Polluted soil landfill area anti-seepage cast-in-place pile and construction method thereof

Abstract

This invention provides a seepage-proof cast-in-place pile for contaminated soil landfill areas and its construction method. The construction method includes the following steps: locating the borehole position for the seepage-proof pile; cutting open the geomembrane on the top surface of the contaminated soil to form a drilling position; drilling at the drilling position until a distance A cm from the bottom geomembrane of the contaminated soil is reached, then manually excavating to the surface of the geomembrane, and then inserting a geomembrane pipe downwards; sealing the bottom of the geomembrane pipe to the geomembrane at the bottom of the contaminated soil; testing the sealing performance of the connection; cutting open the geomembrane below the internal cavity of the geomembrane pipe, continuing to drill downwards, and pouring concrete inside the geomembrane pipe to form a cast-in-place pile after reaching the design elevation; after the cast-in-place pile is completed, sealing the top of the geomembrane pipe to the geomembrane at the top of the contaminated soil. By sealing the geomembrane pipe with the upper and lower geomembranes, the contaminated soil is re-encapsulated, reducing costs while improving the protective effect.

Description

Technical Field

[0001] This invention relates to the field of pile foundation structure technology, specifically to a seepage-proof cast-in-place pile for contaminated soil landfill areas and its construction method. Background Technology

[0002] When constructing docks, bridges, and municipal projects, it may be necessary to pass through contaminated landfill areas. These landfill areas are typically large, and projects cannot completely traverse them. Therefore, pile foundations are required within the landfill area to provide stable support. However, existing contaminated soil often contains toxic and harmful substances such as heavy metals (e.g., lead, cadmium, mercury) and organic pollutants (e.g., benzene, toluene, polycyclic aromatic hydrocarbons). These substances have strong permeability and corrosive properties. In contaminated landfill projects, geomembranes are typically used to completely enclose the contaminated soil to prevent the leakage of harmful substances and contamination of surrounding soil and groundwater. When the pile foundation location in docks, bridges, and municipal projects cannot avoid the contaminated landfill area, construction will disturb the contaminated soil, damaging the original geomembrane seal. If effective seepage prevention measures are not taken, the liquid phase of pollutants may migrate with groundwater into the surrounding soil or groundwater environment, potentially causing serious environmental pollution incidents. Current engineering practices often employ diaphragm walls to completely enclose the landfill area before proceeding with pile foundation construction. This approach not only suffers from limitations such as high treatment costs and long construction periods, but also, while diaphragm walls can prevent the spread of pollutants from the contaminated soil along its perimeter, they cannot prevent the spread of pollutants from the contaminated soil to the bottom. If conventional cast-in-place piles are directly constructed within the contaminated soil area, it can easily lead to damage to the geomembrane, resulting in the leakage of pollutants from the contaminated soil enclosed within the geomembrane and causing environmental pollution.

[0003] In summary, there is an urgent need for a construction method for anti-seepage cast-in-place piles in contaminated soil landfill areas to solve or at least partially solve the problems existing in the current technology. Summary of the Invention

[0004] The purpose of this invention is to provide a method for constructing anti-seepage cast-in-place piles in contaminated soil landfill areas, aiming to solve the problem that existing construction methods are prone to pollutant leakage. The specific technical solution is as follows: A method for constructing anti-seepage cast-in-place piles in contaminated soil landfill areas includes the following steps: S1. Locate the hole position of the anti-seepage pile, cut open the anti-seepage membrane on the top surface of the contaminated soil, and form the drilling position of the pile hole at the cut anti-seepage membrane. S2. Drill at the drilling location. When the distance from the bottom of the geomembrane to the contaminated soil is A cm, stop drilling and continue digging to the surface of the geomembrane by hand or small equipment. Then insert the geomembrane pipe downwards. S3. Seal the connection between the bottom of the impermeable pipe and the impermeable membrane at the bottom of the contaminated soil. S4. Test the sealing performance of the joint. If the seal is good and there is no leakage, proceed to S5. If the seal is not tight and there is leakage, repeat S3 and S4. S5. Cut open the geomembrane located below the cavity inside the geomembrane pipe, continue drilling downwards until the design elevation is reached, stop drilling, and then pour concrete inside the geomembrane pipe to form a cast-in-place pile. S6. After the cast-in-place pile is poured, the top of the anti-seepage pipe is sealed to the anti-seepage membrane on top of the contaminated soil.

