Construction method of landfill horizontal well structure

Abstract

This invention discloses a construction method for a horizontal well structure in a landfill. The method involves horizontally directional drilling into the landfill to form a horizontal well channel. During the pullback process, prestressed tendons, after prestressing tension, drive the horizontal well perforated pipe through both sides of the landfill area, enabling the drainage of leachate and landfill gas between landfill layers. This invention applies prestressed tendon tensioning technology to the perforated pipe structure for horizontal drainage in the landfill, allowing for the horizontal gravity-flow drainage of leachate. This effectively controls the leachate level in the landfill, reduces water retention in the landfill, and ensures the safe operation of the landfill and the stability of the landfill after closure. The method offers advantages such as flexible construction, high cost-effectiveness, rapid progress, and applicability to the construction of horizontal wells in various types of landfills and multi-span areas.

Description

Technical Field

[0001] This invention relates to the field of drainage of leachate and other wastewater from solid waste landfills such as municipal solid waste landfills, and more specifically to a construction method for a horizontal well structure in a landfill. Background Technology

[0002] With the rapid increase in municipal solid waste volume, sanitary landfills built in earlier years are gradually reaching the end of their service life, leading to increasingly acute and challenging problems in waste management. During the operation of these landfills, leachate booster pump stations often experience prolonged leachate drainage problems due to factors such as old equipment, inadequate maintenance, and malfunctions in the pumping system. This results in leachate remaining trapped within the waste pile, leading to high water content and a significant rise in the water level. When the leachate level in the landfill is too high, some leachate may leak laterally along the weakest areas of the cover layer on the slope of the waste pile, polluting the surrounding environment. Simultaneously, it can easily cause slope instability and collapse, resulting in lateral displacement and making stability control extremely difficult.

[0003] If the leachate level is too high, the water holding capacity of the waste will increase, which will inhibit the generation, collection, and drainage of gases such as methane. If the methane gas is not extracted in time, it can easily cause the impermeable layer to bulge and damage the impermeable structure. At the same time, the landfill gas generated in the waste pile will accumulate in the pile, posing an explosion hazard.

[0004] To ensure the safe operation of landfills and the stability of the landfill structure after closure, the leachate level must be controlled below the warning level. For simple landfills with poor leachate drainage systems or no drainage system at all, the following methods are adopted: First, vertical wells are drilled in the waste pile for dewatering. However, drilling of these drainage wells is prone to problems such as borehole collapse and waste subsidence. Insufficient drilling depth, low drainage efficiency, and high operation and maintenance costs are common issues. Furthermore, using only vertical wells for dewatering is insufficient to meet the landfill water level control requirements. Second, a ring-shaped drainage ditch is constructed along the toe of the landfill slope, connected to the bottom drainage system, or a matching extraction well is installed, increasing the structural function of leachate lateral seepage from the landfill. This method can only passively collect leachate that seeps to the side of the slope from the landfill. However, leachate seeping from the upper part of the landfill and from the middle part of the landfill cannot be drained in time. This slows down the drainage of leachate and the overall stabilization of the landfill, which is not conducive to eliminating potential landslides, instability and other hidden dangers that may occur during the later closure of the landfill.

[0005] If a horizontal well structure is adopted, the vertical pressure and frictional resistance of the garbage pile on the horizontal well water pipe will be large. The opening of the water pipe (flower pipe) will weaken the original pipe strength, making it impossible to pull back over a long distance (such as more than 200m). Summary of the Invention

[0006] The purpose of this invention is to solve the problems of difficulty in controlling the leachate level in the landfill area when using a single vertical shaft for pumping, inability of the leachate drainage blind ditch at the toe of the slope to drain leachate in the middle of the landfill in a timely manner, and difficulty in pulling back the water pipe of the horizontal well. The invention provides a construction method for horizontal wells in landfills using prestressed tensioning technology.

[0007] To achieve the above objectives, the present invention provides a construction method for a landfill horizontal well structure, characterized by comprising the following steps:

[0008] (1) Measure and lay out the design drawings to determine the coordinates of the entry and exit points of the horizontal well;

[0009] (2) Select a horizontal directional drilling rig with appropriate tonnage based on the size of the borehole span in the reservoir area, the height of the garbage pile, and the diameter of the perforated pipe for draining leachate.

