A laboratory simulation test method for roof reconstruction effect of caving zone grouting filling

Abstract

The present application relates to a kind of laboratory simulation test methods of collapse zone grouting filling roof reconstruction effect, belong to coal mining and strata control technical field.The method solves the problem that it is difficult to scientifically, quantitatively predict and evaluate the mechanical properties of grouting roof reconstruction in prior art.The technical scheme is as follows: obtain the block size characteristic parameters of field collapse rock mass by numerical simulation, determine the experimental scale ratio based on similarity theory, simulate the grouting cementation process under overburden stress in special device, and finally drill core sample to test its physical and mechanical parameters.The method realizes controllable, measurable laboratory evaluation of reconstruction effect, can provide direct basis for optimizing process parameters, reducing engineering cost and risk, and promote the resource utilization of coal-based solid waste.

Description

Technical Field

[0001] This invention relates to the field of coal mining technology, and in particular to a laboratory simulation test method for the effect of grouting and filling roof reconstruction in caving zones. Background Technology

[0002] The safe and efficient mining of extra-thick coal seams is a crucial issue in coal resource development. Currently, layered mining is the most commonly used mining technique for such seams. This technique first mines the upper layer, and after the roof of the goaf collapses and compacts, and undergoes a relatively long period of natural cementation to form a "regenerated roof," the lower layer is then mined. However, this natural regeneration process is lengthy and its effectiveness is unstable. To ensure the safety of mining the lower layer, artificial false roofs such as metal mesh or plastic mesh are usually laid under the regenerated roof. While this approach improves safety to some extent, it also brings significant drawbacks: firstly, the cost of artificial false roof materials and installation is high, and the process is complex, severely affecting the efficiency of the working face; secondly, the bonding performance between the false roof and the regenerated roof is difficult to guarantee, and during the mining of the lower layer, issues such as mesh blockage, rock leakage, and even localized roof collapses are prone to occur, posing significant safety hazards.

[0003] In recent years, grouting and backfilling roof reconstruction technology has attracted attention as an emerging solution. This technology injects a specific grout into the collapsed rock mass in the goaf to cement the broken rock blocks, thereby artificially accelerating the formation of a complete and stable recycled roof structure. It holds promise as a replacement for traditional artificial false roofs, achieving multiple goals of cost reduction, efficiency improvement, and enhanced safety. However, the actual application effect of this technology is affected by various factors such as geological conditions, rock mass size, grouting material ratio, and grouting pressure, and lacks scientific and quantitative evaluation methods. Currently, on-site engineering mainly relies on experience or post-construction observation, making it difficult to predict and optimize the effects of different schemes before construction, and also hindering the accurate assessment of the mechanical properties of the already formed recycled roof. This restricts the standardized promotion and reliability improvement of this technology.

[0004] Therefore, there is an urgent need to establish a laboratory method that can realistically simulate on-site conditions, is repeatable, and can be quantitatively tested, in order to scientifically evaluate the roof reconstruction effect after grouting and filling of the collapse zone under different conditions, and to provide theoretical basis and technical support for optimizing process parameters and guiding engineering practice. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems in the prior art and provide a laboratory simulation test method for the reconstruction effect of grouting and filling of the roof in a collapse zone. This invention obtains the block size characteristics of the collapsed rock mass in the field through discrete element numerical simulation, determines the geometric and stress conditions for laboratory simulation based on similarity theory, reproduces the grouting and filling process in a controllable device, and finally tests its physical and mechanical parameters by drilling core samples, thereby achieving a quantitative laboratory evaluation and prediction of the roof reconstruction effect of grouting in a collapse zone.

[0006] To achieve the aforementioned objectives, the present invention employs the following technical solution: a laboratory simulation test method for the reconstruction effect of grouting and filling the roof slab in a collapse zone, the specific operation steps of which are as follows:

[0007] (a) Based on the mining geological conditions of the mine, obtain the physical and mechanical parameters of the coal seam, roof and overlying strata, and construct a three-dimensional numerical analysis model using discrete element numerical simulation software.

[0008] (b) Using the aforementioned three-dimensional numerical analysis model, the coal seam mining process was simulated, and data on the size of caving rocks in the caving zone under different roof conditions were extracted. The actual maximum rock particle size D was statistically analyzed. max The Talbot power exponent n of the caving zone rocks was obtained by fitting the data; the discrete element numerical simulation software was 3DEC software.

