High-standard anti-seepage system for controlling percolate of refuse landfill

Abstract

The high-standard anti-seepage system comprises an upper composite anti-seepage wall and a lower grouting anti-seepage curtain, the lower grouting anti-seepage curtain is in lap joint with the upper composite anti-seepage wall, the upper composite anti-seepage wall is of a sandwich structure, the middle of the upper composite anti-seepage wall is an HDPE membrane layer, and the inner side and the outer side of the upper composite anti-seepage wall are self-coagulation mortar layers. The anti-seepage wall is arranged on the upper portion, the curtain is arranged on the lower portion, the anti-seepage wall is formed by combining the HDPE film and the self-solidifying mortar in a rigid-flexible mode, the anti-seepage wall and the grouting curtain are in lap joint up and down, the anti-seepage system achieves multi-layer seepage prevention from the surface layer to the deep layer, and the seepage prevention performance and durability can be greatly improved. The anti-seepage wall is excellent in performance, the HDPE film is adopted as a main body anti-seepage material of the anti-seepage wall, and the anti-seepage performance can be improved for a complex polluted body; the curtain grouting needle is used for filling cracks of the deep bed rock, and the nano silica sol slurry is used for reinforcing grouting for micro crack holes and cracks, so that the anti-seepage effect and the long-term stability can be improved.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of environmental engineering and groundwater pollution control, and specifically relates to a high-standard anti-seepage system for the management of leachate from landfills. Background Technology

[0002] Currently, landfills are the primary disposal method and site for solid waste such as industrial solid waste, hazardous waste, and municipal solid waste. Data shows that in 2023, China had 366 formal municipal solid waste landfills and over 27,000 makeshift municipal solid waste landfills. Makeshift landfills often directly pollute the surrounding environment due to a lack of anti-seepage measures. In contrast, while formal municipal solid waste landfills have higher construction standards, they typically have high leachate levels, making their antifouling liners prone to puncture and side leakage. In-service sanitary landfills are in a precarious state due to long-term overload operation.

[0003] Leachate is a highly concentrated organic wastewater generated during landfilling, which poses a significant hazard and causes serious pollution to the surrounding environment. It is characterized by high load, complex composition, and large fluctuations in water quality and quantity.

[0004] Groundwater pollution is highly concealed, and once contaminated, it poses a continuous threat. Pollutants rise to the surface through capillary action, contaminating the soil and spreading with groundwater flows. Groundwater remediation is extremely costly, making the establishment of long-term barrier mechanisms for landfills of great importance.

[0005] The areas where anti-seepage structures are constructed often face complex geological conditions. Common issues include poor continuity of the anti-seepage wall due to shallow fine-particle layers and artificially compacted strata prone to collapse, and deep bedrock fissures leading to pollutant infiltration around the surface. A single anti-seepage method is insufficient to block complex pollutants. Furthermore, traditional cement-based underground continuous walls, such as concrete continuous walls, high-pressure jet grouting walls, and deep mixing walls, have a maximum permeability coefficient of around 10⁻⁶ cm / s, exhibiting poor resistance to chemical erosion and significant limitations in durability. Therefore, traditional barrier walls struggle to meet the technical standards for pollutant barrier protection required in both economic and environmental fields. Summary of the Invention

[0006] This invention provides a high-standard anti-seepage system for landfill leachate control to solve the technical problems existing in the prior art, with good anti-seepage effect and good durability.

