A method for constructing FRP-confined fly ash geopolymer sidefill infill bodies in roadways

Abstract

This invention discloses a method for constructing FRP-confined fly ash geopolymer roadway backfill, relating to the field of coal mining technology. The method involves first preparing prefabricated FRP pipes, backfill molds, backfill materials containing fly ash, and related backfill systems. After the working face is pushed forward, preparatory work such as roof support is carried out. Then, the prefabricated FRP pipes and backfill molds are installed to form a pipe column to be filled. Fly ash and other materials are mixed at a mixing plant to form fly ash-based polymer backfill material, which is then injected into the backfill molds of the pipe column. After filling, it is wrapped with ultra-high molecular weight polyethylene tape. A leak-proof wall containing metal mesh, ventilation duct cloth, and steel mesh is then constructed, and a concrete layer is laid to seal the goaf. This method makes full use of waste materials such as fly ash, reduces construction costs, solves the problem of thermal damage to backfill in high-temperature mines, enhances the load-bearing capacity of the backfill through FRP confinement, ensures the roof support effect of roadways along the goaf, and is conducive to improving coal resource recovery rates and promoting continuous mining without coal pillars.

Description

Technical Field

[0001] This invention relates to the field of coal mining technology, and in particular to a method for constructing FRP-confined fly ash geopolymer roadway backfill. Background Technology

[0002] The goaf retention method is an important technology for achieving pillarless continuous mining, in which high-water materials are widely used as the core material of the roadway backfill. FRP, or fiber-reinforced polymer, is a high-performance material composed of fiber materials and matrix materials, and it has a wide range of applications in many fields.

[0003] In recent years, extensive research has been conducted on the use of FRP (fiberglass reinforced plastic) confinement methods to enhance the strength of concrete materials. Scientific research and field practice have shown that the strength of FRP-confined roadway backfill materials is related not only to the type of core backfill material but also to the environmental factors such as temperature. Affected by mine temperature and the application method of FRP, the strength growth rate of the internal backfill materials varies, and the overall strength after reaching peak strength is not ideal. Furthermore, some core backfill materials, such as high-water-content materials, can suffer thermal damage under high-temperature environments, leading to reduced strength and loss of load-bearing capacity.

[0004] In addition, to improve coal mine resource recovery rates, reduce the occupation and damage of land resources caused by mining activities, and lower mining costs, some regions utilize the method of constructing gob-side retaining walls using coal gangue-filled wire mesh boxes. This method can fully utilize coal gangue waste materials, effectively reduce the construction cost of gob-side retaining walls, and, in some areas where coal gangue is not required to be transported underground, it can achieve on-site filling underground, greatly facilitating coal gangue processing and reducing processing costs. However, this method is suitable for gob-side retaining in high-temperature mines in eastern regions and some deep mines where the environmental temperature is high. Furthermore, the coal gangue-filled wire mesh box retaining walls, composed of wire mesh boxes and coal gangue, have limited structural strength, requiring the addition of additional cementing materials to improve overall strength. This often results in problems such as insufficient support resistance and increased cementing material costs.

[0005] In summary, existing technologies related to the construction of roadway backfill have their own advantages and limitations in different mining environments. Summary of the Invention

[0006] The purpose of this invention is to provide a method for constructing FRP-confined fly ash geopolymer roadway backfill, in order to solve the problems existing in the prior art and improve the safety of the roadway backfill construction process and the strength of the roadway backfill.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] This invention provides a method for constructing FRP-confined fly ash geopolymer sidefill infill bodies, comprising:

[0009] S1. Prepare prefabricated FRP pipes, filling mold bags, filling materials and filling system, wherein the filling materials include fly ash, slag, alkali activator, coal gangue and crushed stone;

[0010] The filling system is installed underground in the mine. The filling system includes a first mixing station, a first conveying station and a second mixing station. The discharge port of the first mixing station is connected to the inlet of the second mixing station through a slurry pipe. The first conveying station is used to transport materials into the second mixing station. The discharge port of the second mixing station is connected to a filling pipe.

[0011] The prefabricated FRP pipe, the filling mold bag, and the filling material are all transported to the side of the filling system.

