A flexible layer-by-layer construction method for paste slurry based filling retaining wall

Abstract

This invention provides a method for constructing a flexible, layer-by-layer retaining wall using paste-based slurry, belonging to the field of underground backfilling mining technology. The method includes the following steps: S10: When the underground mining is nearing completion, the location for constructing the backfilling retaining wall is planned at the entrance of the mining area or roadway, and the cross-sectional structural parameters of the retaining wall location are accurately measured; S20: Based on the cross-sectional structural parameters of the retaining wall location, the dimensions of the logs, the dimensions of the flexible membrane bags, and the number of layers are designed, and after processing, they are packaged and transported to the vicinity of the target mining area for storage; S30: After mining is completed, the sides and bottom of the retaining wall location are cleaned and leveled. This invention uses paste-based slurry as the construction material for the backfilling retaining wall. Paste is a recycled material from mine tailings solid waste, and the material is abundant and inexpensive. The paste-based slurry is directly branched through the backfilling pipeline to the retaining wall location, saving material transportation costs.

Description

Technical Field

[0001] This invention relates to the field of underground backfill mining technology, specifically to a method for constructing a flexible, layer-by-layer backfill retaining wall based on paste material. Background Technology

[0002] Tailings backfilling mining, due to its characteristic of "treating two problems (mined-out areas and tailings ponds) with one waste (tailings)," has become the mainstream method for underground metal mining. With the depletion of shallow metal resources, deep resource development faces significant challenges such as high stress, high geothermal temperature, high fracture water pressure, and mining disturbance. Paste backfilling technology, with its "three no's" characteristics of no stratification, no segregation, and no dehydration, provides a reliable solution for safe, green, and efficient deep metal mining. More and more mines are upgrading traditional high-concentration backfilling or directly adopting paste backfilling to achieve the goals of no dehydration in the stope, high roof contact rate, and strong mechanical properties.

[0003] In backfilling mining, backfill retaining walls are often installed at the exit of the stope / roadway to seal off the goaf, isolate the working area, and withstand the pressure of the backfill slurry. Their construction technology is a key link to ensure the safe and efficient conduct of backfilling operations. Through years of production practice and innovative research, backfill retaining wall structures and construction methods have developed into types with different functional characteristics.

[0004] In terms of impermeability, almost all existing backfill retaining walls are permeable retaining walls. In addition to their sealing and pressure-bearing functions, they also have a water-filtering function to facilitate the dewatering and discharge of backfill slurry within the mining area. Currently, there are no suitable retaining wall inventions for paste backfilling processes. By eliminating unnecessary water-filtering structures, costs can be reduced, and the integrity and safety of the retaining wall system can be improved.

[0005] In terms of construction materials, commonly used infill retaining walls mainly include: wooden retaining walls, brick retaining walls, concrete retaining walls, steel structure retaining walls, and sandbag retaining walls. All of these retaining wall constructions involve the transportation of materials underground, resulting in large volumes, high costs, and high labor intensity. To alleviate the pressure of underground material transportation, new retaining wall construction materials adhere to the principle of using locally sourced materials. Patent CN202210441374.1 mentions an infill retaining wall and construction method based on an integrated flexible frame. Although it directly fills underground waste rock, the waste rock is not conducive to the sealing of the roadway walls, and the sealing performance of the connection between the retaining wall and the roadway depends on the precision of the 3D-printed flexible frame. Furthermore, this method is only suitable for non-roofed filling in upward-facing horizontally layered filling stopes and is not suitable for the construction of full-section infill retaining walls. Patent CN201810899117.6 proposes a method for backfilling tailings in mining roadways to seal off unfilled areas. A steel cofferdam support is erected at the retaining wall construction location, and backfill bags are laid inside the support. Backfill pipes are connected to the backfill bags via backfill branch pipes. The goaf and backfill bags are filled alternately in the same layer to ensure that the retaining wall and goaf are eventually roofed synchronously. While this patent cleverly utilizes the cemented backfill slurry in the backfill pipes, each layer consists of multiple rows of backfill bags, requiring continuous switching of backfill branch pipes during filling. Furthermore, the grouting operation of the backfill bags (goaf) can only be carried out after the backfill slurry in the previous goaf (backfill bags) has solidified and stood upright. This results in high labor intensity for same-layer construction and a long cycle of alternating layer-by-layer operations.