[0007] The technical solution adopted by this invention to solve the technical problems existing in the prior art is: a high-standard anti-seepage system for landfill leachate control, comprising an upper composite anti-seepage wall and a lower grouting anti-seepage curtain. The upper composite anti-seepage wall adopts a sandwich structure, with an HDPE membrane layer in the middle and self-setting mortar layers on the inner and outer sides. The HDPE membrane layer is composed of multiple HDPE membrane units interconnected by a locking connection structure, and the locking connection structure is equipped with a rubber waterstop. The lower grouting anti-seepage curtain is located below the upper composite anti-seepage wall and forms an overlap area with it in the vertical direction. Construction method of the upper composite seepage barrier wall: S10. Before construction, the HDPE membrane sheet and the interlocking single sheet are welded into an HDPE membrane unit on a special platform. The accessories for the HDPE membrane are prepared, including a detachable bottom counterweight and an orifice pressure plate. A rubber waterstop is provided on the joint surface of the interlocking single sheet. S11, trenching; S12, Clean the tank; S13. Using a dedicated lower roller and the detachable bottom counterweight from step S10, the HDPE membrane unit is vertically lowered into the set position in the wall groove. Then, the counterweight is removed, and the HDPE membrane unit is fixed to the wall groove opening using the orifice pressure plate from step S10. The detachable bottom counterweight and the orifice pressure plate work together to ensure that the HDPE membrane unit maintains a bending deformation of no more than 5 cm in the plane and a sinking offset of no more than 2 cm during the lowering process. S14. A connector box device is installed below; S15. Complete the self-curing mortar pouring operation on both the inner and outer sides of the HDPE membrane unit. S16. Repeat step S13 to continuously install another HDPE membrane unit. Then, use the joint box device to connect the locking pieces of two adjacent HDPE membrane units together. Then, remove the joint box device. The outer shell of the joint box device, which fits against the tank wall, has a mud-proof cavity in the middle and a guide rail for limiting the position of the membrane to prevent mud from entering the locking joint. Repeat step S15. S17. Repeat step S16 until the construction of all the anti-seepage walls is completed; Construction method of the lower grouting anti-seepage curtain: S18. Grouting hole construction: After the upper composite anti-seepage wall is constructed, a row of grouting holes is set on both the inner and outer sides. The construction method of each grouting hole is as follows: seamless steel pipes are embedded in the area covered by the composite anti-seepage wall, and grouting holes are drilled through the seamless steel pipes. The part of the grouting hole located below the pre-embedded pipe is the curtain grouting hole. S19. Grouting construction: The grouting shall be carried out in a row and in sequence. The outer row shall be constructed first, followed by the inner row. Within the same row, the grouting shall be carried out in sequence I, II, and III. The grouting of each grouting hole shall be carried out in sections and in stages using the plugging method until the grouting of the entire hole is completed. Then, the hole shall be sealed by the full hole grouting sealing method.

[0008] Based on the above solution, the present invention has made the following improvements: The overlap length between the lower grouting anti-seepage curtain and the upper composite anti-seepage wall is greater than or equal to 200 mm.

[0009] In step S10, the rubber waterstop is made of self-expanding rubber material, which expands to 3 to 5 times its original volume after being immersed in a standard water environment.

[0010] Step S13 also includes cleaning the tank, cleaning the tank again before lowering the HDPE membrane unit to ensure that the thickness of the sediment at the bottom of the tank meets the design requirements.

[0011] In step S15, the self-setting mortar is poured using the "displacement method". Self-setting mortar is poured simultaneously and continuously on both sides of the HDPE membrane layer from the bottom of the trench, so that the height difference of the mortar liquid level on both sides does not exceed 10 cm, so that the membrane layer remains vertical and the core structure is uniform, avoiding membrane bulging or tearing. At the same time, a mud pump is set up at the orifice to pump the displaced bentonite mud to the return mud tank, which is then recycled as wall protection slurry during trenching, reducing the amount of mud discharged during trenching construction by more than 40%.

[0012] In step S19, when encountering a stratum with high permeability but insufficient grout absorption during curtain grouting construction, nano-silica sol grout is added to the inner and outer rows of sequence III holes after cement grout is injected for reinforcement. The interval between cement grout and silica sol injection is 1 to 4 hours, so that the silica sol can fully penetrate without damaging the structural strength of the cement grout.

[0013] In step S19, when using the grouting method, each grouting should be carried out at the maximum grouting pressure, with an injection rate not exceeding 1L / min, and then continue grouting for 30 minutes to end the current grouting session. Attached Figure Description

[0014] Figure 1 This is a cross-sectional structural diagram of the present invention; Figure 2 This is a partial plan view of the upper composite seepage barrier wall of the present invention; Figure 3 This is an elevation view of the segmented layout of the upper composite anti-seepage wall trench of the present invention; Figure 4 This is a construction drawing of the upper composite anti-seepage wall trench section of the present invention; Figure 5This is a diagram showing the arrangement of grouting holes in the lower grouting anti-seepage curtain of the present invention.

