Micro-nano quick-hardening early-strength grouting reinforcement method for soft coal rock stratum considering mining-induced fracture formation of working face

Abstract

The invention discloses a soft coal rock stratum micro-nano rapid hardening early strength grouting reinforcement method considering working face mining-induced fracture making, and relates to the technical field of soft rock coal seam reinforcement. The method comprises the steps that drill holes are formed in a primary rock stress area in front of a working face, and a stress monitoring device is installed to monitor the change condition of mining-induced stress in real time; acquiring a mining law of the fracture rate; then, grouting holes are formed in the peak position of the mining-induced stress in advance, the optimal arrangement positions of the grouting holes and the distance between every two adjacent grouting holes are arranged according to the fracture development rule, and the depths and the diameters of the grouting holes are arranged according to coal rock stratum mechanical property evaluation; a grouting sleeve and a grouting valve pipe are arranged in the grouting hole; and finally, grouting is conducted, and after grouting is completed, the grouting reinforcement effect is evaluated. The soft coal rock stratum can be rapidly and effectively reinforced under the condition that mining-induced fractures exist.

Description

Technical Field

[0001] The present invention relates to the technical field of soft rock coal seam reinforcement, and particularly relates to a micro-nano rapid-hardening and early-strength grouting reinforcement method for soft coal and rock seams considering mining-induced fractures in the working face. Background Art

[0002] During the coal mine production process, phenomena such as roadway surrounding rock fragmentation and roof cracking caused by stress concentration frequently occur, which not only affect roadway support but also threaten underground safety production. When not affected by mining, the fractures in soft coal and rock seams usually appear in a small and scattered state, making them unsuitable for traditional grouting reinforcement. Taking the 3105 working face of Huolxinhe Coal Mine and the 22205 working face of Huaning Coal Mine as examples, when grouting operations are carried out at a position 50 meters ahead, due to underdeveloped or micro-fracture-rich coal and rock mass fissures, as well as too large particle sizes of grouting materials, the permeability is poor, the slurry intake of the boreholes is relatively small, and the grouting materials cannot effectively penetrate and fill the fissures, resulting in poor grouting effects. However, when these coal and rock seams are affected by mining stress, the original micro-fractures will develop, expand and connect with each other to form a larger fracture network; this change significantly improves the connectivity and permeability of the fissures, providing favorable conditions for the injection and filling of grouting materials. In this case, the grouting effect is significantly improved, the slurry intake also increases accordingly, and the grouting materials can effectively penetrate into the fissures to enhance the stability of the coal and rock seams. In grouting operations, although the injected slurry can enhance the stability of the coal and rock mass, the mining process may still cause secondary damage to the coal and rock mass. In addition, the existing grouting materials also have drawbacks such as poor fluidity and long setting time, which affect their grouting effects.

[0003] Therefore, it can be seen that the reinforcement technology for soft rock coal seams in the prior art still needs to be further improved. Summary of the Invention

[0004] The purpose of the present invention is to provide a micro-nano rapid-hardening and early-strength grouting reinforcement method for soft coal and rock seams considering mining-induced fractures in the working face, which can rapidly and effectively reinforce soft coal and rock seams in the presence of mining fractures by improving grouting materials and grouting reinforcement methods.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A micro-nano rapid-hardening and early-strength grouting reinforcement method for soft coal and rock seams considering mining-induced fractures in the working face successively includes the following steps:

[0007] a. Arrange boreholes in the virgin stress area in front of the working face. The boreholes are connected with stress monitoring devices, and the stress monitoring devices are used to monitor the change of mining stress in real time and determine the peak position of mining stress;

[0008] b. Obtain the mining law of fissure ratio, and evaluate the stability of the rock stratum and the grouting requirement according to the fissure condition;

[0009] c. Advance and arrange grouting holes according to the peak position of the mining stress in step a. The grouting holes are located outside the influence range of the mining stress. Arrange the optimal layout position of the grouting holes and the spacing between adjacent grouting holes according to the fissure development law. Arrange the depth and diameter of the grouting holes according to the mechanical properties of the coal and rock strata to evaluate the depth and diameter of the grouting holes;

[0010] d. Arrange a grouting casing pipe and a grouting valve pipe in the grouting holes set in step c;

[0011] e. When the coal and rock mass is affected by mining and the fissures develop and penetrate, grout into the grouting holes, and the grouting pressure ≤ 20 MPa;

[0012] The grouting materials required for grouting include, by weight percentage:

[0013] 850 - 900 parts of ultrafine sulphoaluminate cement, 5 - 8 parts of water reducer, 50 - 100 parts of silica fume, 10 - 15 parts of retarder, 15 - 25 parts of gypsum, 5 - 10 parts of nano - particles;

[0014] The nano - particles mentioned above are nano - SiO₂ and nano - Al₂O₃;

[0015] f. After grouting is completed, use non - destructive testing methods to scan and detect the grouted coal and rock strata, obtain the distribution range of the grout body, measure the mechanical properties of the grout body, and evaluate the grouting reinforcement effect.