[0012] S2. After the working face is pushed over, high-strength anchor cables are used to support the top plate of the area to be filled in a timely manner, and single hydraulic props are used to support the top plate of the area to be filled.

[0013] S3. Clean the top and bottom slabs of the area to be filled at the construction site to ensure that the top and bottom slabs of the area to be filled are flat.

[0014] S4. Lagging working surface: Install the prefabricated FRP pipe at the designated position, with the distance between two adjacent prefabricated FRP pipes being 800-1200mm;

[0015] S5. A filling mold bag is set in each of the installed prefabricated FRP pipes, so that the prefabricated FRP pipe and the corresponding filling mold bag are combined to form a pipe column to be filled.

[0016] S6. The fly ash, slag, alkali activator, and water are placed into the first mixing station according to the design ratio and mixed for 3-5 minutes to form fly ash-based slurry A. The fly ash-based slurry A is then transported to the second mixing station through the slurry pipe. The coal gangue and crushed stone are transported to the second mixing station through the first conveying station. Water is added to the second mixing station, and the second mixing station is then mixed for 5-10 minutes to form fly ash-based polymer filling material.

[0017] S7. The fly ash-based polymer filling material is filled into the column to be filled to form an FRP-confined fly ash-based polymer material column. The filling method for a single column to be filled is as follows:

[0018] (1) Connect the filling pipe to the filling port of the filling mold bag on the column to be filled, and inject the fly ash-based polymer filling material into the filling mold bag of the column to be filled through the filling pipe.

[0019] (2) Continuously inject the fly ash-based polymer filling material until slurry overflows from the vent of the filling mold bag of the column to be filled;

[0020] (3) The ultra-high molecular weight polyethylene tape is wrapped around the top of the prefabricated FRP pipe of the column to be filled, which has been filled with the fly ash-based polymer filling material, using the wet-laying method;

[0021] S8. Construct a windproof wall along the side of the FRP-confined fly ash base polymer material column near the goaf, and lay a concrete layer on the side of the windproof wall near the roadway to seal the goaf. After the concrete layer has solidified for 24 hours, remove the single hydraulic support.

[0022] S9. Repeat steps S2-S8 until mining is completed, and clean the backfilling system after backfilling is completed.

[0023] Preferably, the filling mold bag is a cylindrical bag made of polyvinyl chloride waterproof membrane, the diameter of the filling mold bag is equal to the inner diameter of the prefabricated FRP pipe, the height of the filling mold bag is 5% greater than the height of the tunnel, and the filling port and the venting port are both located at the top of the filling mold bag.

[0024] The alkaline activator is prepared by mixing a 30% sodium hydroxide solution and a 1.5 mol / L water glass solution in a set ratio.

[0025] Preferably, the particle size of the coal gangue and the particle size of the crushed stone are both less than 100 mm.

[0026] Preferably, the ultra-high molecular weight polyethylene (UHMWPE) tape is cut from UHMWPE fiber cloth, the number of layers of the UHMWPE tape is the same as the number of layers of FRP material in the prefabricated FRP pipe, the length of the circumferential overlap area between the UHMWPE tape and the prefabricated FRP pipe is not less than 1 / 3 of the circumference of the cross-section of the prefabricated FRP pipe, and the length of the axial overlap area between the UHMWPE tape and the prefabricated FRP pipe is not less than 100mm.

[0027] Preferably, the air-proof wall comprises a layer of metal mesh, a layer of ventilation duct cloth, and a layer of steel mesh, wherein the metal mesh is located on the roadway side of the air-proof wall, and the steel mesh is located on the goaf side of the steel mesh; the ventilation duct cloth is sandwiched between the metal mesh and the steel mesh.

[0028] Preferably, for non-high-temperature mines, after step S7 and before step S8, a heating device is used to heat the newly formed FRP-confined fly ash-based polymer material column at high temperature for 12 hours, with a heating temperature of 45℃~55℃. The heating device is a building concrete curing electric heating blanket.