[0006] In terms of cross-sectional shape, retaining walls are mostly constructed in straight wall (slab-like) or right-angled trapezoidal forms. Slab-like retaining walls have poor overturning resistance, while right-angled trapezoidal retaining walls have poor anti-slip resistance. Patent CN201710093444.8 proposes a method for constructing a layered bag-type self-supporting infill retaining wall in a roadway. This method also utilizes filling slurry to construct the bag-type retaining wall and employs a stepped dam-like construction process. While the double-sided stepped layered bag-type retaining wall used in this invention provides good sealing with the roadway sidewalls and exhibits structural stability and strong anti-slip capability, the double-sided stepped construction occupies a significant amount of roadway space. Retaining walls should be installed at the entrance of the mining area / roadway. However, mining areas / roadways typically connect to segmented roadways and other development and preparation projects. The double-stepped retaining walls are symmetrically distributed. The stepped shape closer to the goaf maximizes the sealing effect, while the stepped shape closer to the segmented roadway leads to a significant increase in the roof span of the segmented roadway, severely impacting the stability of adjacent development projects. Patent CN202420630552.X proposes a modular filling retaining wall, which is constructed by overlapping multiple threaded steel gabion meshes fixed to roadway anchor bolts by ring wall reinforcement. A loader loads waste rock into the gabion meshes to form a stepped waste rock retaining wall. While this invention has a simple process, the retaining wall supports are made of threaded steel gabion meshes, which are non-recyclable, resulting in high costs. Furthermore, the gabion meshes have poor sealing against the sidewalls, leading to grout leakage. In addition, due to roadway space constraints, loading waste rock requires loader and hoisting equipment, resulting in low efficiency and poor safety. Therefore, a flexible, layer-by-layer construction method for paste-based filling retaining walls is needed to address the shortcomings of existing technologies. Summary of the Invention

[0007] This invention provides a flexible, layer-by-layer construction method for a paste-based filling retaining wall. The paste is used as the filling retaining wall construction material. The paste is a recycled material from mine tailings solid waste, which is abundant and inexpensive. The paste is directly delivered to the retaining wall construction location through a branch filling pipeline, saving material transportation costs.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] A method for constructing a flexible, layer-by-layer retaining wall based on paste slurry filling includes the following steps:

[0010] S10: When the mining in the underground mining area is about to end, plan the location of the filling retaining wall at the entrance of the mining area or roadway, and accurately measure the cross-sectional structural parameters of the retaining wall location.

[0011] S20: Based on the cross-sectional structural parameters of the retaining wall construction location, design the log size, flexible membrane bag size and number of layers, and after processing, pack and transport them to the vicinity of the target mining area for storage;

[0012] S30: After the mining is completed, the two sides and the bottom plate of the retaining wall construction location will be cleaned and leveled; and a limiting foundation pit will be excavated at a distance of one-third from the left and right sides of the bottom plate, and the logs will be fixed to the limiting foundation pit;

[0013] S40: The flexible membrane bags are nested into the logs in descending order of size through the hollow channels, and the logs position the flexible membrane bags.

[0014] S50: The paste is connected from the filling pipe of the filling mine to the inlet of the first layer of flexible membrane bag through the filling hose, and the paste is filled into the first layer of flexible membrane bag after the valve is opened;

[0015] S60: When the near-end and far-end exhaust ports begin to return slurry sequentially, it indicates that the first layer of flexible membrane bag has been filled. Then close the filling hose valve.

[0016] S70: Continue to connect the filling hose to the inlet of the second layer of flexible membrane bag, and repeat steps S50-S60 until the last layer of flexible membrane bag is filled to the top, and the filling retaining wall is completed.

[0017] Preferably, the planned location of the filling retaining wall in S10 follows the principle of being far away from empty areas and having stable surrounding rock, and the filling retaining wall is located at the entrance of the mining area or roadway and at a section with stable surrounding rock.

[0018] Preferably, the flexible membrane bag of S20 is made of a material with extensibility; the flexible membrane bag is designed as a cuboid shape based on the cross-sectional structural parameters of the retaining wall construction location.

[0019] Preferably, the long side of the flexible membrane bag is set to be perpendicular to the direction of the mining area or roadway, and the length of the flexible membrane bag is the width of the mining area or roadway; wherein, during the deployment process, the side away from the empty area is the near-end long side, and the side closer to the empty area is the far-end long side.

[0020] The width of the flexible membrane bag is specified to be along the direction of the mining area or roadway, and the width of the flexible membrane bag is 2 to 4 m. The flexible membrane bags of different layers have different widths. It is specified that the width of the first layer of flexible membrane bags closest to the bottom plate is not less than 3 m and not more than 4 m, the width of the last layer of flexible membrane bags closest to the top plate is 2 m, and the width of the flexible membrane bags in the middle layers decreases arithmetically according to the number of layers of flexible membrane bags until the last layer of flexible membrane bags is 2 m.

[0021] The thickness of the flexible membrane bag is 0.5m, and the required number of layers of the flexible membrane bag is determined based on the cross-sectional height of the retaining wall construction location.

