Roadway type filling method for coal mine gangue

Abstract

The invention relates to the technical field of gangue filling, in particular to a coal mine gangue roadway type filling method which comprises the following steps: (1) screening gangue, and classifying the gangue into corresponding particle size groups according to particle sizes; (2) designing grading schemes according to the particle size groups divided in the step (1), performing simulation by using PFC2D numerical simulation software to obtain stress-strain curves of the grading schemes, and selecting the grading scheme with the maximum peak stress as the optimal grading scheme; and (3) filling the roadway type filling area according to the optimal grading scheme determined in the step (2). According to the method, the optimal grading scheme is determined by simulating the stress damage process of the internal structure of the original waste rock filling body under different particle size grading schemes through PFC2D, simulation verification shows that the stress concentration condition of the left side and the right side of the filled roadway is improved, the filling body filled in the roadway can replace roadway surrounding rock to bear part of pressure, and the working efficiency is improved. The problem that the crushing pressure is large when small-particle gangue is used in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of gangue filling, and in particular to a method for roadway filling of coal mine gangue. Background Art

[0002] Gangue is a solid waste generated during coal mining, containing various harmful substances. At present, the lifting of gangue to the surface and stacking cause serious environmental problems, and at the same time occupy a large amount of lifting resources and land resources. "No gangue is seen during coal mining, and the mine becomes green mountains". If gangue can be directly used for underground filling, it can reduce pollutant emissions, protect the environment, save land and improve land utilization rate, save the manpower, material and financial costs generated in the subsequent treatment of gangue, and improve economic benefits. At the same time, eliminating gangue can reduce the obstacles in the coal mining process, improve coal mining efficiency, shorten the mining cycle and reduce mining costs.

[0003] Chinese Patent Application for Invention CN 109931095 A discloses a method for engineering design of underground separation and in-situ filling of coal gangue, which can liberate the coal under "three-under" conditions, improve the recovery rate of mine resources, and at the same time reduce the problems such as building and ecological damage caused by surface subsidence. The method includes the following specific steps: The first step is to analyze the washability, economic cost, separation quality requirements and gangue use of coal gangue; the second step is to determine the coal gangue separation method; the third step is to select the separation equipment and design of the separation chamber; the fourth step is to determine the gangue filling capacity M of the working face according to the underground gangue selection capacity M 出 of the working face 充 ; the fifth step is to determine the filling method in combination with the filling requirements; the sixth step is to determine the filling equipment, process and design the filling face parameters according to the filling requirements; the seventh step is to determine the mining-separation-filling production system according to the actual mining and excavation layout of the mine; the eighth step is to verify and feedback and adjust the key parameters of the mining-separation-filling integrated production system.

[0004] The above solution provides technical support for the practical application of gangue filling. However, the filling quality of gangue is directly related to its compaction situation, and the above solution does not consider the influence of gangue gradation on the gangue filling effect. At present, small particle gangue is also used for filling. For example, Chinese Patent Application CN 114233375 A discloses a pure gangue slurry filling material for mine filling. The pure gangue slurry filling material is composed of solid materials and water. Taking the total amount as 100%, the solid materials include 76% - 82% of gangue with a particle size greater than 0.315 mm, and the balance is gangue with a particle size less than or equal to 0.315 mm. Chinese Patent Application CN118063122 A discloses a coal gangue slurry filling material also composed of water and solid components. The solid components include 15% - 40% of coal gangue with a particle size of 4.75 - 1.18 mm, 20% - 50% of coal gangue with a particle size of 1.18 - 0.425 mm, 5% - 15% of coal gangue with a particle size of 0.425 - 0.075 mm, and 10% - 25% of coal gangue with a particle size less than 0.075 mm. Although the above methods can meet the application requirements, the gangue needs to be crushed before filling, and the workload is huge. Summary of the Invention

[0005] Aiming at the technical problem that the crushing pressure is huge when using small particle gangue for filling in the prior art during the filling of coal gangue, the present invention provides a method for roadway filling of coal mine gangue.

[0006] The technical solution of the present invention is as follows: A method for roadway filling of coal mine gangue includes the following steps: (1) Screen the gangue, divide it into n particle size groups according to the particle size, and classify the gangue into the corresponding particle size groups according to the particle size. n is a positive integer greater than or equal to 4; The maximum particle size of the gangue is greater than 300 mm, preferably 600 - 750 mm; (2) Design a gradation plan according to the particle size groups divided in step (1), use PFC2D numerical simulation software to simulate different gradation plans, obtain the stress-strain curves of the gradation plans, and select the gradation plan with the maximum peak stress as the optimal gradation plan; (3) Fill the roadway filling area according to the optimal gradation plan determined in step (2), and the gangue filling direction is carried out from low elevation to high elevation.

[0007] Optionally, the optimal gradation plan in step (2) is: In terms of mass percentage, the particle size of 0-150 mm accounts for 38.07%, the particle size of 150-300 mm accounts for 11.95%, the particle size of 300-450 mm accounts for 21.60%, the particle size of 450-600 mm accounts for 15.85%, and the particle size of 600-750 mm accounts for 12.53%. The above range AB means greater than A and less than or equal to B.

[0008] Optionally, step (3) further includes constructing a gangue retaining wall before filling the tunnel with gangue.

[0009] Optionally, step (3) further includes constructing a slurry stop wall after filling the tunnel with gangue, and then pouring the mixed water-coal ash slurry into the gangue pile through a conveying pipe until it is full, and then stopping the construction.

[0010] Optionally, the water-cement ratio of the coal-lime slurry is 3:1-5:1. Two factors need to be considered when designing the water-cement ratio of the coal-lime slurry. First, the water content in the coal-lime slurry should be minimized, taking into account the bleeding and drainage pressures in the filling area. Second, the fluidity of the coal-lime slurry should be considered. Since the slope of the roadway is generally small, the water-cement ratio of the coal-lime slurry should not be too small to meet the fluidity and viscosity requirements of construction and reduce the resistance along the way.