[0029] The present invention achieves the following technical effects compared to the prior art:

[0030] The FRP-constrained fly ash-based polymer roadway backfill construction method of this invention significantly enhances the strength and load-bearing capacity of the backfill material by utilizing the constraint provided by fiber-reinforced polymer (FRP), thereby significantly improving the ultimate load-bearing capacity and axial deformation capacity of the fly ash-based polymer. As a high-performance material, FRP, when combined with the backfill material, structurally strengthens the backfill, effectively improving its load-bearing performance under external forces such as roadway roof pressure.

[0031] Furthermore, the air-proof wall in this invention comprises a layer of metal mesh, a layer of ventilation duct fabric, and a layer of steel mesh, with each layer having a specific positional layout. The metal mesh is located on the roadway side of the air-proof wall, the steel mesh is located on the goaf side, and the ventilation duct fabric is sandwiched between the metal mesh and the steel mesh. This multi-layered structure design allows each layer of material to work synergistically, forming a relatively tight protective system that effectively blocks airflow between the goaf and the roadway, achieving a sealing effect on the goaf.

[0032] Metal mesh provides initial blocking and support, preventing the passage of larger particles and providing structural strength for the entire air-proof wall. The ventilation duct fabric, with its good flexibility and sealing properties, fills any small gaps between layers, further enhancing the wall's sealing performance. Reinforcing mesh on the goaf side strengthens the wall's impact resistance, preventing damage from geological activity or pressure changes within the goaf and ensuring the continuity of its sealing effect. The air-proof wall creates a relatively stable environment for the roadway backfill and surrounding facilities (such as hydraulic props). Because it effectively blocks airflow and potential material exchange between the goaf and the roadway, it avoids the impact of unstable factors within the goaf (such as airflow impact and dust diffusion) on the backfill and surrounding facilities, helping to maintain the structural integrity and performance stability of the backfill and extending its service life. For example, while waiting for the concrete layer to solidify, the air-proof wall can prevent external factors from interfering with the normal solidification process of the concrete layer, ensuring that the concrete layer can reach the expected strength and performance, thereby better fulfilling its role in the entire roadway filling structure system.

[0033] Furthermore, in constructing the roadway backfill, the present invention uses backfill materials including fly ash, slag, alkali activator, coal gangue, and crushed stone. These materials are mostly wastes or byproducts of industrial production processes; for example, fly ash is a product of coal combustion, and coal gangue is a byproduct of coal mining. By using these wastes as the main components of the backfill, the resource utilization of waste is fully realized, reducing the pressure of waste emissions on the environment and achieving good environmental benefits. Because a large amount of these wastes, which would otherwise require treatment or disposal, are used as backfill materials, the construction cost of the roadway backfill is greatly reduced. Compared with the traditional use of specific and relatively expensive backfill materials, the material selection method of the present invention has significant advantages in cost control, which can effectively save production costs and improve economic efficiency for coal mining enterprises.

[0034] Furthermore, in existing technologies, some core backfill materials, such as high-water materials, suffer thermal damage under high-temperature environments, leading to reduced strength and loss of load-bearing capacity. This poses a serious threat to the stability and safety of roadway backfill in high-temperature mines, affecting the effective implementation of gob-side roadway retention methods. This invention employs fly ash-based polymer backfill materials. Compared to traditional materials susceptible to thermal damage (such as high-water materials), this material exhibits rapid hardening and early strength under high-temperature conditions, effectively resisting the adverse effects of high-temperature environments on the strength of the backfill. It effectively solves the problem of thermal damage to core backfill materials in high-temperature mines, ensuring the strength and stability of the backfill under high-temperature conditions, thereby guaranteeing the safety and reliability of gob-side roadway retention.

[0035] Furthermore, the constraints provided by fiber-reinforced polymer (FRP) significantly enhance the ultimate bearing capacity and axial deformation capacity of fly ash-based polymer materials. As a high-performance material, FRP, when combined with filling materials, can structurally strengthen the filling body, effectively improving its bearing capacity under external forces such as roadway roof pressure.

[0036] Furthermore, by fabricating FRP pipes through alternating winding at specific angles, the ultimate bearing capacity and axial deformation capacity of FRP-confined fly ash-based polymer material columns can be further improved. This special fabrication method optimizes the structural performance of the FRP pipes, enabling them to better collaborate with the filling material, providing stronger support and constraint for the filling body, and further enhancing the overall mechanical properties of the filling body.