[0009] (c) Based on the Talbot gradation power exponent n and the actual maximum rock grain size D max Determine the geometric similarity ratio C of the laboratory simulation test. l The maximum simulated gangue particle size d of the rock block size characteristics of the laboratory-simulated caving zone was calculated. max And the percentage of gangue mass for each particle size, P.

[0010] (d) Calculate the mass M of each particle size gangue based on the mass percentage P of each particle size gangue, the preset packing height h and packing density ρ of the mixed particle size gangue, and load the mixed particle size gangue into the simulation test device.

[0011] (e) Based on the actual coal seam burial depth H, the geometric similarity ratio C l and bulk density ratio C r Calculate the stress similarity ratio C p An axial equivalent force F is applied to the mixed-size gangue in the simulation test device.

[0012] (f) Calculate the porosity φ of the mixed gangue in the simulation test device, prepare the filling slurry, and inject it at a grouting pressure P. f A volume of filling grout of Q is injected through the grouting hole.

[0013] (g) After the filling slurry to be injected has initially set, demolding and curing are carried out, and then a standard sample is drilled at the center of the molded sample.

[0014] (h) Test the physical and mechanical parameters of the standard specimen to obtain laboratory simulation results of the grouting and filling effect of the collapse zone roof reconstruction.

[0015] Furthermore, the simulation testing device has a cylindrical structure that can be disassembled in half, top to bottom, and secured with high-strength bolts. It features grouting holes at the top and is capable of axial equivalent stress loading and pressurized grouting. This specific structure solves the technical problem that traditional experimental devices cannot simultaneously meet the requirements of convenient loading and disassembly, application of axial stress, and simulation of pressurized grouting processes. It achieves efficient and accurate simulation of the on-site grouting environment and facilitates sample removal after the test.

[0016] Further, in step (c), the actual maximum rock grain size D max Geometric similarity ratio C l And the laboratory simulation of the maximum gangue particle size d max All three must meet the following conditions: This constraint solves the problem that improper scaling of rock particle size in laboratory simulations may lead to gradation distortion or difficulties in experimental operation. By setting a reasonable geometric similarity ratio and upper limit of particle size, it ensures that the mixture prepared in the laboratory can accurately reflect the block size characteristics of the rock mass on site, and is also convenient for experimental operation and subsequent testing.

[0017] Further, in step (d), the mass M of the gangue is calculated using the following formula:

[0018] ;

[0019] In the formula: M is the mass of gangue with particle size d, n is the Talbot power exponent, P is the percentage of gangue mass for each particle size, and d is the gangue particle size. max The formula represents the maximum particle size of gangue in the laboratory simulation, where ρ is the bulk density of the mixed-size gangue, and h is the packing height of the mixed-size gangue in the simulation test device. This calculation formula solves the technical problem of how to accurately translate the Talbot gradation theory obtained from numerical simulation into a specific batching scheme in the laboratory. It enables the rapid and accurate calculation of the required mass of each particle size group based on the target gradation index, ensuring the scientific rigor and consistency of the laboratory rock mass structure simulation.

[0020] Furthermore, in step (e), the formula for calculating the axial equivalent stress F is as follows:

[0021] ;

[0022] In the formula: F is the axial equivalent stress, H is the actual coal seam burial depth, and C p For stress similarity ratio, C l For geometric similarity ratio, C rThis is the density ratio. This calculation formula solves the key problem of how to accurately simulate the self-weight stress environment of overburden in the laboratory. Through conversion based on similarity theory, the actual coal seam burial depth is transformed into an equivalent axial stress that can be applied in the laboratory, so that the sample is grouted and cemented under a stress state close to reality, which improves the realism of the simulation experiment and the reliability of the results.

[0023] Further, in step (f), the grouting pressure P f The calculation formula is as follows:

[0024] ;

[0025] In the formula: P f For the grouting pressure simulated in the laboratory, C p For stress similarity ratio, P 实际 This represents the actual grouting pressure. This calculation formula solves the problem of scaling between laboratory grouting pressure and on-site engineering pressure, ensuring that the simulated grouting dynamics in the laboratory follow the same similarity criteria as on-site conditions. This makes the penetration and cementation behavior of the grout in the simulated rock mass more consistent with actual engineering practices.