[0022] Preferably, the flexible membrane bag includes a membrane bag body, a feed inlet located at the bottom corner of a side adjacent to the long side of the near end of the membrane bag body, a near-end exhaust port and a far-end exhaust port arranged on the top surface of the membrane bag, and at least two hollow channels arranged parallel to the long side inside the membrane bag body.

[0023] The feed inlet has a concave hole structure with a hole diameter of φ50~75mm. The feed inlet includes a piping interface on the membrane bag body and an automatic check valve on the piping interface. The piping interface is a quick-connect interface, a threaded interface or a clamp interface, and a sealing pressure ring is provided between the piping interface and the membrane bag body.

[0024] The near-end vent is located on the near-end long side of the membrane bag body near the feed inlet, and the far-end vent is located on the far-end long side of the membrane bag body, with the near-end vent and the far-end vent arranged diagonally.

[0025] Both the near-end vent and the far-end vent are circular patch-type vent valves, each including a base fixed to the membrane bag body by hot-press welding, a one-way diaphragm set in the inner cavity of the base, a valve cover set on the top of the base, an vent hole set on the side wall of the valve cover, and a slurry pipe set in the vent hole.

[0026] The hollow pores are located at a distance of one-third of the width of the left and right sides of the membrane bag body, and at a distance of 1m from the long side of the near end of the membrane bag body. The diameter of the hollow pores is 12-15cm.

[0027] Preferably, in S30, the bottom end of the log is fixed in the limiting pit of the mining area or roadway floor, and the top end is clamped or embedded in the mining area or roadway roof. The diameter of the log is 10-12cm, and the length of the log is 20cm longer than the cross-sectional height of the retaining wall construction location. The diameter of the limiting pit is 10-12cm, and the pit depth is 20cm.

[0028] Preferably, in step S40, the flexible membrane bag is positioned according to the principle of from large to small and from bottom to top, and is nested into the log layer by layer through hollow channels. During the process of laying the flexible membrane bag layer by layer through the log, it is ensured that the exhaust port faces the top plate and the feed port faces away from the goaf.

[0029] Preferably, the S50 filling hose is a corrugated hose with a diameter of φ50~75mm, which matches the specifications of the feed inlet piping interface. The filling hose is directly or connected to the feed inlet of the flexible membrane bag via a trailer pump.

[0030] If the filling paste cannot meet the strength requirements of the filling retaining wall, an early strength agent can be added to improve the strength of the paste slurry-based filling retaining wall. Depending on the mine filling process, the early strength agent can be added directly during surface preparation; or it can be mixed evenly with the paste slurry using a mobile dynamic mixing tank or a static spiral mixer before filling the flexible membrane bag underground.

[0031] Preferably, when the near-end and far-end vents of S60 begin to return slurry sequentially, the slurry return sequence of the near-end and far-end vent pipes is monitored during the grouting process of the flexible membrane bag. When the near-end vent begins to return slurry, it indicates that the flexible membrane bag is about to be filled; when the far-end vent begins to return slurry, it indicates that the flexible membrane bag is filled; when the far-end vent returns slurry first, a short circuit occurs inside the membrane bag, which needs to be investigated and refilled in time.

[0032] Preferably, when filling the ointment with the layered flexible membrane bags, there is no need to wait for the previous layer of membrane bags to cure and solidify. After the retaining wall is constructed layer by layer, the filling operation of the goaf can begin immediately without curing.

[0033] The final constructed infill retaining wall is a single-sided stepped structure. The side facing the goaf is stepped and can be coupled with the paste in the goaf to form an inlaid structure. The side facing away from the goaf is a straight wall.

[0034] As can be seen from the above technical solutions, the present invention has the following beneficial effects:

[0035] 1. In this invention, paste slurry is used as the filling material for the retaining wall. The paste is a recycled material of mine tailings solid waste, which is abundant and inexpensive. The paste slurry is directly branched through the filling pipeline to the location of the retaining wall construction, which can save the cost of material transportation.

[0036] 2. In this invention, a highly ductile flexible membrane bag is used as the framework for the filling retaining wall, which eliminates the rigid framework of traditional retaining wall construction such as steel structure, wood structure, and brick structure. The construction is simple and fast, and it is conducive to the sealing of the filling retaining wall with the two sides and the top side. It is suitable for various cross-sectional forms such as rectangular and three-center arch.

[0037] 3. In this invention, paste slurry is used as the construction material for the filling retaining wall. The paste has the characteristics of not bleeding water, not settling, and high strength. The retaining wall can be constructed layer by layer and the filling of the stope can be seamlessly connected without waiting for the paste to cure and solidify. This reduces the curing time after the retaining wall is constructed layer by layer, shortens the mining and filling cycle operation time, and helps to improve the overall mining efficiency of the mine. Attached Figure Description

[0038] Figure 1 The construction steps of a flexible layer-by-layer construction method for a paste-based filling retaining wall provided by the present invention are shown in the diagram.

