Method for shortening the safe distance between underground reservoir and coal mining space

Abstract

The present invention provides a method for shortening the safe distance between an underground reservoir and a coal mining space. The method comprises: exploring the rock layer between the underground reservoir and the coal mining space to produce an initial standard rock sample; obtaining the mechanical parameters of the initial standard rock sample; conducting an initial simulation experiment based on the mechanical parameters; determining a reinforcement plan based on the experimental results, mining coal according to the initial safe mining distance L1, and after mining, reinforcing the rock layer according to the reinforcement plan; exploring the reinforced rock layer and producing a reinforced standard rock sample based on the exploration results; obtaining the mechanical parameters of the reinforced standard rock sample; conducting a secondary simulation experiment based on the mechanical parameters of the reinforced standard rock sample, and determining the reinforced safe mining distance L2 based on the experimental results. The technical solution provided by the present application can solve the problem in the related art that coal resources within the safe distance cannot be mined, resulting in waste of coal resources.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mining, in particular to a method for shortening the safe distance between an underground reservoir and a coal mining space. Background Art

[0002] Western China is the main coal-producing region in my country, accounting for approximately 70% of national coal production, with an increasing trend. However, located in an arid and semi-arid ecologically fragile region, western China suffers from water scarcity, accounting for only 3.9% of my country's total water resources. Furthermore, surface evaporation is high, exceeding precipitation by more than six times.

[0003] Among the relevant technologies, in response to the large amount of mine water generated by coal mining, after more than 20 years of continuous technological development and engineering practice, the innovative coal mine underground water reservoir technology was proposed, which avoided the problem of large evaporation of ground water storage and land salinization. It was successfully applied in engineering practice, and more than 30 coal mine underground water reservoirs were built with a maximum water storage capacity of 31 million cubic meters, supplying more than 95% of the production, living and ecological water in the mining area, providing water resource guarantee for the development of the mining area.

[0004] However, considering safety factors, due to the existence of underground reservoirs, a safety distance needs to be left when mining the coal seams below the underground reservoirs. Coal resources within the safety distance cannot be mined, resulting in a waste of coal resources. Summary of the Invention

[0005] The present invention provides a method for shortening the safe distance between an underground water reservoir and a coal mining space, so as to solve the problem in the related art that coal resources within the safe distance cannot be mined, resulting in waste of coal resources.

[0006] The present invention provides a method for shortening the safe distance between an underground water reservoir and a coal mining space. The method for shortening the safe distance between an underground water reservoir and a coal mining space includes: exploring the rock strata between the underground water reservoir and the coal mining space, and producing an initial standard rock sample according to the exploration results; obtaining the mechanical parameters of the initial standard rock sample; conducting a primary simulation experiment according to the mechanical parameters of the initial standard rock sample; determining a reinforcement scheme for the rock strata between the underground water reservoir and the coal mining space according to the experimental results of the primary simulation experiment, conducting coal mining according to the initial safe mining distance L1, and after the coal mining space is mined, reinforcing the rock strata between the underground water reservoir and the coal mining space according to the reinforcement scheme; exploring the rock strata between the reinforced underground water reservoir and the coal mining space, and producing a reinforced standard rock sample according to the exploration results; obtaining the mechanical parameters of the reinforced standard rock sample; conducting a secondary simulation experiment according to the mechanical parameters of the reinforced standard rock sample, and determining the safe mining distance L2 of the reinforced coal mining space according to the experimental results of the secondary simulation experiment.

[0007] Furthermore, during the process of coal mining according to the initial safe mining distance L1, or after the coal mining according to the initial safe mining distance L1 is completed, the method of shortening the safe distance between the underground reservoir and the coal mining space also includes: reinforcing the coal mining space using a goaf filling process.

[0008] Furthermore, after the step of reinforcing the rock strata between the underground reservoir and the coal mining space according to the reinforcement plan, the method of shortening the safety distance between the underground reservoir and the coal mining space also includes: conducting safety monitoring of the reinforced rock strata between the underground reservoir and the coal mining space, and performing secondary reinforcement of the rock strata between the underground reservoir and the coal mining space based on the monitoring results.

[0009] Furthermore, the rock strata between the reinforced underground reservoir and the coal mining space are safety monitored, and the steps of reinforcing the rock strata between the underground reservoir and the coal mining space based on the monitoring results include: obtaining the actual mining distance of the coal mining space; when the actual mining distance of the coal mining space is between the initial safe mining distance L1 of the coal mining space and the safe mining distance L2 of the reinforced coal mining space, monitoring the state parameters of the rock strata between the underground reservoir and the coal mining space; when the state parameters of the rock strata between the underground reservoir and the coal mining space are greater than the warning value, performing secondary reinforcement on the rock strata between the underground reservoir and the coal mining space.

