Method and device for filling underground empty roadway with coal gangue concrete pile spraying

Abstract

This invention proposes a method and apparatus for filling underground tunnels with coal gangue concrete using a pile-and-spray technique, belonging to the technical field of coal gangue concrete pile-and-spray filling. First, the tunnel to be filled is ventilated and temporarily supported. Then, coal gangue concrete is filled into the tunnel using a method of simultaneous pile-and-spray filling, removal of supports, and retreat. The coal gangue concrete is a sparingly soluble and structurally stable silicate material formed by mixing a coagulant, a modifier, and powdered coal gangue in a mass ratio of 1:3.2:10 and allowing them to react fully. The apparatus includes a coal gangue filling unit, a slurry delivery pipe, and a spray gun. The slurry preparation unit is connected to the spray gun via a grouting pump and a slurry delivery pipe. The coal gangue filling unit is connected to the spray gun via the gangue delivery pipe. The filling body formed by this invention has strong load-bearing capacity, maintains the integrity of the filling body walls and roof, allows the working face to pass through the tunnel quickly and safely, reduces the complexity of the filling process, and improves filling efficiency, achieving effective load-bearing capacity.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coal gangue concrete heap-spray filling in underground empty roadway, and particularly relates to a method for filling the empty roadway with dry hard raw coal concrete formed by mixing broken coal gangue, setting agent and blending agent in a certain proportion, and a spray filling device. BACKGROUND

[0002] Coal green mining has become inevitable, and coal gangue treatment is imperative.

[0003] At present, according to the filling material, the filling methods include solid filling, paste filling and high water filling. The solid filling is to fill the roadway or goaf with solid materials such as coal gangue and fly ash to form a certain support to the overlying strata. The paste filling is to fill the goaf with broken coal gangue and cementing agent, and the hardened filling body can form a support to the overlying strata. The high water filling is to fill the goaf with high water material mixed with water, and the hardened filling body can also form a support. However, these methods have a common shortcoming that the filling process is relatively complex, and the filling efficiency needs to be improved. SUMMARY

[0004] The present application overcomes the shortcomings of the prior art, and provides a method and device for filling the underground empty roadway with coal gangue concrete. The complexity of the filling process is reduced, the filling efficiency is improved, and the effective bearing capacity is achieved.

[0005] In order to achieve the above-mentioned purposes, the present application is realized by the following technical scheme.

[0006] A method for filling the underground empty roadway with coal gangue concrete, comprising the following steps:

[0007] 1) ventilating and temporarily supporting the empty roadway to be filled;

[0008] 2) filling the empty roadway with coal gangue concrete by the retreat-filling operation mode of accumulating and spraying filling, withdrawing support and retreating; the coal gangue concrete is a silicate substance with difficult solubility and stable structure, which is generated by mixing and fully reacting the setting agent, the blending agent and the powdered coal gangue in a mass ratio of 1:3.2:10, and the compressive strength can reach 30 MPa within 7 days, reaching C 30 The concrete strength; the setting agent of the coal gangue concrete is a powdered mixture of magnesium chloride and light calcined powder, and the weight ratio of magnesium chloride to light calcined powder is 2:3.5; the blending agent is a liquid mixture of water and accelerating agent (retarding agent), and the weight ratio of water to accelerating agent (retarding agent) is 1:0.05-0.08 (selected according to the required reaction time), the accelerating agent can be used when the environmental temperature is lower than 5℃, and the retarding agent can be used when the environmental temperature is higher than 30℃.

[0009] Preferably, the ventilation involves installing a local ventilation fan at the entrance of the empty roadway to be filled at the working face, and ventilating the empty roadway through a flexible ventilation duct.

[0010] Preferably, the temporary support is provided by using capped point pillars, which extend gradually from the outside to the inside of the goaf entrance until the end of the goaf.

[0011] Preferably, step 2) involves placing the filling unit near the entrance of the empty roadway to be filled, arranging the injection pipe of the filling machine at the end of the empty roadway, aiming the nozzle of the injection gun at the cross-section of the empty roadway, starting the equipment, and spraying coal gangue concrete from the nozzle of the filling machine to form a pile-up injection.

