A backfill construction method for underground water-sealed wells

Abstract

The present invention belongs to the technical field of mine sealing and backfilling, and discloses a construction method for backfilling a well with a water seal in a well. One of the underground well sealing and backfilling anti-seepage structures includes a well shaft buried underground, wherein a well bottom anti-seepage layer and an upper anti-seepage layer are sequentially filled in the well shaft from bottom to top. The well bottom anti-seepage layer corresponds to the underground karst water layer and is used for anti-seepage protection of the karst water layer in the well; the well bottom anti-seepage layer includes a first cast concrete layer, a first clay layer, and a first gangue layer, which are sequentially filled in from bottom to top. By setting three anti-seepage layers, the present invention can respectively deal with karst water, sand and salt water, and groundwater, thereby achieving a better barrier effect while achieving layered and classified isolation, and effectively preventing adjacent water layers from being connected in series.

Description

Technical Field

[0001] The invention belongs to the technical field of mine filling, and in particular relates to a backfill construction method for an underground water-sealed well. Background Art

[0002] According to industry safety regulations, after a coal mine closes, the shaft must be permanently sealed to eliminate potential safety hazards and prevent subsequent gas combustion, explosions, asphyxiation, and other secondary disasters. Current regulations require that abandoned vertical shafts be filled or a solid reinforced concrete cover larger than the shaft's cross-section be poured at the shaft's mouth, along with fencing and no-entry signs.

[0003] Among the existing methods of sealing and backfilling mines, most of them only target the situation where there is no water or very little water underneath, and backfilling is carried out directly. However, some deep wells have karst water in addition to groundwater and sand and brine. Karst water is located below groundwater and sand and brine. If karst water is connected in series with sand and brine and groundwater, it will cause pollution, and the upper and lower layers will be affected by the differentiation of karst water, making the water-bearing space and its own distribution tend to be heterogeneous. However, in the prior art, the applicant has not found an effective sealing solution that can target the situation where there is water at the bottom of the mine, and that is karst water. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a backfill construction method for an underground water-sealed well to solve the problem that karst water exists in deep wells and is connected in series with upper water to cause danger.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] Provided is a backfill construction method for an underground water-sealed well, comprising the following steps:

[0007] Prepare mine filling;

[0008] Use the conduit pouring assembly to pour concrete underwater into the well bottom to form a concrete anti-seepage layer at the well bottom;

[0009] Clay and gangue are successively dumped on the anti-seepage layer at the bottom of the well to form a clay layer and a gangue layer. The first anti-seepage layer for preventing the seepage of the karst water layer is composed of the concrete anti-seepage layer at the bottom of the well, the clay layer and the gangue layer;

[0010] A second anti-seepage layer for preventing the seepage of the sandstone layer and a third anti-seepage layer for preventing the seepage of underground water are sequentially filled on the first anti-seepage layer. After the filling is completed, the well is backfilled;

[0011] The step of pouring concrete underwater into the well bottom using a conduit pouring assembly to form a well bottom concrete anti-seepage layer includes the following steps:

[0012] Assembling the catheter perfusion assembly: connecting and fixing at least one section of the catheter to a funnel member with a perfusion control plate at the bottom end; installing an annular limiting ring in the catheter at the bottom end; installing elastic baffle assemblies distributed along the circumference of the catheter at intervals below the limiting ring; the elastic baffle assemblies having a limiting state and a released state; in the released state, the inner diameter of the elastic baffle assembly is larger than the inner diameter of the elastic baffle assembly in the limiting state; and installing a sealing ball between the elastic baffle assembly and the limiting ring; the diameter of the sealing ball is smaller than the inner diameter of the limiting ring and larger than the inner diameter of the elastic baffle assembly in the limiting state;

[0013] Install the catheter grouting assembly: Insert the assembled catheter grouting assembly longitudinally into the well, and make sure the bottom end of the catheter of the catheter grouting assembly is 100-300mm below the water surface at the bottom of the well;

[0014] Pouring concrete: Add concrete to the funnel to the designed amount, then pull open the pouring control panel to allow the concrete to break through the sealing ball under gravity, quickly forming a concrete anti-seepage layer at the bottom of the well.

[0015] In a possible implementation, the catheter perfusion assembly is formed by connecting a plurality of catheters with an outer diameter of 250-300 mm through flanges.