[0026] Further, in step (f), the volume Q of the filling slurry is calculated using the following formula:

[0027] ;

[0028] In the formula: φ represents the porosity of the mixed gangue in the simulation test device; h represents the stacking height of the mixed-size gangue in the simulation test device; and Q represents the volume of the filling grout. This calculation formula solves the technical problem of how to determine the amount of grout injected in the laboratory to precisely fill the pores of the rock mass and avoid grout waste or insufficient filling. Through accurate calculation based on porosity, the grout volume can be reasonably configured to simulate the real filling process of grout in collapsed rock mass.

[0029] Furthermore, the filling slurry includes coal gangue, fly ash, cement, and additives. This specification solves the practical operational problems of selecting and simulating the proportion of grouting materials in the laboratory, clarifies the environmentally friendly and economical proportion using coal-based solid waste as the main raw material, and controls the particle size of coal gangue to ensure that it can be smoothly injected into the simulated rock mass pores at the laboratory scale, thereby effectively evaluating the cementing performance of different material proportions.

[0030] Furthermore, in step (h), the physical and mechanical parameters include uniaxial compressive strength, density, tensile strength, elastic modulus, cohesion, and internal friction angle. This comprehensive testing scheme solves the technical problem of how to comprehensively and quantitatively evaluate the performance of reconstructed roof slabs. By measuring a series of key mechanical parameters, it can systematically characterize the strength, deformation, and stability characteristics of the reconstructed roof slab, providing multi-dimensional scientific data support for evaluating the effectiveness of roof slab reconstruction.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] This invention provides a laboratory simulation testing method for the reconstruction effect of grouting and filling the roof in a collapsed zone. This method creatively integrates numerical simulation, similarity theory, and physical experiments to construct a complete and controllable technical system. By accurately inverting the block size characteristics of the collapsed rock mass after mining using numerical software, key Talbot gradation parameters are obtained. Based on strict geometric and stress similarity criteria, the field engineering conditions are scientifically scaled down to a laboratory scale, and the entire process of pressurized grouting and bonding is reproduced under axial stress using a specialized device. This completely changes the traditional research model that relies on field experience, solving its bottleneck problems of long cycles, high costs, and difficulty in quantitative prediction. It achieves controllable, measurable, and optimizable refined research on the reconstruction effect, providing a brand-new scientific experimental platform for process decision-making.

[0033] The application of this invention will generate significant technical and economic benefits. It makes it possible to systematically evaluate the impact of different geological conditions and process parameters in the laboratory before construction, thereby optimizing the safest and most economical solution and significantly reducing the risks and costs of on-site trial and error. By drilling core samples and conducting a full set of mechanical tests, a precise quantitative evaluation of the reconstructed structure's performance can be obtained, providing crucial data support for replacing traditional artificial false roofs. Simultaneously, this method advocates using solid wastes such as coal gangue and fly ash as the main grouting materials; its optimized proportions directly promote the resource utilization of solid waste, offering both environmental and cost advantages. Therefore, this invention not only has significant value in the mining of extra-thick coal seams but also has broad prospects for application in the field of mine strata control and disaster prevention. Attached Figure Description

[0034] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0035] Figure 1 This is a flowchart of the laboratory simulation test method of the present invention.

[0036] Figure 2 The diagrams show the rock block size distribution in the caving zone under different roof conditions. (a) shows the rock block size distribution under roof condition I; (b) shows the rock block size distribution under roof condition II; and (c) shows the rock block size distribution under roof condition III.

[0037] Figure 3 This is a graph showing the percentage distribution of rock mass of each particle size when the Talbot gradation power index n is 0.45, according to the present invention.

[0038] Figure 4This is a schematic diagram of the simulation testing device of the present invention.

[0039] Figure 5 This diagram illustrates the core sampling locations of samples from grouting and filling reconstructed roof slabs under different roof conditions and grouting material ratios according to the present invention. Specifically, (a) shows the core sampling locations of samples from grouting and filling reconstructed roof slabs under conditions I, II, and III; and (b) shows the core sampling locations of samples from grouting and filling reconstructed roof slabs under conditions 1#, 2#, and 3#.

