A construction method for a landfill gas collection system to prevent landfill settlement

Abstract

This invention provides a construction method for a landfill gas collection system to prevent landfill settlement, comprising: Step S1, surveying the landfill and arranging gas collection well locations based on the survey results; Step S2, drilling gas collection wells at the predetermined locations, and placing a discharge pipe after drilling; Step S3, directly filling the discharge pipe and gas collection well with gravel, and filling the wellhead with clay and compacting it; Step S4, placing an enlarged hole template at the wellhead and laying connecting pipes for each gas collection well in parallel, connecting the discharge pipe to the corresponding connecting pipe; Step S5, filling the enlarged hole template with bentonite and compacting it, then sealing and covering the landfill, and removing the enlarged hole template when the sealing and covering reaches the upper edge of the enlarged hole template; Step S6, continuing the sealing and covering until the covering surface reaches the preset elevation. The gravel filling in the vertical shaft absorbs some of the landfill settlement deformation stress through energy dissipation, while uniformly transmitting stress and preventing settlement stress from damaging the discharge pipe.

Description

Technical Field

[0001] This invention belongs to the field of landfill technology, specifically relating to a construction method for a landfill gas collection system for preventing landfill settlement. Background Technology

[0002] With the continuous increase in urban population and domestic waste, many landfills have reached their designed capacity. According to national standards and regulations, these landfills must be closed. Due to the height of the landfill, much leachate cannot completely infiltrate to the bottom drainage layer. In addition, many existing aeration gabions are not vertically connected. For landfills with a height exceeding 10 meters, this not only worsens the vertical drainage of landfill gas but also hinders the vertical drainage of leachate.

[0003] Existing drainage methods typically involve constructing a complex network of wells with multiple functions, including injection wells, extraction wells, leachate backflow wells, and leachate reinjection wells. However, landfills are prone to settlement, which can deform and damage the gas collection wells and exhaust pipes, making it impossible to maintain normal drainage functions.

[0004] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art. This invention designs a construction method for a landfill gas collection system to prevent landfill settlement.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A construction method for a landfill gas collection system for preventing landfill settlement includes:

[0008] Step S1: Conduct a survey of the landfill and determine the locations of gas collection wells based on the survey results;

[0009] Step S2: Install the gas gathering well at the predetermined location and put in the discharge pipe after drilling is completed;

[0010] Step S3: Gravel is directly buried in the drain pipe and gas collection well, and clay is filled and compacted at the wellhead of the gas collection well.

[0011] Step S4: Place an enlarged hole template at the orifice of the gas gathering well, and lay connecting pipes for each gas gathering well in parallel, and connect the exhaust pipe to the corresponding connecting pipe.

[0012] Step S5: After filling the enlarged hole template with bentonite and compacting it, the landfill is sealed and covered. When the landfill is covered to the upper edge of the enlarged hole template, the enlarged hole template is lifted out.

[0013] Step S6: Continue covering the field until the coverage area reaches the preset elevation.

[0014] Preferably, the stabilizing pipe is an n-shaped pipe. The section of the stabilizing pipe away from the drain pipe is connected to the connecting pipe through a horizontal extension section. A pipe clamp is installed in the horizontal extension section, and grouting is performed below the clamp. After the grout solidifies, the pipe clamp is fixed to the grouting area with expansion bolts.

[0015] Preferably, the connecting tube is a flexible honeycomb tube, and the connecting tube has interconnected air guide holes distributed regularly and / or irregularly.

[0016] A branch pipe is provided at the position of the horizontal extension section corresponding to the connecting pipe, and the branch pipe extends into the horizontal extension section for a certain distance.

[0017] Preferably, the stabilizing pipe has two sections. First, one section of the stabilizing pipe is connected to the drain pipe through a flange. Then, the other short section is anchored in the grouting area. Finally, the two sections of the stabilizing pipe are joined together through a corrugated silicone tube.

[0018] Preferably, during the drilling of the gas gathering well, the construction of the gas guiding kiln well is carried out simultaneously. The landfill is divided into multiple areas, and a gas guiding kiln well is set up in each area. The connecting pipes in the corresponding area extend into the gas guiding kiln well.

[0019] Preferably, the well casing is installed after the gas-carrying kiln well is drilled, and an interface for connecting the connecting pipe is reserved in the middle and lower part of the well casing.

[0020] The upper part of the well casing is equipped with an exhaust pipe, which is connected to a waste gas treatment device.

[0021] Preferably, a blower is installed inside the well casing between the connecting pipe and the air outlet pipe.