[0016] For the above - mentioned method for micro - nano rapid - hardening and early - strength grouting reinforcement of soft coal and rock strata considering mining - induced fissures in the working face, in step a, the stress monitoring device includes an optical fiber stress sensor, a stress gauge, and an optical fiber static demodulator. The optical fiber stress sensor is located inside the drill hole, and the optical fiber static demodulator is connected to the stress gauge; the front of the optical fiber stress sensor is designed to face upward.

[0017] For the above - mentioned method for micro - nano rapid - hardening and early - strength grouting reinforcement of soft coal and rock strata considering mining - induced fissures in the working face, in step b, the fissure condition includes the distribution, density, and connectivity of the fissures.

[0018] The above-mentioned method for grouting reinforcement of soft coal and rock strata with micro-nano rapid hardening and early strength considering the formation of fractures during mining in the working face. In step c, the law of fracture development refers to: real-time monitoring of the change of mining stress through optical fiber stress sensors, combining geological exploration data and the physical and mechanical parameters of coal and rock strata, and establishing a mathematical model of fracture development; predicting the development trend and distribution range of fractures through the established mathematical model; determining the optimal layout position of grouting holes and the spacing between adjacent grouting holes according to the mathematical model of fracture development to ensure that the grouting holes cover the fracture development area.

[0019] The above-mentioned method for grouting reinforcement of soft coal and rock strata with micro-nano rapid hardening and early strength considering the formation of fractures during mining in the working face. In step c, the evaluation of the mechanical properties of coal and rock strata refers to the determination of mechanical parameters, and the mechanical parameters include uniaxial compressive strength, elastic modulus, and internal friction angle. The depth and diameter of grouting holes are adjusted according to the mechanical parameters.

[0020] The above-mentioned method for grouting reinforcement of soft coal and rock strata with micro-nano rapid hardening and early strength considering the formation of fractures during mining in the working face. In step d, the grouting casing is arranged before the coal and rock mass is affected by mining, and a grouting hole sealing capsule belt is used for hole sealing.

[0021] The above-mentioned method for grouting reinforcement of soft coal and rock strata with micro-nano rapid hardening and early strength considering the formation of fractures during mining in the working face. In step e, the weight ratio of nano-SiO2 and nano-Al2O3 is 1:1.

[0022] The above-mentioned method for grouting reinforcement of soft coal and rock strata with micro-nano rapid hardening and early strength considering the formation of fractures during mining in the working face. In step f, the non-destructive testing method is ground penetrating radar or acoustic detection technology.

[0023] The above-mentioned method for grouting reinforcement of soft coal and rock strata with micro-nano rapid hardening and early strength considering the formation of fractures during mining in the working face. In step e, the water reducing agent is sodium lignosulfonate, naphthalene sulfonate, or powdered polycarboxylate.

[0024] The above-mentioned method for grouting reinforcement of soft coal and rock strata with micro-nano rapid hardening and early strength considering the formation of fractures during mining in the working face. In step e, the setting retarder is phosphate, metaphosphate, or sodium fluorosilicate.

[0025] Compared with the prior art, the present invention brings the following beneficial technical effects:

[0026] The grouting material of the present invention features rapid hardening and early strength, and can quickly and effectively reinforce soft coal and rock strata in the presence of mining-induced fractures, improving the stability and safety of roadways. At the same time, the grouting method of the present invention proposes to create fractures for grouting soft coal and rock strata. Through precise fracture monitoring, reasonable arrangement of grouting holes, flexible installation of grouting casings, selection of grouting timing based on setting time, and optimization of grouting position and fracture filling, the efficiency and effect of grouting reinforcement are improved.