[0037] Furthermore, using this invention to construct the roadway-side backfill body ensures effective support for the roof strata of the roadway. Through a series of reasonable construction steps, such as timely support of the roof of the area to be backfilled using high-strength anchor cables and single hydraulic props, combined with the excellent mechanical properties of the backfill body itself, the roof strata can be stably and effectively supported, reducing the risk of safety accidents such as roof collapse and ensuring the normal use and safe production of the roadway. This not only effectively reduces the construction cost of the roadway-side backfill body but also solves the problem of thermal damage to the core backfill material in high-temperature environments, enabling continuous mining without coal pillars and effectively improving coal resource recovery. The combined effects of these technologies make this invention of significant application value in the field of coal mining, meeting the needs of enterprises to reduce costs and improve production efficiency while also taking into account the requirements of environmental protection and effective resource utilization. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the structure of the FRP-confined fly ash geopolymer material column in the FRP-confined fly ash geopolymer roadway backfill construction method of the present invention.

[0040] Figure 2 This is a partial structural diagram of the prefabricated FRP pipe in the FRP-confined fly ash geopolymer roadway backfill construction method of the present invention;

[0041] Figure 3 This is a top view of the construction method for the FRP-confined fly ash geopolymer roadway backfill of the present invention;

[0042] Figure 4 This is a side view of the construction method for the FRP-confined fly ash geopolymer roadway backfill of the present invention. Figure 1 ;

[0043] Figure 5 This is a side view of the construction method for the FRP-confined fly ash geopolymer roadway backfill of the present invention. Figure 2 ;

[0044] Figure 6 This is a schematic diagram of the heating equipment in the method for constructing FRP-confined fly ash geopolymer roadway backfill in this invention;

[0045] Figure 7This is a partial structural schematic diagram of the heating equipment in the FRP-confined fly ash geopolymer roadway side infill construction method of the present invention.

[0046] Figure 8 Stress curves of uniaxial compression test for fly ash-based polymer filling material A;

[0047] Figure 9 Stress curves of uniaxial compression test for fly ash-based polymer filling material B;

[0048] In the diagram: 1. Precast FRP pipe; 2. Fly ash-based polymer filling material; 3. Filling mold bag; 4. Exhaust port; 5. Filling port; 6. Ultra-high molecular weight polyethylene tape; 7. Pipe wall; 8. FRP restraint wound at an 80-degree angle; 9. FRP restraint wound at a 60-degree angle; 10. First mixing station; 11. Slurry pipe; 12. First conveying station; 13. Water pipe; 14. Second mixing station; 15. Filling pipe; 16. High-strength anchor cable; 17. Single hydraulic prop; 18. Pipe column to be filled; 19. FRP-restrained fly ash-based polymer material column; 20. Air leakage prevention wall; 21. Goaf; 22. Coal body; 23. Working face; 24. Hydraulic support; 25. Roof of the area to be filled; 26. Heating equipment; 27. Heating section; 28. Controller; 29. ​​Power supply section. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] The purpose of this invention is to provide a method for constructing FRP-confined fly ash geopolymer roadway backfill, in order to solve the problems existing in the prior art and improve the safety of the roadway backfill construction process and the strength of the roadway backfill.

[0051] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0052] like Figures 1 to 7 As shown, this embodiment provides a method for constructing FRP-confined fly ash geopolymer sidefill infill, including:

[0053] S1. Prepare prefabricated FRP pipes 1, filling mold bags 3, filling materials and filling system. The filling materials include fly ash, slag, alkali activator, coal gangue and crushed stone.

[0054] The filling system is set up underground in the mine. The filling system includes a first mixing station 10, a first conveying station 12 and a second mixing station 14. The discharge port of the first mixing station 10 is connected to the inlet of the second mixing station 14 through a slurry pipe 11. The first conveying station 12 is used to transport materials into the second mixing station 14. The discharge port of the second mixing station 14 is connected to a filling pipe 15.

[0055] And transport the prefabricated FRP pipe 1, filling mold bag 3 and filling material to the side of the filling system;

[0056] S2. After the working face 23 is pushed over, high-strength anchor cables 16 are used to support the top plate 25 of the area to be filled in a timely manner, and single hydraulic props 17 are used to support the top plate 25 of the area to be filled.