[0039] Figure 2This invention provides a three-dimensional structural diagram of a flexible, layer-by-layer construction method for a paste-based filling retaining wall.

[0040] Figure 3 This invention provides a front view of a flexible, layer-by-layer construction structure for a paste-based filling retaining wall.

[0041] Figure 4 The left view of a flexible, layer-by-layer construction structure for a paste-based filling retaining wall provided by the present invention;

[0042] Figure 5 A top view of a flexible, layer-by-layer construction structure for a paste-based filling retaining wall provided by the present invention;

[0043] Figure 6 This is a schematic diagram of the overall structure of the paste-based flexible film bag in a preferred embodiment of the present invention;

[0044] Figure 7 This is a schematic diagram of the inlet structure of the paste-based flexible film bag in a preferred embodiment of the present invention;

[0045] Figure 8 This is a schematic diagram of the exhaust port structure of the paste-based flexible film bag in a preferred embodiment of the present invention.

[0046] In the diagram: 10. Flexible membrane bag; 11. Membrane bag body; 12. Feed inlet; 121. Piping interface; 122. Automatic check valve; 13. Near-end vent; 14. Far-end vent; 15. Hollow channel; 20. Paste; 30. Log; 410. Base; 420. One-way diaphragm; 430. Valve cover; 440. Vent hole; 450. Slurry inlet pipe. Detailed Implementation

[0047] A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

[0048] To achieve the above objectives, the embodiments of the present invention adopt the following technical solutions: (Refer to...) Figure 1 A method for constructing a flexible, layer-by-layer retaining wall based on paste slurry, comprising the following steps:

[0049] S10: When the mining in the underground mining area is about to end, plan the location of the filling retaining wall at the entrance of the mining area or roadway, and accurately measure the cross-sectional structural parameters of the retaining wall location.

[0050] S20: Based on the cross-sectional structural parameters of the retaining wall construction location, design the log size, flexible membrane bag size and number of layers, and after processing, pack and transport them to the vicinity of the target mining area for storage.

[0051] S30: After the mining is completed, the two sides and the bottom of the retaining wall construction site will be cleaned and leveled; and a limiting foundation pit will be excavated at a distance of one-third from the left and right sides of the bottom plate, and the logs will be fixed to the limiting foundation pit.

[0052] S40: The flexible membrane bags are nested into the logs in descending order of size through the hollow channels, and the logs position the flexible membrane bags.

[0053] S50: The paste is connected from the filling pipe of the filling site to the inlet of the first layer of flexible membrane bag through the filling hose, and the paste is filled into the first layer of flexible membrane bag after the valve is opened.

[0054] S60: When the near-end and far-end exhaust ports begin to return slurry in sequence, it indicates that the first layer of flexible membrane bag has been filled. Then close the filling hose valve.

[0055] S70: Continue to connect the filling hose to the inlet of the second layer of flexible membrane bag, and repeat steps S50-S60 until the last layer of flexible membrane bag is filled to the top, and the filling retaining wall is completed.

[0056] As a preferred technical solution in this embodiment, the planned location of the filling retaining wall in S10 follows the principle of "away from the empty area and with stable surrounding rock", and the filling retaining wall is located at the entrance of the mining area or roadway and at a section with stable surrounding rock.

[0057] Furthermore, the flexible membrane bag 10 of S20 is made of a material with extensibility, so that the flexible membrane bag can have good extensibility; at the same time, the size and shape of the flexible membrane bag 10 are cuboid, and the size (length × width × thickness) of the flexible membrane bag 10 depends on the cross-sectional structural parameters of the retaining wall construction location.

[0058] Reference Figure 2 , Figure 3 , Figure 4 , Figure 5 In some embodiments, the long side of the flexible membrane bag 10 is set to be perpendicular to the direction of the mining area or roadway, and the length of the flexible membrane bag 10 is the width of the mining area or roadway; wherein, during the deployment process, the side away from the empty area is the near-end long side, and the side closer to the empty area is the far-end long side.

[0059] The width of the flexible membrane bag 10 is specified to be along the direction of the mining area or roadway, and the width of the flexible membrane bag is 2 to 4 m. The flexible membrane bags of different layers have different widths. It is specified that the width of the first layer of flexible membrane bags closest to the bottom plate is not less than 3 m and not more than 4 m, the width of the last layer of flexible membrane bags closest to the top plate is 2 m, and the width of the flexible membrane bags in the middle layers decreases arithmetically according to the number of layers of flexible membrane bags until the last layer of flexible membrane bags is 2 m.