[0005] Furthermore, S2 also includes the following steps: if the bottom geomembrane of the contaminated soil is broken during excavation by manual labor or with small equipment, the broken area is repaired with geomembrane patch blocks; if the bottom geomembrane is not damaged during excavation, proceed to S3.

[0006] Furthermore, S2 also includes the following steps: when drilling at the borehole location, a temporary steel casing is inserted into the borehole, and the temporary steel casing moves downward synchronously with the drilling, so as to temporarily support the contaminated soil around the borehole location. S6 also includes the following steps: removing the temporary steel casing and simultaneously pouring cement mortar between the seepage prevention pipe and the contaminated soil to form a filling layer.

[0007] Furthermore, in S2, the value of A is greater than or equal to 10 cm and the value of A is less than or equal to 40 cm. The required drilling depth is determined by referring to the design drawings for the contaminated soil landfill.

[0008] Furthermore, S3 includes the following steps: using a geomembrane and a geomembrane made of heat-melting material, the bottom of the geomembrane and the geomembrane are heat-fused together.

[0009] Furthermore, S3 includes the following step: using waterproof adhesive to seal the bottom of the geomembrane and the geomembrane.

[0010] Furthermore, S5 also includes the following steps: after cutting open the bottom geomembrane, a permanent steel casing is lowered, and the drill bit extends into the permanent steel casing to continue drilling. During the drilling process, the permanent steel casing moves downward synchronously with the drilling. The drill bit is then pulled out, and a reinforcing cage is lowered into the permanent steel casing. Concrete is then poured into the permanent steel casing to form a cast-in-place pile.

[0011] Furthermore, S1 to S4 adopt dry operation method, while S5 and S6 adopt mud wall protection operation method.

[0012] On the other hand, this application also provides a seepage-proof cast-in-place pile for contaminated soil landfill areas, including a pile body and a permanent steel casing. The pile body is formed by pouring and curing concrete inside the permanent steel casing. It also includes a seepage-proof pipe and two layers of seepage-proof membranes for wrapping the contaminated soil landfill area from the top and bottom. The seepage-proof pipe is arranged outside the permanent steel casing. Both the upper and lower layers of seepage-proof membranes have through holes, and the two through holes are arranged coaxially. The seepage-proof pipe passes through the two through holes from top to bottom, and the upper edge of the seepage-proof pipe is sealed to the upper seepage-proof membrane, and the lower edge of the seepage-proof pipe is sealed to the bottom seepage-proof membrane. The pile body and the permanent steel casing are arranged from top to bottom through the seepage-proof pipe.

[0013] Furthermore, both the geomembrane and the geomembrane are made of hot-melt material, and the upper and lower ends of the geomembrane are sealed to the upper and lower geomembranes by hot-melt.

[0014] The application of the technical solution of the present invention has the following beneficial effects: This construction method allows the cast-in-place piles to penetrate both layers of geomembrane vertically and be stably supported in the soil. Simultaneously, the geomembrane pipes seal the holes in the geomembranes through which the piles pass, thus completely enclosing the contaminated soil and effectively preventing leakage of pollutants. This allows for the construction of support piles within the contaminated soil area while preventing leakage. The construction process does not require enclosing the entire contaminated soil area; construction only needs to be carried out at the pile holes. This results in low construction costs, and after construction, the geomembrane pipes and the two geomembranes completely enclose the contaminated soil, effectively preventing leakage of pollutants.

[0015] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0016] 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. In the drawings: Figure 1 This is a schematic flowchart of a method for constructing anti-seepage cast-in-place piles in a contaminated soil landfill area according to Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the state before construction in a method for constructing anti-seepage cast-in-place piles in a contaminated soil landfill area according to Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the construction state when the borehole is drilled to a set distance from the bottom impermeable membrane in a construction method for anti-seepage grouting piles in a contaminated soil landfill area according to Embodiment 1 of the present invention. Figure 4 This is a schematic diagram of the construction state when manually excavating to the bottom of the impermeable membrane in a method for constructing impermeable piles in a contaminated soil landfill area according to Embodiment 1 of the present invention. Figure 5 This is a schematic diagram of the construction state after inserting the anti-seepage pipe and welding it to the bottom anti-seepage membrane in a construction method for anti-seepage grouting piles in a contaminated soil landfill area according to Embodiment 1 of the present invention. Figure 6 This is a schematic diagram of the construction state of drilling holes in the bottom impermeable membrane and continuing to drill in a method for constructing anti-seepage cast-in-place piles in a contaminated soil landfill area according to Embodiment 1 of the present invention; Figure 7 This is a schematic diagram of the construction state after welding the top impermeable membrane to the top of the impermeable pipe in a construction method for impermeable piles in a contaminated soil landfill area according to Embodiment 1 of the present invention. Figure 8 This is a schematic diagram of the state after the completion of the construction of an anti-seepage grouting pile in a contaminated soil landfill area according to Embodiment 1 of the present invention; Figure 9 This is a schematic diagram of the overall structure of a seepage-proof cast-in-place pile in a contaminated soil landfill area according to Embodiment 2 of the present invention; Figure 10 yes Figure 9 A magnified view of point A in the middle.