[0057] S3. Clean the top slab 25 and bottom slab of the area to be filled at the construction site to ensure that the top slab 25 and bottom slab of the area to be filled are flat.

[0058] S4. During the mining process, the roof is supported by hydraulic support 24, and the working face 23 of the coal body 22 is delayed. The prefabricated FRP pipe 1 is installed in the designated position, and the distance between two adjacent prefabricated FRP pipes 1 is 800-1200mm.

[0059] It is worth noting that the above-mentioned designated location refers to the area between the rear of the hydraulic support 24 and the single hydraulic prop 17. The specific location needs to be determined by the staff based on the site conditions.

[0060] S5. Set a filling mold bag 3 in each installed prefabricated FRP pipe 1 so that the prefabricated FRP pipe 1 and the corresponding filling mold bag 3 are combined to form a pipe column 18 to be filled.

[0061] S6. Fly ash, slag, alkali activator and water are put into the first mixing station 10 according to the design ratio and mixed for 3 to 5 minutes to form fly ash-based slurry A. Then the fly ash-based slurry A is transported to the second mixing station 14 through the slurry pipe 11. Coal gangue and crushed stone are transported to the second mixing station 14 through the first conveying station 12. At the same time, water is added to the second mixing station 14 through the water pipe 13. Then the second mixing station 14 is mixed for 5 to 10 minutes to form fly ash-based polymer filling material 2.

[0062] S7. Fly ash-based polymer filling material 2 is filled into the column to be filled 18 to form an FRP-confined fly ash-based polymer column 19. The filling method for a single column to be filled 18 is as follows:

[0063] (1) Connect the filling pipe 15 to the filling port 5 of the filling mold bag 3 on the column to be filled 18, and inject the fly ash-based polymer filling material 2 into the filling mold bag 3 of the column to be filled 18 through the filling pipe 15.

[0064] (2) Continuously inject fly ash-based polymer filling material 2 until slurry overflows from the vent 4 of the filling mold bag 3 of the column to be filled;

[0065] (3) The ultra-high molecular weight polyethylene tape 6 is wrapped around the top of the prefabricated FRP pipe 1 of the column to be filled, which has been filled with fly ash-based polymer filling material 2, using the wet-laying method.

[0066] S8. Construct a windproof wall 20 along the side of the FRP-confined fly ash base polymer material column 19 near the goaf 21, and lay a concrete layer on the side of the windproof wall 20 near the roadway to seal the goaf 21. After the concrete layer has solidified for 24 hours, remove the single hydraulic support 17.

[0067] S9. Repeat steps S2-S8 until mining is completed, and clean the backfilling system after backfilling is completed.

[0068] In this embodiment, in step S6, the mass ratio of fly ash, slag, alkali activator and water placed in the first mixing station 10 is 20:20:7:3 to 22:22:8:2.

[0069] In this embodiment, the prefabricated FRP pipe 1 can be made of carbon fiber, glass fiber, basalt fiber, polyethylene fiber, ultra-high molecular weight polyethylene fiber, or other carbon fiber materials. It is prefabricated into a cylindrical shell using a wet-laying method on the mine surface. The height of the prefabricated FRP pipe 1 is 5% less than the height of the roadway. The wall thickness and diameter of the prefabricated FRP pipe 1 are determined by the geomechanical characteristics of the surrounding rock in the goaf-side roadway and the support strength within the roadway. The prefabricated FRP pipe 1 is manufactured using an alternating winding method, with alternating winding angles of 60° and 80°. If a higher support strength is required, the alternating fiber winding angle can be appropriately increased. Figure 2 As shown, the wall 7 of the prefabricated FRP pipe 1 includes an FRP constraint 8 wound at an angle of 80 degrees and an FRP constraint 9 wound at an angle of 60 degrees.

[0070] In the optional schemes of this embodiment, the filling mold bag 3 is preferably a cylindrical bag made of polyvinyl chloride waterproof membrane. The diameter of the filling mold bag 3 is equal to the inner diameter of the prefabricated FRP pipe 1. The height of the filling mold bag 3 is 5% greater than the height of the tunnel. The filling port 5 and the exhaust port 4 are both located at the top of the filling mold bag 3.