[0010] (3) Select the appropriate drill bit according to the drilling target and geological conditions;

[0011] (4) Adjust the horizontal directional drilling rig according to the design angle, drill horizontally, and the borehole channel crosses the reservoir area;

[0012] (5) After drilling is completed, remove the drill bit, replace it with a reamer for pullback, and install the transfer connector.

[0013] (6) Prestressed tendons are inserted into the perforated pipe structure used for draining leachate and assembled into a horizontal well water pipe 11. After prestressing tension, the prestressed tendons are fixed to the lifting ring of the connecting pin of the transfer device. As the drill rod is retracted, the prestressed tendons are pulled, which drives the perforated pipe to be pulled back, so that the horizontal well water pipe can pass through both sides of the reservoir area to realize the drainage of leachate and landfill gas between the layers of the garbage pile.

[0014] (7) After the horizontal well water pipe is pulled back, insert both ends of the horizontal well water pipe into the solid wall pipe to drain the leachate. When the leachate drainage blind ditch is built at the foot of the sealed pile body shaping silo, connect the horizontal well water pipe to the leachate drainage blind ditch, and finally pump the leachate to the leachate regulating tank through the blind ditch.

[0015] Preferably, the perforated tube used in the above method is a slotted perforated tube. The structural feature of the slotted perforated tube is that a water guide groove is opened longitudinally along the outer wall of the slotted perforated tube. The water guide groove is opened at intervals on the outer wall of the perforated tube, and small holes are evenly distributed at the bottom of the water guide groove.

[0016] Preferably, the above-mentioned grooved pipe is made of HDPE.

[0017] Furthermore, in step (1), the design drawings are used to measure and lay out the site, mark the coordinates of the entry and exit points of the horizontal well, and mark the direction of the borehole at intervals of 2m-3m along the slope of the pile and the top membrane.

[0018] Furthermore, in step (2), the diameter of the pipe used during the pullback is De75 or De90, and the nominal pressure is 1.25-1.6MPa.

[0019] Furthermore, in step (3), in order to reduce the entanglement and wrapping of the drill bit by debris and to overcome frictional resistance to drill smoothly, a slanted palm-faced guide drill bit is adopted, with the drill bit having a rounded side without protruding edges.

[0020] Furthermore, in step (4), the horizontal directional drilling rig is placed on a steel plate, the bottom of the drilling head is supported by concrete blocks, the horizontal directional drilling rig is adjusted according to the designed drilling angle, the road surface is fixed by anchor rods, the prestressed tendons are connected to the drilling rig, the drilling rig drills horizontally, forming a horizontal well in the garbage pile, and the drilling channel crosses the storage area.

[0021] Furthermore, in step (5), the reamer used is a steel reamer with a diameter of 250-350mm and a wall thickness of 4-6mm; a steel plate with a width of 2-3cm and a thickness of 4-6mm is welded around the steel reamer near the end of the guide drill rod and ground into an arc shape; at the same time, 6-8 φ14-φ16 steel bars are longitudinally welded around the reamer near the end of the guide drill rod.

[0022] Furthermore, in step (6), the prestressing tendons inserted into the perforated pipe structure for draining leachate are steel wire ropes, and the type of steel wire rope is selected according to the pipe diameter of the perforated pipe. For example, a #10 steel wire rope is inserted into the HDPE slotted perforated pipe structure with a pipe diameter of De75, or a #12 or larger steel wire rope is inserted into the slotted perforated pipe with a pipe diameter of De90.

[0023] Preferably, in step (6), to facilitate the tensioning of prestressing tendons, the structure of the slotted tube is as follows: the slotted tube is 30-45m long in sections, and each section is connected into a whole by an inner tube support and an outer tube anchoring structure. The two ends of the integrated HDPE slotted tube are provided with an inner tube support and an outer tube anchoring structure. After the prestressing tendon is inserted into the integrated HDPE slotted tube, a 1.5-2m long prestressing tendon is reserved at both ends.

[0024] Furthermore, in step (6), the inner pipe support and outer pipe anchoring structure of the pullback end of the De75 slotted flower pipe is as follows: the inner support is made of steel pipe or wooden segment, and the outer support is made of galvanized steel pipe wrapped around the slotted flower pipe. The end of the galvanized steel pipe is welded with a 20-25mm thick steel plate with a hole in the middle. The outer galvanized steel pipe, the slotted flower pipe and the inner support steel pipe or wooden segment are fixed with bolts.