[0016] In a possible embodiment, in the step of assembling the catheter perfusion assembly, when connecting two adjacent catheters, at least one sealing ring is installed between the two catheters, and butter is used to seal the two catheters after the connection is completed.

[0017] In a possible implementation manner, in the step of pouring concrete, the top surface of the poured concrete is more than 1 m higher than the conduit.

[0018] In a possible implementation, in the step of installing the catheter grouting assembly, the bottom catheter of the catheter grouting assembly needs to be lowered to a height of more than 500 mm above the well bottom elevation.

[0019] In a possible implementation, the first anti-seepage layer and the second anti-seepage layer are both composed of a concrete layer, a clay layer, and a gangue layer filled in sequence from bottom to top.

[0020] In a possible embodiment, a second impermeable layer for preventing the seepage of the sandstone layer and a third impermeable layer for preventing the seepage of underground water are sequentially filled on the first impermeable layer. After the filling is completed, the well is backfilled, and before that, the following steps are further included:

[0021] An air guide pipe is installed, with one end of the air guide pipe extending into the second anti-seepage layer and the other end passing upward through the third anti-seepage layer and exposed outside the well.

[0022] In a possible implementation manner, the clay layer is filled with high-plasticity clay and has a thickness greater than or equal to 3 m.

[0023] In a possible implementation, the gangue layer is filled with gangue with a diameter ranging from 100 to 315 mm.

[0024] In one possible embodiment, a second anti-seepage layer for sandstone layer anti-seepage and a third anti-seepage layer for underground water anti-seepage are sequentially filled on the first anti-seepage layer. After the filling is completed, the well is backfilled.

[0025] Excavate and slope the area 1m outside the wellhead;

[0026] Demolish the old wellbore and dump stones to form a dumping layer;

[0027] Installation of reinforced concrete manhole covers;

[0028] Fill the planting soil and compact it layer by layer.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The backfill construction method of a water-sealed well is applicable to the situation where there is water and lava water at the bottom of a deep well. Concrete can be quickly poured under the water at the bottom of the well by gravity through the conduit pouring assembly. Since the density and mass of concrete are greater than that of lava water and it is located at the bottom of the water layer at the bottom of the well, the concrete layer is not easy to be integrated with water, which can effectively avoid the occurrence of segregation and solidification difficulties, thereby effectively preventing seepage by forming an anti-seepage layer of concrete at the bottom of the well.

[0031] 2. The first, second and third anti-seepage layers are composed of concrete, clay and gangue, which can also effectively block the karst water and prevent the connection between the upper and lower water layers, thus avoiding the danger caused by its connection with the upper water layer. In addition, the mutual cooperation of concrete, clay and gangue can improve the barrier and sealing properties.

[0032] 3. By setting up three anti-seepage layers, karst water, sand and salt water and groundwater can be dealt with separately. While achieving layered and classified isolation, it can also play a better barrier role and effectively prevent adjacent water layers from being connected in series. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic structural diagram of an embodiment of the present application when pouring concrete into the well bottom through a conduit pouring assembly to form a well bottom concrete anti-seepage layer;

[0034] Figure 2 This is a schematic diagram of the well structure after the well is backfilled in the embodiment of the present application;

[0035] Figure 3 This is a schematic structural diagram of a catheter irrigation assembly according to an embodiment of the present application;

[0036] Figure 4This is a partially enlarged schematic diagram of the catheter irrigation assembly according to an embodiment of the present application, which shows the elastic baffle assembly in a limited state;

[0037] Figure 5 for Figure 4 Schematic diagram of the structure after the blocking ball is hidden;

[0038] Figure 6 for Figure 5 Schematic diagram of the structure in the released state.

