Barrier method for combined pollution of deep leakage of landfill

Abstract

The invention relates to underground engineering, in particular to a blocking method for combined pollution of deep leakage of a landfill. Aiming at two working conditions of'rock entering after trepanning 'and'upper unconsolidated formation + lower bedrock', a single high-pressure grouting curtain or a combination of an upper stirring curtain and a same-hole bedrock grouting curtain is adopted respectively: firstly stirring in situ in the unconsolidated formation and inserting a guide sleeve, pulling out to form a guide hole after initial setting, then drilling into the bedrock, sealing the hole by a grouting plug at an orifice, and then performing high-pressure grouting. And the adjacent unit amplitude diffusers are in lap joint to form continuous vertical obstruction. Stirring, hole forming, grouting and filling are completed at the same hole site, equipment is conventional, waste slurry is little, the manufacturing cost is low, a deep layer leakage channel is effectively cut off, and pollutant diffusion is blocked.

Description

Technical Field

[0001] This invention relates to underground engineering, and more particularly to waterproofing and seepage prevention technology for complex strata, specifically a method for preventing deep seepage and complex pollution in landfills. Background Technology

[0002] Setting up vertical barrier curtains around solid waste landfills is a common method to cut off deep seepage and control the spread of complex groundwater pollution. For typical sites with a "soil above rock" structure, where the upper part is a loose Quaternary layer and the lower part is karst-developed or fractured bedrock, the curtain must penetrate both the loose layer and the bedrock and meet the design requirement of being continuous and without gaps.

[0003] Existing construction approaches can be categorized into two types: Full-depth replacement method The method involves using a grab bucket, twin-wheel milling machine, or interlocking piles to excavate deep into the bedrock in a single pass, followed by backfilling with a bentonite-cement mixture. This method is reliable in purely loose layers, but when encountering saturated sand, pebbles, or bedrock, the tool wear becomes severe, the trenching speed drops drastically, and a large amount of mud is required for wall protection, multiplying the cost per linear meter. Furthermore, the width of karst fissures is often smaller than the drill bit thickness, making it easy for the trench wall to "hang," resulting in localized gaps in the curtain and the formation of preferential seepage channels later on.

[0004] Single high-pressure grouting method To avoid deep trench excavation, engineers often directly drill through loose layers and bedrock, followed by high-pressure grouting, attempting to create a continuous, overlapping "column-slab" curtain wall. However: In loose layers, excessive grouting pressure can easily cause splitting and uplift, resulting in damage to adjacent linings or guide layers. In bedrock, the fissures are small and the water head is high, so the effective diffusion radius of ordinary cement grout is insufficient, often resulting in the phenomenon of "not being able to be injected or not being able to be sealed tightly". Due to the significant differences in injectability between soil and rock layers, a single parameter cannot be adequately considered, often resulting in the phenomenon of "grout leakage in the upper part and inability to inject into the lower part," making it difficult to guarantee the overall uniformity and impermeability of the curtain.

[0005] Current technologies have not yet provided economical, reliable, and one-time construction methods for two different geological conditions: "full-section rock penetration" and "soil above rock." This has led to a dilemma for deep vertical curtain walls in complex geological landfills: "high cost of excavation and replacement, and uncontrollable single grouting." Therefore, there is an urgent need for a new method that is layered and adaptable, simple in process, uses conventional equipment, and is economical in materials, in order to significantly reduce project costs and construction risks while ensuring seepage prevention performance. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned defects and propose a method for blocking deep seepage and complex pollution in underground landfills with complex strata.