[0011] Optionally, the lane-type filling area of step (3) includes a Y-shaped area formed by three connected lanes and / or a triangular area formed by three connected lanes.

[0012] Optionally, for the Y-shaped area, drainage paths are set up at the low elevation points of the three tunnels to connect to the existing drainage channels, so that the fissure water and water-fuel ash filling sedimentation water in the filling tunnels are discharged and collected into the drainage pipes of the mine, and finally discharged into the central water tank, and discharged to the ground by the central pump room through water pumps and pipelines.

[0013] Optionally, for the triangular area, a sump is set up at a low elevation point in the triangular area to collect the tunnel seepage water inside the triangular area, and then the tunnel seepage water in the sump is pumped to the sedimentation tank through a sewage pump. The sewage in the sedimentation tank enters the central water tank through the existing drainage pipe, and is discharged to the ground by the central pump room through water pumps and pipes.

[0014] Optionally, an inhibitor is sprayed in the tunnel filling area. The inhibitor is an aqueous solution of halide salts. By spraying, a liquid film is formed on the surface of the coal wall or floating coal. The liquid film covers the floating coal and the surface of the coal body cracks, avoiding contact between coal and oxygen, inhibiting the oxidation and spontaneous combustion of the coal wall or floating coal. The relative humidity in the coal mine is relatively high, and the inhibitor film absorbs moisture in the air, increasing the inhibitory effect.

[0015] Optionally, the halide salt aqueous solution is a 20 wt% calcium chloride or magnesium chloride aqueous solution, which has good retardation effect, high cost performance, and convenient transportation and storage.

[0016] The beneficial effects of the present invention are as follows: Through PFC2D simulation, the present invention determines the optimal grading scheme by simulating the stress-damaged process of the internal structure of the original gangue filling body under different particle size grading schemes. After verification by FLAC3D simulation, the stress concentration on both sides of the roadway after filling is improved, and the filling body filled in the roadway can replace the surrounding rock of the roadway to bear part of the pressure. At the same time, the present invention solves the problem of large crushing pressure existing in the existing use of small particle gangue by screening the optimal grading scheme.

[0017] The coal mine gangue roadway filling method provided by the present invention has important guiding significance for solving problems such as the safe mining of corner coal pillars in mining areas, the non-out-of-well production of production gangue, the elimination of environmental pollution and damage caused by surface gangue accumulation, and surface subsidence control in the mining area, and has significant social and environmental benefits. Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 It is a schematic diagram of the original gangue filling load using the PFC2D numerical simulation software in Embodiment 1.

[0020] Figure 2 It is the simulation result of the particle size grading design scheme A obtained by using the PFC2D numerical simulation software in Embodiment 1.

[0021] Figure 3 It is the simulation result of the particle size grading design scheme B obtained by using the PFC2D numerical simulation software in Embodiment 1.

[0022] Figure 4 It is the simulation result of the particle size grading design scheme C obtained by using the PFC2D numerical simulation software in Embodiment 1.

[0023] Figure 5 It is the simulation result of the particle size grading design scheme D obtained by using the PFC2D numerical simulation software in Embodiment 1.

[0024] Figure 6 It is the simulation result of the particle size grading design scheme E obtained by using the PFC2D numerical simulation software in Embodiment 1.

[0025] Figure 7 It is a schematic diagram of the layout, filling sequence and direction of the Y-shaped area filling roadway in Embodiment 1.

[0026] Figure 8 It is a schematic diagram of the gangue transportation location and the gangue transportation route of the filling working face in Embodiment 1.

[0027] Figure 9 It is the vertical stress distribution diagram after the roadway excavation in Embodiment 1.

[0028] Figure 10 It is the vertical stress distribution diagram after the roadway filling in Embodiment 1.

[0029] Figure 11 It is the cross-section stress nephogram of the turnout branch roadway in Embodiment 1, where the left figure is the cross-section stress nephogram when the turnout branch roadway excavation is completed, and the right figure is the cross-section stress nephogram when the turnout branch roadway filling is completed.

[0030] Figure 12 It is the cross-section stress nephogram of the downhill branch roadway in Embodiment 1, where the left figure is the cross-section stress nephogram when the downhill branch roadway excavation is completed, and the right figure is the cross-section stress nephogram when the downhill branch roadway filling is completed.

[0031] Figure 13 It is the cross-section stress nephogram of the return airway of the 130205 working face in Embodiment 1, where the left figure is the cross-section stress nephogram when the return airway of the 130205 working face excavation is completed, and the right figure is the cross-section stress nephogram when the return airway of the 130205 working face filling is completed.

[0032] Figure 14 It is a schematic diagram of the layout of the gangue filling area-level roadway, the filling sequence and direction in Embodiment 2. Detailed implementation manners

[0033] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] A coal mine gangue roadway filling method includes the following steps: (1) Screen the gangue, divide it into n particle size groups according to the particle size, and classify the gangue into the corresponding particle size groups according to the particle size, where n is a positive integer greater than or equal to 4; The maximum particle size of the gangue is greater than 300 mm, preferably 600 - 750 mm; (2) Design a grading scheme according to the particle size groups divided in step (1), use the PFC2D numerical simulation software to simulate different grading schemes, obtain the stress-strain curves of the grading schemes, and select the grading scheme with the maximum peak stress as the optimal grading scheme; (3) Fill the roadway filling area according to the optimal gradation scheme determined in step (2), and the filling direction of gangue is carried out from low elevation to high elevation.

[0035] As a preferred embodiment of the present invention, the raw gangue filling material is a non-uniform product composed of gangue particles of different sizes. Therefore, the parallel bond model is adopted in step (2). When the raw gangue particles are subjected to external forces during the filling process, the forces between the particles and the contact points with the wall change, resulting in a change in the internal stress field of the model. A 500mm×550mm area is selected for simulation in the PFC2D numerical simulation software.

[0036] As a preferred embodiment of the present invention, in step (3), a trackless rubber-tyred vehicle is used to transport the gangue material to the target roadway, and then a loader is used to stack the gangue blocks.