[0010] Furthermore, the step of conducting coal mining based on the initial safe mining distance L1 includes: determining the initial safe mining distance L1 of the coal mining space based on the experimental results of the initial simulation experiment, and conducting coal mining based on the initial safe mining distance L1; the method of shortening the safety distance between the underground reservoir and the coal mining space also includes: conducting an initial simulation experiment based on the mechanical parameters of the initial standard rock sample, and determining the unstable mining distance L3 of the rock stratum between the underground reservoir and the coal mining space based on the experimental results of the initial simulation experiment; and determining the casing construction parameters of the reinforcement scheme based on the unstable mining distance L3 of the rock stratum between the underground reservoir and the coal mining space.

[0011] Furthermore, the steps of conducting an initial simulation experiment based on the mechanical parameters of the initial standard rock sample, determining the initial safe mining distance L1 of the coal mining space based on the initial simulation experiment, and determining the unstable mining distance L3 of the rock stratum between the underground reservoir and the coal mining space based on the initial simulation experiment include: conducting numerical simulation experiments and similarity simulation experiments based on the mechanical parameters of the initial standard rock sample; analyzing the development of cracks and permeability of the rock stratum between the underground reservoir and the coal mining space during the mining process based on the numerical simulation experiments and similarity simulation experiments; determining the initial safe mining distance L1 of the coal mining space and the unstable mining distance L3 of the rock stratum between the underground reservoir and the coal mining space based on the development of cracks and permeability of the rock stratum between the underground reservoir and the coal mining space.

[0012] Furthermore, a secondary simulation experiment is conducted based on the mechanical parameters of the reinforced standard rock sample, and the steps of determining the safe mining distance L2 of the reinforced coal mining space based on the experimental results of the secondary simulation experiment include: conducting numerical simulation experiments and similarity simulation experiments based on the mechanical parameters of the reinforced standard rock sample; analyzing the development of cracks and permeability of the rock strata between the underground reservoir and the coal mining space during the mining process based on the numerical simulation experiments and similarity simulation experiments; determining the safe mining distance L2 of the reinforced coal mining space based on the development of cracks and permeability of the rock strata between the underground reservoir and the coal mining space.

[0013] Furthermore, the steps of conducting a preliminary simulation experiment based on the mechanical parameters of the initial standard rock sample, determining an initial safe mining distance L1 of the coal mining space based on the preliminary simulation experiment, and conducting a preliminary simulation experiment based on the mechanical parameters of the initial standard rock sample, and determining an unstable mining distance L3 of the rock stratum between the underground reservoir and the coal mining space based on the experimental results of the preliminary simulation experiment include: obtaining the initial safe mining distance L1 of the coal mining space and the unstable mining distance L3 of the rock stratum between the underground reservoir and the coal mining space by the following formula:

[0014] ,

[0015] ,

[0016] Among them, k is the safety factor for calculating the coal pillar dam;

[0017] S1 is the horizontal distance between the mining face of the coal mining space and the groundwater reservoir when the mining stress is equal to the shear strength of the initial standard rock sample; S2 is the horizontal distance between the mining face of the coal mining space and the groundwater reservoir when the cracks in the rock strata between the groundwater reservoir and the coal mining space are undisturbed and continue to expand; S3 is the horizontal distance between the mining face of the coal mining space and the groundwater reservoir when the cracks below the groundwater reservoir are connected to the cracks in the rock strata between the groundwater reservoir and the coal mining space.

[0018] Furthermore, the step of determining the safe mining distance L2 of the reinforced coal mining space according to the experimental results of the secondary simulation experiment includes: obtaining the safe mining distance L2 of the reinforced coal mining space by the following formula:

[0019] ,

[0020] Among them, k is the safety factor for calculating the coal pillar dam;

[0021] S1 S2 is the horizontal distance between the mining face and the underground reservoir in the coal mining space when the mining stress is equal to the shear strength of the reinforced standard rock sample; S3 is the horizontal distance between the mining face of the coal mining space and the underground reservoir when the cracks in the rock strata between the reinforced underground reservoir and the coal mining space continue to expand without being disturbed; It is the horizontal distance between the mining face of the coal mining space and the underground reservoir when the fissures below the underground reservoir are connected to the fissures in the rock strata between the reinforced underground reservoir and the coal mining space.

[0022] Furthermore, the step of obtaining the mechanical parameters of the initial standard rock sample includes: conducting axial cyclic loading mechanics and seepage experiments on the initial standard rock sample to obtain the fatigue strength and first permeability of the rock formation between the underground reservoir and the coal mining space under mining conditions; conducting unloading confining pressure creep mechanics and seepage experiments on the initial standard rock sample to obtain the long-term strength and second permeability of the rock formation between the underground reservoir and the coal mining space under mining conditions.