[0015] In the diagram: 1. Upper part of the grouting hole; 2. Self-curing mortar layer; 3. Lower grouting anti-seepage curtain; 4. Curtain grouting hole; 5. HDPE membrane layer; 5-1. HDPE membrane; 5-2. Locking single piece; 5-3. Locking connection structure; 6. Rotary drilling pilot hole main hole; 7. Rotary drilling pilot hole secondary hole; 8. Upper area of ​​the wall trench; 9. Middle and lower area of ​​the wall trench; 10. Sequence I hole; 11. Sequence II hole; 12. Sequence III hole; 13. Upper composite anti-seepage wall. Detailed Implementation

[0016] To further understand the invention's content, features, and effects, the following embodiments are provided, along with detailed descriptions in conjunction with the accompanying drawings: Please see Figure 1 A high-standard seepage prevention system for landfill leachate control includes an upper composite seepage prevention wall and a lower grouting seepage prevention curtain 3. The lower grouting seepage prevention curtain 3 overlaps with the upper composite seepage prevention wall, and the overlap length is recommended to be greater than or equal to 200mm.

[0017] Please see Figures 2-4 The upper composite seepage barrier wall adopts a sandwich structure, with an HDPE membrane layer 5 in the middle and self-setting mortar layers 2 on the inner and outer sides. The HDPE membrane layer is composed of multiple HDPE membrane units connected to each other by interlocking connection structure 5-3. The interlocking connection structure 5-3 is equipped with a rubber waterstop.

[0018] The lower grouting anti-seepage curtain 3 is located below the upper composite anti-seepage wall and forms an overlap area with it in the vertical direction.

[0019] Construction method of the upper composite seepage barrier wall: S10. Before construction, the HDPE membrane 5-1 and the interlocking single piece 5-2 are welded together on a special platform to form an HDPE membrane unit. The accessories for the HDPE membrane are prepared, including a detachable bottom counterweight and an orifice pressure plate. A rubber waterstop is provided on the joint surface of the interlocking single piece 4. The welding quality of the HDPE membrane unit should be inspected before use.

[0020] S11. Complete the wall trench construction. Please refer to the wall trench section layout diagram. Figure 3 , Figure 3 This is an elevation view showing the layout of the composite anti-seepage wall trench sections. Dimensions 2800 and 2000 in the drawing represent length values ​​in mm. The area with dimension 2800 is the main milling area for trenching, and the area with dimension 2000 is the secondary milling area for trenching. 6 represents the main rotary drilling pilot hole, and 7 represents the secondary rotary drilling pilot hole. Please refer to [link / reference]. Figure 4 , Figure 4The diagram shows the construction of the upper composite anti-seepage wall trench section. In the diagram, 8 represents the upper area of ​​the trench, which is constructed using a grab bucket. 9 represents the lower middle area of ​​the trench, which is constructed using a double-wheel milling machine. In the middle is a pilot hole with a diameter of 0.8m, constructed using a rotary drilling rig.

[0021] More specifically, under the action of mud wall protection, rotary drilling is used to prepare the borehole, and the "milling method" of hydraulic double wheel milling machine and hydraulic grab bucket is used to complete the construction of the diaphragm wall trench section. The trench section width should meet the width of the HDPE membrane, and the trench section length should have a certain margin for work.

[0022] S12. Trench Cleaning: After trenching and before laying the HDPE membrane, a hole cleaning operation is carried out to clean the drilling slag and mud deposits at the bottom of the trench section to avoid affecting the impermeability of the wall base and the bedrock contact area and causing damage to the wall quality.

[0023] S13. Using the dedicated lower roller and the detachable bottom counterweight prepared in step S10, the HDPE membrane unit is vertically lowered into the set position in the wall groove. After the lower end is fixed, the counterweight is removed. The HDPE membrane unit is fixed to the wall groove opening using the orifice pressure plate prepared in step S10. The detachable bottom counterweight and the orifice pressure plate work together to ensure that the HDPE membrane unit maintains a bending deformation of no more than 5 cm in the plane and a sinking offset of no more than 2 cm during the lowering process.

[0024] During construction, the HDPE membrane unit is assembled and fixed into a dedicated lower roller, arranged in the lower groove section as needed, and the membrane counterweight is fixed at the same time. Under the action of the lower counterweight, the membrane is vertically lowered, and the lower counterweight is removed by motor drive, and the HDPE membrane is fixed at the groove opening.

[0025] Before lowering the HDPE membrane unit, clean the trench again to ensure that the thickness of the sediment at the bottom of the trench meets the design requirements. If the HDPE membrane is laid for too long or other reasons cause a significant increase in sediment accumulation at the bottom of the borehole, the sediment accumulation at the bottom of the borehole should be re-measured before replacing the wall-stabilizing mud, and a second trench cleaning should be performed if necessary.