[0017] Among them, 1. Pile body; 2. Permanent steel casing; 3. Anti-seepage pipe; 31. Anti-seepage inner layer; 32. Intermediate support layer; 33. Anti-seepage outer layer; 4. Anti-seepage membrane; 41. Through hole. Detailed Implementation

[0018] To facilitate understanding of the present invention, a more comprehensive description is provided below, along with preferred embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0020] Example 1: See Figures 1-8 This embodiment provides a method for constructing anti-seepage cast-in-place piles in contaminated soil landfill areas, including the following steps: S1. Locate the borehole positions for the anti-seepage piles by cutting open the geomembrane covering the top of the contaminated soil. Specifically, measure the location of the anti-seepage piles according to the design drawings and mark the drilling positions to determine the drilling locations. Cut open the geomembrane to facilitate subsequent drilling operations using drilling machinery or manually.

[0021] S2. Drilling is carried out at the drilling location using drilling machinery. This is a process hole. Drilling is stopped when the distance from the bottom of the geomembrane in the contaminated soil is A centimeters. Specifically, A ranges from 10 centimeters to 40 centimeters; in this embodiment, 30 centimeters is used. Specifically, the depth of the contaminated soil filling is determined by the design drawings of the contaminated soil landfill, which in turn determines the height difference between the upper and lower geomembranes, and thus determines the depth to which the drill bit needs to drill downwards.

[0022] Then, continue digging to the surface of the geomembrane using manual labor or small equipment to prevent the drilling machinery from damaging the bottom geomembrane. Care must also be taken during the manual or small machinery digging process to prevent damage to the bottom geomembrane. After that, the geomembrane pipe is inserted into the drilled hole from top to bottom. It should be noted that if the drilling is too close to the bottom geomembrane of the contaminated soil, it is easy to damage the bottom geomembrane. If the distance is too far, the manual cleaning time will be too long, and the labor intensity and cost will be high.

[0023] S3. Seal the bottom of the seepage-proof pipe to the seepage-proof membrane at the bottom of the contaminated soil, so that the seepage-proof pipe and the bottom seepage-proof membrane are sealed to form a barrel-shaped structure. S4. Test the sealing performance of the joint. If the seal is good and there is no leakage, proceed to S5. If the seal is not tight and leakage occurs, repeat S3 and S4. Specifically, in this embodiment, the sealing performance test is conducted by filling the annular gap between the outer wall of the geotextile and the inner wall of the process hole. Water is poured into the annular gap between the bottom of the geotextile and the geomembrane inside the geotextile to determine if there is any leakage. This water-filling test method allows operators to easily observe the connection between the geotextile and the geomembrane, resulting in high accuracy and reliable results in determining whether there is leakage. Furthermore, if leakage occurs, it can be directly repaired by heat fusion inside the geotextile, which improves the efficiency of construction and testing.

[0024] Of course, in some other embodiments of this application, air inflation can also be used for sealing checks. Specifically, the top of the geotextile is sealed, and an air pipe connecting the inside of the geotextile is installed at the top of the geotextile. A pressure gauge and a control valve are installed on the air pipe, with the control valve installed on the side of the pressure gauge away from the geotextile. By inflating gas into the geotextile, the pressure gauge is kept at a certain pressure, which is greater than atmospheric pressure. Then the control valve is closed, and the pressure value of the pressure gauge is recorded. After a set time, the pressure gauge value is observed again. If the pressure gauge value does not change, it means that the geotextile and the bottom geomembrane are well sealed and there is no leakage. If the pressure gauge value decreases, there is a leakage between the geomembrane and the geotextile.