[0023] By applying the technical solution of the present invention, the method for shortening the safe distance between the underground reservoir and the coal mining space includes exploring the rock strata between the underground reservoir and the coal mining space to understand the composition, structure and thickness of the rock strata, and making initial standard rock samples based on the exploration results, conducting experiments using the initial standard rock samples, and then obtaining the mechanical parameters of the initial standard rock samples. By obtaining the mechanical parameters of the initial standard rock samples, an initial simulation experiment is conducted to understand the fracture development and permeability of the rock strata between the underground reservoir and the coal mining space, and then determining a reinforcement plan for the rock strata, so that when the coal is mined and mined to the initial safe mining distance L1, the rock strata can be reinforced. The rock stratum between the underground reservoir and the coal mining space is reinforced, and the reinforced rock stratum is explored to understand the composition, structure and thickness of the reinforced rock stratum. Based on the exploration results, reinforced standard rock samples are made, and experiments are carried out using the reinforced standard rock samples to obtain the mechanical parameters of the reinforced standard rock samples. A secondary simulation experiment is carried out by obtaining the mechanical parameters of the reinforced standard rock samples to understand the fracture development and permeability of the reinforced rock stratum, and then determine the safe mining distance L2 after reinforcement, and continue to mine coal, so that after the rock stratum is reinforced, it is possible to continue to mine coal, and the coal mining rate can be increased without damaging the rock stratum. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0025] Figure 1 A flow chart of a method for shortening the safe distance between an underground reservoir and a coal mining space provided by an embodiment of the present invention is shown;

[0026] Figure 2 A flowchart of safety monitoring of a rock layer between a reinforced underground reservoir and a coal mining space and reinforcing the rock layer between the underground reservoir and the coal mining space based on the monitoring results is shown according to an embodiment of the present invention;

[0027] Figure 3 A flow chart of determining a safe mining distance of a reinforced coal mining space according to secondary simulation test results provided in an embodiment of the present invention is shown;

[0028] Figure 4 A schematic diagram showing a safe mining distance before coal seam mining reinforcement according to an embodiment of the present invention is shown;

[0029] Figure 5 A schematic diagram of grouting in an underground reservoir according to an embodiment of the present invention is shown;

[0030] Figure 6A schematic diagram showing the safe mining distance from coal seam mining to reinforcement provided by an embodiment of the present invention is shown.

[0031] The above drawings include the following reference numerals:

[0032] 10. Underground reservoir; 20. Coal mining space; 30. Goaf; 40. Casing;

[0033] L1, initial safe mining distance; L2, safe mining distance; L3, unstable mining distance. DETAILED DESCRIPTION

[0034] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] like Figures 1 to 6 As shown, an embodiment of the present invention provides a method for shortening the safety distance between an underground reservoir and a coal mining space. The method for shortening the safety distance between an underground reservoir 10 and a coal mining space 20 includes:

[0036] S100, exploring the rock layer between the underground water reservoir 10 and the coal mining space 20, and preparing an initial standard rock sample based on the exploration results;

[0037] S200, obtaining mechanical parameters of an initial standard rock sample;

[0038] S300, conducting an initial simulation experiment based on the mechanical parameters of the initial standard rock sample;

[0039] S400: Determine a reinforcement plan for the rock layer between the underground reservoir 10 and the coal mining space 20 based on the experimental results of the initial simulation experiment, conduct coal mining based on the initial safe mining distance L1, and after the coal mining space 20 is mined, reinforce the rock layer between the underground reservoir 10 and the coal mining space 20 according to the reinforcement plan;

[0040] S500, exploring the rock layer between the reinforced underground water reservoir 10 and the coal mining space 20, and preparing a reinforcement standard rock sample based on the exploration results;

[0041] S600, obtaining mechanical parameters of the reinforced standard rock sample;

[0042] S700 , performing a secondary simulation experiment based on the mechanical parameters of the reinforced standard rock sample, and determining a safe mining distance L2 of the reinforced coal mining space 20 based on the experimental results of the secondary simulation experiment.

[0043] The method for shortening the safe distance between the underground reservoir and the coal mining space provided by the present embodiment includes exploring the rock strata between the underground reservoir 10 and the coal mining space 20 to understand the composition, structure and thickness of the rock strata, and making initial standard rock samples based on the exploration results, and conducting experiments using the initial standard rock samples to obtain the mechanical parameters of the initial standard rock samples. By obtaining the mechanical parameters of the initial standard rock samples, an initial simulation experiment is conducted to understand the crack development and permeability of the rock strata between the underground reservoir 10 and the coal mining space 20, and then determine a reinforcement plan for the rock strata, so that when the coal is mined and mined, the rock strata can be reinforced. When the initial safe mining distance L1 is reached, the rock stratum between the underground water reservoir 10 and the coal mining space 20 is reinforced, and the reinforced rock stratum is explored to understand the composition, structure and thickness of the reinforced rock stratum, and a reinforced standard rock sample is made according to the exploration results. The reinforced standard rock sample is used for experiments to obtain the mechanical parameters of the reinforced standard rock sample. A secondary simulation experiment is carried out by obtaining the mechanical parameters of the reinforced standard rock sample to understand the fracture development and permeability of the reinforced rock stratum, and then determine the safe mining distance L2 after reinforcement, and continue to mine coal, so that after the rock stratum is reinforced, it is possible to continue to mine coal, and the coal mining rate can be improved without damaging the rock stratum.

[0044] It should be noted that the initial safe mining distance L1 refers to the horizontal distance between the coal mining face and the boundary of the coal pillar dam of the underground water reservoir 10 when mining from right to left. In the related art, coal resources within the safe distance cannot be mined, resulting in waste of coal resources. The safety distance referred to is the initial safe mining distance L1.