[0060] Furthermore, the thickness of the flexible membrane bag 10 is 0.5m, and the number of layers of the flexible membrane bag 10 is determined based on the cross-sectional height of the retaining wall construction location.

[0061] Furthermore, refer to Figure 2 , Figure 6 The flexible film bag 10 includes a film bag body 11, a feed inlet 12, a near-end exhaust port 13, a far-end exhaust port 14, and hollow channels 15. The feed inlet 12 is located at the bottom corner of the side adjacent to the near-end long side of the film bag body 11. The near-end exhaust port 13 and the far-end exhaust port 14 are arranged on the top surface of the film bag body 11. There are at least two hollow channels 15, and the two hollow channels 15 are arranged parallel to the inner long side of the film bag body.

[0062] Specifically, refer to Figure 7 The feed inlet 12 has a concave hole structure with a hole diameter of φ50~75mm. The feed inlet 12 includes a piping interface 121 disposed on the membrane bag body 11 and an automatic check valve 122 disposed on the piping interface. The piping interface 121 is any form of quick connection interface such as quick-connect interface, threaded interface, clamp interface, etc., and a sealing pressure ring is provided between the piping interface 121 and the membrane bag body 11.

[0063] The proximal exhaust port 13 is located on the proximal long side of the membrane bag body 11 near the feed inlet 12, and the distal exhaust port 13 is located on the distal long side of the membrane bag body 11, with the proximal exhaust port 13 and the distal exhaust port 13 arranged diagonally.

[0064] Furthermore, refer to Figure 8 Both the near-end exhaust port 13 and the far-end exhaust port 14 are circular patch-type exhaust valves. Both include a base 410, a one-way diaphragm 420, a valve cover 430, an exhaust port 440, and a slurry pipe 450. The base 410 is fixed to the membrane bag body 11 by hot-press welding. The one-way diaphragm 420 is located in the inner cavity of the base 410, and a "cross" or "Y" shaped cut is opened on the surface of the one-way diaphragm 420. The valve cover 430 is located on the top of the base 410, and the exhaust port 440 is located on the side wall of the valve cover 430. The valve cover 430 and the exhaust port 440 are integrally injection molded. The slurry pipe 450 is located inside the exhaust port 440. It should be noted that the slurry pipe 450 is a transparent small tube, which can clearly monitor the return slurry status.

[0065] Specifically, in this embodiment, there are two hollow channels 15. The hollow channels 15 are used to insert logs 30 and fix and restrict the sliding of the filling film bag. The hollow channels 15 are arranged at a position one-third of the length of the left and right sides of the film bag body 11, and at a position 1m away from the long side of the near end of the film bag body 11. The diameter of the hollow channel 15 is 12-15cm.

[0066] Furthermore, in S30, the bottom end of the log 30 is fixed in the limiting pit of the bottom plate of the mining area or roadway, and the top end is clamped or embedded in the top plate of the mining area or roadway. The diameter of the log 30 is 10-12cm, and the length of the log 30 is 20cm longer than the cross-sectional height of the retaining wall construction location. The diameter of the limiting pit is 10-12cm, and the pit depth is 20cm.

[0067] Furthermore, in step S40, the flexible membrane bag 10 is positioned according to the principle of "from large to small, bottom to top", and nested into the log layer by layer through the hollow channel 15. During the process of laying the flexible membrane bag 10 through the log 30 layer by layer, it is ensured that the exhaust port 440 faces the top plate and the feed port 12 faces away from the goaf.

[0068] In some embodiments, the S50 filling hose is a corrugated hose, which is easily movable and connected to the inlet position of the flexible membrane bag 10 with different layers. The diameter of the filling hose is φ50~75mm, which matches the specification of the inlet piping interface 121. In use, the grouting method can be selected as pumping or gravity conveying depending on the pipeline conditions. That is, the filling hose is directly or through a trailer pump connected to the inlet 12 of the flexible membrane bag.

[0069] If the filling paste cannot meet the strength requirements of the filling retaining wall, an early strength agent can be added to improve the strength of the paste slurry-based filling retaining wall. Specifically, depending on the mine filling process, the early strength agent can be added directly during surface preparation; or, before filling the flexible membrane bag 10 underground with the paste, the early strength agent can be uniformly mixed with the paste slurry using a mobile dynamic mixing tank or a static spiral mixer before filling the flexible membrane bag 10.