[0025] Specifically, in step (6), the diameter of the slotted pipe is De75, and the inner pipe support and outer pipe anchoring structure between the slotted pipes is as follows: the two ends of the slotted pipe are supported by steel pipes, and the outer side is wrapped with galvanized steel pipes. The outer galvanized steel pipe, the slotted pipe and the inner support steel pipe are fixed by bolts; a 20-25mm thick steel plate is welded to the middle position inside the galvanized steel pipe, with a hole in the middle, and anchors for prestressing tension are installed at both ends of the steel plate.

[0026] Further, in step (6), the diameter of the slotted pipe is De75, and the inner pipe support and outer pipe anchoring structure of the slotted pipe tail is as follows: the slotted pipe is supported by a steel pipe inside, and the slotted pipe is wrapped by a galvanized steel pipe outside; a 20-25mm thick steel plate is welded to the tail of the galvanized steel pipe, with a hole in the middle, and the outer galvanized steel pipe, the slotted pipe and the inner support steel pipe are fixed by bolts.

[0027] Furthermore, in step (6), the prestressed tendons are prestressed and tensioned using anchors of the corresponding type and then pulled back.

[0028] The beneficial effects of this invention are: the construction method provided by this invention is flexible, economical, efficient, and fast, and can be applied to the construction of horizontal wells in various types of landfills and multi-span areas. As a type of gravity-flow drainage well that requires no power, the horizontal well has advantages such as no need for dedicated personnel for management, the ability to drain leachate from inside the landfill, a large cross-sectional area for water collection, and high work efficiency. When used in conjunction with the slope toe leachate drainage blind ditch and suitable vertical wells, horizontal wells can achieve multi-dimensional drainage in both longitudinal and transverse directions, better meeting the needs of leachate level control within the landfill and ensuring the safe operation of the landfill and the stability of the landfill after closure. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the horizontal well drilling pullback construction mode based on the present invention;

[0030] Figure 2 This is a schematic diagram of a horizontal directional drilling bit used in a specific embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the horizontal directional drilling and reamer used in a specific embodiment of the present invention;

[0032] Figure 4 A schematic diagram of the HDPE slotted perforated pipe structure used for guiding and draining seepage fluid in a horizontal well in a specific embodiment of the present invention;

[0033] Figure 5 This is a schematic diagram of the application of wire rope in the horizontal pullback connection of a horizontal well water guide pipe in a specific embodiment of the present invention;

[0034] Figure 6This is a schematic diagram of the connection structure of the HDPE slotted pipe pullback end after the steel wire rope is inserted in a specific embodiment of the present invention.

[0035] Figure 7 This is a schematic diagram of the connection structure of the intermediate pipe section of the HDPE grooved perforated pipe after inserting the steel wire rope in a specific embodiment of the present invention.

[0036] Figure 8 This is a schematic diagram of the connection structure of the HDPE slotted pipe back to the tail end after the steel wire rope is inserted in a specific embodiment of the present invention.

[0037] In the diagram: 1. Waste pile, 2. Horizontal well, 3. Plant ground, 4. Silo bottom line, 5. Guide drill rod, 6. Drill bit, 7. Reamer, 8. Diverter, 9. Perforated pipe, 91. Water channel, 92. Small hole, 10. Wire rope, 11. Horizontal well water guide pipe, 12. Inner pipe support and outer pipe anchoring structure, 13. Pullback end, 14. Pullback tail, 15. Reinforcing bar, 121. Inner support sleeve, 122. Outer galvanized steel sleeve, 123. Outer sleeve end cap steel plate and outer sleeve end cap steel plate, 124. Bolt, 16. Anchor, 17. Intermediate tension steel plate, 18. Outer sleeve opening. Detailed Implementation

[0038] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0039] In a specific embodiment of the present invention, a construction method for a landfill horizontal well using prestressed tensioning technology is described, and the specific construction procedures are as follows (see...). Figure 1-8 ):

[0040] (1) Horizontal well point location: such as Figure 1 As shown, the left arrow indicates the drilling direction, and the right arrow indicates the pullback direction. Based on the design drawings, the coordinates of the entry and exit points of the horizontal well 2 in the waste pile 1 are determined by measurement and layout. According to the design plan of horizontal well 2, the coordinates of the entry and exit points are marked on the east and west sides of the storage area. Guide drilling direction marks are also made at 2-3m intervals along the slope of the waste pile and on the top membrane surface to determine the drilling extension direction. During the actual drilling, a long-distance rope will be used to assist in guiding the drilling direction.