[0025] In another embodiment of this application, water is injected into the geomembrane to observe whether there is leakage at the connection between the geomembrane and the bottom geomembrane. This requires checking around the entire geomembrane. It should be noted that the diameter of the geomembrane is smaller than the diameter of the process orifice, so that after the geomembrane and the geomembrane are sealed together, there is a gap between the geomembrane and the inner wall of the process orifice. This gap facilitates observation of the connection between the bottom of the geomembrane and the geomembrane to determine if there is leakage. Specifically, the distance between the geomembrane and the inner wall of the process orifice is more than 8 cm to facilitate observation of the connection between the geomembrane and the bottom geomembrane.

[0026] S5. Cut open the geomembrane located below the cavity inside the geomembrane pipe, and continue drilling downwards inside the geomembrane pipe to form a pile foundation hole. The diameter of the pile foundation hole is smaller than the diameter of the process hole mentioned above, so that the drilling can proceed smoothly without damaging the geomembrane pipe, until the pile foundation hole is drilled to the design elevation of the cast-in-place pile, then stop drilling, and then pour concrete inside the geomembrane pipe to form a cast-in-place pile. S6. After the cast-in-place piles are poured, seal the top of the geomembrane to the top of the contaminated soil. This prevents contaminated soil from leaking through the upper geomembrane and causing pollution.

[0027] This construction method allows the cast-in-place piles to penetrate both layers of geomembrane vertically and be stably supported in the soil. Simultaneously, the geomembrane pipes seal the holes in the geomembranes through which the piles pass, thus completely enclosing the contaminated soil and effectively preventing leakage of pollutants. This allows for the construction of support piles within the contaminated soil area while preventing leakage. The construction process does not require enclosing the entire contaminated soil area; construction only needs to be carried out at the pile holes. This results in low construction costs, and after construction, the geomembrane pipes and the two geomembranes completely enclose the contaminated soil, effectively preventing leakage of pollutants.

[0028] It should be noted that the leakage mentioned here refers to the prevention of the leakage of pollutants in the contaminated soil area after construction. The contaminated soil extracted during the drilling process needs to be treated in a unified manner to render it harmless. This means that the contaminated soil extracted during the drilling process is transported to another location and treated by wrapping it with an impermeable membrane and burying it or by other harmless treatment methods.

[0029] In a preferred embodiment, step S2 further includes the following step: if the geomembrane at the bottom of the contaminated soil is punctured during excavation, either manually or using small equipment, a geomembrane patch is used to repair the puncture; if the bottom geomembrane is not damaged during excavation, proceed to step S3. Specifically, the patch is made of a hot-melt material, and the material of the patch is consistent with that of the geomembrane. The patch is completely adhered to the punctured area of ​​the geomembrane using a hot-melt method. Alternatively, the patch can be installed using adhesive or other methods, as long as it ensures that there is no leakage at the patch.

[0030] By promptly repairing the breach, subsequent sealing tests can be conducted smoothly.

[0031] As a preferred embodiment, S2 further includes the following step: when drilling at the borehole position, a temporary steel casing is inserted into the borehole, and the temporary steel casing moves downward synchronously with the drilling, so as to temporarily support the contaminated soil around the borehole position; it can be understood that by using the temporary steel casing to temporarily support the contaminated soil outside the process hole, the contaminated soil outside the process hole is prevented from collapsing during the drilling process.

[0032] S6 also includes removing the temporary steel casing, followed by concrete pouring. Specifically, while removing the temporary steel casing, cement mortar is poured between the geomembrane and the contaminated soil on the outer wall of the process borehole to form a filling layer. The filling layer is poured in two stages. First, the bottom part is poured, ensuring that the cement mortar completely covers the connection joint between the bottom geomembrane and the geomembrane. After the cement mortar has initially cured, the remaining part is poured. By setting up layered pouring, the amount of cement mortar poured in the first stage is small, and the pressure applied to the connection joint between the geomembrane and the geomembrane is low, thus reducing the likelihood of leakage at the connection. This improves the stability of the connection between the geomembrane and the geomembrane and enhances its subsequent seepage prevention. Simultaneously, the pouring of the filling layer ensures that the cement mortar promptly fills the gap between the process borehole and the outer wall of the geomembrane, preventing the contaminated soil outside the process borehole from collapsing when the temporary steel casing is removed.

[0033] As a preferred embodiment, S3 includes the following steps: using a geomembrane and a geomembrane made of heat-melting material, the bottom of the geomembrane and the geomembrane are heat-fused together by heating.