[0045] like Figure 4 and Figure 5 As shown, during the process of coal mining according to the initial safe mining distance L1, or after the coal mining according to the initial safe mining distance L1 is completed, the method of shortening the safe distance between the underground reservoir 10 and the coal mining space 20 further includes:

[0046] The coal mining space 20 is reinforced by using a filling process for the goaf 30. Through the above steps, coal mining is carried out after determining the initial safe mining distance L1. During the mining process, the goaf 30 is filled and reinforced using the filling process to avoid the development of cracks and prevent rock collapse. Alternatively, after mining reaches the initial safe mining distance L1, when mining is resumed, the goaf 30 is filled, thereby avoiding the need to continue mining after reaching the initial safe distance L1, preventing the problem of rock cracks being connected to the underground water reservoir 10, and thus reinforcing the rock stratum and improving the coal mining rate.

[0047] In this embodiment, after step S400 of reinforcing the rock layer between the underground reservoir 10 and the coal mining space 20 according to the reinforcement plan, the method of shortening the safe distance between the underground reservoir 10 and the coal mining space 20 further includes:

[0048] The rock stratum between the reinforced underground water reservoir 10 and the coal mining space 20 is subjected to safety monitoring, and secondary reinforcement of the rock stratum between the underground water reservoir 10 and the coal mining space 20 is performed based on the monitoring results. Through the above steps, after the rock stratum between the underground water reservoir 10 and the coal mining space 20 is reinforced, the rock stratum is subjected to safety monitoring, and the cracks and permeability of the rock stratum can be monitored in real time. Then, based on the monitoring results, it can be determined whether the rock stratum between the underground water reservoir 10 and the coal mining space 20 should be subjected to secondary reinforcement. This can ensure the safety and reliability of the coal mining process and improve the coal mining rate.

[0049] like Figure 2 As shown, the steps of conducting safety monitoring on the rock layer between the reinforced underground reservoir 10 and the coal mining space 20 and reinforcing the rock layer between the underground reservoir 10 and the coal mining space 20 according to the monitoring results include:

[0050] S410, obtaining the actual mining distance of the coal mining space 20;

[0051] S420, when the actual mining distance of the coal mining space 20 is between the initial safe mining distance L1 of the coal mining space 20 and the safe mining distance L2 of the reinforced coal mining space 20, monitoring the state parameters of the rock formation between the underground water reservoir 10 and the coal mining space 20;

[0052] S430: When the state parameter of the rock stratum between the underground reservoir 10 and the coal mining space 20 is greater than the warning value, the rock stratum between the underground reservoir 10 and the coal mining space 20 is reinforced for a second time. Through the above steps, after the rock stratum between the underground reservoir 10 and the coal mining space 20 is reinforced, the coal seam in the coal mining space 20 is mined again. By obtaining the actual mining distance of the coal mining space 20, when the actual mining distance of the coal mining space 20 is between the initial safe distance L1 and the reinforced safe mining distance L2, the state parameter of the rock stratum is monitored in real time. When the state parameter is greater than the warning value, the rock stratum is reinforced for a second time to prevent the further development of rock stratum cracks, thereby ensuring the safety of coal mining work while continuing to mine coal.

[0053] It should be noted that the safety monitoring measures are to arrange optical fibers and flow meters in the fracture development area to monitor the fractures, stress and seepage status of the rock formation when the mining distance exceeds the initial safe mining distance L1 and does not reach the reinforced safe mining distance L2.

[0054] Among them, the prevention and control measures are to reserve grouting holes in the tunnels around the underground reservoir. When the monitored value exceeds the warning value, grouting reinforcement is carried out through the reserved grouting holes. The reserved grouting holes and sensors are drilled downward in the tunnels around the underground reservoir 10.

[0055] Specifically, the stress warning value is set to a detected long-term load value exceeding 0.8 times the long-term strength of the reinforced rock layer, and the seepage warning value is set to 0.7 times the permeability after the reinforced rock layer is connected to the underground reservoir 10.

[0056] like Figure 4 As shown, the step of mining coal according to the initial safe mining distance L1 includes: determining the initial safe mining distance L1 of the coal mining space 20 based on the experimental results of the initial simulation experiment, and mining coal according to the initial safe mining distance L1. Through the above steps, the initial safe mining distance L1 can be determined based on the experimental results of the initial simulation experiment, so that when mining coal, it is avoided to continue mining when the initial safe mining distance L1 is reached, thereby avoiding dangerous accidents.

[0057] like Figure 4 As shown, the method of shortening the safe distance between the underground water reservoir 10 and the coal mining space 20 also includes:

[0058] Conducting a preliminary simulation experiment based on the mechanical parameters of the initial standard rock sample, and determining the unstable mining distance L3 of the rock layer between the underground water reservoir 10 and the coal mining space 20 based on the experimental results of the preliminary simulation experiment;

[0059] The reinforcement scheme's casing 40 construction parameters are determined based on the unstable mining distance L3 of the rock formation between the underground reservoir 10 and the coal mining space 20. Through the above steps, the unstable mining distance L3 of the rock formation between the underground reservoir 10 and the coal mining space 20 is determined based on the experimental results of the initial simulation experiment, thereby determining the fracture development boundary. This allows the use of casing 40 to reinforce the rock formation during construction, thereby preventing further expansion of fractures and improving the reinforcement effect of the rock formation.