[0012] Preferably, the coagulant is pumped into the slurry mixing tank by a powder feeder, and the modifier is injected into the slurry mixing tank through a pipeline by a quantitative grouting pump. After mixing at a mass ratio of 1:3.2, the mixture is placed in a slurry buffer tank. Powdered coal gangue is injected into the feed inlet of the filling machine, and at the same time, the slurry mixed in the slurry buffer tank is injected into the grouting pump. The grouting pump sprays the slurry into the nozzle of the filling machine to mix with the powdered coal gangue and sprays it out from the nozzle.

[0013] Even better, the admixture is heated by a pipe heater during operation, so that the temperature of the final coal gangue concrete mixture is ≤60℃.

[0014] An apparatus for a method of backfilling underground tunnels with coal gangue concrete includes a mixing agent tank, a coagulant tank, a slurry preparation unit, a coal gangue filling unit, a grouting pump, a slurry delivery pipe, and a spray gun. The mixing agent tank and the coagulant tank are respectively connected to the inlet of the slurry preparation unit through pipelines. The slurry preparation unit is connected to the spray gun through the grouting pump and the slurry delivery pipe. The coal gangue filling unit is connected to the spray gun through the gangue delivery pipe.

[0015] Preferably, the slurry preparation unit includes a slurry mixing tank and a slurry buffer tank. The slurry mixing tank is connected to a metering pump and a powder feeder. The modifier material tank is connected to the metering pump via a hose. The coagulant material tank is connected to the powder feeder via a powder suction pipe. The discharge port of the slurry mixing tank is connected to the slurry buffer tank, and the slurry buffer tank is connected to the grouting pump.

[0016] Preferably, the coal gangue backfilling unit includes a crusher, a belt feeder, and a backfiller; the bottom discharge port of the crusher is connected to the belt feeder, the discharge port of the belt feeder is connected to the backfiller, and the backfiller is connected to the spray gun through a gangue conveying pipe.

[0017] Preferably, the bottom of the blending agent material tank, the coagulant material tank, the slurry preparation unit, and the coal gangue filling unit are all equipped with a walking device.

[0018] The beneficial effects of this invention compared to the prior art are as follows:

[0019] 1. This invention targets old goafs (areas) within re-mining faces. It utilizes crushed coal gangue, mixed with a coagulant and modifier in a specific ratio, to perform all-around roof-to-roof compaction spraying and filling, forming a dry-hardened raw coal concrete with a certain strength, thus creating a support system for the goaf. The filling material formed by this invention has a large load-bearing capacity, supporting the basic roof while transmitting the resistance of the hydraulic supports, maintaining the integrity of the filling material walls and roof. When the working face passes through the goaf, the coal and filling material are cut off, preventing roof collapse and side fall accidents during the working face advancement, allowing the working face to pass through the goaf quickly and safely.

[0020] 2. This invention uses coal gangue concrete to partially fill the empty roadway, restoring its basic structure to or near its original rock state. The original empty roadway location is replaced by the filling material, replacing the normal working face of the coal seam. This eliminates the need for roadway maintenance, prevents the coal pillar between the roadway and the working face from fracturing as before, and maintains strong load-bearing capacity, and allows harmful gases such as methane to be expelled in advance. When the working face passes through the empty roadway, it can directly cut the filling material as in normal coal mining, enabling the working face to safely and quickly pass through the empty roadway.

[0021] 3. This invention combines structural mechanics with backfilling support as its theoretical basis. It uses dry-hard coal gangue concrete with a compressive strength of 5–30 MPa to pre-fill goaf roadways parallel to or intersecting the cutting roadways at an angle of less than 45 degrees within the coal-bearing area. During the backfilling process, high-strength dry-hard raw coal concrete forms a phased structural support for the goaf roadway. To further reduce costs, low-strength dry-hard raw coal concrete is then used for backfilling in the remaining stages, forming a comprehensive, dense, roof-connected, phased, and compressive-resistant structural support system for the goaf roadway. This system is then mined along with the backfill during the raw coal mining process. This restores the coal mining procedure to a state free from the damage of small coal mines, without altering any existing mining equipment or methods.