[0040] In the figure: 1. Roof; 2. Coal seam; 3. Collapsed rock in the caving zone; 4. Floor; 5. Vent hole; 6. Grouting hole; 7. Axial equivalent stress; 8. Base of simulation test device; 9. Fixing bolt; 10. Grouting pump; 11. Mixed particle size gangue. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Of course, the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0042] like Figure 1 As shown, this invention provides a laboratory simulation test method for the reconstruction effect of grouting and filling the roof slab in a collapse zone, specifically including the following steps:

[0043] a. Based on the mining geological conditions, obtain the physical and mechanical parameters of the coal seam, roof and overlying strata, and construct a three-dimensional numerical analysis model using discrete element numerical simulation software.

[0044] b. Using the 3DEC three-dimensional numerical analysis model to simulate the coal seam mining process, extract the block size data of the caving rock in the caving zone under different roof conditions, and statistically analyze the actual maximum rock particle size D. max The Talbot power exponent n of the caving zone rocks was obtained by fitting the data.

[0045] c. Based on the Talbot power exponent n and the actual maximum rock grain size D max Determine the geometric similarity ratio C of the laboratory simulation test. l The laboratory simulation of the maximum gangue particle size d of the rock block size characteristics in the caving zone was obtained. max and the percentage of gangue mass of each particle size, P, of which .

[0046] d. Based on the mass percentage P of each particle size of gangue, the packing height h and packing density ρ of the mixed gangue of the particle sizes to be tested, calculate the gangue mass M of each particle size, and load the mixed gangue of the particle sizes into the simulation testing device; where,

[0047] In the formula: d is the particle size of gangue, in mm; n is the Talbot power exponent for gradation, determined by the block size characteristics of the collapsed rock in the 3DEC numerical simulation; ρ is the bulk density of the mixed gangue, in g / cm³; h is the height of the mixed-size gangue in the simulation test device, in cm.

[0048] The simulation testing device, such as Figure 4 As shown, it includes: a cylindrical device body 8, the inner cavity of which is used to fill mixed particle size gangue 11; a grouting hole 6 and an exhaust hole 5 provided on the upper part of the device body; a loading system for applying axial equivalent force 7 to the gangue in the device body; and a grouting pump 10 for injecting filling slurry through the grouting hole 6; the device body 8 is composed of two parts that can be split in half and connected by fixing bolts 9.

[0049] e, based on the actual coal seam burial depth H and geometric similarity ratio C l and bulk density ratio C r Calculate the stress similarity ratio C p An axial equivalent force F is applied to the mixed-size gangue in the simulation test device, wherein... And C p =C l C r .

[0050] f, calculate the porosity φ of the mixed gangue in the simulation test device, prepare filling slurries with different proportions, and inject them at a grouting pressure P. f A filling grout of volume Q is injected through the grouting hole, wherein , P 实际 The actual grouting pressure is specified. The filling slurry consists of coal gangue, fly ash, cement, and additives, wherein the maximum particle size of the coal gangue is less than 5 mm.

[0051] g. After the sample has initially set, been demolded, and cured, core the sample by drilling at the center of the sample.

[0052] h. Finally, the laboratory simulation results of the grouting and filling effect of the roof slab reconstruction in the collapse zone are obtained by testing the physical and mechanical parameters of the standard specimens. The physical and mechanical parameters include at least uniaxial compressive strength, tensile strength, density, elastic modulus, cohesion and internal friction angle.

[0053] The present invention will now be described in detail with reference to two specific embodiments:

[0054] Example 1

[0055] A western coal mine primarily mines the No. 2 coal seam, a typical extra-thick coal seam characterized by shallow burial and high thickness. According to the mine's geological data, the average burial depth is 265m, and the average thickness is 12m. The roof is mainly composed of siltstone, fine-grained sandstone, and sandy mudstone, with significant differences in the degree of roof fragmentation in different areas. Currently, the working face mainly employs a layered mining process. To accelerate the roof regeneration effect after layered mining, a caving-filling roof reconstruction technique is used on-site. To understand the effectiveness of grouting-filling roof reconstruction under different roof conditions, laboratory simulations and tests are conducted.

[0056] Step a: Based on the mining geological conditions, obtain the physical and mechanical parameters of the coal seam, roof, and overlying strata, and construct a three-dimensional numerical analysis model using 3DEC discrete element numerical simulation software. The physical and mechanical parameters of each stratum are shown in Table 1.