[0037] As a preferred embodiment of the present invention, in step (3), before the gangue filling operation is carried out in the roadway, the construction of the gangue retaining wall is carried out first. First of all, the gangue retaining wall can provide a stable boundary support for the subsequent gangue filling, prevent the gangue from rolling and scattering randomly during the filling process, ensure that the gangue can be accurately stacked in the predetermined area, ensure the orderly progress of the filling operation, and improve the filling efficiency. Secondly, the gangue retaining wall enhances the overall structural stability of the roadway to a certain extent. After the gangue is filled, it can assist in bearing the lateral pressure of the gangue, act together with the structure formed by the subsequent filling, better maintain the spatial form of the roadway, reduce the risk of deformation and collapse of the roadway caused by filling operations or geological changes, lay a solid foundation for the safe production of the mine, and effectively guarantee the smooth progress of subsequent mining activities.

[0038] As a preferred embodiment of the present invention, after the gangue filling of the roadway in step (3), a grout stopping wall is constructed, and then grouting is carried out. The mixed water coal ash slurry is poured into the gangue pile through a conveying pipeline until it is full, and then the construction is stopped. The grout stopping wall can effectively prevent the subsequent poured water coal ash slurry from flowing out, ensure that the slurry plays a role in the designated area, improve the tightness and integrity of the filling operation, create a stable environment for the subsequent pouring of water coal ash slurry, and guarantee the filling quality. Pouring the water coal ash slurry into the gangue pile can make full use of the characteristics of water coal ash to fill the voids between the gangue, make the filling structure more dense, enhance the overall stability of the roadway filling body, improve the supporting force on the surrounding rock of the roadway, reduce the risk of roadway deformation and collapse. Moreover, the pouring of the water coal ash slurry can reduce the friction between the gangue to a certain extent, reduce the energy release caused by the movement and extrusion of the gangue, improve the safety of the roadway under complex geological conditions, and guarantee the smooth progress of the safe production operation of the mine.

[0039] When designing the water-to-coal ash ratio of water coal ash slurry, two factors need to be weighed. On the one hand, to reduce the water seepage phenomenon in the filling area and lower the drainage pressure, the water consumption in the water coal ash slurry should be minimized as much as possible. On the other hand, considering that the roadway slope is generally small, to ensure the smooth flow of the water coal ash slurry, meet the requirements of construction for fluidity and viscosity, and at the same time reduce the frictional resistance during transportation, the water-to-coal ash ratio should not be set too small. Therefore, the water-to-coal ash ratio of the water coal ash slurry is preferably 3:1 - 5:1.

[0040] As a preferred embodiment of the present invention, the present invention proposes specific filling schemes for two types of roadway filling areas. One is the Y-shaped area formed by three interconnected roadways, and the other is the triangular area formed by three interconnected roadways.

[0041] As a preferred embodiment of the present invention, for the Y-shaped area, the specific operation is to set drainage paths at the low and high points of the three roadways respectively and connect them to the existing drainage pipes. The fissure water in the filling roadway and the water precipitated after the water coal ash filling can be smoothly discharged through these drainage paths and collected into the mine drainage pipes, and finally flow into the central sump. The central pump house will use pumps and pipelines to drain the water in the central sump to the ground.

[0042] As a preferred embodiment of the present invention, when dealing with the roadway water seepage problem in the triangular area, the specific operation is to set a sump at the low and high points of the triangular area. The sump is used to collect the roadway water seepage in the triangular area, and then use a sewage pump to pump the roadway water seepage collected in the sump to the sedimentation tank. The sewage in the sedimentation tank will flow along the existing drainage pipes into the central sump, and finally the central pump house will use pumps and pipelines to drain the sewage to the ground.

[0043] As a preferred embodiment of the present invention, a retarding agent is sprayed in the roadway filling area. The retarding agent uses an aqueous solution of halide salts. Through spraying operations, a liquid film can be quickly formed on the surface of the coal wall or floating coal. This liquid film can completely wrap the floating coal and the surface of the coal body fissures, effectively blocking the contact between the coal and oxygen, inhibiting the oxidation reaction of the coal wall and floating coal from the root cause, and preventing spontaneous combustion. Considering the relatively high humidity environment characteristics inside the coal mine, the retarding agent film can also absorb the moisture in the air, further enhancing the retarding effect.

[0044] As a preferred embodiment of the present invention, the aqueous solution of halide salts uses a 20wt% calcium chloride aqueous solution or a magnesium chloride aqueous solution. Such solutions have excellent retarding effects, low costs, high cost performance, and are convenient for transportation and storage.

[0045] Example 1 The annual gangue output of Zaoquan Coal Mine is about 1.4 million tons, mainly generated from coal mining and tunneling operations. The mining area is located at the edge of the Mu Us Desert, 62 kilometers southeast of Lingwu City, Ningxia. The generation of a large amount of gangue has led to many problems such as hoisting transportation and the environment. Using the filling technology of the present invention, the following areas of Zaoquan Coal Mine are studied for the roadway filling technology: The filling area is located on the north side of the stop line of the 130205 working face in the 13th mining area of the third mining district, and the coal seam mined is coal seam 2. The filling roadway involves the return airway of the 130205 working face on the north side of the stop line, and two branch roads respectively connected to the +880m middle shaft yard and the 13th mining area downhill, presenting an overall "Y" shape (referred to as the Y-shaped area). Among them, the filling length of the shaft yard branch road is 67.5m, the filling length of the downhill branch road is 62m, and the filling length of the 130205 working face return airway is 96.5m, with a total filling length of 226m. The roadway section is 5300×5000mm, and the filling space reaches 5990m 3 , and the statistical information of the filling roadway length is shown in Table 1 below.