[0022] 4. This invention utilizes crushed coal gangue, mixed with coagulants and modifiers in a specific ratio to form dry-hardened raw coal concrete with high and low strength. This concrete is then used for all-around roof compaction and backfilling in goaf roadways, forming a support system. After compaction and backfilling in the goaf roadways, the backfill material is mined along with the raw coal during the mining process. The role of the backfill material is only for advance support and sealing; it does not need to be separated from the raw coal, thus reducing labor intensity. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the connection of the device for spraying coal gangue concrete to fill underground tunnels according to the present invention.

[0024] Figure 2 This is a flowchart of the filling process for underground tunnels using coal gangue concrete spraying, as described in this invention.

[0025] Figure 3 This is a schematic diagram of the partial filling of underground tunnels using coal gangue concrete spraying as described in this invention.

[0026] In the diagram, 1-mixing agent material tank, 2-coagulant material tank, 3-slurry preparation unit, 4-coal gangue filling unit, 5-hose, 6-powder suction pipe, 7-quantitative pump, 8-slurry mixing tank, 9-powder feeder, 10-rinsing water pipe, 11-slurry buffer tank, 12-grouting pump, 13-slurry conveying pipe, 14-crusher, 15-belt feeder, 16-filling machine, 17-gangue conveying pipe, 18-CNC panel, 19-valve, 20-spray gun, 21-flatbed trolley. Detailed Implementation

[0027] To make the technical problems, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail with reference to the embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. The technical solutions of this invention are described in detail below with reference to the embodiments and accompanying drawings, but the scope of protection is not limited thereto.

[0028] 1. Project Background

[0029] The 41109 fully mechanized longwall face in a certain mine has an advanceable length of approximately 650m. The face was completed at the end of 2013 and closed in 2015 due to limitations in mining technology at the time. Since the face has been closed for nearly seven years, considering factors such as the roof, ventilation, and on-site construction safety, after reopening the face, backfilling will begin from the roadway opening towards the face cut. Based on the face's recovery length, the backfilling will be divided into three stages: Stage I (200m), Stage II (200m), and Stage III (250m).

[0030] 2. Filling scheme

[0031] To ensure safe mining of the 41109 working face, prevent roof collapse under the advance support pressure of the longwall face, and guarantee the safe and rapid passage of the working face through the required backfill material and backfilling process, the following characteristics must be met:

[0032] (1) Ensure that the sprayed filling body can fill the space to be filled and that the connection effect is good.

[0033] (2) The solidified body of raw coal concrete material must have sufficient strength to effectively support the roof; it must have good plastic deformation characteristics to meet the requirements of roof sinking under the pressure of advance support and maintain the stability of the roof in the roadway.

[0034] (3) To achieve the best filling effect in the shortest construction time.

[0035] (4) The construction process is relatively simple, avoiding cumbersome operating procedures, and is easy for staff to master.

[0036] According to the above filling scheme, the filling is carried out using the device described in Example 1 and the method described in Example 2.

[0037] Example 1

[0038] Reference Figure 1 This embodiment proposes a device for spraying coal gangue concrete into underground tunnels. The device specifically includes a mixing agent material tank 1, a coagulant material tank 2, a slurry preparation unit 3, a coal gangue filling unit 4, a grouting pump 12, a slurry delivery pipe 13, and a spray gun 20.

[0039] The slurry preparation unit 3 includes a slurry mixing tank 8 and a slurry buffer tank 11. The slurry mixing tank 8 is connected to a metering pump 7 and a powder feeder 9. The slurry mixing tank 8 is connected to a flushing water pipe 10, and the slurry buffer tank 11 is equipped with a CNC panel 18. The modifier material tank 1 is connected to the metering pump 7 via a hose 5; the coagulant material tank 2 is connected to the powder feeder 9 via a powder suction pipe 6; the discharge port of the slurry mixing tank 8 is connected to the slurry buffer tank 11, and the slurry buffer tank 11 is connected to a grouting pump 12. The grouting pump 12 is connected to a spray gun 20 via a slurry delivery pipe 13. A valve 19 is installed at the connection between the slurry delivery pipe 13 and the spray gun 20.

[0040] The coal gangue backfilling unit 4 includes a crusher 14, a belt feeder 15, and a backfiller 16; the bottom discharge port of the crusher 14 is connected to the belt feeder 15, the discharge port of the belt feeder 15 is connected to the backfiller 16, and the backfiller 16 is connected to the spray gun 20 through the gangue conveying pipe 17.