[0057] Table 1 Physical and mechanical parameters of coal and rock strata

[0058]

[0059] Step b: Use 3DEC discrete element numerical simulation software to construct a three-dimensional numerical model to simulate roof collapse under conditions I, II, and III. The rock block size distribution of the collapse zone under conditions I, II, and III is as follows: Figure 2 As shown in (a) to (c), Figure 2 In the diagram, 1 represents the roof, 2 represents the coal seam, 3 represents the caving rock in the caving zone, and 4 represents the floor. The actual maximum rock particle size D in the caving zone is calculated. max The Talbot power exponent n of the caving zone rocks was obtained by fitting. The actual maximum rock grain size D of the caving zone rocks under different roof conditions was also determined. max The Talbot power exponent n is shown in Table 2.

[0060] Table 2. Actual maximum rock grain size D in the caving zone under different roof conditions. max and Talbot power exponent n

[0061]

[0062] Step c: Based on the Talbot power exponent n and the actual maximum rock grain size D... max Determine the geometric similarity ratio C of the laboratory simulation test. l =100:1, the laboratory-simulated maximum gangue particle size d of the rock block size characteristics of the caving zone was obtained. max and the mass percentage P of gangue of various particle sizes; where the mass percentage of gangue of different particle sizes is as follows when the Talbot power index n=0.45. Figure 3 As shown; the laboratory simulation of the maximum gangue particle size d maxSee Table 3. The percentage of gangue mass P for each particle size in the laboratory simulation test is shown in Table 4.

[0063] Table 3 Maximum particle size of mixed gangue in laboratory simulation tests

[0064]

[0065] Table 4. Percentage of gangue mass for each particle size in laboratory simulation tests.

[0066]

[0067] Step d: Calculate the bulk density ρ of mixed gangue with different gradations and power exponents n, as shown in Table 5. The bulk density ρ of mixed gangue with different gradations and power exponents n is shown in Table 5, and the gangue mass M of each particle size is shown in Table 6.

[0068] Table 5 Bulk Density of Mixed Gangue with Different Gradation Power Index n

[0069]

[0070] Based on the mass percentage P of gangue of each particle size, and assuming a stacking height h = 25 cm for the mixed gangue of the proposed particle size, calculate the mass M of gangue of each particle size, as shown in Table 6. Then, load the mixed gangue of the particle size into the simulation testing device. The simulation testing device and its dimensions are as follows: Figure 4 As shown.

[0071] Table 6 Mass of Gangue by Particle Size

[0072]

[0073] Step e: Based on the coal seam burial depth H=300m, the geometric similarity ratio C l =100:1 and bulk density ratio C r =1:1, calculate the stress similarity ratio C p =100:1, and an axial equivalent stress F=0.075MPa is applied to the mixed-size gangue in the simulation test device.

[0074] Step f: The porosity φ of the mixed gangue was tested to be 18%, 25%, and 30% respectively; the stacking height of the mixed gangue particles in the simulated testing device was h = 25 cm, and the volume of grouting material Q injected was 2208.93 cm³. 3 3067.96cm 3 3681.56cm 3 The grouting material has a solid mass fraction of 82%, and its main components and mass percentages are as follows: gangue 35%, cement 35%, fly ash 25%, and additives 5%; with a grouting pressure P... f Grouting was performed at a pressure of 0.01 MPa until the grout filled the pores. A schematic diagram of the grouting process, as shown in the laboratory simulation test, is as follows. Figure 4As shown.

[0075] Step g: After the sample has initially set, demolded, and cured in a constant temperature curing chamber at 20±2℃ and 95% relative humidity, core samples are taken from the center of the sample using a core drilling method to complete the core sampling of standard cylindrical samples. The dimensions of the compressive strength samples are L=100mm and R=50mm, the tensile strength samples are L=20mm and R=50mm, and the shear strength samples are L=50mm and R=50mm. The core sampling locations for the top slab samples from the grouting and reconstruction of the slab under conditions I, II, and III are as follows: Figure 5 As shown in Figure (a).

[0076] Step h: Test the physical and mechanical parameters of the standard specimen to obtain laboratory simulation results of the grouting and filling effect on the roof reconstruction of the collapse zone. The main physical and mechanical parameters of the standard specimen are shown in Table 7.