[0071] The alkali activator is prepared by mixing a 30% sodium hydroxide solution and a 1.5 mol / L water glass solution in a set ratio. In this embodiment, the mass ratio of the sodium hydroxide solution to the water glass solution is 2:2.3. The alkali activator can utilize alkaline wastewater or waste alkali solution generated in industries such as chemical, petroleum, and pharmaceutical. The pH value of the wastewater must be not less than 13. If it contains trace amounts of heavy metals or other toxic and harmful substances, it needs to be simply treated to meet the standards before use.

[0072] In this embodiment, the fly ash shall not be lower than the secondary ash standard, and the mass of fly ash particles with a particle size of less than 100 μm shall exceed 80% of the total mass.

[0073] In the optional schemes of this embodiment, it is more preferred that the particle size of the coal gangue, the particle size of the slag, and the particle size of the crushed stone are all less than 100mm.

[0074] It is worth noting that in the fly ash-based slurry, the mass concentration of fly ash is controlled between 74% and 75%, the mass proportion of slag is 40%, the mass concentration of alkali activator is controlled between 25% and 26%, the concentration of the alkali activator itself is controlled at around 30%, and the water-cement ratio is controlled at around 0.5. Coal gangue and crushed stone need to be fully soaked in advance, and the water-material ratio is less than 0.5.

[0075] In the optional schemes of this embodiment, it is more preferred that the ultra-high molecular weight polyethylene (UHMWPE) strip 6 is cut from UHMWPE fiber cloth, the number of layers of UHMWPE strip 6 is the same as the number of layers of FRP material in the prefabricated FRP pipe 1, the length of the circumferential overlap area between UHMWPE strip 6 and prefabricated FRP pipe 1 is not less than 1 / 3 of the cross-sectional perimeter of prefabricated FRP pipe 1, and the length of the axial overlap area between UHMWPE strip 6 and prefabricated FRP pipe 1 is not less than 100mm.

[0076] In the optional schemes of this embodiment, the preferred one is that the air-proof wall 20 includes a layer of metal mesh, a layer of ventilation duct cloth and a layer of steel mesh, with the metal mesh located on the roadway side of the air-proof wall 20 and the steel mesh located on the goaf 21 side of the steel mesh; the ventilation duct cloth is sandwiched between the metal mesh and the steel mesh.

[0077] In practical applications, for non-high-temperature mines, after step S7 and before step S8, heating equipment 26 is used to heat the newly formed FRP-confined fly ash-based polymer material column 19 at a high temperature for 12 hours, with a heating temperature of 45℃~55℃. Heating equipment 26 uses an electric heating blanket for concrete curing, typically consisting of a heating section 27, a controller 28, and a power supply section 29, and wraps the roadway-side filling material for high-temperature heating.

[0078] In addition, the applicant conducted extensive experiments on fly ash-based polymer backfill materials, and prepared two types of fly ash-based polymer backfill materials with different material ratios, A and B. The specific material ratios (by mass) are shown in the table below:

[0079]

[0080] The aggregates listed in the table above are coal gangue, crushed stone, or slag.

[0081] The results of the uniaxial compression test for fly ash-based polymer filling material A are as follows: Figure 8 As shown, the uniaxial compression test results for fly ash-based polymer filling material B are as follows: Figure 9 As shown, the test results indicate that the compressive strength of the fly ash-based polymer filling material in this embodiment fully meets the usage requirements.