[0039] In the figure: 1-excavated shaft; 2-retained shaft; 3-ground; 4-slope; 5-planting soil; 6-reinforced concrete manhole cover; 7-dumping stone layer; 8-catheter pouring assembly; 81-funnel piece; 82-catheter; 83-limiting ring; 84-elastic baffle assembly; 841-arc baffle; 842-spring telescopic rod; 85-sealing ball; 86-pouring control panel; 9-first anti-seepage layer; 91-bottom concrete anti-seepage layer; 92-clay layer; 93-waste rock layer; 10-second anti-seepage layer; 11-third anti-seepage layer. DETAILED DESCRIPTION

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0041] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0042] Please refer to Figure 1-6 As shown, an embodiment of the present application provides a backfill construction method for a water-sealed well, comprising the following steps:

[0043] Step S1: Prepare for mine filling;

[0044] Step S2: using the conduit pouring assembly 8 to pour concrete underwater into the well bottom to form a well bottom concrete anti-seepage layer 91;

[0045] Step S3: Clay and gangue are successively dumped on the bottom well anti-seepage layer to form a clay layer 92 and a gangue layer 93. The bottom well concrete anti-seepage layer 91, the clay layer and the gangue layer constitute the first anti-seepage layer 9 for preventing the seepage of the karst water layer;

[0046] Step S4: a second impermeable layer 10 for preventing the seepage of the sandstone layer and a third impermeable layer 11 for preventing the seepage of underground water are sequentially constructed on the first impermeable layer 9. After the construction is completed, the well is backfilled.

[0047] Through the above technical solution, the first impermeable layer 9, the second impermeable layer 10 and the third impermeable layer 11 are composed of concrete, clay and gangue, which can effectively block the karst water and prevent the connection between the upper and lower water layers, thereby avoiding the danger caused by its connection with the upper water layer. In addition, through the mutual cooperation of concrete, clay and gangue, the barrier and sealing properties are better.

[0048] In the embodiment of the present application, the steps of pouring concrete underwater into the well bottom using the conduit pouring assembly 8 to form the well bottom concrete anti-seepage layer 91 may include the following steps:

[0049] Step S21: Assemble the catheter perfusion assembly 8: connect and fix at least one section of the catheter 82 to the funnel piece 81 with a perfusion control plate 86 at the bottom end, and install an annular limiting ring 83 in the catheter 82 at the bottom end. Elastic baffle assemblies 84 distributed circumferentially along the catheter 82 are installed below the limiting ring 83. The elastic baffle assembly 84 has a limiting state and a release state. In the release state, the inner diameter of the elastic baffle assembly 84 is larger than the inner diameter of the elastic baffle assembly 84 in the limiting state. A sealing ball 85 is provided between the elastic baffle assembly 84 and the limiting ring 83. The diameter of the sealing ball 85 is smaller than the inner diameter of the limiting ring 83 and larger than the inner diameter of the elastic baffle assembly 84 in the limiting state.

[0050] In this step, when the conduit grouting assembly 8 is not poured with concrete, the sealing ball 85 in the bottom conduit 82 is restricted between the limiting ring 83 and the elastic baffle assembly 84. The limiting ring 83 and the sealing ball 85 can prevent the underground water from overflowing from the conduit grouting assembly 8 from the bottom of the well through the conduit 82, and act as a one-way valve, making the grouting safer and the control more effective. When pouring concrete through the catheter pouring assembly 8, the concrete impacts the sealing ball 85 under the action of gravity, and the sealing ball 85 squeezes the elastic baffle assembly 84 under strong pressure, so that the elastic baffle assembly 84 switches to a released state, that is, the channel formed by the inner diameter in this state can be used for the sealing ball 85 to pass through, and then can be reopened by the concrete to seal the ball 85, thereby facilitating the rapid formation of a concrete anti-seepage layer underwater at the bottom of the well. Because it is formed quickly, the concrete can have better integrity and can be better separated from the water body above. At the same time, under the action of water pressure and the difference in the physical properties of the concrete itself, the concrete can also be more stable underwater, so that the concrete layer is not easy to merge with water, effectively avoiding the occurrence of segregation and solidification difficulties, and thus can be effectively anti-seepage through the formed bottom well concrete anti-seepage layer 91. In a specific implementation, the elastic baffle assembly 84 may include multiple sets of spring baffle components evenly arranged along the circumference of the catheter 82. The spring baffle components include an arcuate baffle 841 hinged to the catheter 82 and a spring telescopic rod 842 hinged between the bottom of the arcuate baffle 841 and the inner wall of the catheter 82. The spring telescopic rod 842 allows the arcuate baffle 841 to have two states, thereby allowing the catheter perfusion assembly 8 to have a limited state for support and a released state for passage. The blocking ball 85 is a disposable blocking ball 85, which can be made of a biodegradable material.