[0077] Table 7 Results of Laboratory Simulation Tests

[0078]

[0079] Example 2:

[0080] A western coal mine primarily mines the No. 2 coal seam, a typical extra-thick coal seam characterized by shallow burial and high thickness. According to the mine's geological data, the average burial depth is 265m, and the average thickness is 12m. The roof is mainly composed of siltstone, fine-grained sandstone, and sandy mudstone, with significant differences in the degree of roof fragmentation in different areas. Currently, the working face mainly employs a layered mining process. To accelerate the roof regeneration effect after layered mining, a caving-zone grouting and roof reconstruction technique is used on-site. To understand the roof reconstruction effect under different grouting material ratios, laboratory simulations and tests are conducted.

[0081] Step a: Based on the mining geological conditions of the mine, obtain the physical and mechanical parameters of the coal seam, roof and overlying rock strata, and construct a three-dimensional numerical analysis model using 3DEC discrete element numerical simulation software. The physical and mechanical parameters of each rock stratum are shown in Table 1.

[0082] Step b: Use 3DEC discrete element numerical simulation software to construct a three-dimensional numerical model to simulate the roof collapse and statistically analyze the actual maximum rock particle size D in the collapse zone. max =1200mm and the Talbot power index n=0.48 of the caving zone rock was obtained by fitting.

[0083] Step c: Based on the Talbot power exponent n and the actual maximum rock grain size D... max Determine the geometric similarity ratio C of the laboratory simulation test. l=100:1, the laboratory-simulated maximum gangue particle size d of the rock block size characteristics of the caving zone was obtained. max =12mm and the mass percentage P of gangue of each particle size; the mass percentage of gangue of each particle size is shown in Table 8.

[0084] Table 8. Percentage of gangue mass for different particle sizes in laboratory simulation tests.

[0085]

[0086] Step d: The bulk density ρ of the mixed gangue with a Talbot power index n=0.48 was obtained from the test, which was 1.98 g / cm³. 3 Based on the mass percentage P of each particle size of gangue, and the stacking height h = 25 cm of the mixed gangue of the desired particle size, the mass M of each particle size of gangue is calculated and loaded into the simulation testing device. The dimensions of the simulation testing device are as follows: Figure 4 As shown in Table 9, the mass of gangue with different particle sizes is shown in Table 9.

[0087] Table 9 Mass of Gangue by Particle Size

[0088]

[0089] Step e: Based on the coal seam burial depth H=300m, the geometric similarity ratio C l =100:1 and bulk density ratio C r =1:1, calculate the stress similarity ratio C p =100:1, and an axial equivalent stress F=0.075MPa is applied to the mixed-size gangue in the simulation test device.

[0090] Step f: The porosity φ of the mixed gangue is 20%; the stacking height of the mixed gangue particles in the simulation test device is h = 25 cm, and the volume of injected grouting material is Q = 2454.37 cm³. 3 ; with grouting pressure P f Grouting was carried out at a pressure of 0.01 MPa until the grout filled the pores. The solid mass fraction of the grouting material was 82%, and the specific proportions are shown in Table 10. The laboratory simulation test of the grouting process is illustrated in the figure below. Figure 4 As shown.

[0091] Table 10 Proportions of Different Grouting Materials

[0092]

[0093] Step g: After the sample has initially set, demolded, and cured in a constant temperature curing chamber at 20±2℃ and 95% relative humidity, core samples are taken from the center of the sample using a core drilling method. The dimensions for the compressive strength sample are L=100mm and R=50mm, the tensile strength sample is L=20mm and R=50mm, and the shear strength sample is L=50mm and R=50mm. The core drilling locations for the grouting material mix and the grouting filling and reconstruction of the roof slab in the collapse zone under conditions #1, #2, and #3 are as follows. Figure 5 As shown in Figure (b) of the document.

[0094] Step h: Test the physical and mechanical parameters of the standard specimens to obtain laboratory simulation results of the grouting and filling effect on the roof reconstruction of the collapse zone. The physical and mechanical parameters of the standard specimens are shown in Table 11.