[0041] The mixing agent material tank 1, the coagulant material tank 2, the slurry preparation unit 3, the coal gangue filling unit 4, and the grouting pump 12 are all placed on the flatbed trolley 21 for easy movement of the entire device.

[0042] Liquid binder from binder material tank 1 and coagulant powder from coagulant material tank 2 are drawn into slurry mixing tank 8 in slurry preparation unit 3 via hose 5 and powder suction pipe 6, respectively. Quantitative control is achieved by metering pump 7 and powder feeder 9, and the water volume in slurry mixing tank 8 is controlled by flushing water pipe 10. Material parameters after slurry mixing are monitored by CNC panel 18 inside slurry buffer tank 11, and then transported by slurry conveying pipe 13 under the pressure of grouting pump 12. Gangue is crushed by crusher 14 in coal gangue filling unit 4, transported by belt conveyor 15 to filling machine 16, and then enters spray gun 20 of spraying machine via gangue conveying pipe 17. In the cavity of spray gun 20, slurry and coal gangue powder are mixed and reacted, and then sprayed into the goaf for backfilling.

[0043] The selected coal gangue concrete backfilling equipment is primarily pneumatic; if the air source is insufficient, electric equipment can be selected, depending on the actual conditions. All equipment is mounted on flatbed trolleys 21, allowing for mobile backfilling underground via tracks within the tunnel. The equipment consists of two backfilling units, with a pipeline transport distance (horizontal transport) of 300m. Therefore, during backfilling operations, the equipment is generally placed at the entrance of the goaf roadway. For special long-distance backfilling exceeding 300m, the equipment is then moved.

[0044] Example 2

[0045] Reference Figure 2 and Figure 3 This embodiment proposes a method for backfilling underground tunnels with coal gangue concrete. When the backfill material is subjected to advance support pressure, the tunnel remains in a triaxial stress state, exhibiting high compressive strength, several times that of uniaxial compressive strength. Considering laboratory tests, numerical calculations, backfill material properties, and previous engineering practices, the final material ratio (by mass) was determined as follows: coagulant (material A): binder (material B): coal gangue powder = 1:3.2:10. Backfilling is performed using the backfilling device described in Embodiment 1. After the backfill materials are mixed according to the ratio, they are used to fill the area to be filled through a slurry conveying pipeline.

[0046] The specific steps are as follows:

[0047] (1) Preparation, transportation and storage of filling materials

[0048] The filling material consists of powdered coal gangue, coagulant (material A), and blending agent (material B).

[0049] The coal gangue concrete setter (Component A) is a powdered mixture of magnesium chloride and lightly calcined powder, with a weight ratio of magnesium chloride:lightly calcined powder = 2:3.5. The admixture (Component B) is a liquid mixture of water and an accelerator (retarder), with a weight ratio of water:accelerator (retarder) = 1:0.05~0.08 (selected according to the required reaction time). The accelerator can be used when the ambient temperature is below 5℃, and the retarder can be used when the ambient temperature exceeds 30℃. The coal gangue concrete has a compressive strength of 30 MPa within 7 days; reaching C... 30 Concrete strength (laboratory test results are shown in the table below).

[0050]

[0051] Coal gangue, washed and processed in the surface screening workshop or coal preparation plant, is transported to the required backfilling face via mine cars or return conveyor belts. It is then crushed by the crusher in the self-propelled backfilling unit. The crushed gangue is a mixture of particles and powder with a particle size of less than 2mm (no gradation requirements). The pre-crushed powdered coal gangue can be stored in spare mine cars as a material buffer storage area to prevent insufficient backfilling at the working face due to malfunctions in the mine's coal gangue transportation system, which could lead to crusher shutdowns and ensure normal backfilling operations are not affected by the presence of powdered raw coal.

[0052] The coagulant is a bagged powder. The bagged powdered coagulant is poured into the coagulant material bucket on the flatbed truck of the self-propelled filling unit.

[0053] The binder is a liquid material. Several binder containers are placed on the flatbed truck of the self-propelled filling unit to hold the binder. The storage temperature of the binder should not be lower than 6℃, otherwise crystals will precipitate, affecting its use.