[0041] (2) Drilling rig selection: In this embodiment, the span of the reservoir area is about 200m, the vertical height between the top of the garbage pile 1 and the horizontal well 2 is about 17m, the horizontal directional drilling requires a hole of 200m, and the pullback uses a perforated pipe with a diameter of De75 to drain the leachate. The GS420-L type horizontal directional drilling rig can be selected for drilling.

[0042] (3) Drill bit selection: such as Figure 2 Show, Figure 2The middle arrow indicates the drilling direction. To reduce debris entanglement and wrapping around the drill bit, and to overcome frictional resistance for smooth drilling, a slanted palm-faced guide drill bit (flat triangle) is used. The drill bit has rounded sides without protruding edges.

[0043] (4) Drilling Rig Installation: In this embodiment, because the entry point of the horizontal well 2 is located at the toe of the slope of the garbage heap 1, which is 80cm higher than the top of the reservoir dam, and a ring-shaped rainwater ditch 20cm higher than the road surface is constructed between the ring road and the original reservoir top anchoring ditch, such as... Figure 1 As indicated, given the aforementioned site conditions, stable installation of the drilling rig is crucial. The method employed on-site involved placing the horizontal directional drilling rig on a steel plate, supporting the bottom of the drill head with concrete blocks, adjusting the rig according to the designed drilling angle, and securing it to the road surface with two approximately 60cm long ground anchors. A steel wire rope was used to connect the rig to prevent it from tilting forward during operation. In cases of poorly constructed roadbeds, an additional ground anchor was added to increase the stress on the ground anchors and prevent equipment slippage. Horizontal well drilling: [The text abruptly ends here, likely due to an incomplete sentence or missing information.] Figure 1 , 2 As shown, the drilling rig guide rod 5 drives the drill bit 6 to drill horizontally, forming a horizontal well 2 within the waste pile 1. The borehole channel traverses the storage area. During drilling, clean water needs to be injected to cool the drill bit and lubricate and reduce drag.

[0044] (5) Installation of the pullback reamer: (e.g.) Figure 3 Show, Figure 3 The middle arrow indicates the pullback direction. After drilling is completed, replace drill bit 6 with a smooth reamer 7 for pullback, install and connect the transfer switch 8, and pull back the horizontal well water guide pipe 11. The reamer 7 has a diameter of 250-350mm and a wall thickness of about 5mm. Due to the complex composition of the waste pile 1, in order to reduce the wear of the reamer 7 by steel bars, wires, stones and other debris, weld a 2-3cm wide and 4-6mm thick steel plate around the reamer 7 near the end of the guide drill rod, and grind the edges into an arc shape. At the same time, weld 6-8 φ14-φ16 steel bars longitudinally around the reamer 7 near the end of the guide drill rod to increase its wear resistance.

[0045] (6) Installation of prestressed steel wire rope: such as Figure 5 As shown, in this embodiment, the prestressing tendon used is a steel wire rope. A No. 10 steel wire rope 10 is inserted into the perforated pipe 9 for draining leachate and assembled into a horizontal well water guide pipe 11. After prestressing tension, the steel wire rope 10 is fixed to the lifting ring of the connecting pin of the transfer device 8. As the drill rod 5 is retracted, the steel wire rope 10 is pulled, which drives the perforated pipe 9 to be pulled back, so that the horizontal well water guide pipe 11 can pass through both sides of the reservoir area, realizing the drainage of leachate and landfill gas between the layers of the garbage pile.

[0046] (7) The horizontal well water guide pipe 11, composed of perforated pipes, is pulled back. Both ends of the water guide pipe 11 are inserted into HDPE solid-wall pipes with a diameter of De110 to guide the leachate. After connecting the drainage pipeline, it can drain the leachate on its own. When constructing a leachate drainage blind ditch at the foot of the landfill closure and shaping silo, the HDPE solid-wall pipe with a diameter of De110 can be removed, and the horizontal well water guide pipe 11 is connected to the leachate drainage blind ditch. Finally, the leachate is pumped to the regulating tank through the blind ditch.