[0026] S14, with a connector box device installed below.

[0027] S15. Complete the self-curing mortar pouring operation on both the inner and outer sides of the HDPE membrane unit to form the self-curing mortar layer 2.

[0028] After installing the joint box device, the self-setting mortar is poured using the "replacement method." Self-setting mortar is poured simultaneously and continuously from the bottom of the trench on both sides of the HDPE membrane layer, ensuring the mortar level difference between the two sides does not exceed 10 cm. This maintains the verticality of the membrane layer and the uniformity of the sandwich structure, preventing membrane bulging or tearing. During replacement, the pump pipe is lowered into the trench 50-100 cm from the bottom, and the mud pump is started to pump fresh self-setting mortar to the bottom of the trench. Before the replacement is completed, samples are taken at the outlet pipe to test the mud properties; the results serve as the basis for the mortar replacement index. Simultaneously, a mud pump is installed at the orifice to pump the replaced bentonite mud to the return mortar tank. This returned mud is then recycled as wall-protecting mortar during trenching, reducing mud discharge during trenching construction by more than 40%.

[0029] S16. Repeat step S13 to continuously lower another HDPE membrane unit. Then, use the joint box device to connect the locking pieces of two adjacent HDPE membrane units together. Then, remove the joint box device and repeat step S15. The outer shell of the joint box device, which fits against the tank wall, has a mud-proof cavity in the middle, which serves as a guide rail to restrict the position of the membrane and prevent mud from entering the locking joint. The locking connection structure has two rubber waterstops for composite sealing. The rubber waterstops are made of self-expanding rubber material, which expands to 3-5 times its original volume after immersion in standard water.

[0030] S17. Repeat step S16 until the construction of all the anti-seepage walls is completed.

[0031] Construction method of the lower grouting anti-seepage curtain 3: S18. Grouting hole construction: After the upper composite anti-seepage wall is constructed, a row of grouting holes is set on both the inner and outer sides. The construction method of each grouting hole is as follows: seamless steel pipes are embedded in the area covered by the composite anti-seepage wall, and grouting holes are drilled through the seamless steel pipes. The part of the grouting hole located below the pre-embedded pipe is the curtain grouting hole. S19. Grouting construction: The grouting shall be carried out in a row and in sequence. The outer row shall be constructed first, followed by the inner row. Within the same row, the grouting shall be carried out in sequence I, II, and III. The grouting of each grouting hole shall be carried out in sections and in stages using the plugging method until the grouting of the entire hole is completed. Then, the hole shall be sealed by the full hole grouting sealing method.

[0032] Please see Figure 5 The specific details are explained below with reference to the embodiments: Two rows of grouting holes are arranged, one on the inner side and one on the outer side of the upper composite anti-seepage wall 13, with a row spacing of 1.5m. The two rows of holes are staggered on the plane. Each row of holes consists of sequence I hole 10, sequence II hole 11 and sequence III hole 12. The spacing between holes in the same row is 2m. Each row of grouting holes is arranged vertically.

[0033] Grouting is carried out according to the principle of row and sequence, with the outer row constructed first and the inner row constructed later. Within the same row, the grouting is carried out in the order of I, II, III.

[0034] The upper part of the grouting hole is located within the composite anti-seepage wall coverage area and does not require grouting; this section uses a pre-embedded pipe for transition. The pre-embedded pipe is generally a seamless steel pipe. The construction method for the seamless steel pipe is as follows: After the self-setting mortar layer of the upper composite anti-seepage wall is poured, the pre-embedded pipe is installed. A concentrated grout with a water-cement ratio of 0.5 is injected into the pre-embedded pipe and returns from the outer orifice. The pre-embedded pipe is fixed and allowed to set for 48 hours to complete the pre-embedded pipe installation. Subsequently, drilling is performed along with the pipe to form the grouting hole. The upper part (1) of the grouting hole is located within the composite anti-seepage wall coverage area and does not require grouting. The lower part (4) of the grouting hole is located below the seamless steel pipe and is a curtain grouting hole. Curtain grouting is performed in sections and stages using the plugging method. The grouting plug is placed inside the concrete, and pure pressure or circulating grouting is used. After the entire curtain grouting hole is grouted, it is sealed using the full-hole grouting sealing method.