[0034] It is known that the connection made by heat fusion has good stability and is less prone to loosening and cracking, which helps to prevent leakage.

[0035] As a preferred embodiment, S3 includes the following step: using waterproof adhesive to seal the bottom of the seepage-proof pipe and the seepage-proof membrane.

[0036] It should also be noted that in some other embodiments of this application, the geomembrane and the geomembrane can be connected in other ways to achieve a seal.

[0037] In a preferred embodiment, step S5 further includes the following steps: after cutting open the bottom geomembrane, a permanent steel casing is lowered, and the drill bit extends into the permanent steel casing to continue drilling. During drilling, the permanent steel casing moves downward synchronously with the drill bit. The drill bit is then pulled out, and a reinforcing cage is lowered into the permanent steel casing. Concrete is then poured inside the permanent steel casing to form a cast-in-place pile. It should be noted that sand is filled between the permanent steel casing and the geomembrane. This allows the cast-in-place pile to slide downward relative to the geomembrane when it settles later, preventing the geomembrane or geofiltration pipe from cracking during the pile's sinking.

[0038] As a preferred embodiment, S1 to S4 employ dry drilling methods, while S5 and S6 employ mud-wall protection methods. Mud-wall protection helps prevent borehole edge collapse.

[0039] The core principle of this method for constructing anti-seepage cast-in-place piles in contaminated soil landfill areas is to precisely avoid the risk of pollutant leakage caused by damage to the original anti-seepage membrane during construction through step-by-step control of "positioning, drilling, sealing of anti-seepage pipe, sealing test, casting of piles, and top sealing": First, the anti-seepage pile hole positions are accurately located and the top anti-seepage membrane is cut to form the drilling position, which ensures drilling accuracy and avoids blind excavation that damages the top anti-seepage system; when drilling is close to the bottom anti-seepage membrane, manual excavation is used, which can effectively avoid the impact force of mechanical drilling from damaging the bottom anti-seepage membrane; after inserting the anti-seepage pipe, the top sealing is then carried out. The bottom of the pipe is sealed to the bottom geomembrane and the seal is tested to form a closed loop for bottom seepage prevention, preventing pollutants from leaking from the connection between the bottom geomembrane and the geomembrane pipe. After the seal test is qualified, the geomembrane below the cavity inside the geomembrane pipe is cut open and drilling and concrete pouring are continued. This can strictly control the damage area of ​​the geomembrane to the inside of the geomembrane pipe, avoiding the exposure of the damaged area and the spread of pollution. Finally, through the sealed connection between the top of the geomembrane pipe and the top geomembrane, a complete seepage prevention system of "top-geomembrane-bottom" is formed. Combined with the bearing capacity of the concrete pile, the integration of seepage prevention and support is achieved. Based on this principle, its beneficial effects are significant: First, it maximizes the protection of the integrity of the original geomembrane, limiting the damage area to a controllable zone, effectively blocking the seepage channels of pollutants through the damaged geomembrane, avoiding pollution and diffusion, and solving the industry pain point that traditional drilling construction easily damages the geomembrane and leads to pollutant leakage. This aligns with the core prevention and control requirements of "cutting off the main flow channel + controlling the priority pollution path" in contaminated soil landfill areas. Second, the bidirectional sealing design of the geomembrane and the geopipe, combined with the sealing test procedure, ensures no leakage at the geomembrane connection, and the reliability of the geomembrane is far superior to that of conventional cast-in-place pile construction, significantly reducing the risk of groundwater pollution. Third, the construction process is simple and controllable, requiring no large-scale excavation, resulting in high construction efficiency and minimal disturbance to the original structure of the landfill area, avoiding secondary pollution during construction. Fourth, the synergistic effect of the cast-in-place pile and the geomembrane takes into account both the geomembrane function and the structural bearing capacity, effectively adapting to uneven settlement of the landfill, avoiding micro-cracks in the geomembrane structure due to settlement, and extending the service life of the geomembrane system.