[0060] It should be noted that the reinforcement plan is to determine the position of the grouting hole in the rock formation when the coal mining space is mined to the initial safe mining distance L1, and install the casing 40 through the grouting hole, and inject grouting reinforcement material into the rock formation from the small holes on the side wall of the casing 40. The height of the grouting hole is not less than 60% of the thickness of the interlayer rock mass, and the connection between the rock formation cracks and the underground water reservoir 10 cracks is blocked.

[0061] Grouting materials include cement and water glass double slurry and chemical slurry. The water-cement ratio of cement and water glass double slurry is between 1:0.4 and 1:0.6, and the volume ratio of cement slurry to water glass is between 1:0.6 and 1:0.8. Chemical slurry is a mixture of urea-formaldehyde resin and acidic curing agent, with a ratio between 3:1 and 3.5:1. Taking into account factors such as material cost and construction time, the most economical grouting solution should be selected. After grouting reinforcement, the permeability of the reinforced rock layer should be reduced to less than 0.8 times the pre-reinforcement rate.

[0062] Specifically, by determining the unstable mining distance L3 of the rock formation between the underground reservoir 10 and the coal mining space 20, and then determining the boundary where the rock formation becomes unstable and the cracks expand and become conductive, and then determining the distance and angle of the crack expansion, the length and angle of the casing inserted into the grouting hole during grouting can be determined, so that the expanded cracks can be reinforced by grouting to ensure the stability of the rock formation between the underground reservoir 10 and the coal mining space.

[0063] In this embodiment, the steps of conducting an initial simulation experiment based on the mechanical parameters of an initial standard rock sample, determining an initial safe mining distance L1 of the coal mining space 20 based on the initial simulation experiment, and determining an unstable mining distance L3 of the rock stratum between the underground water reservoir 10 and the coal mining space 20 based on the initial simulation experiment include:

[0064] Numerical simulation experiments and similarity simulation experiments are carried out based on the mechanical parameters of the initial standard rock samples;

[0065] Based on numerical simulation experiments and similar simulation experiments, the development of fractures and permeability of the rock layer between the underground water reservoir 10 and the coal mining space 20 during the mining process is analyzed;

[0066] The initial safe mining distance L1 of the coal mining space 20 and the unstable mining distance L3 of the rock stratum between the underground reservoir 10 and the coal mining space 20 are determined based on the development of fractures and permeability of the rock stratum between the underground reservoir 10 and the coal mining space 20. Through the above steps, numerical simulation experiments and similar simulation experiments are carried out based on the mechanical parameters of the initial standard rock samples, so that the obtained mechanical parameters are used to carry out simulation experiments on the standard rock samples under working conditions to obtain the changes in fracture development and permeability. The development of fractures and permeability of the rock stratum during the coal mining process is determined through similar simulation experiments, which facilitates the determination of the initial safe mining distance L1 and the unstable mining distance L3 of the rock stratum between the underground reservoir 10 and the coal mining space 20, thereby improving the safety of coal mining.

[0067] It should be noted that physical and mechanical tests are carried out on the initial standard rock samples, among which the physical and mechanical tests include water absorption test, saturated water absorption test, Brazilian splitting test, uniaxial test, and conventional triaxial test to obtain the basic physical and mechanical parameters of the rock formation, such as water absorption rate, saturated water absorption rate, uniaxial compressive strength, triaxial compressive strength, permeability coefficient and elastic modulus.

[0068] like Figure 3 As shown, a secondary simulation experiment is performed based on the mechanical parameters of the reinforced standard rock sample, and step S700 of determining the safe mining distance L2 of the reinforced coal mining space 20 based on the experimental results of the secondary simulation experiment includes:

[0069] S710. Conduct numerical simulation experiments and similarity simulation experiments based on the mechanical parameters of the reinforced standard rock sample;

[0070] S720, analyzing the development of fractures and permeability of the rock layer between the underground water reservoir 10 and the coal mining space 20 during the mining process based on numerical simulation experiments and similar simulation experiments;

[0071] S730: Determine the safe mining distance L2 of the reinforced coal mining space 20 based on the development of fractures and permeability in the rock strata between the underground water reservoir 10 and the coal mining space 20. Through the above steps, numerical simulation experiments and similarity simulation experiments are conducted on the mechanical parameters obtained from the secondary experiments on the reinforced standard rock samples. The obtained mechanical parameters are then used to simulate the reinforced standard rock samples under working conditions to determine changes in fracture development and permeability. Similarity simulation experiments are then used to determine changes in fractures and permeability in the rock strata during coal mining. This facilitates determining the safe mining distance L2 of the reinforced coal mining space 20 and improves coal mining safety.