[0070] Furthermore, when the near-end and far-end vents of S60 begin to return slurry sequentially, the slurry return sequence of the near-end and far-end vent pipes is monitored during the grouting process of the flexible membrane bag 10. When the near-end vent 13 begins to return slurry, it indicates that the flexible membrane bag 10 is about to be filled; when the far-end vent 14 then begins to return slurry, it indicates that the flexible membrane bag 10 has been filled; if the far-end vent 14 returns slurry first, a short circuit occurs inside the membrane bag, which needs to be investigated and refilled in time.

[0071] Furthermore, when filling the layered flexible membrane bag 10 with paste, there is no need to wait for the previous layer of membrane bag to cure and solidify, and the filling operation of the goaf can start immediately after the filling retaining wall is constructed layer by layer without curing.

[0072] In this way, the final constructed filling retaining wall is a single-sided stepped structure. The side facing the goaf is stepped and can be coupled with the paste in the goaf to form an inlaid structure, while the side facing away from the goaf is a straight wall.

[0073] The following detailed explanation, with reference to a specific embodiment, illustrates the flexible layer-by-layer construction method for paste-based filling retaining walls described in this invention.

[0074] A nickel mine in Gansu Province uses a mechanized downward-entry layered backfilling mining method, with paste backfilling used in the goaf. After the mining of the access stope is completed, a backfilling retaining wall needs to be constructed at the intersection of the stope and the layered roadway. The original backfilling retaining wall was a brick retaining wall structure with the following specifications: stope span of 5m, stope height of 4m, and retaining wall thickness of 0.8m (retaining wall bricks are 600mm thick, with 20mm cement bonding between two bricks, and plain shotcrete of no less than 100mm on both the inside and outside of the retaining wall); the shape is a straight wall, close to and parallel to the layered roadway.

[0075] The construction process for the brick retaining wall is as follows: A foundation 0.2m below the base slab at the construction site is excavated. A metal mesh is laid on top of the foundation, with the inner side of the retaining wall overlapping the metal mesh used for the access road, and extending 1m outwards. Hooked anchor bolts are pre-installed 1m from the bottom slab of the mining area. After the retaining wall is constructed, the mesh is fixed to the retaining wall using hooked anchor bolts, with a 1m spacing between the anchor bolts. After the retaining wall is completed, a metal mesh with a grid spacing of 150mm × 150mm is fixed to the retaining wall using hooked anchor bolts, and shotcrete is applied to a thickness of 100mm. Simultaneously, the 2m mine pillar at the connection between the retaining wall and the access road must be thoroughly shotcreted to a thickness of not less than 100mm to prevent water seepage and grout leakage.

[0076] Since its application, brick retaining walls have demonstrated high strength and stability. However, the complex materials, cumbersome processes, and high labor intensity of brick retaining walls have resulted in high costs and low construction efficiency. Subsequent optimizations have led to the development of paste-based slurry-filled retaining walls. Furthermore, a flexible, layer-by-layer construction method for paste-based slurry-filled retaining walls has been invented. The construction steps are explained in detail below with accompanying illustrations:

[0077] When the underground mining is about to end, the location for the filling retaining wall is planned at the entrance of the mining area, and the cross-sectional structural parameters of the retaining wall location are accurately measured.

[0078] Based on the cross-sectional structural parameters of the retaining wall construction location, the design specifies that the logs are 10cm in diameter and 4.2m long; the flexible membrane bags are 5m long and 0.5m thick, requiring a total of 8 layers of flexible membrane bags. The first layer (near the bottom plate) has a width of 4m, and the width of the second to seventh layers decreases uniformly with each layer, until the last layer has a width of 2m. The inlet diameter of the flexible membrane bag is φ50mm, and the piping interface is a threaded quick-connect interface equipped with an automatic check valve. The outlet diameter of the flexible membrane bag is φ10mm. From the surface of the flexible membrane bag upwards, the components are: base, one-way diaphragm, valve cover, vent, and grout pipe. The one-way diaphragm surface is decorated with a "cross" shaped cut. The hollow structure has a diameter of 12cm and is located at a distance of 1.67m and 3.33m from one side of the flexible membrane bag, and 1m from the near end of the long side of the flexible membrane bag. After the construction materials are processed, they are packaged and transported to a storage location near the mining area.

[0079] After the mining is completed, the two sides and the bottom of the retaining wall construction site will be cleaned and leveled. A limiting pit will be excavated at a distance of 1.67m from the left and right sides of the bottom plate. The limiting pit has a diameter of 10cm and a depth of 20cm. The logs will be fixed to the limiting pit.

[0080] The flexible membrane bags are nested into the logs in descending order of size through a hollow structure, and the logs then position the flexible membrane bags.