[0051] Step S22: Install the catheter perfusion assembly 8: Extend the assembled catheter perfusion assembly 8 longitudinally into the well, and make the bottom end catheter 82 of the catheter perfusion assembly 8 extend 100-300 mm below the water surface at the bottom of the well.

[0052] In this step, by extending the conduit 82 into the water at a greater depth and facilitating the pouring of concrete, a well bottom concrete anti-seepage layer 91 that is not easily integrated with the water body can be formed.

[0053] Step S23: pouring concrete: pour concrete into the funnel 81 to the designed amount, then pull open the pouring control plate 86 to allow the concrete to break through the blocking balls 85 under gravity, quickly forming a well bottom concrete anti-seepage layer 91 at the well bottom.

[0054] In this step, the funnel 81 can facilitate the filling of concrete and serve as a temporary storage and quantity control. After the designed amount is filled, the pouring control panel 86 can be used to allow the concrete to quickly pass through the conduit 82 into the bottom of the water under its own high pressure, and underwater pouring can be performed with sufficient pressure to achieve better pouring effects.

[0055] It should be noted that the catheter pouring assembly 8 is mainly used for pouring the bottom well concrete anti-seepage layer 91. During the pouring process, it needs to be lifted to a certain extent for better pouring. After the bottom well concrete anti-seepage layer 91 is formed, the catheter pouring assembly 8 can be retained to facilitate the pouring of concrete for the second anti-seepage layer 10 and the third anti-seepage layer 11. Of course, it can also be retained and poured through other pouring devices.

[0056] The above-mentioned technical solution is applicable to the situation where there is water at the bottom of a deep well. Concrete can be quickly poured under the water at the bottom of the well by gravity through the catheter pouring assembly 8. Since the density and mass of concrete are greater than those of lava water and it is located at the bottom of the water layer at the bottom of the well, the concrete layer is not easy to be fused with water, which can effectively avoid the occurrence of segregation and solidification difficulties, thereby effectively preventing seepage by forming an anti-seepage layer 91 of concrete at the bottom of the well.

[0057] In one embodiment, the catheter perfusion assembly 8 is formed by connecting a plurality of catheters 82 with an outer diameter of 250-300 mm through flanges.

[0058] In this way, the conduit filling assembly 8 can be adapted to mine backfilling operations at different depths by assembling a plurality of conduits 82 , and conduits 82 with an outer diameter of 250-300 mm can also be easily filled.

[0059] Furthermore, in order to improve the sealing between two adjacent conduits 82, in the step of assembling the conduit perfusion assembly 8, when connecting two adjacent conduits 82, at least one sealing ring is installed between the two conduits 82, and is sealed with butter after the connection is completed.

[0060] Furthermore, in order to reduce the influence of water on the concrete being poured during the pouring process, in the step of pouring concrete, the top surface of the poured concrete is higher than the conduit 821m. In this way, the poured concrete can be located below the poured concrete and is more stable.

[0061] During the specific implementation process, during the step of installing the conduit pouring assembly 8, the bottom conduit 82 of the conduit pouring assembly 8 must be lowered to a depth of at least 500 mm above the well bottom. This depth facilitates underwater pouring and also allows subsequent concrete to be positioned below the already poured concrete, allowing the concrete to accumulate from the bottom up, thereby reducing the impact of the water on the poured concrete.

[0062] In the embodiment of the present application, the first anti-seepage layer 9 and the second anti-seepage layer 10 are both composed of a concrete layer, a clay layer and a gangue layer filled in sequence from bottom to top.

[0063] The anti-seepage structure composed of such clay layer and gangue can effectively play an anti-seepage role.

[0064] Furthermore, in the step of sequentially filling a second impermeable layer 10 for preventing the seepage of the sandstone layer and a third impermeable layer 11 for preventing the seepage of underground water on the first impermeable layer 9, after the filling is completed, the well is backfilled, and the following steps are also included before:

[0065] Step S31: Install an air pipe (not shown in the figure), one end of the air pipe extends into the second impermeable layer 10, and the other end passes upward through the third impermeable layer 11 and is exposed outside the well.