[0072] In this embodiment, the steps of conducting an initial simulation experiment based on the mechanical parameters of the initial standard rock sample, determining an initial safe mining distance L1 of the coal mining space 20 based on the initial simulation experiment, and conducting an initial simulation experiment based on the mechanical parameters of the initial standard rock sample, and determining an unstable mining distance L3 of the rock layer between the underground water reservoir 10 and the coal mining space 20 based on the experimental results of the initial simulation experiment include:

[0073] The initial safe mining distance L1 of the coal mining space 20 and the unstable mining distance L3 of the rock stratum between the underground reservoir 10 and the coal mining space 20 are obtained by the following formula:

[0074] ,

[0075] ,

[0076] Among them, k is the safety factor for calculating the coal pillar dam;

[0077] S1 is the horizontal distance between the mining face of the coal mining space 20 and the underground water reservoir 10 when the mining stress is equal to the shear strength of the initial standard rock sample;

[0078] S2 is the horizontal distance between the mining working face of the coal mining space 20 and the underground reservoir 10 when the cracks in the rock strata between the underground reservoir 10 and the coal mining space 20 continue to expand without being disturbed;

[0079] S3 is the horizontal distance between the mining face of coal mining space 20 and underground reservoir 10 when the fissures beneath underground reservoir 10 are connected to the fissures in the rock formation between underground reservoir 10 and coal mining space 20. The above steps facilitate confirmation of the initial safety distance L1 and the unstable mining distance L3, thereby facilitating coal mining.

[0080] The safety factor k ranges from 1.1 to 1.3.

[0081] In this embodiment, the step S700 of determining the safe mining distance L2 of the reinforced coal mining space 20 according to the experimental results of the secondary simulation experiment includes:

[0082] The safe mining distance L2 of the reinforced coal mining space 20 is obtained by the following formula:

[0083] ,

[0084] Among them, k is the safety factor for calculating the coal pillar dam;

[0085] S1 is the horizontal distance between the mining face of the coal mining space 20 and the underground water reservoir 10 when the mining stress is equal to the shear strength of the reinforced standard rock sample;

[0086] S2 is the horizontal distance between the mining working face of the coal mining space 20 and the underground reservoir 10 when the cracks in the rock strata between the reinforced underground reservoir 10 and the coal mining space 20 continue to expand without being disturbed;

[0087] S3 This is the horizontal distance between the mining working face of coal mining space 20 and underground reservoir 10 when the fissures beneath underground reservoir 10 communicate with the fissures in the rock strata between the reinforced underground reservoir 10 and coal mining space 20. Through the above steps, the safe mining distance L2 of the reinforced coal mining space 20 can be determined, thereby ensuring the safety of the mining process and improving the coal recovery rate during coal mining.

[0088] In this embodiment, the step of obtaining the mechanical parameters of the initial standard rock sample includes:

[0089] Conducting axial cyclic loading mechanics and seepage tests on the initial standard rock sample to obtain the fatigue strength and first permeability of the rock formation between the underground water reservoir 10 and the coal mining space 20 under mining conditions;

[0090] The initial standard rock sample is subjected to unloading confining pressure creep mechanics and seepage tests to obtain the long-term strength and second permeability of the rock formation between the underground water reservoir 10 and the coal mining space 20 under mining conditions. Through the above steps, when obtaining the mechanical parameters of the initial standard rock sample, it is necessary to conduct circumferential cyclic loading mechanics and seepage tests on the initial standard rock sample to obtain the fatigue strength and first permeability of the rock formation that can be obtained when coal is mined, and then determine the development of cracks in the rock formation during mining. After the circumferential cyclic loading mechanics and seepage tests are completed, the standard rock sample is subjected to unloading confining pressure creep mechanics and seepage tests to obtain the long-term strength and second permeability of the rock formation, which is convenient for measurement. The mechanical parameters of the initial standard rock sample are further determined through the above experiments to facilitate mining of the coal mining space below the rock formation.

[0091] It should be noted that the circumferential cyclic loading mechanics and seepage test simulates the effects of mining-induced disturbance stress on the strength and permeability of the rock formation, determining fatigue strength and permeability under mining conditions. Based on fatigue strength, the Mohr-Coulomb criterion can be used to determine the shear strength of the rock formation under mining conditions, thereby determining the initial safe distance L1 for fracture conduction. Axial and confining pressures are first applied to the initial stress state of the standard rock sample, where the triaxial stresses are equal. The axial and confining pressures are then simultaneously unloaded to simulate mining disturbance. Finally, maintaining the confining pressure constant, the axial stress is applied at a gradient of 10% of the triaxial compressive strength until the initial standard rock sample fails. Permeability is measured after each stress cycle.

[0092] The unloading confining pressure creep mechanics and seepage experiment simulates the effects of long-term underground reservoir operation on rock formation strength and permeability. The physical and mechanical parameters obtained include long-term strength and permeability under disturbance conditions. Based on the long-term strength, the Mohr-Coulomb criterion is used to determine the shear strength of the rock formation under long-term mining disturbance. The permeability obtained provides a basis for determining the fracture conductivity standard when determining the safety distance. The loading path for the unloading confining pressure creep mechanics and seepage experiment is as follows: first, axial pressure and confining pressure are applied to the original rock stress state, at which the three-dimensional stresses are equal; then, while maintaining the confining pressure constant, the axial pressure is applied to a predetermined value, which is generally the long-term load of the rock sample during mining disturbance; finally, while maintaining the axial pressure constant, the confining pressure is unloaded step by step, with each confining pressure gradient maintaining the stress state for at least 24 hours. Permeability is measured after each stress change.