[0081] After the flexible membrane bags are laid, the paste is connected from the filling pipeline in the filling area to the inlet of the first layer of flexible membrane bags through a 50mm diameter filling hose. To ensure the strength of the filling retaining wall, an early-strength agent is added to the paste. After the agent is added, the valve is opened to start filling the first layer of flexible membrane bags with paste. When slurry begins to return sequentially from the near-end vent and the far-end vent, it indicates that the first layer of flexible membrane bags has been filled. The filling hose valve is then closed. The filling hose is then connected to the inlet of the second layer of flexible membrane bags. Without waiting for the paste in the first layer of flexible membrane bags to solidify, the above filling steps are repeated directly until the last layer of flexible membrane bags is filled to the top, and the filling retaining wall is completed. After the retaining wall is constructed, filling work can be carried out immediately without waiting for the retaining wall to cure and solidify.

[0082] The final infill retaining wall is shown in the attached image. Figure 2 As shown, it is a single-sided stepped retaining wall. The side facing the goaf is stepped, which can couple with the paste in the goaf to form an inlaid structure, which is beneficial to the stability of the retaining wall.

[0083] The field application achieved good results. No safety accidents such as grout leakage, retaining wall cracking, or collapse occurred during the filling process in the test mining area.

[0084] Compared to the traditional brick masonry filling retaining wall construction, the construction process for paste-based filling retaining walls is simpler, reducing construction time from 6 hours / 4 people to 4 hours / 2 people, thus lowering labor intensity. From a time perspective, construction efficiency is increased by at least 33%.

[0085] Compared to the original brick masonry filling retaining wall construction, the paste-based filling retaining wall can be used immediately for mine filling operations after its construction. This eliminates the need for the spraying and curing of brick masonry filling retaining walls, saving 8 hours, reducing the cycle time of mining and filling operations, and improving the overall mining efficiency.

[0086] The slurry-based retaining wall construction material includes slurry, flexible membrane bags, logs, and an early-strength agent, while the brick retaining wall construction material includes fly ash hollow bricks, manufactured sand, cement, wood planks, and metal mesh. Although the retaining wall thickness increases from 0.8m to a stepped structure of 2-4m, considering that the increased thickness itself requires slurry filling, replacing hollow bricks with slurry does not increase costs due to the increased thickness. The cost of the slurry-based retaining wall construction material only includes the cost of logs, flexible membrane bags, and the early-strength agent. The cost of brick retaining wall construction material is 1986.1 yuan per wall, while the cost of slurry-based retaining wall construction material is 1330 yuan per wall. Compared to the original brick-built retaining walls, using this invention to construct retaining walls can save 33% in material costs.

[0087] The above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for constructing a flexible, layer-by-layer retaining wall using a paste-based filling material, characterized in that, Includes the following steps: S10: When the mining in the underground mining area is about to end, plan the location of the filling retaining wall at the entrance of the mining area or roadway, and accurately measure the cross-sectional structural parameters of the retaining wall location. S20: Based on the cross-sectional structural parameters of the retaining wall construction location, design the log size, flexible membrane bag size and number of layers, and after processing, pack and transport them to the vicinity of the target mining area for storage; S30: After the mining is completed, the two sides and the bottom plate of the retaining wall construction location will be cleaned and leveled; and a limiting foundation pit will be excavated at a distance of one-third from the left and right sides of the bottom plate, and the logs will be fixed to the limiting foundation pit; S40: The flexible membrane bags are nested into the logs in descending order of size through the hollow channels, and the logs position the flexible membrane bags. S50: The paste is connected from the filling pipe of the filling mine to the inlet of the first layer of flexible membrane bag through the filling hose, and the paste is filled into the first layer of flexible membrane bag after the valve is opened; S60: When the near-end and far-end exhaust ports begin to return slurry sequentially, it indicates that the first layer of flexible membrane bag has been filled. Then close the filling hose valve. S70: Continue to connect the filling hose to the inlet of the second layer of flexible membrane bag, and repeat steps S50-S60 until the last layer of flexible membrane bag is filled to the top, and the filling retaining wall is completed. The flexible membrane bag of S20 is made of a stretchable material; the flexible membrane bag is designed as a cuboid shape based on the cross-sectional structural parameters of the retaining wall construction location; The long side of the flexible membrane bag is set to be perpendicular to the direction of the stope or roadway, and the length of the flexible membrane bag is the width of the stope or roadway; wherein, during the deployment process, the side away from the empty area is the near-end long side, and the side closer to the empty area is the far-end long side. The width of the flexible membrane bag is specified to be along the direction of the mining area or roadway, and the width of the flexible membrane bag is 2 to 4 m. The flexible membrane bags of different layers have different widths. It is specified that the width of the first layer of flexible membrane bags closest to the bottom plate is not less than 3 m and not more than 4 m, the width of the last layer of flexible membrane bags closest to the top plate is 2 m, and the width of the flexible membrane bags in the middle layers decreases arithmetically according to the number of layers of flexible membrane bags until the last layer of flexible membrane bags is 2 m. The thickness of the flexible membrane bag is 0.5m, and the required number of layers of the flexible membrane bag is determined based on the cross-sectional height of the retaining wall construction location.