[0047] In a specific embodiment of the present invention, the perforated pipe used is an HDPE grooved perforated pipe 9, which is made of HDPE material, and its specific structure is as follows. Figure 4 As shown, the HDPE grooved pipe 9 has a diameter of De75 and a nominal pressure of 1.6MPa. Grooves are cut along the outer wall of the pipe to form a water guide groove 91. The water guide groove 91 is spaced apart on the outer wall of the ring. Small holes 92 are evenly distributed at the bottom of the water guide groove 91, which can guide the leachate to the holes 92 in an organized manner.

[0048] In a specific embodiment of the present invention, given the significant vertical pressure and frictional resistance exerted by the waste pile 1 on the HDPE slotted pipe 9, the opening 92 of the slotted pipe weakens the strength of the original HDPE pipe. If the slotted pipe is pulled back, according to field tests, it will deform and break at the opening position after approximately 50m of pullback. A 10# steel wire rope 10 is inserted into the HDPE slotted pipe 9 structure. After prestressing, the steel wire rope will bear almost all the tensile and frictional forces during the pullback. If the reservoir span is large, a De90 diameter drainage slotted pipe 9 can be selected; when the waste pile 1 is high, due to the greater vertical pressure and frictional resistance experienced by the HDPE slotted pipe 9, a 12# or higher grade steel wire rope 10 can be selected.

[0049] In a specific embodiment of the present invention, the horizontal well water guide pipe 11 is installed as follows: Figure 5 As shown, to facilitate the tensioning of the steel wire rope 10, the HDPE slotted pipe 9 is divided into 30-45m sections. Each section is anchored to the outer pipe through an inner pipe support and an outer pipe anchoring structure 12 to form a whole. The ends and tails of the slotted pipe are also assisted by the inner pipe support and outer pipe anchoring structure 12 for pullback. The steel wire rope 10 is pre-inserted into the pipe, and about 1.5-2m of steel wire rope 10 is reserved at the pullback end 13 and pullback tail 14 of the slotted pipe 9. To facilitate the insertion of the steel wire rope 10 into the pipe and related accessories, 40-50cm long φ8-φ10 steel bars are welded to both ends of the steel wire rope 10 to assist in threading.

[0050] In a specific embodiment of the present invention, the inner pipe support and outer pipe anchoring structure 12 of the HDPE slotted perforated pipe 9 pullback end 13 in the horizontal well water guide pipe 11 is as follows: Figure 6As shown, at the pull-back end 13 of the HDPE slotted pipe 9 with a diameter of De75, an internal support sleeve 121 with a length of 400-500mm, a diameter of φ60, and a wall thickness of 3-4mm is used. Alternatively, a φ60 piece of wood can be used as the internal support. Externally, a galvanized steel sleeve 122 with a length of 400-500mm, a diameter of φ89, and a wall thickness of 4-6mm is used to wrap around the slotted pipe 9. A 20-25mm thick outer sleeve end-sealing steel plate 123 is welded to the end of the outer sleeve 122, with a φ12 hole in the middle for easy insertion of a steel wire rope 10. The outer sleeve 122, the slotted pipe 9, and the inner support sleeve 121 are fixed with bolts 124. The prestressing anchor 16 is installed on the outer sleeve end-sealing steel plate 123. The rough-surface film scraps used for on-site sealing can be used to wrap the grooved perforated pipe 9, and then the outer galvanized steel sleeve 122 can be installed to adjust and reduce the gap between the two pipes, making the bolt 124 anchor more securely. For example, Figure 6 As shown, one side anchor 16 is used to grip the wire rope 10 during pullback to make it bear force, and the other side anchor 16 is used to tighten the wire rope 10 when installing and connecting the HDPE slotted pipe 9, so as to ensure that the wire rope 10 and the horizontal well water guide pipe 11 advance synchronously.