[0093] The technical solution provided by the embodiment has the following beneficial effects:

[0094] (1) When mining coal to the initial safe mining distance L1, the rock layer between the underground reservoir 10 and the coal mining space 20 is reinforced, and the reinforced rock layer is explored, and reinforced standard rock samples are prepared. Experiments are conducted using the reinforced standard rock samples to understand the fracture development and permeability of the reinforced rock layer, and then the safe mining distance L2 after reinforcement is determined, and coal mining continues to improve the coal mining rate;

[0095] (2) After the rock layer between the underground reservoir 10 and the coal mining space 20 is reinforced, the rock layer is monitored for safety, and the cracks and permeability of the rock layer can be monitored in real time. Then, according to the monitoring results, it can be determined whether the rock layer between the underground reservoir 10 and the coal mining space 20 should be reinforced for a second time, which can ensure the safety and reliability of the coal mining process and improve the coal mining rate;

[0096] (3) Based on the results of the initial simulation experiment, the unstable mining distance L3 of the rock layer between the underground water reservoir 10 and the coal mining space 20 is determined, and then the fracture development boundary is determined, so that when the rock layer is reinforced, the rock layer is constructed by using the casing 40, and then the rock layer is reinforced by using the casing 40, thereby preventing the fracture from continuing to expand and improving the reinforcement effect of the rock layer.

[0097] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0098] Unless otherwise specifically stated, the relative arrangement of the parts and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to actual proportional relationships. The technology, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of the exemplary embodiments can have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, and therefore, once an item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0099] In the description of the present invention, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "horizontal, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention; the directional words "inside and outside" refer to the inside and outside relative to the outline of each component itself.

[0100] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used herein to describe the spatial positional relationship of a device or feature to other devices or features as shown in the figures. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figures. For example, if the device in the drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0101] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0102] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for shortening the safe distance between underground reservoirs and coal mining space, characterized in that: The method for shortening the safe distance between the underground reservoir and the coal mining space includes: Exploring the rock layer between the underground water reservoir (10) and the coal mining space (20), and preparing an initial standard rock sample based on the exploration results; Obtaining mechanical parameters of the initial standard rock sample; performing an initial simulation experiment based on the mechanical parameters of the initial standard rock sample; Determining a reinforcement scheme for the rock layer between the underground water reservoir (10) and the coal mining space (20) based on the experimental results of the initial simulation experiment, performing coal mining based on the initial safe mining distance L1, and after the coal mining space (20) is mined, reinforcing the rock layer between the underground water reservoir (10) and the coal mining space (20) based on the reinforcement scheme; Exploring the rock layer between the reinforced underground water reservoir (10) and the coal mining space (20), and producing reinforced standard rock samples based on the exploration results; Obtaining mechanical parameters of the reinforced standard rock sample; Conducting a secondary simulation experiment based on the mechanical parameters of the reinforced standard rock sample, and determining a safe mining distance L2 of the reinforced coal mining space (20) based on the experimental results of the secondary simulation experiment; The step of mining coal according to the initial safe mining distance L1 includes: determining the initial safe mining distance L1 of the coal mining space (20) according to the experimental results of the initial simulation experiment, and mining coal according to the initial safe mining distance L1; the method of shortening the safe distance between the underground reservoir and the coal mining space also includes: conducting an initial simulation experiment according to the mechanical parameters of the initial standard rock sample, and determining the unstable mining distance L3 of the rock layer between the underground reservoir (10) and the coal mining space (20) according to the experimental results of the initial simulation experiment; and determining the construction parameters of the casing (40) of the reinforcement scheme according to the unstable mining distance L3 of the rock layer between the underground reservoir (10) and the coal mining space (20); The steps of performing a primary simulation experiment based on the mechanical parameters of the initial standard rock sample, determining the initial safe mining distance L1 of the coal mining space (20) based on the primary simulation experiment, performing a primary simulation experiment based on the mechanical parameters of the initial standard rock sample, and determining the unstable mining distance L3 of the rock layer between the underground reservoir (10) and the coal mining space (20) based on the experimental results of the primary simulation experiment include: obtaining the initial safe mining distance L1 of the coal mining space (20) and the unstable mining distance L3 of the rock layer between the underground reservoir (10) and the coal mining space (20) by the following formula: ， ， wherein k is a safety factor for calculating the coal pillar dam; S1 is a horizontal distance between the mining face of the coal mining space (20) and the underground reservoir (10) when the mining stress is equal to the shear strength of the initial standard rock sample; S2 is a horizontal distance between the mining face of the coal mining space (20) and the underground reservoir (10) when the cracks in the rock stratum between the underground reservoir (10) and the coal mining space (20) are not disturbed and continue to expand; S3 is a horizontal distance between the mining face of the coal mining space (20) and the underground reservoir (10) when the cracks below the underground reservoir (10) and the cracks in the rock stratum between the underground reservoir (10) and the coal mining space (20) are connected; The step of determining the safe mining distance L2 of the reinforced coal mining space (20) according to the experimental results of the secondary simulation experiment includes: obtaining the safe mining distance L2 of the reinforced coal mining space (20) by the following formula: ， Wherein, k is the safety factor for calculating the coal pillar dam body; S1 is the horizontal distance between the mining face of the coal mining space (20) and the underground water reservoir (10) when the mining stress is equal to the shear strength of the reinforced standard rock sample; S2 is the horizontal distance between the mining face of the coal mining space (20) and the underground water reservoir (10) when the cracks in the rock stratum between the reinforced underground water reservoir (10) and the coal mining space (20) are not disturbed and continue to expand; S3 is the horizontal distance between the mining face of the coal mining space (20) and the underground water reservoir (10) when the cracks below the underground water reservoir (10) are connected to the cracks in the rock stratum between the reinforced underground water reservoir (10) and the coal mining space (20).