[0022] Preferably, after the field is covered, turf is laid on top of the covered area and drainage ditches are constructed.

[0023] Preferably, the location of the connecting pipe corresponding to the landfill cover layer is set as gravel, slag, or construction waste.

[0024] Beneficial effects: The shaft is filled with gravel, which can absorb some of the stress caused by the settlement deformation of the pile body through energy dissipation, and at the same time uniformly transmit the stress, avoiding damage to the drainage pipe by the settlement stress.

[0025] An enlarged hole filled with bentonite is provided. The enlarged hole is used for the installation of the gas gathering well connection pipe and the stabilizing pipe. If the installation of the gas gathering well connection pipe and the stabilizing pipe is damaged, the enlarged hole can be dug open for repair and replacement. Attached Figure Description

[0026] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein:

[0027] Figure 1 This is a simplified diagram of the gas gathering well structure in a specific embodiment provided by the present invention;

[0028] Figure 2 This is a schematic diagram of the connection between the sleeve and the drain tube in a specific embodiment of the present invention;

[0029] Figure 3 for Figure 2 Enlarged view of point A in the middle;

[0030] Figure 4 This is a schematic diagram of the gas collection system structure in a specific embodiment of the present invention.

[0031] In the diagram: 1. Enlarged hole; 2. Stabilizing pipe; 3. Collection well connecting pipe; 4. Corrugated silicone tube; 5. Control valve; 6. Stabilizing support; 7. Drainage pipe; 8. Casing; 9. Strip hole; 10. Pin; 11. Nut; 12. Support column; 13. Strip groove; 14. Hinge shaft; 15. Rotating component; 16. Gas delivery well; 17. Connecting pipe; 18. Gas outlet pipe. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0033] In the description of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. The terms "connected" and "linked" used in this invention should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; they can refer to a direct connection or an indirect connection through intermediate components. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0034] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0035] To address the challenges of landfill gas collection, this application provides a construction method for a landfill gas collection system to prevent landfill settlement. The method includes: Step S1, surveying the landfill to determine its depth, internal composition, and decomposition status. The generation of landfill gas is a complex biological, chemical, and physical process, with biodegradation being the most crucial. Depending on the source and composition of the landfill waste, landfill gas contains 30%–55% methane by volume, 30%–45% carbon dioxide by volume, and small amounts of air, odorous gases, and other trace gases. Based on the survey results, collection well locations are determined. Surveying can be conducted using borehole drilling.

[0036] The depth of the gas collection wells after detection is a certain proportion of the landfill depth, for example, one-third of the landfill depth; the density of the gas collection wells is determined based on the actual source and composition of the landfill waste.

[0037] Step S2: Drill the gas collection well at the predetermined location. The drilling method is to drill a hole. After drilling, insert the exhaust pipe 7. The length of the exhaust pipe 7 is adapted to the depth of the gas collection well, and the upper end of the exhaust pipe 7 extends out of the wellhead of the gas collection well. Step S3: Fill the space between the exhaust pipe 7 and the gas collection well with gravel. Filling the space between the exhaust pipe 7 and the gas collection well with gravel provides sufficient support without affecting the gas exhaust. At the same time, the gravel can deform when the landfill settles, thus buffering the exhaust pipe 7. The crushed stone can absorb some of the stress of the landfill settlement deformation and uniformly transfer stress. Fill the wellhead of the gas collection well with clay and compact it. Seal the wellhead of the gas collection well with compacted clay to prevent polluting gas from directly overflowing from the wellhead.

[0038] Step S4: Place the enlarged hole 1 template at the orifice of the gas gathering well, and lay the connecting pipes of each gas gathering well in parallel. Connect the drain pipe 7 to the corresponding connecting pipe. The lower edge of the enlarged hole 1 template can be provided with a notch or perforation for the corresponding connecting pipe.

[0039] Step S5: After filling the enlarged hole 1 template with bentonite and compacting it, the landfill is sealed and covered. The construction of this system is carried out together with the landfill remediation, which can optimize the construction steps and improve the efficiency of pipeline pre-laying. When the sealing and covering reaches the upper edge of the enlarged hole 1 template, the enlarged hole 1 template is lifted out. The enlarged hole 1 template can be reused. When maintenance is required, the enlarged hole 1 can be dug up to carry out the maintenance of the stabilizing pipe 2.

[0040] Step S6: Continue covering the field until the coverage area reaches the preset elevation.

[0041] In this embodiment, in order to overcome the problem of poor air permeability caused by the forming of a smooth surface on the inner wall of the gas gathering well after drilling, the inner wall is roughened after drilling.