2. The method for constructing a flexible, layer-by-layer retaining wall based on paste slurry according to claim 1, characterized in that, The planned location of the filling retaining wall in S10 follows the principle of being far away from the empty area and having stable surrounding rock. The filling retaining wall is located at the entrance of the mining area or roadway and at a section with stable surrounding rock.

3. The method for constructing a flexible, layer-by-layer retaining wall based on paste slurry according to claim 1, characterized in that, The flexible membrane bag includes a membrane bag body, a feed inlet located at the bottom corner of a side adjacent to the long side of the near end of the membrane bag body, a near-end exhaust port and a far-end exhaust port arranged on the top surface of the membrane bag, and at least two hollow channels arranged parallel to the long side inside the membrane bag body. The feed inlet has a concave hole structure with a hole diameter of φ50~75mm. The feed inlet includes a piping interface on the membrane bag body and an automatic check valve on the piping interface. The piping interface is a quick-connect interface, a threaded interface or a clamp interface, and a sealing pressure ring is provided between the piping interface and the membrane bag body. The near-end vent is located on the near-end long side of the membrane bag body near the feed inlet, and the far-end vent is located on the far-end long side of the membrane bag body, with the near-end vent and the far-end vent arranged diagonally. Both the near-end vent and the far-end vent are circular patch-type vent valves, each including a base fixed to the membrane bag body by hot-press welding, a one-way diaphragm set in the inner cavity of the base, a valve cover set on the top of the base, an vent hole set on the side wall of the valve cover, and a slurry pipe set in the vent hole. The hollow pores are located at a distance of one-third of the width of the left and right sides of the membrane bag body, and at a distance of 1m from the long side of the near end of the membrane bag body. The diameter of the hollow pores is 12-15cm.

4. The method for constructing a flexible, layer-by-layer retaining wall based on paste slurry according to claim 3, characterized in that, In S30, the bottom end of the log is fixed in the limiting pit of the mining area or roadway floor, and the top end is clamped or embedded in the mining area or roadway roof. The diameter of the log is 10-12cm, and the length of the log is 20cm longer than the cross-sectional height of the retaining wall construction location. The diameter of the limiting pit is 10-12cm, and the pit depth is 20cm.

5. The method for constructing a flexible, layer-by-layer retaining wall based on paste slurry according to claim 4, characterized in that, The S40 positions the flexible membrane bag according to the principle of from large to small and from bottom to top, and nests it layer by layer into the log through hollow channels. During the process of laying the flexible membrane bag layer by layer through the log, it ensures that the exhaust port faces the top plate and the feed port faces away from the goaf.

6. The method for constructing a flexible, layer-by-layer retaining wall based on paste slurry according to claim 5, characterized in that, The S50 filling hose is a corrugated hose with a diameter of φ50~75mm, which matches the specifications of the feed inlet piping interface. The filling hose is directly or connected to the feed inlet of the flexible membrane bag via a trailer pump. If the filling paste cannot meet the strength requirements of the filling retaining wall, an early strength agent can be added to improve the strength of the paste slurry-based filling retaining wall. Depending on the mine filling process, the early strength agent can be added directly during surface preparation; or it can be mixed evenly with the paste slurry using a mobile dynamic mixing tank or a static spiral mixer before filling the flexible membrane bag underground.

7. The method for constructing a flexible, layer-by-layer retaining wall based on paste slurry according to claim 6, characterized in that, When the near and far exhaust ports of S60 begin to return slurry sequentially, the slurry return sequence of the near and far exhaust port slurry pipes is monitored during the grouting process of the flexible membrane bag. When the near exhaust port begins to return slurry, it indicates that the flexible membrane bag is about to be filled; when the far exhaust port then begins to return slurry, it indicates that the flexible membrane bag is filled; if the far exhaust port returns slurry first, a short circuit has occurred inside the membrane bag, which needs to be investigated and refilled in time.

8. The method for constructing a flexible, layer-by-layer retaining wall based on paste slurry according to claim 7, characterized in that, When filling the ointment with layered flexible membrane bags, there is no need to wait for the previous layer of membrane bags to cure and solidify. After the retaining wall is constructed layer by layer, the filling operation of the goaf can begin immediately without curing. The final constructed infill retaining wall is a single-sided stepped structure. The side facing the goaf is stepped and can be coupled with the paste in the goaf to form an inlaid structure. The side facing away from the goaf is a straight wall.

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