2. The method for shortening the safe distance between underground reservoirs and coal mining space according to claim 1, characterized in that: During the process of coal mining according to the initial safe mining distance L1, or after the coal mining according to the initial safe mining distance L1 is completed, the method of shortening the safe distance between the underground water reservoir and the coal mining space further includes: The coal mining space (20) is reinforced by using a goaf (30) filling process.

3. The method for shortening the safe distance between underground reservoirs and coal mining space according to claim 1, characterized in that: After the step of reinforcing the rock layer between the underground reservoir (10) and the coal mining space (20) according to the reinforcement scheme, the method of shortening the safe distance between the underground reservoir and the coal mining space further comprises: Safety monitoring is performed on the rock layer between the reinforced underground water reservoir (10) and the coal mining space (20), and secondary reinforcement is performed on the rock layer between the underground water reservoir (10) and the coal mining space (20) based on the monitoring results.

4. The method for shortening the safe distance between underground reservoirs and coal mining space according to claim 3, characterized in that: The steps of conducting safety monitoring on the rock layer between the reinforced underground water reservoir (10) and the coal mining space (20), and reinforcing the rock layer between the underground water reservoir (10) and the coal mining space (20) according to the monitoring results include: Obtaining an actual mining distance of the coal mining space (20); When the actual mining distance of the coal mining space (20) is between the initial safe mining distance L1 of the coal mining space (20) and the safe mining distance L2 of the reinforced coal mining space (20), monitoring the state parameters of the rock layer between the underground water reservoir (10) and the coal mining space (20); When the state parameter of the rock layer between the underground water reservoir (10) and the coal mining space (20) is greater than the warning value, the rock layer between the underground water reservoir (10) and the coal mining space (20) is reinforced for the second time.

5. The method for shortening the safe distance between underground reservoirs and coal mining space according to claim 1, characterized in that: The steps of performing a primary simulation experiment based on the mechanical parameters of the initial standard rock sample, determining the initial safe mining distance L1 of the coal mining space (20) based on the primary simulation experiment, and determining the unstable mining distance L3 of the rock layer between the underground water reservoir (10) and the coal mining space (20) based on the primary simulation experiment include: Performing numerical simulation experiments and similarity simulation experiments based on the mechanical parameters of the initial standard rock sample; Analyze the development of cracks and permeability of the rock layer between the underground water reservoir (10) and the coal mining space (20) during the mining process based on the numerical simulation experiment and the similarity simulation experiment; The initial safe mining distance L1 of the coal mining space (20) and the unstable mining distance L3 of the rock stratum between the underground reservoir (10) and the coal mining space (20) are determined based on the fracture development and permeability development conditions of the rock stratum between the underground reservoir (10) and the coal mining space (20).

6. The method for shortening the safe distance between underground reservoirs and coal mining space according to claim 1, characterized in that: The steps of performing a secondary simulation experiment based on the mechanical parameters of the reinforced standard rock sample and determining the safe mining distance L2 of the reinforced coal mining space (20) based on the experimental results of the secondary simulation experiment include: Conducting numerical simulation experiments and similarity simulation experiments based on the mechanical parameters of the reinforced standard rock sample; Analyze the development of cracks and permeability of the rock layer between the underground water reservoir (10) and the coal mining space (20) during the mining process based on the numerical simulation experiment and the similarity simulation experiment; The safe mining distance L2 of the reinforced coal mining space (20) is determined based on the crack development and permeability development conditions of the rock layer between the underground water reservoir (10) and the coal mining space (20).

7. The method for shortening the safe distance between underground reservoirs and coal mining space according to claim 1, characterized in that: The step of obtaining the mechanical parameters of the initial standard rock sample includes: Performing axial cyclic loading mechanics and seepage tests on the initial standard rock sample to obtain fatigue strength and first permeability of the rock layer between the underground water reservoir (10) and the coal mining space (20) under mining conditions; The initial standard rock sample is subjected to unloading confining pressure creep mechanics and seepage experiments to obtain the long-term strength and second permeability of the rock layer between the underground reservoir (10) and the coal mining space (20) under mining conditions.

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