[0082] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for constructing FRP-confined fly ash geopolymer sidefill infill, characterized in that, include: S1. Prepare prefabricated FRP pipes, filling mold bags, filling materials and filling system, wherein the filling materials include fly ash, slag, alkali activator, coal gangue and crushed stone; The filling system is installed underground in the mine. The filling system includes a first mixing station, a first conveying station and a second mixing station. The discharge port of the first mixing station is connected to the inlet of the second mixing station through a slurry pipe. The first conveying station is used to transport materials into the second mixing station. The discharge port of the second mixing station is connected to a filling pipe. The prefabricated FRP pipe, the filling mold bag, and the filling material are all transported to the side of the filling system. S2. After the working face is pushed over, high-strength anchor cables are used to support the top plate of the area to be filled in a timely manner, and single hydraulic props are used to support the top plate of the area to be filled. S3. Clean the top and bottom slabs of the area to be filled at the construction site to ensure that the top and bottom slabs of the area to be filled are flat. S4. Lagging working surface: Install the prefabricated FRP pipe at the designated position, with the distance between two adjacent prefabricated FRP pipes being 800-1200mm; S5. A filling mold bag is set in each of the installed prefabricated FRP pipes, so that the prefabricated FRP pipe and the corresponding filling mold bag are combined to form a pipe column to be filled. S6. The fly ash, slag, alkali activator, and water are placed into the first mixing station according to the design ratio and mixed for 3-5 minutes to form fly ash-based slurry A. The fly ash-based slurry A is then transported to the second mixing station through the slurry pipe. The coal gangue and crushed stone are transported to the second mixing station through the first conveying station. Water is added to the second mixing station, and the second mixing station is then mixed for 5-10 minutes to form fly ash-based polymer filling material. S7. The fly ash-based polymer filling material is filled into the column to be filled to form an FRP-confined fly ash-based polymer material column. The filling method for a single column to be filled is as follows: (1) Connect the filling pipe to the filling port of the filling mold bag on the column to be filled, and inject the fly ash-based polymer filling material into the filling mold bag of the column to be filled through the filling pipe. (2) Continuously inject the fly ash-based polymer filling material until slurry overflows from the vent of the filling mold bag of the column to be filled; (3) The ultra-high molecular weight polyethylene tape is wrapped around the top of the prefabricated FRP pipe of the column to be filled, which has been filled with the fly ash-based polymer filling material, using the wet-laying method; S8. Construct a windproof wall along the side of the FRP-confined fly ash base polymer material column near the goaf, and lay a concrete layer on the side of the windproof wall near the roadway to seal the goaf. After the concrete layer has solidified for 24 hours, remove the single hydraulic support. S9. Repeat steps S2-S8 until mining is completed, and clean the backfilling system after backfilling is completed.

2. The method for constructing FRP-confined fly ash geopolymer roadway side infill bodies according to claim 1, characterized in that: The filling mold bag is a cylindrical bag made of polyvinyl chloride waterproof membrane. The diameter of the filling mold bag is equal to the inner diameter of the prefabricated FRP pipe. The height of the filling mold bag is 5% greater than the height of the tunnel. The filling port and the venting port are both located at the top of the filling mold bag. The alkaline activator is prepared by mixing a 30% sodium hydroxide solution and a 1.5 mol / L water glass solution in a set ratio.

3. The method for constructing FRP-confined fly ash geopolymer roadway side infill bodies according to claim 1, characterized in that: The particle size of both the coal gangue and the crushed stone is less than 100 mm.

4. The method for constructing FRP-confined fly ash geopolymer roadway side infill bodies according to claim 1, characterized in that: The ultra-high molecular weight polyethylene (UHMWPE) tape is cut from UHMWPE fiber cloth. The number of layers of the UHMWPE tape is the same as the number of layers of FRP material in the prefabricated FRP pipe. The length of the circumferential overlap area between the UHMWPE tape and the prefabricated FRP pipe is not less than 1 / 3 of the circumference of the cross-section of the prefabricated FRP pipe. The length of the axial overlap area between the UHMWPE tape and the prefabricated FRP pipe is not less than 100mm.

5. The method for constructing FRP-confined fly ash geopolymer roadway side infill bodies according to claim 1, characterized in that: The air-proof wall comprises a layer of metal mesh, a layer of ventilation duct cloth, and a layer of steel mesh, with the metal mesh located on the roadway side of the air-proof wall and the steel mesh located on the goaf side of the steel mesh; the ventilation duct cloth is sandwiched between the metal mesh and the steel mesh.

6. The method for constructing FRP-confined fly ash geopolymer roadway side infill bodies according to claim 1, characterized in that: For non-high-temperature mines, after step S7 and before step S8, a heating device is used to heat the newly formed FRP-confined fly ash-based polymer material column at high temperature for 12 hours at a temperature of 45℃ to 55℃. The heating device is a building concrete curing electric heating blanket.

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