[0027] In the grouting material of the present invention, nano-SiO2 and nano-Al2O3 cooperate with each other and act together. On the one hand, nano-SiO2 improves the microstructure of the cement paste, providing a better environment for the reaction of nano-Al2O3, enabling nano-Al2O3 to react more fully with components such as gypsum. On the other hand, the micro-expansion effect generated by nano-Al2O3 can offset the local stress concentration that may be caused when nano-SiO2 fills voids, making the strength development of the paste more uniform and stable. This synergistic effect enables the grouting material of the present invention to quickly and effectively penetrate and fill fractures in the presence of mining-induced fractures, forming a high-strength and high-density reinforcement body, significantly improving the stability and safety of soft coal and rock strata. Brief Description of the Drawings

[0028] The present invention will be further described below with reference to the accompanying drawings:

[0029] Figure 1 It is a schematic diagram of the connection state of the grouting device of the present invention;

[0030] In the figure: 1. Grouting pump, 2. Grouting barrel, 3. Suction port, 4. First pressure relief valve, 5. Discharge port, 6. Three-way joint, 7. Pressure gauge, 8. Second pressure relief valve, 9. Goaf side wall, 10. Hole packer, 11. Grouting pipe, 12. Grouting hole. Detailed Embodiments

[0031] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application.

[0032] It can be understood that the connection relationship described in the present application refers to direct or indirect connection. For example, when A is connected to B, it can be either that A is directly connected to B or that A and B are indirectly connected through one or more other electrical components. For example, it can be that A is directly connected to C and C is directly connected to B, so that A and B are connected through C. It can also be understood that "A is connected to B" described in the present application can be that A is directly connected to B or that A and B are indirectly connected through one or more other electrical components.

[0033] In the description of this application, unless otherwise specified, " / " means "or". For example, A / B can mean A or B. "And / or" in this text is merely a relational description of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone.

[0034] In the description of this application, words such as "first" and "second" are only used to distinguish different objects, and do not limit the quantity and execution order. Moreover, words such as "first" and "second" do not necessarily limit to being different. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion.

[0035] The technical solution of this application will be further described in detail below with reference to the accompanying drawings.

[0036] As Figure 1 shown, the grouting device of the present invention includes a grouting pump 1, a grouting barrel 2, a slurry suction port 3, a first pressure relief valve 4, a slurry outlet 5, a three-way joint 6, a pressure gauge 7, a second pressure relief valve 8, a backfill side wall 9, a hole sealer 10, and a grouting pipe 11. Among them, the grouting material prepared by the present invention is placed in the grouting barrel 2. The grouting barrel is connected to the slurry suction port 3 of the grouting pump through a pipeline. The first pressure relief valve 4 is arranged near the slurry suction port 3. The slurry outlet 5 of the grouting pump 1 is connected to the three-way joint 6 through a pipeline. The three-way joint 6 is connected to the grouting pipe 11. The grouting pipe 11 is located in the grouting hole 12, and the grouting hole 12 is sealed by the hole sealer 10.

[0037] As one of the improvement points of the present invention, by improving the formula and raw material ratio of the grouting material, the defects of poor fluidity and poor setting property of the grouting material can be improved. The required grouting material includes, by weight percentage: 850 - 900 parts of ultra-fine sulphoaluminate cement, 5 - 8 parts of water reducer, 50 - 100 parts of silica fume, 10 - 15 parts of retarder, 15 - 25 parts of gypsum, and 5 - 10 parts of nano-particles; the nano-particles are nano-SiO2 and nano-Al2O3. The weight ratio of nano-SiO2 to nano-Al2O3 is 1:1.

[0038] As a preferred scheme of the present invention, the water reducer is sodium lignosulfonate, naphthalene sulfonate or powdered polycarboxylate.

[0039] As a preferred scheme of the present invention, the retarder is phosphate, metaphosphate or sodium fluorosilicate.

[0040] According to different selected components and ratios, the formula of the grouting material of the present invention can have the following combinations:

[0041] Combination 1:

[0042] 850 parts of ultra-fine sulphoaluminate cement, 5 parts of sodium lignosulphonate, 50 parts of silica fume, 10 parts of phosphate, 15 parts of gypsum, 2.5 parts of nano-SiO₂, 2.5 parts of nano-Al₂O₃.

[0043] Combination Two:

[0044] 900 parts of ultra-fine sulphoaluminate cement, 8 parts of water reducer, 100 parts of silica fume, 15 parts of metaphosphate, 25 parts of gypsum, 5 parts of nano-SiO₂, 5 parts of nano-Al₂O₃.