[0040] Example 2: See Figure 9 and Figure 10This embodiment provides a seepage-proof cast-in-place pile for contaminated soil landfill areas, constructed using the construction method of Embodiment 1 described above. It includes a pile body 1 and a permanent steel casing 2. The pile body 1 is formed by pouring and curing concrete inside the permanent steel casing 2. It also includes a seepage-proof pipe 3 and two layers of seepage-proof membrane 4 used to wrap the contaminated soil landfill area from the top and bottom. The seepage-proof pipe 3 is coaxially arranged outside the permanent steel casing 2. Both the upper and lower layers of seepage-proof membrane 4 have through holes 41, and the two through holes 41 are coaxially arranged. The seepage-proof pipe 3 passes through the two through holes 41 from top to bottom, with the upper edge of the seepage-proof pipe 3 sealed to the upper seepage-proof membrane 4, and the lower edge of the seepage-proof pipe 3 sealed to the bottom seepage-proof membrane 4. The pile body 1 and the permanent steel casing 2 are arranged from top to bottom through the seepage-proof pipe 3.

[0041] It is understood that by sealing the bottom edge of the geomembrane 4 with the bottom edge of the geomembrane 3 and the top edge of the geomembrane 4 with the top edge of the geomembrane 4, a through-hole is formed in the contaminated soil area, isolating the contaminated soil. This facilitates the construction of the pile body 1 within the hole, which is used to support wharves, bridges, and municipal engineering projects. Because the geomembrane 3 and the two layers of geomembranes 4 completely enclose the contaminated soil, pollutants in the contaminated soil area will not leak. This achieves the construction of cast-in-place piles while ensuring that pollutants within the contaminated soil do not leak.

[0042] It should be noted that the pile body 1 also includes a reinforcing cage, which is arranged inside the permanent steel casing 2.

[0043] In a preferred embodiment, both the geomembrane 4 and the geopipe 3 are made of hot-melt material, and the upper and lower ends of the geomembrane 4 are sealed to the upper and lower geomembranes 4 by hot-melt connection. Hot-melt connection has better connection stability and is less prone to leakage.

[0044] As a preferred embodiment, the impermeable pipe 3 includes an impermeable inner layer 31, an intermediate support layer 32, and an impermeable outer layer 33. The hardness of the intermediate support layer 32 is greater than that of the impermeable inner layer 31 and the impermeable outer layer 33. Both the impermeable inner layer 31 and the impermeable outer layer 33 are made of flexible materials that are easy to deform.

[0045] It is understood that the intermediate support layer 32 enhances the overall rigidity of the geotextile 3, preventing it from flattening during construction and thus avoiding damage during drilling. Simultaneously, the two-layer geotextile design (inner layer 31 and outer layer 33) improves the geotextile 3's impermeability. The outer layer 33 and inner layer 31 are tightly connected to the intermediate support layer 32 through fusion. Furthermore, the inner and outer layers 31 are made of easily deformable flexible materials, allowing the top and bottom edges of the outer layer 33 to be flipped outwards during installation for heat fusion bonding with the lower and upper geomembranes 4.

[0046] In a preferred embodiment, the inner impermeable layer 31, the outer impermeable layer 33, and the geomembrane 4 are all made of a flexible hot-melt material. The inner impermeable layer 31 and the geomembrane 4, as well as the outer impermeable layer 33 and the geomembrane 4, are sealed together by hot-melt connection. Specifically, the material can be polyethylene, polyvinyl chloride, polypropylene, etc.

[0047] By using a hot-melt material, the inner impermeable layer 31 and the geomembrane 4 are connected by hot-melt, as are the outer impermeable layer 33 and the geomembrane 4. This hot-melt connection method results in a tight bond, reducing the likelihood of leakage. Furthermore, it only requires heating the material above its melting point, leading to low construction costs and excellent connection performance.

[0048] In a preferred embodiment, at the bottom of the geomembrane 3, the outer geomembrane 33 is turned outward and extended in all directions, and the outer geomembrane 33 is attached to the top of the lower geomembrane 4; the portion of the geomembrane 4 located inside the geomembrane 3 is bent inward toward the geomembrane 3, and the portion of the geomembrane 4 located inside the geomembrane 3 is embedded between the intermediate support layer 32 and the inner geomembrane 31 to form a clamping structure, which is beneficial to improving waterproofness.

