] A method for preparing grout for underground space grouting in mines can be found in [reference needed]. Figure 1 As shown, the specific steps include the following; the system used can be found in [link to system documentation]. Figure 2 and Figure 3 As shown: 1. One-time iron removal At the coal gangue stockpile 1, large impurities (such as metal and wood) are first manually removed from the coal gangue to avoid damaging the equipment. The coal gangue is then transferred to the coal gangue hopper 2 using transport equipment. The iron separator 3 is installed above the head of the feeder conveyor belt 4.

[0047] A suspended permanent magnet self-unloading iron remover is installed on the coal gangue conveyor belt. After passing through the magnetic separator, the magnetic separator uses magnetic force to adsorb magnetic materials and iron-containing particles from the coal gangue. The adsorbed iron-containing particles are separated from other minerals through different partitions or collection devices.

[0048] The RCYD(C)-12 permanent magnet self-unloading iron separator has the following technical parameters: suitable belt width ≤1200 mm, rated lifting height h ≤350 mm, material thickness ≤300 mm, magnetic field strength ≥70 mt (≈700 gs), drive power ≤4.0 kW, belt speed ≤4.5 m / s, continuous working, weight 3350 kg, and external dimensions (length × width × height × lifting height × other dimensions) 2900 × 1720 × 1550 × 1010 × 1515 mm. It can remove magnetic materials from 0.1 to 35 kg.

[0049] The RCYD(C)-12 permanent magnet self-unloading magnetic separator uses a neodymium iron boron permanent magnet core, which features high magnetic field strength, strong attraction, and resistance to demagnetization. The machine has a compact structure with few components, facilitating hoisting and management, and is economical and practical. The control unit can be interlocked with the belt conveyor, enabling both local manual control and centralized control.

[0050] 2. Coarse crushing Large coal gangue is crushed to medium size ≤250mm and then evenly fed to jaw crusher 5 by a feeder to form a crushing base material with a particle size of 20-90 mm (preferably ≤50 mm), which is suitable for the feeding requirements of subsequent secondary crushing.

[0051] The primary crushing equipment is a PEX-300×1300 jaw crusher, with the following technical parameters: feed opening size 300×1300 mm, maximum feed particle size ≤250 mm, discharge particle size 20-90 mm (adjustable), processing capacity 16-105 t / h, motor power 55-75 kW (6-pole motor), eccentric shaft speed 300 r / min, equipment weight 11-15.6 t, and overall dimensions (length×width×height) 1900×2320×1724 mm. It can be used to crush various ores and rocks with compressive strength of 147-350 MPa, such as limestone, granite, marble, and pebbles.

[0052] 3. Finely chopped Impact crushers, cone crushers, and high-strength compound crushers can be used, with high-strength compound crushers being preferred. The coal gangue with a particle size of 20-90 mm (preferably ≤50 mm) is crushed to 3-5 mm (preferably ≤4 mm) to improve particle density, reduce the proportion of coarse particles, and minimize the discharge particle size to ensure the function of subsequent coal gangue grinding and reduce energy consumption.

[0053] The fine crushing equipment is a QL1600 high-strength compound crusher, with the following technical parameters: feed particle size ≤180 mm, discharge particle size 3-5 mm (accounting for 60%-90%, adjustable), processing capacity 70-100 t / h, main shaft speed 500 r / min, motor power 132 kW, equipment weight 11-13.7 t, and overall dimensions (length × width × height) 3100 × 1900 × 2200 mm.

[0054] The core working principle of the QL1600 high-strength compound crusher is primarily centrifugal impact crushing, combined with impact and grinding effects. Material is thrown against the surrounding impact plates by the high-speed rotating impeller and crushed through collisions within the material flow. Key performance characteristics include a large crushing ratio, adjustable discharge particle size, good adaptability to material moisture (less prone to clogging), relatively simple structure, and convenient maintenance. Typical application materials include cement raw / clinker, coal gangue, iron ore, sandstone, gypsum, lump coal, various metallurgical slags, and medium-hard materials such as manufactured building sand and gravel.

[0055] 4. Secondary iron removal The iron separator 7 is installed above the head of the fine material conveyor belt. After passing through the magnetic separator, the magnetic separator uses magnetic force to adsorb iron-containing particles from the coal gangue. The adsorbed iron-containing particles are separated from other minerals through different baffles or collection devices.

[0056] 5. Grinding Coal gangue is processed into granular material of 3-5 mm by fine crushing equipment, and then evenly fed into the feed end of ball mill 8 through the feeding device. The rotation of the cylinder causes the steel balls to squeeze and grind the material, and the material to grind the cylinder liner, further refining the crushed material.

[0057] After grinding, the material moves towards the discharge end with the airflow or gravity. After being screened by the drum screen 9 at the discharge end, the coarse particles (≥0.35 mm) that do not meet the fineness requirements are intercepted and re-enter the ball mill to participate in grinding, forming "circular grinding"; the fine particles <0.35 mm (45 mesh) enter the coal gangue bin 10 for standby.