[0045] Combination Three:

[0046] 880 parts of ultra-fine sulphoaluminate cement, 6 parts of water reducer, 80 parts of silica fume, 12 parts of sodium fluorosilicate, 20 parts of gypsum, 4 parts of nano-SiO₂, 4 parts of nano-Al₂O₃.

[0047] Combination Four:

[0048] 860 parts of ultra-fine sulphoaluminate cement, 7 parts of water reducer, 70 parts of silica fume, 13 parts of metaphosphate, 18 parts of gypsum, 3 parts of nano-SiO₂, 3 parts of nano-Al₂O₃.

[0049] Under the guidance of the above combinations, those skilled in the art can also obviously obtain other combination methods.

[0050] In the formula of the present invention, the role of nano-SiO₂: Nano-SiO₂ has a large specific surface area and activity, and can undergo a secondary hydration reaction with the hydration products in ultra-fine sulphoaluminate cement to generate more hydrated calcium silicate gel, thereby improving the early strength and density of the grouting material. At the same time, nano-SiO₂ can fill the voids between cement particles, improve the microstructure of the cement paste, reduce the porosity of the paste, and further enhance the strength and durability of the paste.

[0051] The role of nano-Al₂O₃: Nano-Al₂O₃ can react with gypsum to generate expansive hydration products such as ettringite. These expansive hydration products can produce micro-expansion in the grouting material, compensate for the shrinkage during the hardening process of the paste, reduce the generation of cracks, and improve the crack resistance and integrity of the paste. In addition, nano-Al₂O₃ can also accelerate the hydration reaction of cement, shorten the setting time, enable the grouting material to reach the early strength faster, and meet the special requirements for the rapid hardening of the grouting material in coal mine mining.

[0052] The above components cooperate with each other, and the prepared grouting material has good fluidity and excellent setting performance.

[0053] Applying the above grouting material to the present invention, a micro-nano rapid hardening and early strength grouting reinforcement method for soft coal and rock strata considering the mining-induced fractures in the working face, successively includes the following steps:

[0054] Step 1: Drill holes in the virgin stress area in front of the working face. The drill holes are connected with stress monitoring devices. The stress monitoring devices are used to monitor the change of mining-induced stress in real time and determine the peak position of the mining-induced stress.

[0055] Furthermore, the diameter and depth of the drill holes are fixed. The stress monitoring device includes an optical fiber stress sensor, a stress gauge and an optical fiber static demodulator. The optical fiber stress sensor is located inside the drill hole. The optical fiber static demodulator is connected with the stress gauge; the front of the optical fiber stress sensor is designed to face upwards. The optical fiber stress sensor is pushed into the bottom of the drill hole by a push rod. The change of mining-induced stress is monitored in real time by connecting the stress gauge through the optical fiber static regulator, and the peak position of the mining-induced stress is further determined.

[0056] Step 2: Obtain the mining law of the fracture rate and evaluate the stability of the rock stratum and the grouting demand according to the fracture situation; this evaluation can be completed by analyzing the distribution, density and connectivity of the fractures. The level of the fracture rate directly affects the selection of grouting materials and the layout of grouting holes.

[0057] Step 3: Arrange grouting holes in advance according to the peak position of the mining-induced stress in Step 1. The specific advance distance is determined by those skilled in the art according to the on-site situation and the characteristics of the rock stratum to ensure the grouting effect. The grouting holes are located outside the influence range of the mining-induced stress. The best layout position of the grouting holes and the spacing between adjacent grouting holes are arranged according to the fracture development law. The depth and diameter of the grouting holes are arranged according to the evaluation of the mechanical properties of the coal and rock strata.

[0058] The fracture development law means: the change of mining-induced stress is monitored in real time by the optical fiber stress sensor, and combined with geological exploration data and the physical and mechanical parameters of the coal and rock strata, a mathematical model of fracture development is established; the development trend and distribution range of fractures are predicted through the established mathematical model; the best layout position of the grouting holes and the spacing between adjacent grouting holes are determined according to the mathematical model of fracture development to ensure that the grouting holes cover the fracture development area. The layout of the grouting holes should focus on the fracture development area to achieve more effective fracture filling and reinforcement.

[0059] The evaluation of the mechanical properties of the coal and rock strata means measuring the mechanical parameters, and the mechanical parameters include uniaxial compressive strength, elastic modulus and internal friction angle. The depth and diameter of the grouting holes are adjusted according to the mechanical parameters.