[0054] 1-ton anti-static plastic buckets can be used for coagulant and blending agent materials.

[0055] (2) Ventilation of tunnels and temporary support in empty tunnels

[0056] ① Roadway ventilation: Local ventilation fans are arranged at the entrance of the 41109 working face. After selecting the goaf roadway to be filled, the goaf area is ventilated through flexible ventilation ducts in order from near to far. The gas and other toxic and harmful gases are detected in time. Personnel can only enter after the working standards are met.

[0057] ② Empty tunnel support: After personnel enter, temporary support must first be provided for the roof of the empty tunnel. Capped support pillars are used to support the roof of the empty tunnel, starting from the entrance and gradually extending from the outside to the inside until the end of the empty tunnel can be filled. After the support is completed and accepted and meets the work safety standards, filling can begin from the inside to the outside. The support pillars are removed while filling until the work is completed.

[0058] (3) Filling operation in empty tunnels

[0059] The self-propelled filling unit is positioned near the entrance of the empty roadway to be filled in the material or transport roadway of the working face. After connecting the self-propelled filling machine, the injection pipe of the filling machine is positioned at the end of the empty roadway to be filled. The nozzle of the injection gun is aligned with the cross-section of the empty roadway, and the equipment is started. A-material coagulant is pumped into the slurry mixing tank via a powder feeder, and B-material modifier is injected into the slurry mixing tank via a metered injection pump. After mixing at a mass ratio of 1:3.2, the mixture is placed in a slurry buffer tank. Powdered raw coal is injected into the filling machine inlet, and simultaneously, the slurry mixed in the slurry buffer tank is injected into the injection pump. The injection pump then injects the slurry into the nozzle of the filling machine to mix with the powdered raw coal (mass ratio of A-material coagulant: B-material modifier: powdered coal gangue = 1:3.2:10). The mixture is then sprayed out from the nozzle of the filling machine and piled up for spraying. Personnel operate under safety supports (or use remote control for automatic spraying and filling), ensuring safety and reliability. The filling process employs a method of simultaneous spraying and filling, support removal, and retreat.

[0060] The filling unit and other equipment are positioned near the entrance of the goaf that needs filling, where the material or transport roadway connects. The injection pipes of the filling machine and grouting pump are placed at the end of the goaf. The nozzles of the injection guns are aimed at the goaf cross-section. The equipment is started, and powdered raw coal is injected into the filling machine's inlet. Simultaneously, the slurry mixed in the mixing tank is injected into the grouting pump, which sprays the slurry into the filling machine's injection gun nozzle to mix with the powdered raw coal. Then, both are sprayed out from the filling machine's injection gun nozzle, resulting in a cumulative spraying operation. Personnel operate under safety supports (or remote control for automatic spraying), ensuring safety and reliability. A reverse filling operation method is used, where the support supports are removed while the filling is being carried out, and the operation is performed while retreating. A partial filling diagram is shown below. Figure 2 As shown.

[0061] The coal gangue concrete spraying material, after being piled and filled, can achieve a strength of 5-7 MPa.

[0062] In this case, the material does not generate heat of hydration in the entire reaction system during the concrete formation process, so fires caused by excessive heat of hydration during underground operations are not considered.

[0063] Among them, components A and B are chemical additives, and their reaction rate is closely related to the ambient temperature. When the ambient temperature reaches about 35℃, raw coal concrete can be fully set in 4 to 6 hours. However, the temperature at the underground working face is generally between 16 and 23℃. To achieve rapid solidification, the admixture needs to be heated through a pipeline heater during operation. The heating temperature should be controlled so that the concrete formation temperature does not exceed 60℃.

[0064] (4) Cleaning and filling equipment

[0065] When the filling is almost finished, all equipment continues to work, but the feeding into the mixing tank is stopped. Instead, water is used to rinse the tank while the work is being carried out until all the slurry in the mixing tank, grouting pump, and grouting pump spray pipe is used up. At this point, the strength of the sprayed filling material decreases from high to low. This material can be used to fill the gaps at the top after filling, or it can be sprayed or applied to the existing filling body. This ensures that the ground is dry and free of water and silt accumulation, keeping the bottom plate clean and tidy without material waste.