[0042] The roughening is achieved by using a roughening tool, for example, a cylindrical tool with a closed bottom, whose outer wall is adapted to the inner wall of the gas collection well. Multiple evenly distributed cones are provided on the outer wall of the roughening tool. The roughening tool is filled with water or sand and gravel, and then hoisted by a crane and moved back and forth in the gas collection well to roughen the inner wall and restore air permeability.

[0043] In another optional embodiment, each gas collection well is provided with a discharge pipe 7 and a stabilizing pipe 2. One end of the stabilizing pipe 2 is detachably connected to the end of the discharge pipe 7 that extends out of the cover surface, and the other end extends into the cover surface through a bend and is correspondingly connected to the pre-buried gas collection well connecting pipe. The gas collection well connecting pipe discharges the gas to the purification station, thereby purifying the landfill gas and avoiding pollution caused by the discharge of harmful gases such as methane into the atmosphere.

[0044] The wellhead of the gas gathering well is lower than the cover surface. An enlarged hole 1 is opened above the wellhead of the gas gathering well. The enlarged hole 1 is used for the installation of the gas gathering well connecting pipe and the stabilizing pipe 2. After the installation is completed, bentonite is filled and compacted in the enlarged hole 1 to further fix the stabilizing pipe 2.

[0045] A stabilizing bracket 6 is provided at the enlarged hole 1 corresponding to the drain pipe 7. The stabilizing bracket 6 is a truss extending along the plane, and the drain pipe 7 is sleeved in the middle by a tubular structure.

[0046] In this embodiment, the gas collecting well connecting pipe is disposed on the plane where the bottom surface of the enlarged hole 1 is located. The gas collecting well connecting pipe extends along the plane where the bottom surface of the enlarged hole 1 is located and is led out accordingly, thereby guiding the exhaust gas to the purification device.

[0047] In this embodiment, the exhaust pipe 7 is located in the gas gathering well section and is evenly distributed with support frames along the longitudinal direction. The support frames are square trusses arranged in the horizontal direction and are used to support and position the exhaust pipe 7.

[0048] The square truss includes a square frame, with a support column 12 set at each corner of the square frame. The support column 12 is fixed to the sleeve 8 to form a fixed support, so that it will not affect the downward placement of gravel during construction.

[0049] In this embodiment, a sleeve 8 adapted to the outer wall of the drain pipe 7 is fixed in the middle of the support frame. The drain pipe 7 has a multi-segment structure, and two connected drain pipe segments 7 are slidably assembled at both ends of the sleeve 8, so that the two connected drain pipe segments 7 can slide inside the sleeve 8. Furthermore, there is a gap between the two drain pipe segments 7 inside the sleeve 8, so that when the landfill settles, the drain pipe 7 can slide to make way, thereby offsetting the settlement deformation and ensuring that the drain pipe 7 is not affected by the settlement.

[0050] In this embodiment, the sleeve 8 is provided with at least one limiting component corresponding to one end of the drain tube 7. Specifically, a limiting component corresponding to the drain tube 7 can be provided at the upper end of the sleeve 8. Of course, in order to ensure stability, limiting components can be provided at both ends of the sleeve 8.

[0051] The limiting component includes multiple pins 10, which are evenly distributed around the circumference of the sleeve 8. The number of pins 10 should not be less than three, and can be three, four, five, six, etc. The pins 10 pass through the sleeve 8 from the outside to the inside and extend into the drain pipe 7. The drain pipe 7 has a strip hole 9 on its side wall. The width of the strip hole 9 is adapted to the pins 10 and extends along its axial direction. The strip hole 9 can make way for the drain pipe 7 and the sleeve 8 when there is axial relative displacement.

[0052] In this embodiment, a strip groove 13 is provided at one end of the pin 10 that extends into the drain pipe 7. The strip groove 13 extends axially from the end of the pin 10 and is located at the center line of its cross section. A rotating member 15 is provided in the strip groove 13. The middle part of the rotating member 15 is hinged in the strip groove 13 by a hinge shaft 14. The hinge shaft 14 is hinged at the position of the pin 10 corresponding to the opening end of the strip groove 13. The rotating member 15 is strip-shaped, with a length greater than the width of the strip hole 9 and a thickness that matches the width of the strip groove 13. The hinge shaft 14 is located at the midpoint of the rotating member 15 near one end of the sleeve 8. After the pin 10 is inserted, the rotating member 15 rotates under gravity, thus becoming perpendicular to the pin 10. At this time, the pin 10 is rotated. Since the length of the rotating member 15 is greater than the width of the strip hole 9, the entire pin 10 is rotated to block the strip hole 9 through the rotating member 15, thereby limiting the sleeve 8 and the drain pipe 7 and assembling them into a whole.