[0046] Table 1 Information table of gangue filling roadway in Example 1

[0047] The gangue to be filled and reused is screened. A total of 5 sieves are used, and the sieve hole diameters are 750mm, 600mm, 450mm, 300mm, and 150mm respectively. Using the residue method, first, the weighed gangue is passed through the 750mm sieve. After screening, the mass of the gangue with a particle size greater than 750mm is obtained, and the maximum particle size of this part is measured at the same time. Then the remaining part is passed through the 600mm sieve to obtain the mass of the gangue with a particle size of 600 - 750mm; and so on. Finally, the mass of each particle size group is obtained. Taking the content of each particle size group as the vertical axis and the particle size of the particle size group as the horizontal axis, the particle size composition curve can be obtained; at the same time, taking the percentage content greater than a certain particle size as the vertical axis and the particle size as the horizontal axis, the particle size cumulative distribution curve can be obtained.

[0048] According to the obtained gangue particle size distribution, the PFC2D numerical simulation software is used to simulate different particle size ratio schemes. The particle flow code PFC is a commonly used numerical simulation software for the discrete element method. Its ball can be used to represent a certain particle in the medium or a small part of the block bonded together. This program can also use the powerful embedded programming language Fish to simulate the generation, expansion, and penetration of random cracks according to the set loading and unloading boundary conditions, and conduct a comprehensive study on the mechanical properties of the original gangue particles from the macro and mesoscopic perspectives through the PFC numerical simulation of the original gangue filling process.

[0049] The original gangue filling material is a non-uniform product composed of gangue particles of different sizes. Therefore, the parallel bond model is adopted for the numerical simulation of the original gangue filling body. When the original gangue particles are subjected to external forces during the filling process, the forces between the particles and at the contact points with the wall change, resulting in a change in the internal stress field of the model. The PFC2D numerical simulation software is used to simulate different particle size ratio schemes. Considering the smoothness and aesthetic effect of the simulation, an area reduced by a ratio of 500mm×550mm is selected for observation. Since the numerical simulation is in a 1:10 ratio with the actual situation, the PFC numerical simulation particle sizes are set to 0-15mm, 10-30mm, 30-45mm, 45-60mm, and 60-75mm to determine the proportion of each particle size of the gangue particles. The specific PFC numerical simulation particle size grading design scheme is shown in Table 2 below.

[0050] Table 2 PFC numerical simulation particle size grading design scheme (mass percentage)

[0051] Five grading schemes are simulated. The schematic diagram of the original gangue filling load is as shown in Figure 1 and the stress-strain results are as shown in Figures 2 - 6 .

[0052] According to Figure 2 , when the particle size of 0-15mm accounts for 61.70%, the particle size of 15-30mm accounts for 12.13%, the particle size of 30-45mm accounts for 11.45%, the particle size of 45-60mm accounts for 8.27%, and the particle size of 60-75mm accounts for 6.45%, the peak stress under this scheme is 8.87MPa.

[0053] According to Figure 3 , when the particle size of 0-15mm accounts for 52.53%, the particle size of 15-30mm accounts for 13.09%, the particle size of 30-45mm accounts for 14.97%, the particle size of 45-60mm accounts for 10.87%, and the particle size of 60-75mm accounts for 8.54%, the peak stress under this scheme is 6.95MPa.

[0054] According to Figure 4 , when the particle size of 0-15mm accounts for 44.72%, the particle size of 15-30mm accounts for 12.97%, the particle size of 30-45mm accounts for 18.35%, the particle size of 45-60mm accounts for 13.40%, and the particle size of 60-75mm accounts for 10.56%, the peak stress under this scheme is 8.81MPa.

[0055] According to Figure 5It can be seen that when the particle size of 0-15 mm accounts for 38.07%, the particle size of 15-30 mm accounts for 11.95%, the particle size of 30-45 mm accounts for 21.60%, the particle size of 45-60 mm accounts for 15.85%, and the particle size of 60-75 mm accounts for 12.53%, the peak stress under this scheme is 7.89 MPa.

[0056] according to Figure 6 It can be seen that when the particle size of 0-15 mm accounts for 32.41%, the particle size of 15-30 mm accounts for 10.18%, the particle size of 30-45 mm accounts for 24.71%, the particle size of 45-60 mm accounts for 18.24%, and the particle size of 60-75 mm accounts for 14.46%, the peak stress under this scheme is 4.48 MPa.

[0057] The stress-strain curves for the different particle size grading schemes above show that as the proportion of small-size waste rock fill decreases and the proportion of larger-size waste rock fill increases, the peak stress generally shows a downward trend. In the stress-strain curves, the peak stress is positively correlated with the proportion of small-size waste rock fill.

[0058] Using PFC2D to analyze the crack evolution during the failure of waste rock fill with different particle size distributions, researchers found that, under external load, cracks propagate and evolve in a single pattern. When the stress reaches its peak, macrocracks appear on the surface of the specimen model, accompanied by partial particle spalling. Microcracks continue to form within the model, propagating and eventually forming primary cracks. After the stress reaches its peak, microcracks accumulate and continue to develop along the tips of the original macrocracks, ultimately forming prominent primary cracks at the upper and middle portions of the model. Notably, during the crack evolution process, most cracks lie along a single straight line, resulting in a single primary crack propagation direction at the macroscopic level. When the stress reaches the post-peak stage of the stress-strain curve, the model retains a certain load-bearing capacity, although not yet completely destroyed. As the load continues to increase, the crack propagation direction deviates due to uneven local stress on the particles within the model, forming secondary cracks that ultimately lead to the failure of the model specimen.

[0059] Using PFC2D to analyze the force contact situation during the failure process of the original gangue filling, it is found that the contact force is not evenly distributed among all particles, but shows an obvious skeletal force chain structure. The force chains formed between large gangue particles are thicker than those between small particles, indicating that the main bearing capacity of the gangue filling body comes from the gangue with larger particle sizes. At the initial stage of loading, the force chains formed between small particles break first, resulting in fine cracks inside the filling body. As the stress continues to be loaded, the force chains between large and small particles also begin to break until a larger failure area is formed, ultimately causing the gangue filling body specimen to lose its bearing capacity. By observing the force chain diagram after failure, it can be found that the stronger force chains formed between large particles still remain intact, which means that in the actual filling process, even when the ultimate stress is reached and failure occurs, the filling body still has a certain bearing capacity.