[0060] Step 4: Arrange grouting sleeves and grouting valve pipes in the grouting holes set in Step 3; the diameter of the grouting sleeves should be selected according to the diameter of the boreholes and the requirements of the grouting materials. The casing should be installed before the cracks in the coal and rock mass begin to develop, that is, the casing should be installed in advance before the coal and rock mass is affected by mining. A hole sealer is used for hole sealing. The hole depth is determined according to the length of the working face. One hole is arranged on each side, and the hole depth is about half of the length of the working face.

[0061] Step 5: When the cracks in the coal and rock mass develop and penetrate after being affected by mining, grout is injected into the grouting holes. The grouting pressure ≤ 20 MPa to avoid excessive disturbance to the rock stratum. Considering the existence of cracks, the design of the grouting sleeves and valve pipes should be more flexible to adapt to the irregularity of the cracks. Grouting should be carried out after the working face has advanced a certain distance. The selection of the grouting position should consider the development of the strength of the grouting material to ensure that the effect of grouting reinforcement matches the advancing speed of the working face, so as to ensure that the grouting material has enough time to solidify and play a reinforcement role, and ensure that the grouting material can fully fill the cracks.

[0062] The control of the above-mentioned grouting pressure should not only consider the penetration of cracks after being affected by mining, but also combine the rheological properties of the grouting material and the permeability of the coal and rock strata. Analysis of the rheological properties of the grouting material: Determine the rheological parameters such as the yield stress and plastic viscosity of the grouting material through experiments. According to the rheological properties of the grouting material, determine a reasonable range of grouting pressure. For grouting materials with higher yield stress and larger plastic viscosity, appropriately increase the grouting pressure to overcome the yield stress of the material and enable it to be smoothly injected into the cracks; for grouting materials with lower yield stress and smaller plastic viscosity, appropriately reduce the grouting pressure to prevent the material from spreading excessively in the cracks and causing waste. Evaluation of the permeability characteristics of the coal and rock strata: Measure the permeability parameters such as the permeability coefficient and porosity of the coal and rock strata. According to the permeability characteristics of the coal and rock strata, adjust the grouting pressure. For coal and rock strata with larger permeability coefficient and higher porosity, appropriately reduce the grouting pressure to reduce the flow rate of the grouting material in the cracks and enable it to have enough time to react with the crack walls to form a stable solidified body; for coal and rock strata with smaller permeability coefficient and lower porosity, appropriately increase the grouting pressure to increase the penetration distance of the grouting material and improve the reinforcement effect.

[0063] Step 6: After grouting is completed, use non-destructive testing methods such as ground penetrating radar or acoustic detection technology to scan and detect the grouted coal and rock strata, obtain the distribution range of the grouted body, measure the mechanical properties of the grouted body, and evaluate the grouting reinforcement effect.

[0064] Furthermore, based on the monitoring data of the grouting effect, an evaluation index system for the grouting effect is established, including indexes such as the filling rate of the grouted body, the strength growth rate, and the stability coefficient of the coal and rock strata. By comparing the mechanical properties and stability of the coal and rock strata before and after grouting, the grouting effect is comprehensively evaluated. If the grouting effect fails to meet the expected goal, the reasons are analyzed and corresponding remedial measures are taken, such as re-arranging the grouting holes, adjusting the grouting material formula or grouting process parameters, etc., until a satisfactory reinforcement effect is achieved. The specific evaluation indexes and evaluation criteria are shown in Table 1.

[0065] Furthermore, the evaluation of the grouting monitoring effect: The high-precision drilling exploration technology system is adopted. Through arranging borehole cameras with the function of coal and rock mass identification for comprehensive geological exploration, the obtained coal and rock strata samples are scanned and analyzed, a physical and mechanical parameter database of the coal and rock mass is established, the lithologic interfaces of the coal seam roof and floor are accurately divided, and the tectonic fracture zones and stress abnormal areas are identified.

[0066] Table 1

[0067]

[0068] The parts not described in this invention can be realized by referring to the prior art.

[0069] Those of ordinary skill in the art of this technology should recognize that the above embodiments are only used to illustrate this application, rather than to limit this application. As long as it is within the scope of the essential spirit of this application, appropriate changes and variations made to the above embodiments fall within the scope of the protection of the claims of this application.