[0066] In this step, since there may be some flammable and explosive gases in the mine, the gas accumulated inside can be discharged out of the well through the gas duct, thereby reducing the risk in the well after blocking.

[0067] In some embodiments, the clay layer may be filled with high plasticity clay and have a thickness greater than or equal to 3 m.

[0068] The gangue layer can be filled with gangue with a diameter ranging from 100 to 315 mm.

[0069] In the embodiment of the present application, a second impermeable layer 10 for preventing the seepage of the sandstone layer and a third impermeable layer 11 for preventing the seepage of underground water are sequentially filled on the first impermeable layer 9. After the filling is completed, the well is backfilled, and then the following steps are further included:

[0070] Step S5: excavate and slope the area within 1m of the wellhead;

[0071] Step S6: demolishing the old shaft and dumping rocks to form a dumping layer 7;

[0072] Step S7: Installing reinforced concrete manhole cover 6;

[0073] Step S8: Fill the planting soil 5 and compact it layer by layer. Specific embodiment:

[0075] Taking a vertical shaft mine as an example, the upper 2m of the shaft is brick-lined and the lower part is cement-lined. It is damaged and unfilled, and is surrounded by woodland. Its environmental risk is high. The mine is a 2*2.5m rectangular mine with a depth of 75 meters and a bottom area of ​​5m2. At the same time, there is water at the bottom of the mine, which is karst water. The upper water is sand-salt water and groundwater. The mine has a shaft, which consists of two parts: a retained shaft 2 and an excavated shaft 1.

[0076] The underground sealing and backfilling construction method adopted for this mine is:

[0077] Well sealing and backfilling plan: 3 layers of anti-seepage sealing (concrete and clay anti-seepage + waste rock filling at the bottom of the well, concrete and clay anti-seepage + waste rock filling at 50m, concrete and clay anti-seepage + waste rock filling at 30m) + reinforced concrete well cover + reclamation;

[0078] Construction equipment: mixers, excavators, bulldozers, vibrators, loaders, transport vehicles, formwork, rammers, underground televisions, measuring ropes, etc.

[0079] Procedure: Clean up the slag pile → Level the construction site → Build enclosures → Underground TV detection → Pour concrete to 74m through the catheter pouring assembly → Fill with clay to 71m → Fill with waste rock to 50m → Pour concrete to 49m → Fill with clay to 46m → Fill with waste rock to 30m → Pour concrete to 29m → Fill with clay to 26m → Lower the air guide pipe (also serving as a hydrological observation hole) → Fill with waste rock to 2m → Excavate within 1m of the outer edge of the wellhead → Demolish the old wellbore and fill to a depth of 1.3m → Concrete the manhole cover to 0.3m → Compact and cover the soil in layers to 0m → Loosen, level and reclaim the temporary roads and site → Set up signboards → Completion acceptance.

[0080] Technical Parameters: Temporary road one-way width ≥ 3.5m, meeting island width ≥ 6.5m; turning area ≥ 12m; enclosure height ≥ 2m; anti-seepage concrete grade C40, thickness ≥ 1m, waiting for more than 24 hours before proceeding to the next step; manhole covers are reinforced concrete, grade C40, pouring thickness ≥ 1m, covered and cured after initial setting, sprayed with water after final setting (24 hours), curing time ≥ 5 days; anti-seepage clay is natural, impurity-free, and highly plastic clay, thickness ≥ 3m; waste rock diameter 100-315mm; concrete construction ambient temperature 5℃-35℃; construction is not suitable in rainy days or in winds above level 5. Rain protection measures should be taken before curing. Backfill planting soil thickness ≥ 0.5m (cultivated land) or ≥ 0.3 (forest land), compacted in layers, with a compaction coefficient ≥ 0.94, and maintained at the same elevation as the surrounding area. The air guide holes (hydrological monitoring holes) are made of steel pipes, extending to the level of the Quaternary interface above the impermeable layer and ≥0.5m above the ground surface. A protective plug is installed at the top to facilitate subsequent water level monitoring and sampling. Garbage is sorted and transported to the municipal landfill.