[0053] In this embodiment, the other end of the pin 10 is connected to a nut 11. One end of the pin 10 corresponding to the nut 11 is a threaded end. Rotating the nut 11 provides a certain support force to the inner wall of the drain pipe 7, thereby preventing the pin 10 from rotating and falling off during installation.

[0054] The axial force applied by rotating the nut 11 should not exceed 10N, so as to ensure that the friction between the two will not affect the relative movement of the sleeve 8 and the drain pipe 7.

[0055] In another optional embodiment, the stabilizing pipe 2 is an n-shaped pipe, comprising two sections. The two sections of the stabilizing pipe 2 are connected by a corrugated silicone pipe 4. A control valve 5 is provided at the end of the stabilizing pipe 2 near the drain pipe 7. When the pile settles unevenly, it can ensure that the connecting pipe 3 of the collection well and the drain pipe 7 maintain a reliable connection and maintain the normal and stable function of the structure. First, the section of the stabilizing pipe 2 away from the drain pipe 7 is connected to the connecting pipe through a horizontal extension section. A pipe clamp is set in the horizontal extension section, and grouting is performed below the ring clamp. After the grout solidifies, the pipe clamp is fixed to the grouting area with expansion bolts.

[0056] In this embodiment, the stabilizing pipe 2 is fixed to the drain pipe 7 by a flange, thereby achieving a detachable connection.

[0057] In another optional embodiment, the connecting pipe is a flexible honeycomb pipe, which can offset stress through flexible deformation after landfill settlement occurs, thus ensuring the product's service life. The connecting pipe has regularly and / or irregularly distributed interconnected air vents to meet end-of-life requirements.

[0058] A branch pipe is provided at the position of the horizontal extension section corresponding to the connecting pipe 2, and the branch pipe extends into the horizontal extension section for a certain distance.

[0059] In another alternative embodiment, one section of the stabilizing pipe 2 is first connected to the drain pipe 7 via a flange, and then the other short section is anchored in the grouting area. The two sections of the stabilizing pipe 2 are then joined together via a corrugated silicone tube 4. The grouting area enhances the stability of the stabilizing pipe 2.

[0060] In another optional embodiment, during the drilling of the gas collection well, the construction of the gas guide well 1716 is carried out simultaneously, dividing the landfill into multiple areas, with one gas guide well 1716 set up in each area, and the connecting pipe in the corresponding area extending into the gas guide well 1716. The gas guide well 1716 is used to collect the landfill gas in the area, and then uniformly purify it.

[0061] In another optional embodiment, after the gas-carrying kiln well 1716 is drilled, a well pipe is installed. The well pipe can be a steel pipe or a prefabricated pipe, preferably a prefabricated pipe. An interface for connecting the pipe is reserved in the middle and lower part of the well pipe. An exhaust pipe 18 is provided in the upper part of the well pipe, and the exhaust pipe 18 is connected to the waste gas treatment device, so that docking can be easily achieved.

[0062] The well casing is equipped with a blower located between the connecting pipe and the vent pipe 18. The blower can create negative pressure, which helps to conduct the internal landfill gas.

[0063] In another alternative embodiment, after the field closure is completed, turf is laid on top of the closure surface and drainage ditches are constructed.

[0064] The landfill cover layer is made of gravel, slag, or construction waste at the location of the connecting pipe, and the thickness can be 20-30cm.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention shall be within the scope of protection of the pending claims of the present invention.