[0035] To ensure full grouting, during each grouting session, after the injection rate is no more than 1 L / min at the maximum grouting pressure, continue grouting for 30 minutes to end the current grouting session.

[0036] If there is a strongly weathered tuff stratum, and the stratum has high permeability but insufficient absorption of grout, after cement grouting is completed in the third-order borehole, nano-silica sol grout is used for reinforcement grouting. The interval between cement grouting and silica sol injection is 1 to 4 hours, so that the silica sol can fully penetrate without damaging the structural strength of the cement grout.

[0037] After the anti-seepage axis construction is completed, the integrity of the anti-seepage wall section and the pressure test of the curtain grouting are carried out to accept the overall anti-seepage construction. Working principle of the invention: HDPE membrane is a sheet-like thin film structure made of linear high-density polyethylene molecules with a density of 0.941-0.965 g / cm³. Van der Waals forces between molecular chains form dense crystalline regions (crystal thickness 10-50 nm), with a porosity of <0.1%. It is a polymeric waterproofing material with special dimensions customized according to construction requirements.

[0038] For upper loose geology or intermittent large-fracture rock strata, an HDPE membrane-self-curing mortar composite seepage barrier is constructed. Vertically, the HDPE membrane (1.5-3.0mm thick) is centrally positioned, and the two sides are wrapped with self-curing mortar (≥150mm thick). On the vertical surface, adjacent membranes are connected using self-developed interlocking joints, and composite sealing is achieved using rubber waterstops with a volume expansion coefficient of 4. The HDPE membrane bears more than 90% of the tensile stress, and the self-curing mortar provides lateral confinement to prevent membrane buckling instability, forming a three-dimensional structural barrier with a mechanical synergy mechanism.

[0039] For deep bedrock fissures, based on geological survey results and fluid dynamics control principles, a curtain grouting process is used. This process employs specialized grouting pumps, and selects appropriate cement grout mix ratios and grouting pressures according to the width and depth of the fissures. During the grouting process, precise control of pumping speed and pressure ensures that the grout can uniformly and fully fill the fissures, forming a continuous curtain barrier. This not only effectively prevents the spread of polluted water but also enhances the stability and impermeability of the bedrock.

[0040] This invention addresses the risk of leachate leakage from newly built and dilapidated landfills by controlling pollutants entering the soil and groundwater at the source. It utilizes vertical barrier technology to achieve underground containment and sealing of landfill leachate. This highly efficient and green vertical barrier technology combines a rigid-flexible composite vertical barrier wall section with HDPE membrane-self-curing mortar and curtain grouting. In high-risk leakage areas or downstream of the landfill water level, a combined "wall + curtain" process is employed, namely the HDPE membrane self-curing mortar composite barrier wall and curtain grouting beneath the wall. The two processes are effectively overlapped at their junction to ensure the integrity of the barrier curtain. In low-risk areas, curtain grouting strengthens the soil's impermeability, forming a closed vertical barrier system around the landfill. This targeted barrier blocks the flow path of landfill leachate, isolating it at the side of the landfill, reducing pollution to surrounding groundwater and soil, and improving the safe disposal of solid waste and the ecological restoration capabilities of contaminated sites.

[0041] The seepage prevention system proposed in this invention belongs to the vertical barrier system, combining multiple materials and technologies, including HDPE membrane, self-setting mortar, and curtain grouting, to form a multi-layer seepage prevention structure from the surface to the depths: HDPE membrane: As a surface impermeable material, HDPE membrane has an extremely low permeability coefficient (typically less than 10⁻¹² cm / s), effectively blocking the migration of pollutants and groundwater. Its high tensile strength and chemical stability ensure long-term impermeability. Self-setting mortar: formulated with cement, bentonite, admixtures, and water, it possesses self-leveling, self-compacting, and self-hardening properties. Self-setting mortar can fill shallow pores and cracks, forming a continuous impermeable body, while also tightly bonding with the HDPE membrane, protecting the membrane and enhancing the overall impermeability. Curtain grouting: Cement-based grout is pumped under high pressure to penetrate deep fissures and fracture zones in the strata to form a stable anti-seepage curtain. Curtain grouting can address deep geological problems that HDPE membranes and self-setting mortar cannot cover, ensuring the integrity of the anti-seepage system. Nano-silica sol grouting: For special strata, such as strongly weathered tuff strata, which have the characteristic of absorbing water but not grout, cement grouting is first performed on the corresponding strongly weathered tuff strata of the inner and outer drainage sequence III holes, and then nano-silica sol grouting is used for reinforcement grouting. It is suitable for micro-cracks (pores) less than 0.1mm, has controllable setting time, excellent engineering properties, and good durability.