[0060] Through PFC numerical simulation of the failure process of the internal structure of the original gangue filling body under stress and the interaction between particles with different particle size gradation schemes, the evolution of the force chains and the crack propagation of the gangue filling body are studied from the mesoscopic perspective. At the mesoscopic level, the deformation of the gangue filling body is not caused by the deformation of the particles themselves, but by the insufficient interaction force between particles, resulting in displacement changes of the particles.

[0061] According to the PFC2D numerical simulation results, considering various technical and economic factors, when the passing rate of the particle size of 0 - 15mm for the original gangue filling is 44.72%, the passing rate of the particle size of 15 - 30mm is 12.97%, the passing rate of the particle size of 30 - 45mm is 18.35%, the passing rate of the particle size of 45 - 60mm is 13.40%, and the passing rate of the particle size of 60 - 75mm is 10.56%, the peak stress is the largest. Therefore, the gradation scheme C is selected as the optimal gradation scheme (it should be enlarged proportionally during actual filling).

[0062] Since the filling roadway includes three roadways: the yard branch roadway, the downhill branch roadway, and the return airway of the 130205 working face, considering the comprehensive factors such as the elevation, ventilation, and drainage of the three roadways, there is a spatio-temporal relationship among the three. To ensure filling safety, the roadway filling should be carried out from the lower elevation to the higher elevation. The corresponding elevations of the yard branch roadway A - D - E - B are +858.697m, +860.952m, +861.264m, +862.057m, showing a trend from low to high; the corresponding elevations of the downhill branch roadway C - D are +866.683m, +860.952m, showing a trend from high to low; the corresponding elevations of the return airway of the 130205 working face E - F are +861.264m, approximately 850m, showing a trend from high to low.

[0063] Based on the elevation difference, the filling direction sequence and filling direction are designed as shown in Table 3 and Figure 7 as follows.

[0064] Table 3 List of filling direction sequence and filling direction of Example 1

[0065] The design is to transport the gangue produced by the development roadway in the 13 mining area to different locations according to the filling stage, as shown in Table 4 and Figure 8 shown.

[0066] Table 4 List of waste rock transportation locations in Example 1

[0067] The specific steps are as follows: ① First, conduct a hidden disaster inspection on the target filling tunnel, and take corresponding measures to eliminate the hidden dangers found in a timely manner.

[0068] ② In accordance with the design requirements for the retaining wall, a 1500mm thick retaining wall was constructed at the opening of the waste rock filling tunnel using C30 concrete formwork. Prior to pouring, two rows of φ21.8×4300mm anchor cables were installed in the top slab within the retaining wall construction area, and two rows of 22#-M24-2500BHRB500 high-strength left-handed, unreinforced threaded steel anchor bolts were installed in the bottom slab, with a spacing of 1200×900mm. Two rows of φ21.8×4300mm anchor cables were installed on each side, with a spacing of 2500×900mm. All anchor cables were exposed 1000mm. A 300×300×16mm manganese steel dome tray was fixed 500mm from the end and secured with a KM22 lock. The top, side, and bottom anchor cables were then connected using anchor cables of appropriate lengths based on site conditions, and the connections were secured with wire. After construction was completed, formwork was set up to the specified thickness and the concrete wall was poured.

[0069] The slag retaining (or slurry stopping) wall is further reinforced on the chute side using steel formwork (or wooden planks) and single hydraulic struts with bracing columns. Grooves are cut in the bottom plate and sides of the chute side of the slag retaining wall, each with a depth of 30mm. A waterproof sheet is placed in the groove and compacted with a baffle. The baffle is then propped up. After tightening the bottom plate, sides, and top plate, single hydraulic struts are used to support the wall on all sides. The initial support force of each hydraulic strut is no less than 14.8MPa. Two drainage observation ports with shut-off valves and pressure monitoring are also installed on the top plate.

[0070] ③ Establish an underground water-fuel ash mixing station. This project selects the B point of the belt lane of the 130203 working face near the cavern as the location of the mixing station and silo.

[0071] ④ After the tunnel excavation is completed, a water-fuel ash conveying pipe (φ200mm) is arranged on the tunnel roof along the tunnel centerline, and slurry unloading holes are left at intervals of 1.5m on the conveying pipe wall, and a connection is established between the mixing station and the water-fuel ash conveying pipeline of the target tunnel.

[0072] ⑤ The gangue produced by the excavation of the development tunnel in the 13 mining area will be transported to the backfill working face of the filling tunnel by trackless rubber-wheeled vehicles.

[0073] ⑥ Raw gangue filling: After the gangue is unloaded, it is first piled using a forklift, followed by loading with a loader to improve the filling efficiency. When using a loader, considering the actual roadway height of 5.5m, a "temporary slope" filling method can be used to maximize the loader's arm length. The maximum loading height of the loader is 3.5m, and the temporary slope height is 2m. The natural angle of repose of the gangue is approximately 55°.

[0074] Alternatively, a 40T scraper conveyor can be used, and a self-moving or dragging device can be installed with an inclination angle of 30° and a length of 9.2m.

[0075] ⑦ After the filling is completed, the slurry stop wall is constructed according to the same construction method as the gangue retaining wall, and the water-fuel ash filling process is carried out. The mixed water-fuel ash slurry is poured into the gangue pile through the conveying pipe until it is full, and then the construction is stopped.

[0076] ⑧ Then proceed to fill the next tunnel until all tunnel filling operations are completed.

[0077] Because some fissure water and sedimentation water from the coal-ash filling process exist within the backfill tunnel, they exert pressure on the retaining wall (slurry stop), impacting its structural stability. Therefore, this water must be drained. For the drainage system, the water flow direction is opposite to that of the backfill process. Specific drainage target locations are shown in Table 5.