[0051] The connection structure of the intermediate pipe section 9 of the HDPE grooved perforated pipe in the horizontal well water guide pipe 11 is as follows: Figure 7 As shown, at both ends of the intermediate pipe section of the HDPE slotted perforated pipe 9 with a diameter of De75, internal support sleeves 121 with a length of 400-500mm, a diameter of φ60, and a wall thickness of 3-4mm are used for support. Externally, galvanized steel sleeves 122 with a length of 980-1180mm, a diameter of φ89, and a wall thickness of 4-6mm are used to wrap around the slotted perforated pipe 9. The galvanized steel sleeves 122, the slotted perforated pipe 9, and the internal support sleeves 121 are fixed together with bolts 124. A 20-25mm thick intermediate tensioning steel plate 17 is welded to the middle connection position inside the galvanized steel sleeve 122, with a hole in the middle to facilitate the insertion of the wire rope 10 for tensioning. The galvanized steel sleeve 122 has an opening 18, and anchors 16 for prestressing are installed at both ends of the steel plate. Wherein, as... Figure 7 As shown, one side anchor 16 is used to grip the wire rope 10 to make it bear force when pulling back, and the other side anchor 16 is used to tighten the wire rope when installing and connecting the HDPE slotted pipe 9, so as to ensure that the wire rope 10 and the horizontal well water guide pipe 11 advance synchronously.

[0052] The HDPE grooved perforated pipe 9 in the horizontal well water guide pipe 11 has an inner pipe support and an outer pipe anchoring structure 12, as shown in the figure. Figure 8As shown, the HDPE grooved pipe 9 with a diameter of De75 has a tail pull-back connection 14. Internally, it uses a 200mm long, φ60mm thick, 3mm wall thickness inner support sleeve 121. Externally, it uses a 200mm long, φ89mm thick, 5mm wall thickness outer galvanized steel sleeve 122 to wrap around the grooved pipe 9. A 20mm thick outer sleeve sealing steel plate 123 is welded to the tail of the outer galvanized steel sleeve 122, with a φ12 hole in the middle for easy insertion of a steel wire rope 10. The outer galvanized steel sleeve 122, the grooved pipe 9, and the inner support sleeve 121 are fixed together by bolts 124. For example, Figure 8 As shown, the anchor 16 is used to grip the wire rope 10 during pullback to apply force.

[0053] In a specific embodiment of the present invention, the #10 steel wire rope 10 is prestressed and tensioned using a corresponding model of #10 anchor 16 for installation and pullback. After prestressing, the steel wire rope 10 in the horizontal well guide pipe 11 is connected to the welded reinforcing steel bar 15 (e.g., at the end of the horizontal well guide pipe 11) at the connection point of the steel wire rope 10 and the end of the horizontal well guide pipe 11. Figure 5 , 6 As shown, the wire rope 10 is installed at the U-shaped lifting ring of the connecting pin of the transfer device 8 and is fixed by a buckle. As the drill rod 5 is retracted, the prestressed tension wire rope 10 is pulled, which drives the horizontal well water guide pipe 11 to be pulled back, so that the horizontal well water guide pipe 11 can pass through both sides of the reservoir area, realizing the drainage of leachate and landfill gas between the first layer of the garbage pile.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications or equivalent substitutions made within the scope of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of constructing a landfill horizontal well structure, characterized by, Includes the following steps: (1) Measure and lay out the design drawings to determine the coordinates of the entry and exit points of the horizontal well; (2) Based on the size of the borehole span in the reservoir area, the height of the garbage pile and the diameter of the perforated pipe for draining leachate, the perforated pipe used is a slotted perforated pipe, and a horizontal directional drilling rig with appropriate tonnage is selected. (3) Select the appropriate drill bit according to the drilling target and geological conditions; (4) Adjust the horizontal directional drilling rig according to the design angle, drill horizontally, and the borehole channel crosses the reservoir area; (5) After drilling is completed, remove the drill bit, replace it with a reamer for back-pulling, and install the connecting transfer case; (6) Prestressed tendons are inserted into the slotted pipe used for leachate drainage and assembled into a horizontal well water guide pipe. After prestressing tension, the prestressed tendons are fixed to the lifting ring of the transfer pin. As the drill rod is retracted, the prestressed tendons are pulled, which drives the slotted pipe back, so that the horizontal well water guide pipe can pass through both sides of the reservoir area to realize the drainage of leachate and landfill gas between the layers of the landfill. In order to facilitate the tensioning of the prestressed tendons, the structure of the slotted pipe is as follows: the slotted pipe is 30-45m in section, and each section is connected into a whole by an inner pipe support and an outer pipe anchoring structure. The two ends of the slotted pipe are provided with an inner pipe support and an outer pipe anchoring structure. After the prestressed tendons are inserted into the slotted pipe, 1.5-2m long prestressed tendons are reserved at both ends. (7) After the horizontal well water pipe is pulled back, insert both ends of the horizontal well water pipe into the solid wall pipe to drain the leachate. When the leachate drainage blind ditch is built at the foot of the sealed pile body shaping silo, connect the horizontal well water pipe to the leachate drainage blind ditch, and finally pump the leachate to the leachate conditioning tank through the blind ditch.