[0042] This invention utilizes engineering methods to control and remediate contaminated sites and groundwater. It develops efficient barrier and remediation technologies for contaminated sites such as landfills, industrial sites, and mine tailings ponds. By constructing vertical seepage barriers, it achieves zero leachate ingress into the groundwater system, protecting water resources, reducing the potential risks of contaminated sites to the surrounding environment and human health, and meeting environmental regulations. In application, different barrier technologies are selected and matched according to the actual strata and groundwater flow direction, and appropriate technical optimization and innovation are carried out. Ultimately, a closed vertical barrier system is established around the landfill, achieving high-standard fully enclosed seepage prevention. This forms a replicable and scalable key technology for vertical leachate barrier systems in formal or informal landfills with high risk levels and significant site recycling application needs. HDPE membrane-self-curing mortar composite anti-seepage wall and under-wall curtain grouting are used to form a closed vertical barrier system around the landfill. In high-risk leakage areas or downstream areas of the landfill water level, a "wall + curtain" combined process is adopted, namely the HDPE membrane self-curing mortar composite anti-seepage wall process and under-wall curtain grouting. The junction of the two processes is effectively overlapped to ensure the integrity of the anti-seepage curtain. In low-risk areas, curtain grouting technology is used to strengthen the impermeability of the strata, forming a closed vertical barrier system around the landfill. Targeted blocking of landfill leachate flow pathways, isolating it at the side of the waste pile, reduces pollution to surrounding groundwater and soil, and enhances the capacity for safe disposal of solid waste and ecological restoration of contaminated sites.

[0043] Technical advantages of the present invention: Highly efficient seepage prevention: Through material composites and multi-layered seepage prevention mechanisms, the permeability coefficient is significantly reduced, effectively blocking the migration of pollutants.

[0044] Highly adaptable: It can adapt to complex geological conditions and handle pores and fractures of different sizes.

[0045] Convenient construction: Modular construction technology improves construction efficiency and reduces project costs.

[0046] Long-term stability: The material has excellent properties and the seepage prevention system has high durability, which can maintain the seepage prevention effect for a long time.

[0047] This invention has the following technical features: (1) HDPE membrane has excellent anti-permeability and chemical stability, and can effectively block leachate; (2) High-precision laying equipment is used to ensure that the HDPE membrane is laid flat, reducing wrinkles and gaps. Hot-melt welding technology is used to connect the seams between the membranes to ensure the sealing of the seams. After welding, the quality of the seams is verified by air tightness testing; (3) Optimize the mix ratio of self-setting mortar according to geological conditions and seepage prevention requirements to ensure its fluidity, filling and hardening properties so that it can closely adhere to the strata and form a continuous seepage barrier; (4) The combination of HDPE membrane and self-setting mortar has a mechanical synergy mechanism. HDPE membrane bears most of the tensile stress, while self-setting mortar provides lateral confinement. (5) The HDPE membrane coupling interlock connection device and the HDPE membrane are made of the same material, the connection process is mature and easy to implement; (6) Based on geological exploration data, design the layout and depth of grouting holes to ensure that the grout can cover the target fissures and fracture zones. Use high-pressure grouting equipment to monitor the grouting pressure and grout diffusion range in real time, and dynamically adjust construction parameters to ensure grouting effect.

[0048] (7) Nano-silica solution can be used to reinforce grouting in special fine-grained strata, thereby improving the overall seepage prevention performance of the wall section.

[0049] (8) During the construction process, the construction quality of the anti-seepage system is monitored in real time by means of ground-penetrating radar, permeability test and other means. After the project is completed, the actual effect of the anti-seepage system is evaluated by long-term monitoring of groundwater level and pollutant concentration.

[0050] Although preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other modifications under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these modifications are within the scope of protection of the present invention.