[0078] Table 5 List of drainage target locations in Example 1

[0079] The seepage from the parking lot branch tunnel is collected at point A and is connected to the parking lot, where there is a parking lot drainage ditch. The seepage from the return air tunnel of the 130205 working face is collected at the 130205 stop mining line and finally flows into the 130205 goaf. The seepage from the downhill branch tunnel is collected at point D of the parking lot branch tunnel and is collected in the main drainage channel of the mine. It is finally discharged to the central water tank and discharged to the ground through the central pump room through water pumps and pipelines. The seepage from the return air tunnel of the 130205 working face is directly discharged to the goaf and can be ignored. The filling length of the parking lot branch tunnel is 67.5m, the filling length of the downhill branch tunnel is 62m, and the filling seepage length is 129.5m. The cross-section of the support tunnel is 5300×5000mm, and the total filling volume can be calculated to be 3432m 3 Calculated based on a filling rate of 70%, the water-coal ash filling ratio is 30%, approximately 1030m 3 .

[0080] The total exudate volume is: 。

[0081] Since the time for a branch roadway to be filled is about 12 hours, and it takes 2 - 4 hours for the filling paste to change from initial setting to no water secretion, the water secreted by the paste will be evenly secreted within 14 - 16 hours with a small amount of water. Therefore, the maximum water secretion is about 5.6 m 3 / h. Since the amount of water secreted is small, a separate sedimentation tank does not need to be designed. The drainage ditch of the bottom car park is directly used for drainage, and the sediment should be cleaned during the drainage process.

[0082] To meet the ventilation requirements of this area, relying on the "Y"-shaped roadway layout and the filling time - space relationship, the ventilation path of this area is designed in two stages: First stage: At the outlet position B of the branch roadway in the car park, a local fan is set up to supply air to both the branch roadway in the car park and the return air roadway of the 130205 working face simultaneously. The air supply method is forced ventilation.

[0083] Second and third stages: The ventilation method of the branch roadway in the car park follows that of the first stage. When filling the downhill branch roadway, a local fan (at point C) is set up in the return airway of the 13th mining area downhill, and forced ventilation is carried out into the downhill branch roadway (section CD).

[0084] Since the roadway is basically a full - coal roadway, during the filling process, fire prevention and extinguishing design for the roadway is required.

[0085] The inhibitor is mainly an aqueous solution of magnesium chloride with a concentration of 20%. The inhibitor solution is pressed along the φ25mm high - pressure rubber hose laid along the gate roadway to the working face through an inhibitor pump and connected to a φ13mm rubber hose. A tee and a stop valve are installed every 20m. A rubber hose with a diameter of φ13mm is used to connect the gun. Special personnel are arranged to operate the inhibitor spray gun, and during the time when the loader is stacking, the upper and lower end areas of the fully - mechanized mining face and the gob area are evenly sprayed through the gaps between the supports to fully wet the coal wall. Through spraying, a liquid film is formed on the surface of the coal wall or floating coal. The liquid film covers the surface of the floating coal and the coal body fissures, avoiding the contact between coal and oxygen, inhibiting the oxidation and spontaneous combustion of the coal wall or floating coal. The relative humidity in the coal mine is relatively high, and the inhibitor liquid film absorbs the moisture in the air, increasing the inhibitory effect.

[0086] To further improve the fire - extinguishing effect, secondary filling of gangue with water - coal ash can also be carried out.

[0087] According to the scheme of Embodiment 1, a numerical model with length, width and height of 180m×300m×132m is established in the FLAC3D software. The model is divided into 11 layers from bottom to top, and the specific parameters assigned to the model are shown in Table 6.

[0088] Table 6 Mechanical parameters of each rock stratum in the numerical model

[0089] According to the roadway filling design drawing, the branch roadway of the yard, the downhill branch roadway, and the return airway of the 130205 working face are excavated and calculated in the model, and a section is made at 52 m in the z direction of the model. Compare Figure 9 , Figure 10 From the vertical stress distribution diagrams of the completed roadway excavation and the completed roadway filling, it can be seen that the stress concentration on both sides of the roadway has been improved. The filling body filled in the roadway can replace the surrounding rock of the roadway to bear part of the pressure. However, due to the too short filling time, the supporting effect on the roadway is not yet significant enough.

[0090] By comparing and analyzing the stress concentration of the surrounding rock on both sides of the filled roadway and the unfilled roadway, the stress condition of the filling body can be judged, so as to judge whether the filling body plays a role.

[0091] As Figure 11 shown, in the cross-section stress comparison of the yard branch roadway, the maximum vertical stress of the surrounding rock on both sides of the unfilled roadway is 15.8 Mpa, and the maximum vertical stress of the surrounding rock on both sides of the filled roadway is 14.3 Mpa. Compared with the maximum vertical stress of the unfilled roadway, it has decreased by 1.5 Mpa. The pressure borne by the filling body is 3 Mpa. In subsequent mining, due to the influence of mining, the pressure that the filling body can bear will continue to increase, and the surrounding rock stress on both sides of the roadway will gradually decrease, and the stress concentration condition will be improved.

[0092] As Figure 12 shown, in the cross-section stress comparison of the downhill branch roadway, the maximum vertical stress of the surrounding rock on both sides of the unfilled roadway is 16.6 Mpa, and the maximum vertical stress of the surrounding rock on both sides of the filled roadway is 14.6 Mpa, which is 2 Mpa lower than the former. The pressure borne by the filling body is 4.2 Mpa. It can be seen from this that the filling body plays a good supporting effect in it.

[0093] As Figure 13 shown, in the stress comparison of the return airway of the 130205 working face, the maximum vertical stress of the surrounding rock on both sides of the unfilled roadway is 15.4 Mpa, which is 1.2 Mpa greater than the maximum vertical stress of the surrounding rock after filling. The pressure borne by the right filling body after filling is 3.9 Mpa. It can be seen that the addition of the filling body transfers the stress of the surrounding rock on both sides to the middle, and the stress on both sides decreases.