[0049] When constructing the bottom of the geomembrane 4 pipe, first heat the outer geomembrane 33 and the geomembrane 4, and then heat-melt the outer geomembrane 33 onto the geomembrane 4. After that, a water filling test is carried out on the outer periphery of the geomembrane pipe 3. If there is leakage, the leaking part is heat-melted and connected until there is no leakage. Next, the bottom geomembrane 4 is cut open, leaving a ring of geomembrane 4 extending into the geomembrane pipe 3 (i.e., the diameter of the circular hole cut in the geomembrane 4 is smaller than the inner diameter of the geomembrane pipe 3). Then, the bottom geomembrane inner layer 31 of the geomembrane pipe 3 is lifted upwards, separating the bottom part of the geomembrane inner layer 31 from the intermediate support layer 32. The geomembrane 4 extending into the geomembrane pipe 3 is surface-heat-fused, and the heat-fused geomembrane 4 is bent upwards and attached to the inner wall of the intermediate support layer 32. Then, the upwardly bent geomembrane 4 and the lifted geomembrane inner layer 31 are heat-fused together. Then, the lifted geomembrane inner layer 31 is attached downwards to the inner wall of the geomembrane 4, so that the geomembrane inner layer 31 and the intermediate support layer 32 form a clamping structure for the geomembrane 4, thereby further improving the waterproofness.

[0050] In a preferred embodiment, at the top of the geomembrane 3, the outer geomembrane 33 is turned outward and extended in all directions, and the outer geomembrane 33 is attached to the bottom of the upper geomembrane 4; the portion of the geomembrane 4 located inside the geomembrane 3 is bent towards the inside of the geomembrane 3, and the portion of the geomembrane 4 located inside the geomembrane 3 is embedded between the intermediate support layer 32 and the inner geomembrane 31 to form a clamping structure, which is beneficial to improving waterproofness.

[0051] It should be noted that the overall length of the intermediate support layer 32 is equal to the overall length of the inner impermeable layer 31, and the overall length of the intermediate support layer 32 is less than the overall length of the outer impermeable layer 33. The portion of the geomembrane 4 extending into the impermeable pipe 3 is sandwiched between the intermediate support layer 32 and the inner impermeable layer 31. The two sides of the geomembrane 4 are respectively heat-fused to the intermediate support layer 32 and the inner impermeable layer 31, which further improves the tightness of the connection between the impermeable pipe 3 and the geomembrane 4, and is conducive to improving the waterproof effect.

[0052] In some embodiments, the thickness of the intermediate support layer 32 is greater than the thickness of the inner impermeable layer 31, and the thickness of the intermediate support layer 32 is greater than the thickness of the outer impermeable layer 33.

[0053] The working principle and basic operation process of this invention are as follows: First, locate the holes for the anti-seepage piles. Cut open the anti-seepage membrane 4 on the top surface of the contaminated soil at the location. Drill a process hole at the cut anti-seepage membrane 4. Drill to a point 430 cm from the bottom anti-seepage membrane, then remove the drill bit and manually excavate until reaching the bottom anti-seepage membrane 4. Do not damage the bottom anti-seepage membrane 4 during excavation; if damaged, repair it immediately. Simultaneously with drilling the process hole, a temporary steel casing needs to be lowered. The temporary steel casing moves downwards with the drilling to prevent the contaminated soil from collapsing. Next, lower the anti-seepage pipe 3 and heat-weld the bottom of the anti-seepage pipe 3 to the bottom anti-seepage membrane 4. After welding, the anti-seepage pipe 3... The weld seal between the geomembrane 4 and the geomembrane 3 is tested by internal water injection. If there is no leakage, proceed to the next step. If there is leakage, the water is pumped out and the hot-melt welding is repeated, followed by another water injection test until there is no leakage. Then, the geomembrane 4 is cut open at the position inside the geomembrane 3, and the drill bit continues to drill downwards to form a pile foundation hole. Before drilling the pile foundation hole, a permanent steel casing 2 is inserted to guide the drill bit, and the permanent steel casing 2 moves downwards with the drill bit. After drilling to the design elevation, the drill bit is removed, a reinforcing cage is inserted into the permanent steel casing 2, and concrete is poured inside the permanent steel casing 2 to form a cast-in-place pile. Sand is filled into the gap between the permanent steel casing 2 and the geomembrane 4, and concrete is filled between the geomembrane 4 and the contaminated soil. Finally, the top edge of the geomembrane 3 is hot-melt sealed to the top geomembrane 4.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for constructing a bored pile for preventing seepage in a contaminated soil landfill site, characterized by, Includes the following steps: S1. Locate the hole position of the anti-seepage pile, cut open the anti-seepage membrane on the top surface of the contaminated soil, and form the drilling position of the pile hole at the cut anti-seepage membrane. S2. Drill at the drilling location. When the distance from the bottom of the geomembrane to the contaminated soil is A cm, stop drilling and continue digging to the surface of the geomembrane by hand or small equipment. Then insert the geomembrane pipe downwards. S3. Seal the connection between the bottom of the impermeable pipe and the impermeable membrane at the bottom of the contaminated soil. S4. Test the sealing performance of the joint. If the seal is good and there is no leakage, proceed to S5. If the seal is not tight and there is leakage, repeat S3 and S4. S5. Cut open the geomembrane located below the cavity inside the geomembrane pipe, continue drilling downwards until the design elevation is reached, stop drilling, and then pour concrete inside the geomembrane pipe to form a cast-in-place pile. S6. After the cast-in-place pile is poured, the top of the anti-seepage pipe is sealed to the anti-seepage membrane on top of the contaminated soil.