[0095] Table 11 Results of Laboratory Simulation Tests

[0096]

[0097] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A laboratory simulation test method for the reconstruction effect of grouting and filling the roof slab in a collapse zone, characterized in that, The specific steps are as follows: (a) Based on the mining geological conditions of the mine, obtain the physical and mechanical parameters of the coal seam, roof and overlying strata, and construct a three-dimensional numerical analysis model using discrete element numerical simulation software; (b) A three-dimensional numerical analysis model was used to simulate the coal seam mining process, and data on the size of caving rocks in the caving zone under different roof conditions were extracted. The actual maximum rock particle size D was statistically analyzed. max And the Talbot power exponent n of the caving zone rocks was obtained by fitting; (c) Based on the Talbot power exponent n and the actual maximum rock grain size D max Determine the geometric similarity ratio C of the laboratory simulation test. l The maximum simulated gangue particle size d of the rock block size characteristics of the laboratory-simulated caving zone was calculated. max and the percentage of gangue mass for each particle size, P; (d) Based on the percentage of gangue mass P of each particle size, preset the packing height h and packing density ρ of the mixed gangue, calculate the gangue mass M of each particle size, and load the mixed gangue into the simulation test device; (e) Based on the actual coal seam burial depth H, the geometric similarity ratio C l and bulk density ratio C r Calculate the stress similarity ratio C p An axial equivalent force F is applied to the mixed-size gangue in the simulation test device; (f) Calculate the porosity φ of the mixed gangue in the simulation test device, prepare the filling slurry, and inject it at a grouting pressure P. f Inject filling grout of volume Q through the grouting hole; (g) After the filling slurry to be injected has initially set, demolding and curing are carried out, and then a standard sample is drilled at the center of the molded sample. (h) Test the physical and mechanical parameters of the standard specimens to obtain laboratory simulation results of the reconstruction effect of grouting and filling the roof of the collapse zone.

2. The laboratory simulation test method for the reconstruction effect of grouting and filling roof slab in a collapse zone according to claim 1, characterized in that: The simulation testing device has a cylindrical structure. It can be disassembled in half or from top to bottom and fixed with high-strength bolts. The upper part of the simulation testing device is provided with grouting holes. The simulation testing device can realize axial equivalent stress loading and pressurized grouting.

3. The laboratory simulation test method for the reconstruction effect of grouting and filling roof slab in a collapse zone according to claim 1, characterized in that: In step (c), the actual maximum rock grain size D max Geometric similarity ratio C l And the laboratory simulation of the maximum gangue particle size d max The following conditions must be met: .

4. The laboratory simulation test method for the reconstruction effect of grouting and filling roof slab in a collapse zone according to claim 1, characterized in that: In step (d), the mass M of the gangue is calculated using the following formula: In the formula: M is the mass of gangue with particle size d, n is the Talbot power exponent, P is the percentage of gangue mass for each particle size, and d is the gangue particle size. max ρ represents the maximum particle size of gangue in the laboratory simulation, h represents the bulk density of the mixed-size gangue, and h represents the packing height of the mixed-size gangue in the simulation test device.

5. The laboratory simulation test method for the reconstruction effect of grouting and filling roof slab in a collapse zone according to claim 1, characterized in that: In step (e), the formula for calculating the axial equivalent stress F is as follows: In the formula: F is the axial equivalent stress, H is the actual coal seam burial depth, and C p For stress similarity ratio, C l For geometric similarity ratio, C r This refers to the bulk density ratio.

6. The laboratory simulation test method for the reconstruction effect of grouting and filling roof slab in a collapse zone according to claim 1, characterized in that: In step (f), the grouting pressure P f The calculation formula is as follows: In the formula: P f For grouting pressure, C p For stress similarity ratio, P 实际 This represents the actual grouting pressure.

7. The laboratory simulation test method for the reconstruction effect of grouting and filling roof slab in a collapse zone according to claim 1, characterized in that: In step (f), the volume Q of the filling slurry is calculated using the following formula: In the formula: φ is the porosity of the mixed gangue in the simulation test device; h is the stacking height of the mixed gangue particles in the simulation test device; and Q is the volume of the filling slurry.

8. The laboratory simulation test method for the reconstruction effect of grouting and filling roof slab in a collapse zone according to claim 7, characterized in that: The filling slurry includes coal gangue, fly ash, cement, and additives.

9. The laboratory simulation test method for the reconstruction effect of grouting and filling roof slab in a collapse zone according to claim 1, characterized in that: In step (h), the physical and mechanical parameters include uniaxial compressive strength, density, tensile strength, elastic modulus, cohesion, and internal friction angle.

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