[0066] (5) Filling cost and economic benefits

[0067] The cost of coal gangue concrete backfilling consists of the cost of backfilling equipment, the cost of direct backfilling materials, and the cost of backfilling labor. Considering cost savings, the total estimated cost of backfilling mining per ton of coal is approximately 14 yuan / ton.

[0068] 1. Cost of filling materials

[0069] The coal gangue concrete filling material is made of material A and material B combined with coal gangue powder. The ratio of coal gangue concrete material used is: material A: material B: coal gangue powder = 1:3.2:10.

[0070] The price of material A (excluding tax and freight) is 2077 yuan / ton, and the price of material B is 1424 yuan / ton. The coal gangue powder uses waste coal gangue from the mine (cost not considered).

[0071] The cost of 1 ton of coal gangue concrete backfill material is: 3500 yuan / 14.2 ton = 246.5 yuan / ton;

[0072] The empty roadway of the 41109 fully mechanized longwall mining face is approximately 3000m long, with an average cross-section of 6m. 2 Therefore, the required volume of the empty tunnel to be filled is: 3000m × 6m 2 =18000 m 3 The density of coal gangue concrete is 1500 kg / m³. 3 Therefore, the estimated amount of coal gangue concrete material required for backfilling is 18,000 m³. 3 ×1500kg / m 3 =27,000t

[0073] The cost of the filling material is: 27,000 tons × 246.5 yuan / ton = 6.66 million yuan.

[0074] Cost per ton of coal for filling material: 6.66 million yuan / 624,000 tons = 10.7 yuan / ton.

[0075] 2. Filling system equipment costs

[0076] The investment cost of the filling system equipment is 1.488 million yuan. After filling, the 41109 fully mechanized longwall face can produce 624,000 tons of coal. The cost of the filling system equipment per ton of coal is 2.4 yuan / ton.

[0077] 3. Filling labor costs

[0078] The backfilling test face should only be mined after the backfilling of the empty roadway in the working face is completed. A "three-eight" work schedule is implemented, with two shifts per day for backfilling. Excluding equipment installation and debugging time, and site cleanup after backfilling, the effective backfilling time is 12 hours per day, and the backfilling machine's backfilling efficiency is 25m. 3 If the filling time required for the 41109 working face is 18000 / 25 / 12=60d, it is estimated to take 2 months. It is estimated that the number of registered personnel required for filling in the mine for two shifts will be 16. The wages of the personnel are calculated based on the average wage of 10,000 yuan / person underground. Therefore, the labor cost for filling ton of coal is 0.5 yuan / ton.

[0079] Total filling cost C f0 =C1+C2+C3=10.7+2.4+0.5=13.6 yuan / t

[0080] The equipment used in this filling process is all low-power equipment or pneumatic equipment. After considering the electricity cost per ton of coal for filling, the additional cost per ton of coal for filling is calculated as 14 yuan.

[0081] The normal production cost per ton of coal in the mine is about 800 yuan / ton. After adopting the filling process for the old goaf roadways in the working face, the cost per ton of coal increases by about 14 yuan / ton. The total cost per ton of coal for mining the working face is about 814 yuan / ton. Based on the current selling price of No. 11 coal at 2,300 yuan / ton, the profit per ton of coal is 1,486 yuan / ton. Assuming that the recoverable coal resources of the 41109 fully mechanized longwall face are 624,000 tons, the net profit from mining this working face is about 927 million yuan, which is very economically significant.

[0082] The above description is a further detailed explanation of the present invention in conjunction with specific preferred embodiments. It should not be considered that the specific embodiments of the present invention are limited to this. For those skilled in the art, several simple deductions or substitutions can be made without departing from the present invention, and all of these should be considered to fall within the scope of patent protection determined by the submitted claims.