[0094] Example 2 A study of tunnel-type filling technology was conducted in a triangular area (referred to as the "Triangle") located in Mining Area 11 of the Zaoquan Coal Mine's First Division. This triangle is located to the north of the goaf of the 110201 (III) working face, to the southwest of the goaf of the 120203 working face, and to the west of the goaf of the 120201 working face. It is bounded by the goaf of the 110201 (III) working face, the auxiliary transport tunnels of Mining Areas 13 and 14, and the belt tunnel of the 110201 (III) working face. Nineteen tunnels were designed for filling in this triangle, totaling 2,079.9 meters in length. The longest tunnel was 160.8 meters long, and the shortest was 42.5 meters. The tunnels had a cross-section of 5,300 × 5,000 mm, with 6-meter safety coal pillars between tunnels. Construction length increases from north to south, and the estimated coal replacement volume is 71,700 tons, with 57,900 tons of waste rock to be filled. The tunnels are numbered from south to north, namely, tunnels 1 to 19. The statistics of the filling tunnel lengths are shown in Table 7 below.

[0095] Table 7 Example 2 Gangue Filling Tunnel Information Table

[0096] The gangue particles were screened in the same manner as in Example 1, and the PFC2D numerical simulation software was used to simulate different particle size ratio schemes to obtain the optimal grading scheme.

[0097] According to the elevation comparison of the east and west sides of Lane 1, Lane 11 and Lane 20, the floor elevations at the east ends of Lane 1, Lane 11 and Lane 20 are +1228.06m, +1245.283m and 1252.189m respectively, and the floor elevations from the east ends of Lane 1 to Lane 20 gradually increase; the floor elevations at the west ends of Lane 1, Lane 11 and Lane 20 are +1239.845m, +1243.668m and 1252.128m respectively, and the floor elevations from the west ends of Lane 1 to Lane 20 gradually increase, showing an overall trend of high in the west and low in the east. Based on the elevation difference, the filling direction of the tunnel is designed to be from east to west, and the filling and excavation mode is "one south and one north" alternating excavation, that is, after the south side waste rock backfill process tunnel is connected, the filling group will directly carry out the filling operation, and the excavation group will move to the north side waste rock backfill process tunnel for excavation, and so on to form a filling system, such as Figure 14 shown.

[0098] The specific steps are as follows: ① First, conduct a hidden disaster inspection on the target filling tunnel, and take corresponding measures to eliminate the hidden dangers found in a timely manner.

[0099] ②Construct the slag retaining wall; the process can refer to Example 1.

[0100] ③ Establish an underground water-fuel ash mixing station. This project selects the 110201 (III) return air tunnel chamber as the location of the mixing station and silo.

[0101] ④ After the roadway driving is completed, a water coal ash conveying pipe (φ200mm) is arranged along the center line of the roadway roof. Slurry discharge holes are left at intervals of 1.5 m on the pipe wall of the conveying pipe, and the connection relationship between the mixing station and the water coal ash conveying pipeline of the target roadway is established.

[0102] ⑤ The gangue generated from the development roadway driving in the 14th mining area is transported to the backfilling face of the filling roadway by a trackless rubber-tyred vehicle.

[0103] ⑥ Original gangue filling: a. The filling driving mode is "north-south double area" alternate driving; first drive the 1# lane as the system return air lane. After the driving is completed, construct the 2# lane. After the construction is completed, drive the 11# lane, and at the same time parallelly fill the 2# lane, and so on. The filling and driving sequence is shown in Table 8 below.

[0104] Table 8 Filling and driving sequence table of Example 2

[0105] After the original gangue material is self-unloaded, first use a forklift to stack it, and then use a loader for stacking to improve the stacking compaction rate. When using a loader for filling, considering that the actual height of the roadway reaches 5.5 m, the "temporary stacking slope" filling method can be adopted to make the loader boom reach the maximum filling height. After checking, the maximum loading height of the loader is 3.5 m, and the temporary stacking slope height is 2 m. Combining with the natural angle of repose of the original gangue is 55°.

[0106] It is also possible to use a 40T scraper conveyor, and process a self-shifting or dragging device, install an inclination angle of 30°, and a length of 9.2 m.

[0107] ⑦ After the stacking is completed, construct a grout-stop wall according to the same construction method as the gangue retaining wall, and carry out the water coal ash filling process. Pour the mixed water coal ash slurry into the gangue pile through the conveying pipeline until it is full, and then stop the construction.

[0108] ⑧ Then carry out the filling of the next roadway until all the roadway filling operations are completed.

[0109] Since there is partial fissure water and water coal ash filling precipitation and water separation in the filling roadway, it will generate water pressure on the gangue retaining (grout-stop) wall, affecting its structural stability. Therefore, this part of the water needs to be discharged. For the drainage system, the water flow direction is opposite to the gangue filling direction. As analyzed in detail for the working face elevation before, the overall trend of the triangular area is high in the north and low in the south, and high in the west and low in the east. Therefore, the roadway return water flows eastward and converges into the 13th and 14th mining area main haulage roadways, and is discharged southward along its drainage channel.

[0110] There are a total of 19 filling roadways, with a total length of 2079.9 m. The cross-section of the supported roadway is 5300×5000 mm, and the total filling volume can be calculated as 5.52×10 4 m3 , calculated according to the filling rate of 70%, it can be known that the filling ratio of fly ash is 30%, about 1.66×10 4 m 3 .

[0111] Then the total bleeding water volume is: .

[0112] Since the time for a branch roadway to be filled is about 12 hours, and it takes 2 - 4 hours for the filling paste to change from initial setting to no water secretion, the bleeding water volume of the paste will be secreted relatively evenly within 14 - 16 hours, and the water volume is small. Considering that the longest roadway is roadway No. 2, with a length of 151.2m and a filling volume of 4006.8m 3 , then the maximum bleeding water volume under this working condition is: .

[0113] Therefore, the maximum bleeding water volume per hour is about 22m 3 .

[0114] According to the bleeding water volume, a three - stage sedimentation tank is designed. The total capacity of the three - stage sedimentation tank is 30m 3 >22m 3 . The size of the sedimentation tank is 4m (length) × 2.5m (width) × 1m (depth), and the capacity of each stage of the sedimentation tank is 10m 3 . Considering the height difference problem, the bleeding water from roadway No. 2 - 19 cannot flow into the sedimentation tank in roadway No. 1 by gravity. Therefore, a sump is designed at the coal pillar position between roadway No. 1 and roadway No. 2 to collect the bleeding water from roadway No. 2 - 19.