Claims

1. A method for grouting reinforcement of soft coal and rock strata with micro-nano rapid hardening and early strength considering mining-induced fractures in the working face, characterized in that, The following steps are included in sequence: a. Arranging a borehole in the original rock stress zone in front of the working face, wherein the borehole is connected to a stress monitoring device, and the stress monitoring device is used to monitor the change of mining stress in real time and determine the peak position of the mining stress; b. Obtain the mining law of fracture rate and evaluate the stability of rock formation and grouting requirements according to the fracture situation; c. Arrange grouting holes in advance according to the peak position of the mining stress in step a. The grouting holes are located outside the influence range of the mining stress. The optimal arrangement positions of the grouting holes and the spacing between adjacent grouting holes are arranged according to the law of fracture development. The depth and diameter of the grouting holes are arranged according to the evaluation of the mechanical properties of the coal and rock formations; d. Arrange the grouting sleeve and the grouting valve pipe in the grouting hole set in step c; e. When the coal rock mass is affected by mining and cracks develop and penetrate, grouting is carried out into the grouting hole, and the grouting pressure is ≤20MPa; The grouting materials required for grouting include the following in percentage by weight: 850-900 parts of ultrafine sulphoaluminate cement, 5-8 parts of water reducing agent, 50-100 parts of silica fume, 10-15 parts of retarder, 15-25 parts of gypsum, 5-10 parts of nanoparticles; The nanoparticles are nano-SiO2 and nano-Al2O3; f. After the grouting is completed, the coal and rock layers after grouting are scanned and tested using non-destructive testing methods to obtain the distribution range of the grouting body, measure the mechanical properties of the grouting body, and evaluate the grouting reinforcement effect.

2. The micro-nano rapid-hardening and early-strengthening grouting reinforcement method for soft coal and rock strata considering mining-induced fractures on the working face according to claim 1 is characterized in that: In step a, the stress monitoring device includes an optical fiber stress sensor, a strain gauge and an optical fiber static demodulator. The optical fiber stress sensor is located inside the borehole, and the optical fiber static demodulator is connected to the strain gauge. The front side of the optical fiber stress sensor is designed to face upward.

3. A method for grouting reinforcement of soft coal and rock strata with micro-nano rapid hardening and early strength, which takes into account the mining-induced fractures on the working face, as claimed in claim 1, is characterized in that: In step b, the crack conditions include the distribution, density and connectivity of the cracks.

4. A method for grouting and strengthening weak coal and rock strata with micro-nano rapid hardening and early strength, considering the mining-induced fractures in the working face, as claimed in claim 2, wherein: In step c, the crack development law refers to: monitoring the changes in mining stress in real time through optical fiber stress sensors, combining geological exploration data and the physical and mechanical parameters of coal and rock formations to establish a mathematical model of crack development; predicting the development trend and distribution range of cracks through the established mathematical model; determining the optimal layout position of grouting holes and the spacing between adjacent grouting holes based on the mathematical model of crack development to ensure that the grouting holes cover the crack development area.

5. The method for grouting reinforcement of weak coal and rock strata with micro-nano rapid hardening and early strength considering mining-induced fractures on the working face according to claim 2, characterized in that: In step c, the evaluation of the mechanical properties of the coal rock formation refers to the measurement of mechanical parameters, which include uniaxial compressive strength, elastic modulus, and internal friction angle. The depth and diameter of the grouting hole are adjusted according to the mechanical parameters.

6. A method for grouting reinforcement of soft coal and rock strata with micro-nano fast-hardening and early-strengthening, considering the mining-induced fractures in the working face, as claimed in claim 1, wherein: In step d, the grouting casing is arranged before the coal rock mass is affected by mining, and the hole is sealed with a grouting sealing bag.

7. A method for grouting reinforcement of soft coal and rock strata with micro-nano fast-hardening and early strength considering mining-induced fractures on the working face, characterized in that: In step e, the weight ratio of nano-SiO2 to nano-Al2O3 is 1:

1.

8. A method for grouting reinforcement of soft coal and rock strata with micro-nano fast-hardening and early-strengthening considering mining-induced fractures on the working face, characterized in that: In step f, the non-destructive testing method is geological radar or acoustic wave detection technology.

9. The method for micro-nano rapid hardening and early strength grouting reinforcement of soft coal and rock strata considering mining-induced fractures on the working face according to claim 1, characterized in that: In step e, the water reducing agent is sodium lignin sulfonate, naphthalene sulfonate, or powdered polycarboxylate.

10. A method for micro-nano rapid-hardening and early-strengthening grouting reinforcement of soft coal and rock strata considering mining-induced fractures in the working face, characterized in that: In step e, the retarder is phosphate, metaphosphate or sodium fluorosilicate.

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