2. The method of constructing a landfill horizontal well structure according to claim 1, wherein, The grooved tube is characterized by the following: a water guide groove is longitudinally opened along the outer wall of the grooved tube, the water guide groove is opened at intervals on the outer wall of the tube, and small holes are evenly distributed at the bottom of the water guide groove.

3. A method of constructing a landfill horizontal well structure according to claim 2, wherein, The slotted pipe is made of HDPE.

4. A construction method for a landfill horizontal well structure as described in any one of claims 1-3, characterized in that, In step (1), the design drawings are used to measure and lay out the layout, mark the coordinates of the entry and exit points of the horizontal well, and mark the direction of the borehole at intervals of 2m-3m along the slope of the pile and the top membrane.

5. A method of constructing a landfill horizontal well structure as claimed in any one of claims 1 to 3, wherein, In step (2), the diameter of the flower tube used during the pullback is De75 or De90, and the nominal pressure is 1.25-1.6MPa.

6. The method of constructing a landfill horizontal well structure according to any one of claims 1 to 3, wherein, In step (3), the selected drill bit is a slanted palm-face guide drill bit.

7. The method of constructing a landfill horizontal well structure according to any one of claims 1-3, wherein, In step (4), the horizontal directional drilling rig is placed on a steel plate, the bottom of the drilling head is supported by concrete blocks, the horizontal directional drilling rig is adjusted according to the designed drilling angle, it is fixed in the road surface by anchor rods, the prestressed tendons are connected to the drilling rig, the drilling rig drills horizontally, and forms a horizontal well in the garbage pile, and the drilling channel runs across the storage area.

8. A construction method for a landfill horizontal well structure as described in any one of claims 1-3, characterized in that, In step (5), the hole expander used is a steel hole expander with a diameter of 250-350mm and a wall thickness of 4-6mm; a steel plate with a width of 2-3cm and a thickness of 4-6mm is welded around the steel hole expander near the end of the guide drill rod.

9. The method of constructing a landfill horizontal well structure according to any one of claims 1 to 3, wherein, In step (6), the prestressed tendons inserted into the perforated pipe structure for draining leachate are steel wire ropes, and the type of steel wire rope is selected according to the diameter of the perforated pipe.

10. The method of constructing a landfill horizontal well structure according to claim 3, wherein, In step (6), the inner pipe support and outer pipe anchoring structure of the pull-back end of the slotted flower pipe is as follows: the inner support is made of steel pipe or wooden segment, and the outer support is made of galvanized steel pipe wrapped around the slotted flower pipe. The end of the galvanized steel pipe is welded with a 20-25mm thick steel plate with a hole in the middle. The outer galvanized steel pipe, the slotted flower pipe and the inner support steel pipe or wooden segment are fixed with bolts.

11. The method of constructing a landfill horizontal well structure of claim 3, wherein, In step (6), the diameter of the slotted pipe is De75. The inner pipe supports the outer pipe anchoring structure between the slotted pipes as follows: the two ends of the slotted pipe are supported by steel pipes, and the outer side is wrapped with galvanized steel pipes. The outer galvanized steel pipe, the slotted pipe and the inner support steel pipe are fixed by bolts. A 20-25mm thick steel plate is welded to the middle position inside the galvanized steel pipe, with a hole in the middle. Anchors for prestressing tensioning are installed at both ends of the steel plate.

12. The method of constructing a landfill horizontal well structure according to claim 3, wherein, In step (6), the diameter of the slotted pipe is De75. The inner pipe support and outer pipe anchoring structure of the slotted pipe tail is as follows: the slotted pipe is supported by a steel pipe inside and wrapped with a galvanized steel pipe outside; a 20-25mm thick steel plate is welded to the tail of the galvanized steel pipe, with a hole in the middle, and the outer galvanized steel pipe, the slotted pipe and the inner support steel pipe are fixed by bolts.

13. The method of constructing a landfill horizontal well structure according to claim 3, wherein, In step (6), the prestressed tendons are prestressed and pulled back using anchors of the corresponding model.

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