[0081] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A backfill construction method for a well with a water seal, characterized by: The following steps are involved: Prepare mine filling; Use the conduit pouring assembly to pour concrete underwater into the well bottom to form a concrete anti-seepage layer at the well bottom; Clay and gangue are successively dumped on the anti-seepage layer at the bottom of the well to form a clay layer and a gangue layer. The first anti-seepage layer for preventing the seepage of the karst water layer is composed of the concrete anti-seepage layer at the bottom of the well, the clay layer and the gangue layer; A second anti-seepage layer for preventing the seepage of the sandstone layer and a third anti-seepage layer for preventing the seepage of underground water are sequentially filled on the first anti-seepage layer. After the filling is completed, the well is backfilled; The step of pouring concrete underwater into the well bottom using a conduit pouring assembly to form a well bottom concrete anti-seepage layer includes the following steps: Assembling the catheter perfusion assembly: connecting and fixing at least one section of the catheter to a funnel member with a perfusion control plate at the bottom end; installing an annular limiting ring in the catheter at the bottom end; installing elastic baffle assemblies distributed along the circumference of the catheter at intervals below the limiting ring; the elastic baffle assemblies having a limiting state and a released state; in the released state, the inner diameter of the elastic baffle assembly is larger than the inner diameter of the elastic baffle assembly in the limiting state; and installing a sealing ball between the elastic baffle assembly and the limiting ring; the diameter of the sealing ball is smaller than the inner diameter of the limiting ring and larger than the inner diameter of the elastic baffle assembly in the limiting state; Install the catheter grouting assembly: Insert the assembled catheter grouting assembly longitudinally into the well, and make sure the bottom end of the catheter of the catheter grouting assembly is 100-300mm below the water surface at the bottom of the well; Pouring concrete: add concrete to the funnel to the designed amount, then pull open the pouring control panel to allow the concrete to break through the blocking balls under gravity, quickly forming a concrete anti-seepage layer at the bottom of the well; The first, second and third anti-seepage layers are composed of concrete, clay and gangue.

2. A backfill construction method for an underground water-sealed well according to claim 1, characterized in that: The catheter perfusion assembly is formed by connecting a plurality of catheters with an outer diameter of 250-300 mm through flanges.

3. A backfill construction method for a well with water seal in an underground well according to claim 2, characterized in that: In the step of assembling the catheter perfusion assembly, when connecting two adjacent catheters, at least one sealing ring is installed between the two catheters, and is sealed with butter after the connection is completed.

4. The backfill construction method for a well with water seal in an underground well according to claim 1, characterized in that: In the step of pouring concrete, the top surface of the poured concrete is more than 1m higher than the conduit.

5. The backfill construction method for a well with water seal in an underground well according to claim 1, characterized in that: In the step of installing the catheter grouting assembly, the bottom catheter of the catheter grouting assembly must be lowered to a height of more than 500 mm above the well bottom elevation.

6. A backfill construction method for a well with water seal in an underground well according to any one of claims 1 to 5, characterized in that: The first anti-seepage layer and the second anti-seepage layer are both composed of a concrete layer, a clay layer and a gangue layer filled in sequence from bottom to top.

7. A backfill construction method for a well with water seal in an underground well according to claim 6, characterized in that: In the step, a second anti-seepage layer for preventing the seepage of the sandstone layer and a third anti-seepage layer for preventing the seepage of underground water are sequentially filled on the first anti-seepage layer. After the filling is completed, the well is backfilled. Before that, the method further includes: An air guide pipe is installed, with one end of the air guide pipe extending into the second anti-seepage layer and the other end passing upward through the third anti-seepage layer and exposed outside the well.

8. The backfill construction method for a well with water seal in an underground well according to claim 7, characterized in that: The clay layer is filled with high-plastic clay and has a thickness greater than or equal to 3m.

9. The backfill construction method for a water-sealed well in an underground well according to claim 8, characterized in that: The gangue layer is filled with gangue with a diameter ranging from 100 to 315 mm.

10. The backfill construction method for a well with water seal in an underground well according to claim 1, characterized in that: In the step, a second anti-seepage layer for preventing the seepage of the sandstone layer and a third anti-seepage layer for preventing the seepage of underground water are sequentially filled on the first anti-seepage layer. After the filling is completed, the well is backfilled. The method further includes: Excavate and slope the area 1m outside the wellhead; Demolish the old wellbore and dump stones to form a dumping layer; Installation of reinforced concrete manhole covers; Fill the planting soil and compact it layer by layer.

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