Claims

1. A method for filling underground mine tunnels with coal gangue concrete, characterized in that, For the old working faces in the re-mining face, comprehensive roof compaction and backfilling are carried out to form a support system; including the following steps: 1) Ventilate and temporarily support the empty tunnels to be filled; 2) Coal gangue concrete is filled in the empty roadway using a method of simultaneous pile-up spray filling, simultaneous removal of supports, and simultaneous retreat. The coal gangue concrete is a sparingly soluble and structurally stable silicate material formed by mixing a coagulant, a modifier, and powdered coal gangue in a mass ratio of 1:3.2:10 and allowing them to react fully. The compressive strength of the coal gangue concrete within 7 days is 30 MPa. The coagulant is a powdered mixture of magnesium chloride and lightly calcined coal powder, with a weight ratio of magnesium chloride:lightly calcined coal powder = 2:3.

5. The modifier is a liquid mixture of water and an accelerator, with a weight ratio of water:accelerator = 1:0.05~0.

08. The powdered coal gangue is a mixture of particles with a particle size of less than 2 mm and powder. The filling unit is positioned near the entrance of the empty roadway to be filled. The injection pipe of the filling machine is placed at the end of the empty roadway, and the nozzle of the injection gun is aimed at the cross-section of the empty roadway. The coagulant is pumped into the slurry mixing tank through the powder feeder, and the modifier is injected into the slurry mixing tank through the pipeline via the metered grouting pump. After mixing at a mass ratio of 1:3.2, the mixture is placed in the slurry buffer tank. Powdered coal gangue is injected into the inlet of the filling machine, and at the same time, the slurry mixed in the slurry buffer tank is injected into the grouting pump. The grouting pump sprays the slurry into the nozzle of the filling machine to mix with the powdered coal gangue, forming coal gangue concrete. The equipment is started, and the coal gangue concrete is sprayed out from the nozzle of the filling machine to form a pile spray.

2. The method for filling underground mine tunnels with coal gangue concrete according to claim 1, characterized in that, The ventilation mentioned above involves installing local ventilation fans at the entrance of the empty roadway to be filled at the working face, and ventilating the empty roadway through flexible ventilation ducts.

3. The method for filling underground mine tunnels with coal gangue concrete according to claim 1, characterized in that, The temporary support mentioned above is provided by using capped point pillars for support, starting from the entrance of the goaf and gradually extending the support from the outside inward until the end of the goaf.

4. The method for filling underground mine tunnels with coal gangue concrete according to claim 1, characterized in that, During the operation, the admixture is heated through a pipeline heater to ensure that the temperature of the final coal gangue concrete mixture is ≤60℃.

5. The method for filling underground mine tunnels with coal gangue concrete according to claim 1, characterized in that, The apparatus includes a blending agent material tank (1), a coagulant material tank (2), a slurry preparation unit (3), a coal gangue filling unit (4), a grouting pump (12), a slurry conveying pipe (13), and a spray gun (20). The blending agent material tank (1) and the coagulant material tank (2) are respectively connected to the inlet of the slurry preparation unit (3) through pipelines. The slurry preparation unit (3) is connected to the spray gun (20) through the grouting pump (12) and the slurry conveying pipe (13). The coal gangue filling unit (4) is connected to the spray gun (20) through the gangue conveying pipe (17).

6. The method for filling underground mine tunnels with coal gangue concrete according to claim 5, characterized in that, The slurry preparation unit (3) includes a slurry mixing tank (8) and a slurry buffer tank (11). The slurry mixing tank (8) is connected to a metering pump (7) and a powder feeder (9). The modifier material tank (1) is connected to the metering pump (7) through a hose (5). The coagulant material tank (2) is connected to the powder feeder (9) through a powder suction pipe (6). The outlet of the slurry mixing tank (8) is connected to the slurry buffer tank (11), and the slurry buffer tank (11) is connected to the grouting pump (12).

7. The method for filling underground mine shafts with coal gangue concrete according to claim 5, characterized in that, The coal gangue filling unit (4) includes a crusher (14), a belt feeder (15) and a filling machine (16); the bottom discharge port of the crusher (14) is connected to the belt feeder (15), the discharge port of the belt feeder (15) is connected to the filling machine (16), and the filling machine (16) is connected to the spray gun (20) through the gangue conveying pipe (17).

8. The method for filling underground mine tunnels with coal gangue concrete according to claim 5, characterized in that, The bottom of the blending agent material tank (1), the coagulant material tank (2), the slurry preparation unit (3), and the coal gangue filling unit (4) are all equipped with walking devices.

Images