Claims

1. A construction method for a landfill gas collection system for preventing landfill settlement, characterized in that, include: Step S1: Conduct a survey of the landfill and determine the locations of gas collection wells based on the survey results; Step S2: Install the gas gathering well at the predetermined location and put in the discharge pipe after drilling is completed; Step S3: Gravel is directly buried in the drain pipe and gas collection well, and clay is filled and compacted at the wellhead of the gas collection well. Step S4: Place an enlarged hole template at the orifice of the gas gathering well, and lay connecting pipes for each gas gathering well in parallel, and connect the exhaust pipe to the corresponding connecting pipe. Step S5: After filling the enlarged hole template with bentonite and compacting it, the landfill is sealed and covered. When the landfill is covered to the upper edge of the enlarged hole template, the enlarged hole template is lifted out. Step S6: Continue to cover the site until the coverage reaches the preset elevation; the stabilizing pipe is an n-shaped pipe. The section of the stabilizing pipe away from the drain pipe is connected to the connecting pipe through a horizontal extension section. Pipe clamps are installed in the horizontal extension section. Grouting is performed below the ring clamps. After the grout solidifies, the pipe clamps are fixed to the grouting area with expansion bolts. The stabilizing pipe has two sections. First, one section of the stabilizing pipe is connected to the drain pipe through a flange. Then, the other short section is anchored in the grouting area. Finally, the two sections of the stabilizing pipe are joined together through a corrugated silicone tube. The exhaust pipe is located in the gas gathering well section and is evenly supported by support frames along the longitudinal direction. The support frames are square trusses arranged in the horizontal direction and are used to support and position the exhaust pipe. The square truss includes a square frame, with a support column at each corner of the square frame. The support columns are fixed to the sleeve to form a fixed support. The support frame has a sleeve that fits the outer wall of the drain pipe. The drain pipe has a multi-segment structure. Two connected drain pipe segments are slidably assembled at both ends of the sleeve, so that the two connected drain pipe segments can slide inside the sleeve. There is a gap between the two drain pipe segments inside the sleeve. The sleeve is provided with at least one limiting component corresponding to one end of the drain tube. A limiting component corresponding to the drain tube is provided at the upper end of the sleeve. The limiting component includes multiple pins. The pins are evenly distributed around the circumference of the sleeve. The pins pass through the sleeve from the outside to the inside and extend into the drain tube. The drain tube has a strip-shaped hole on its side wall. The width of the strip-shaped hole is adapted to the pin and extends along its axial direction. The strip-shaped hole makes way when there is a relative axial displacement between the drain tube and the sleeve. The end of the pin that extends into the drain pipe is provided with a strip groove. The strip groove extends axially from the end of the pin and is located at the center line of its cross section. A rotating part is provided in the strip groove. The middle part of the rotating part is hinged in the strip groove by a hinge shaft. The hinge shaft is hinged at the position of the pin corresponding to the opening end of the strip groove. The rotating part is strip-shaped, with a length greater than the width of the strip hole and a thickness that matches the width of the strip groove. The hinge is located at the midpoint of the rotating part near one end of the sleeve. After the pin is inserted, the rotating part rotates under gravity, thus becoming perpendicular to the pin. At this time, the pin is rotated. Since the length of the rotating part is greater than the width of the strip hole, the entire pin is rotated and then the rotating part stops the strip hole, thereby limiting the sleeve and the drain pipe and assembling the two into a whole. The other end of the pin is connected to a nut. The end of the pin corresponding to the nut is a threaded end. Rotating the nut provides support to the inner wall of the drain pipe. The axial force applied by rotating the nut is no more than 10N, so as to ensure that the friction between the two will not affect the relative movement of the sleeve and the drain pipe.

2. The construction method of the landfill gas collection system for preventing landfill settlement according to claim 1, characterized in that, The connecting tube is a flexible honeycomb tube, and there are interconnected air guide holes distributed regularly or irregularly inside the connecting tube; A branch pipe is provided at the position of the horizontal extension section corresponding to the connecting pipe, and the branch pipe extends into the horizontal extension section for a certain distance.

3. The construction method of the landfill gas collection system for preventing landfill settlement according to claim 1, characterized in that, During the drilling of the gas gathering well, the construction of the gas guiding kiln well is carried out simultaneously. The landfill is divided into multiple areas, and a gas guiding kiln well is set up in each area. The connecting pipes in the corresponding area extend into the gas guiding kiln well.

4. The construction method of the landfill gas collection system for preventing landfill settlement according to claim 3, characterized in that, After the gas-carrying kiln well is drilled, the well pipe is installed, and an interface for connecting the pipe is reserved in the middle and lower part of the well pipe. The upper part of the well casing is equipped with an exhaust pipe, which is connected to a waste gas treatment device.

5. The construction method of the landfill gas collection system for preventing landfill settlement according to claim 4, characterized in that, The well casing is equipped with a blower located between the connecting pipe and the air outlet pipe.

6. The construction method of the landfill gas collection system for preventing landfill settlement according to claim 1, characterized in that, After the field is covered, turf is laid on top of the covered area and drainage ditches are constructed.

7. The construction method of the landfill gas collection system for preventing landfill settlement according to claim 1, characterized in that, The location of the connecting pipe corresponding to the landfill cover layer is set as gravel, slag, or construction waste.

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