Claims

1. A high-standard impermeable system for landfill leachate management, characterized in that, The upper composite impervious wall and the lower grouting impervious curtain, The upper composite impervious wall adopts a sandwich structure, the middle is an HDPE film layer, and the inner and outer sides are self-setting mortar layers, the HDPE film layer is composed of a plurality of HDPE film units connected by a lock buckle connection structure, and a rubber waterstop is arranged on the lock buckle connection structure; The lower grouting impervious curtain is located below the upper composite impervious wall and forms a lap area with the upper composite impervious wall in the vertical direction; The construction method of the upper composite impervious wall: S10, before construction, weld the HDPE film and the lock buckle sheet into an HDPE film unit on a special platform, and prepare accessories under the HDPE film, including a detachable bottom counterweight and an orifice pressing plate, and a rubber waterstop is arranged on the joint surface of the lock buckle sheet; S11, groove forming; S12, groove cleaning; S13, use the special lower roller and the detachable bottom counterweight in step S10 to vertically lower the HDPE film unit into the set position in the wall groove, then remove the counterweight, use the orifice pressing plate in step S10 to fix the HDPE film unit at the orifice of the wall groove, and the detachable bottom counterweight and the orifice pressing plate jointly act to make the in-plane bending deformation of the HDPE film unit not more than 5 cm and the sinking deviation not more than 2 cm during the lowering process; S14, lower joint box device; S15, complete the self-setting mortar pouring operation on the inner and outer sides of the HDPE film unit; S16, repeat step S13 to continuously lower another HDPE film unit, then connect the lock buckle sheets of the two adjacent HDPE film units by using the joint box device, then take out the joint box device, the outer shell of the joint box device is attached to the groove wall, the mud separation cavity in the middle is used to limit the position of the film unit, the guide rail is used to prevent mud from entering the lock buckle joint part, and repeat step S15, S17, repeat step S16 until the construction of the entire impervious wall is completed; The construction method of the lower grouting impervious curtain: S18, grouting hole construction: after the construction of the upper composite impervious wall is completed, one row of grouting holes is arranged on each of the inner and outer sides of the upper composite impervious wall, and the construction method of each grouting hole is as follows: seamless steel pipes are inlaid in the covered area of the composite impervious wall, grouting holes are drilled through the seamless steel pipes, and the part of the grouting hole below the embedded pipe is a curtain grouting hole; S19, grouting construction: according to the principle of division and sequence, the outer row is constructed first and then the inner row, and in the same row, the construction is performed in the order of I, II and III, the grouting of each grouting hole is performed by using the plug method in sections and times, and after the whole hole grouting is completed, the whole hole grouting hole sealing method is used to seal the hole.

2. The high standard impermeable system for landfill leachate management according to claim 1, characterized in that, The overlap length of the lower grouting impervious curtain and the upper composite impervious wall is greater than or equal to 200 mm.

3. The high standard impermeable system for landfill leachate management according to claim 1, characterized in that, In step S10, the rubber waterstop is made of self-expanding rubber material, which expands to 3-5 times of the original volume after soaking in standard water environment.

4. The high standard impermeable system for landfill leachate management according to claim 1, characterized in that, In step S13, groove cleaning is further included, and the groove is cleaned again before the HDPE film unit is lowered to ensure that the thickness of the sediment at the bottom of the groove meets the design requirements.

5. The high standard impermeable system for landfill leachate management according to claim 1, characterized in that, The step S15 uses the "replacement method" to carry out the self-solidifying mortar pouring operation, synchronously and continuously pours the self-solidifying mortar from both sides of the HDPE film layer from the bottom of the groove, makes the height difference of the mortar liquid surface on both sides not more than 10 cm, makes the film layer keep vertical, and makes the uniformity of the sandwich structure, avoids the film inflation or tearing; meanwhile, a slurry pump is arranged on the orifice, the bentonite slurry replaced is pumped to the slurry return pool, and is used as the wall protection slurry liquid for recycling when the groove is formed, so that the slurry discharge amount of the groove forming construction is reduced by more than 40%.

6. The high standard impermeable system for landfill leachate management according to claim 1, characterized in that, The step S19, when the curtain grouting construction is carried out, the stratum with high permeability but insufficient slurry absorption is encountered, the inner and outer two rows of Ⅲ sequence holes are additionally grouted with the nano silicon sol slurry after the cement slurry is grouted, the interval time of the cement slurry and the silicon sol grouting is 1-4 hours, so that the silicon sol can be fully penetrated but does not damage the structural strength of the cement slurry.

7. The high standard impermeable system for landfill leachate management according to claim 1, characterized in that, The step S19, when the grouting is carried out by using the cassette method, the injection rate is not more than 1 L / min after the injection under the maximum grouting pressure, and then the grouting is continuously carried out for 30 min, and the present section grouting is ended.

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