[0058] Coal gangue grouting slurry; coal gangue particle size distribution: d≥0.35mm, 1-10%, optimal is 5%; 0.35mm > d ≥ 0.20mm, 40-70%, optimal is 60%; 0.20mm > d ≥ 0.074mm, 20-50%, optimal is 30%; d < 0.074 mm, 1-10%, optimal is 5%; 0.35mm (45 mesh), 0.20mm (75 mesh), 0.074mm (200 mesh).

[0059] The grinding was performed using an MQG3245 ball mill, whose main technical parameters are: cylinder diameter of 3200 mm, length of 4500 mm, and effective volume of 32.8 m³. 3 The cylinder rotation speed is 18 r / min, the maximum ball loading capacity is 65 t, the feed particle size is ≤25 mm, the discharge particle size is 0.074-0.4 mm, the motor power is 800 kW, the processing capacity is 95-110 t / h, and the equipment weight is approximately 147 t.

[0060] ST-0825 drum screen technical parameters: screen cylinder diameter is 800 mm, length is 2500 mm, processing capacity is 60-100 t / h, motor power is 2.2 kW, screen surface size is 3000 mm in length, screen aperture size is 0.35-50 mm, maximum feed particle size is ≤50 mm, and equipment weight is approximately 500 kg.

[0061] 6. Pulping (1) Coal gangue slurry preparation The finely ground coal gangue particles are weighed from the coal gangue bin via the coal gangue weighing hopper 11 and then transferred to the mixing tank 16. The water-reducing agent in the liquid water-reducing agent storage tank 14 and the pulping water in the water storage tank 12 are weighed via the water scales 13 and 15 respectively and then injected into the mixing tank 16 and stirred evenly.

[0062] Polycarboxylate superplasticizers include solid and liquid agents, with liquid agents being preferred. The solids content of the liquid agent is 10-50%, preferably 20%. The dosage range for the superplasticizer is 0.1-3.0% of the mass of the pulping material when the solids content is 20%, preferably 1.2%.

[0063] The water-ash ratio of the coal gangue slurry is 0.5~1.2, preferably 0.7; the water-reducing agent dosage is 1.2% (solid content is 20%), and after adding the water-reducing agent, the mass percentage of coal gangue in the slurry is 58.4%, the mass percentage of water is 38.1%, and the mass percentage of water-reducing agent is 3.5%.

[0064] 1) Formula for calculating water-cement ratio W / C = m W ÷m C W / C — Water-cement ratio, dimensionless; m W —The mass of water in the slurry, in kg; m C —The mass of solid phase in the slurry, such as cement, sand, coal gangue, pulverized coal, slag, etc., in kg.

[0065] 2) Formula for water-reducing agent dosage m SP = m C ×μ m CAS = m SP ÷C m CW = m CAS ×(1-C) m CAS= m SP +m CW m SP —Mass of solid phase in liquid water-reducing agent, kg; m CAS —Mass of liquid water-reducing agent, kg; m CW —The mass of water in the liquid water-reducing agent, in kg; μ—Water-reducing agent dosage, which is the mass ratio of the water-reducing agent solid phase to the pulping material; C—solid content, dimensionless.

[0066] 4) Formula for calculating water used in pulping m W0 = m C ×W / C m W1 = m W0 -m CW m W0—Theoretical water mass for pulping, kg; m W1 —Actual mass of water used for pulping, kg; 5) Slurry proportion formula ω(C)=m C ÷ (m C +m W1 +m CAS )×100 ω(w)= m W1 ÷ (m C +m W1 +m CAS )×100 ω(CAS) = m CAS ÷ (m C +m W1 +m CAS )×100 ω(C) — mass percentage of solids in the slurry, % ω(W) — Percentage of water in the slurry by mass, % ω(CAS) — percentage of liquid reducing agent in the slurry (%).

[0067] (2) Preparation of coal gangue-fly ash mixed slurry The finely ground coal gangue particles are weighed and then transported to the mixing tank from the coal gangue bin. At the same time, the fly ash in the fly ash bin 23 is weighed and then transported to the mixing tank 16 from the fly ash weighing hopper 24. The water-reducing agent and the pulping water are weighed and then injected into the mixing tank and mixed evenly.

[0068] The water-ash ratio is 0.5-1.2, preferably 0.7. The mass ratio of coal gangue to fly ash is 0.3-3, preferably 1.

[0069] The dosage of polycarboxylate superplasticizer, when converted to a solid content of 20%, is 0.1-3.0% of the mass of the pulp solids, with a preferred dosage of 1.2%.

[0070] 1) Mass ratio of coal gangue to fly ash C / F=m CGW / m FA m C = m CGW +m FA C / F — the mass ratio of coal gangue to fly ash, dimensionless; m CGW —Mass of coal gangue, kg; m FA — Mass of fly ash, kg; 2) Percentage of coal gangue and fly ash by mass ω(C) = ω(CGW) + ω(FA) ω(CGW)= m CGW ÷ (m C +m W1 +m CAS )×100 ω(FA)= m FA ÷ (m C +m W1 +m CAS )×100 ω(CGW) — Percentage of coal gangue in the slurry by mass, % ω(FA) — Percentage of fly ash in the slurry by mass, % 7. Conveying slurry Grout is transported to grouting hole 22 via grouting pipe 17 and grouting pump 18. Under pressure, the grout is injected into the underground space, and the grout is compacted and bleeds to form a filling support. A grouting pipe valve 19 is installed on grouting pipe 17 to control the grouting switch and speed. A pressure gauge 20 and flange 21 are also installed on grouting hole 22 to monitor grouting pressure and implement hole sealing.