2. The construction method for anti-seepage cast-in-place piles in contaminated soil landfill areas according to claim 1, characterized in that: S2 also includes the following steps: if the bottom geomembrane of the contaminated soil is broken during excavation by manual labor or with small equipment, the broken area is repaired with geomembrane patch blocks; if the bottom geomembrane is not damaged during excavation, proceed to S3.

3. The construction method for anti-seepage cast-in-place piles in contaminated soil landfill areas according to claim 2, characterized in that: S2 also includes the following steps: when drilling at the borehole location, a temporary steel casing is inserted into the borehole, and the temporary steel casing moves downward synchronously with the drilling, so as to temporarily support the contaminated soil around the borehole location. S6 also includes the following steps: removing the temporary steel casing and simultaneously pouring cement mortar between the seepage prevention pipe and the contaminated soil to form a filling layer.

4. The construction method of anti-seepage cast-in-place piles in contaminated soil landfill areas according to claim 1, characterized in that: In S2, the value of A is greater than or equal to 10 cm and less than or equal to 40 cm. The required drilling depth is determined by referring to the design drawings for the contaminated soil landfill.

5. The construction method for anti-seepage cast-in-place piles in contaminated soil landfill areas according to claim 1, characterized in that: S3 includes the following steps: using a geomembrane and a geomembrane made of heat-melting material, the bottom of the geomembrane and the geomembrane are heat-fused together.

6. The method for constructing anti-seepage cast-in-place piles in contaminated soil landfill areas according to claim 1, characterized in that: S3 includes the following steps: using waterproof adhesive to seal the bottom of the geomembrane and the geomembrane.

7. The construction method for anti-seepage cast-in-place piles in contaminated soil landfill areas according to claim 1, characterized in that: S5 also includes the following steps: after cutting open the bottom geomembrane, a permanent steel casing is lowered, and the drill bit extends into the permanent steel casing to continue drilling. During the drilling process, the permanent steel casing moves downward synchronously with the drilling. The drill bit is then pulled out, and a reinforcing cage is lowered into the permanent steel casing. Concrete is then poured into the permanent steel casing to form a cast-in-place pile.

8. The construction method for anti-seepage cast-in-place piles in contaminated soil landfill areas according to claim 1, characterized in that: Dry operation is used for S1 to S4, while mud wall protection is used for S5 and S6.

9. A seepage-proof cast-in-place pile for contaminated soil landfill areas, comprising a pile body (1) and a permanent steel casing (2), wherein the pile body (1) is formed by pouring and curing concrete inside the permanent steel casing (2), characterized in that: It also includes a seepage-proof pipe (3) and two layers of seepage-proof membrane (4) for wrapping the contaminated soil landfill area from the top and bottom. The seepage-proof pipe (3) is arranged outside the permanent steel casing (2). Both the top and bottom layers of the seepage-proof membrane (4) have through holes (41) and the two through holes (41) are arranged coaxially. The seepage-proof pipe (3) is inserted into two through holes (41) from top to bottom, and the upper edge of the seepage-proof pipe (3) is sealed to the upper seepage-proof membrane (4), and the lower edge of the seepage-proof pipe (3) is sealed to the bottom seepage-proof membrane (4). The pile body (1) and the permanent steel casing (2) are arranged from top to bottom through the seepage prevention pipe (3).

10. A seepage-proof cast-in-place pile for contaminated soil landfill areas according to claim 9, characterized in that: Both the geomembrane (4) and the geomembrane pipe (3) are made of hot-melt material, and the upper and lower ends of the geomembrane (4) are sealed to the upper and lower geomembranes (4) by hot-melt method.

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