[0115] The sump is 6m (length) × 2.5m (width) × 1.5m (depth), and the water collection capacity is 22.5m 3 >22m 3 . A WQ25 - 24 - 3 type sewage pump is configured in the sump. Its flow rate is 25m 3 / h>22m 3 , with a head of 24m and a power of 3kW. The sewage in the sump is pumped to the No. I sedimentation tank, and then flows into the No. II sedimentation tank and No. III sedimentation tank in sequence by gravity.

[0116] The sewage in the three - stage sedimentation tank flows into the drainage ditch of the auxiliary transportation main roadway in 13 and 14 by gravity, and then enters the mine centralized drainage system through the drainage ditch. The "static" and "dynamic" reserves of the sewage pump and the sedimentation tank exceed 47m 3 / h. The dynamic drainage of the sewage pump and the static water storage of the sedimentation tank form a dynamic balance relationship.

[0117] To meet the ventilation requirements of this area, relying on the roadway layout of the "+1283 yard triangle area", the ventilation path of this area is designed. The fresh air flow enters the belt roadway of the 110201 (III) working face → the auxiliary transportation return air reduction standard roadway of the 13th and 14th panels → the auxiliary transportation main roadway of the 13th and 14th panels. During the driving process of the filling roadway, it is necessary to supply fresh air flow to the driving face to meet the breathing, heat dissipation and dust removal of the workers at the working face. Since the roadway is constructed by the single-heading driving method, the single-heading forced ventilation can be adopted.

[0118] Since the roadway is basically a full-coal roadway, during the filling process, it is necessary to carry out fire prevention and extinguishing design for the roadway.

[0119] The inhibitor is mainly magnesium chloride aqueous solution with a concentration of 20%. The inhibitor solution is pressed along the φ25mm high-pressure rubber hose laid along the sublevel roadway to the working face by using an inhibitor pump and connected to the φ13mm rubber hose. A tee and a stop valve are installed every 20m. The φ13mm rubber hose is used to connect the spray gun. Special personnel are arranged to operate the inhibitor spray gun. Using the loader stacking time, the upper and lower end areas of the fully mechanized mining face and the gob are evenly sprayed from the gaps between the supports to fully wet the coal wall. Through spraying, a liquid film is formed on the surface of the coal wall or floating coal. The liquid film covers the surface of the floating coal and the coal body fissures, avoiding the contact between coal and oxygen, inhibiting the oxidation and spontaneous combustion of the coal wall or floating coal. The relative humidity in the coal mine is relatively high, and the inhibitor liquid film absorbs the moisture in the air, increasing the inhibition effect.

[0120] To further improve the fire extinguishing effect, the gangue can also be used for secondary filling of water coal ash.

[0121] Although the present invention has been described in detail by referring to the attached drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, those of ordinary skill in the art can make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions should all be within the scope of the present invention. / Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention.

Claims

1. A method for roadway filling of coal mine gangue, characterized in that, It includes the following steps: (1) Screen the gangue, divide it into n particle size groups according to the particle size, and classify the gangue into the corresponding particle size groups according to the particle size. n is a positive integer greater than or equal to 4; The maximum particle size of the gangue is greater than 300 mm; (2) Design a grading scheme according to the particle size groups divided in step (1), use the PFC2D numerical simulation software to simulate different grading schemes, obtain the stress-strain curves of the grading schemes, and select the grading scheme with the maximum peak stress as the optimal grading scheme; (3) Fill the roadway filling area according to the optimal grading scheme determined in step (2), and the gangue filling direction is carried out from the low elevation to the high elevation.

2. The coal mine gangue roadway filling method according to claim 1, characterized in that, The optimal grading scheme of step (2) is: By mass percentage, the particle size of 0 - 150 mm accounts for 38.07%, the particle size of 150 - 300 mm accounts for 11.95%, the particle size of 300 - 450 mm accounts for 21.60%, the particle size of 450 - 600 mm accounts for 15.85%, and the particle size of 600 - 750 mm accounts for 12.53%. The above range A - B means greater than A and less than or equal to B.

3. The coal mine gangue roadway filling method according to claim 1, characterized in that, Step (3) also includes constructing a gangue retaining wall before filling the roadway with gangue.

4. The coal mine gangue roadway filling method according to claim 1, characterized in that, Step (3) also includes constructing a grout stop wall after filling the roadway with gangue, and then carrying out grouting filling. The mixed water coal ash slurry is poured into the gangue pile through the conveying pipeline until it is full, and then the construction stops.

5. The method for filling coal mine gangue roadway as claimed in claim 4, wherein The water-cement ratio of the water coal ash slurry is 3:1 - 5:

1.

6. The coal mine gangue roadway filling method according to claim 1, wherein The roadway filling area in step (3) includes a Y-shaped area formed by three connected roadways and / or a triangular area formed by three connected roadways.

7. The coal mine gangue roadway filling method according to claim 6, characterized in that, For the Y-shaped area, a drainage path is set at the low elevation points of the three roadways to connect to the existing drainage channel, so that the fissure water and the water separated from the sedimentation of the water coal ash filling in the filling roadway are discharged and collected into the mine drainage pipeline, and finally discharged into the central sump, and then pumped to the ground by the central pump house through pumps and pipelines.

8. The coal mine gangue roadway filling method according to claim 6, characterized in that, For the triangular area, a sump is set at the low elevation point of the triangular area to collect the roadway seepage water inside the triangular area, and then the roadway seepage water in the sump is pumped to the sedimentation tank by a sewage pump. The sewage in the sedimentation tank enters the central sump through the existing drainage pipeline, and is pumped to the ground by the central pump house through pumps and pipelines.

9. The method for filling coal mine gangue roadway as claimed in claim 1, wherein Spray an inhibitor in the roadway filling area, and the inhibitor is an aqueous solution of halide salts.

10. A method for filling coal mine gangue in roadway type as described in claim 9, characterized in that, The aqueous solution of halide salts is an aqueous solution of calcium chloride or magnesium chloride with a concentration of 20 wt%.

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