[0071] Using the grout from this embodiment for grouting, the grout bleeding rate (under pressure) can be 60%-70%, the porosity of the filling body is about 0.2, and the strength of the stone body can reach 2-3 MPa.

[0072] This invention relates to a grout for underground space grouting in mines and its preparation method. The method involves multi-stage crushing and grinding of solid waste such as coal gangue to small particles of 0.35 mm or less. A certain amount of high-efficiency water-reducing agent is added to significantly reduce the water-ash ratio. Water, the water-reducing agent, and a mixture of small coal gangue particles or fly ash and small coal gangue particles are mixed together by stirring to form the grout. This invention effectively ensures the fluidity and diffusion radius of the grout while significantly reducing water consumption, significantly increasing the particle size of solid particles in the grout, significantly reducing the bleeding rate of the grout, reducing grout preparation energy consumption, and enhancing the grout's setting strength and stability. This makes it suitable for mines with insufficient water supply. Simultaneously, it enhances the grout's setting strength and stability, rapidly forming effective support for the strata, preventing the upward development of water-conducting fracture zones, protecting the integrity of overlying strata and aquifers, and enhancing surface subsidence reduction.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A grout for grouting underground spaces in mines, characterized in that, The slurry is composed of a slurry solid material, water, and a water-reducing agent. The water-cement ratio of the slurry is 0.5 to 1.

2. The dosage of the water-reducing agent is 0.1% to 3.0% of the total mass of the slurry solid material, based on its solid phase mass. The slurry solid material includes coal gangue particles, and the particle size distribution of the coal gangue particles is as follows: Particles with a diameter d ≥ 0.35 mm account for 1% to 10% of the total mass. Particles with a diameter of 0.35 mm and a depth of d ≥ 0.20 mm account for 40% to 70% of the total mass. Particles with a diameter of 0.20 mm and a depth of d ≥ 0.074 mm account for 20% to 50% of the total mass. Particles with d < 0.074 mm account for 1% to 10% of the total mass.

2. The slurry according to claim 1, characterized in that, The particle size distribution of the coal gangue particles is as follows: Particles with a diameter d ≥ 0.35 mm account for 3% to 7% of the total mass. Particles with a diameter of 0.35 mm and a depth of d ≥ 0.20 mm account for 55% to 65% of the total mass. Particles with a diameter of 0.20 mm and a depth of d ≥ 0.074 mm account for 25% to 40% of the total mass. Particles with d < 0.074 mm account for 3% to 8% of the total mass.

3. The slurry according to claim 1 or 2, characterized in that, The water-reducing agent is a polycarboxylate water-reducing agent.

4. The slurry according to claim 3, characterized in that, The polycarboxylate superplasticizer is a liquid agent with a solid content of 10% to 50%, preferably 15% to 30%, and the dosage is 1% to 2% of the total mass of the pulp solids based on its solid phase mass.

5. The slurry according to any one of claims 1 to 4, characterized in that, The water-cement ratio is 0.5~1.

0.

6. The slurry according to any one of claims 1 to 5, characterized in that, The slurry solids also include fly ash, and the mass ratio of coal gangue to fly ash is 0.3~3, preferably 0.5~2.

7. A method for preparing a grout for underground space grouting in a mine, as described in any one of claims 1 to 6, characterized in that, Includes the following steps: The coal gangue is crushed to obtain coal gangue particles with a particle size of no more than 0.35 mm. The coal gangue particles are mixed with water and a water-reducing agent and stirred evenly to obtain the grouting slurry.

8. The preparation method according to claim 7, characterized in that, The crushing process of coal gangue specifically includes: Iron removal treatment is carried out on coal gangue; The iron-removed coal gangue is then subjected to coarse and fine crushing in sequence to obtain finely crushed material; Grind the finely crushed materials; The ground material is sieved, and the material that passes through the sieve is returned to the grinding step, while the material that passes through the sieve is the coal gangue particles.

9. The preparation method according to claim 8, characterized in that, The coarse crushing is to a particle size of 20-90 mm, preferably ≤50 mm; the fine crushing is to a particle size of 3-5 mm, preferably ≤4 mm. Preferably, the coarse crushing is performed using a jaw crusher; Preferably, the fine crushing is carried out using an impact crusher, a cone crusher, or a high-strength compound crusher, with a high-strength compound crusher being the preferred choice.

10. The preparation method according to claim 8 or 9, characterized in that, Finely crushed materials undergo secondary iron removal before grinding; Preferably, the grinding is performed using a ball mill or a vertical mill; the sieving is performed using a drum screen with a screen aperture size of 0.35 mm.

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