[0007] To achieve the above objectives, the present invention is implemented as follows: A method for containing deep seepage and complex pollution in landfills involves forming a continuous vertical barrier curtain using two different approaches based on the geological conditions revealed by boreholes: (a) Geological conditions where drilling directly enters the rock: a) Drill holes along the design axis to the control depth using a drilling rig; b) Clean the bottom and walls of the hole; c) After installing the grouting plug at the borehole and sealing it with pressure, high-pressure grouting is injected into the bedrock fissures to form a grouting curtain; d) After grouting is completed, the cavity is filled to finish a single curtain wall; (II) Geological conditions of the upper loose strata and the lower bedrock: a) Along the design axis, cement-based curing agent is first mixed in situ in the upper loose layer using a mixing process to form a mixing curtain, with the mixing depth extending below the bedrock surface; b) Before the initial setting of the mixing curtain, insert a removable guide sleeve at its center, with the lower end of the sleeve extending below the bedrock surface; c) After the stirring curtain has initially solidified, pull out the guide sleeve to obtain continuous guide holes; d) Drill down through the pilot hole into the bedrock to the designed resistance depth, and clean the bottom and walls of the hole; e) After installing a grouting plug at the borehole opening in the bedrock and applying pressure to seal the borehole, high-pressure grouting forms a grouting curtain; f) After grouting is completed, the cavity is filled, and a composite pollution barrier curtain consisting of "mixing curtain + grouting curtain" is finally obtained in the upper loose layer and the lower bedrock. Adjacent unit sections are constructed in accordance with method (i) or (ii) above and overlap each other to form a continuous deep-seepage composite pollution barrier curtain along the perimeter of the landfill.

[0008] In the above-mentioned method for blocking deep seepage and complex pollution in landfills, in method (ii), the bottom end of the mixing curtain extends below the bedrock surface to ensure that the mixing section and the subsequent grouting section are connected at the bedrock surface.

[0009] In the above-mentioned method for blocking deep seepage and complex pollution in landfills, in method (ii), the lower end of the guide sleeve enters below the bedrock surface to ensure that the center of the guide hole is aligned with the center of the mixing curtain.

[0010] In both Method (I) and Method (II) of the above-mentioned methods for blocking deep seepage and complex pollution in landfills, after the grouting plug is installed, "pressure sealing" is performed, and the sealing pressure is maintained until the grouting is completed to prevent the grout from flowing back along the borehole wall.

[0011] In the above-mentioned method for blocking deep seepage and complex pollution in landfills, in method (ii), the guide sleeve is pulled out after the initial setting of the mixing curtain to ensure that the guide hole wall stands upright and does not collapse.

[0012] The above-mentioned method for blocking deep seepage and complex pollution in landfills involves constructing adjacent unit sections in the same manner (I) or (II), so that the curtains overlap continuously in the axial direction.

[0013] In the above-mentioned method for blocking deep seepage and complex pollution in landfills, in step b) of method (II), the guide sleeve is inserted before initial setting and removed after initial setting, and both insertion and removal are completed using the original winch system of the mixing pile machine, without the need for additional drilling.

[0014] In the above-mentioned method for blocking deep seepage and complex pollution in landfills, in step d) of method (II), drilling continues along the center of the guide hole to ensure that the bedrock borehole is coaxial with the upper mixing curtain and to avoid curtain misalignment.

[0015] In both Method (I) and Method (II), the above-mentioned methods for blocking deep seepage and complex pollution in landfills involve high-pressure grouting after "installing a grouting plug at the bedrock borehole and applying pressure to seal the borehole," so that the grouting pressure acts directly on the bedrock fissures and reduces the backflow of grout along the borehole.

[0016] In the above-mentioned method for blocking deep seepage and complex pollution in landfills, in method (ii), the mixing curtain adopts one of "single-axis, multi-axis or milling mixing", and the mixing sinking and lifting are completed in one go without repeated spraying to prevent excessive cutting from causing the diameter to expand.

[0017] This invention addresses two typical seepage scenarios: "full-penetration into bedrock" and "soil above, bedrock below," providing two curtain-forming paths: "single-hole high-pressure grouting" and "upper mixing-lower simultaneous grouting." Utilizing the same vertical borehole, the loose layer is first mixed in situ. After initial setting and pipe extraction, the drilling extends directly into the bedrock. A single high-pressure grouting is performed after sealing the borehole with a grout plug, forming a continuous, overlapping vertical barrier curtain. The entire process requires only conventional mixing pile machines and geological drilling rigs, eliminating the need for large milling equipment. It minimizes grout waste, shortens the construction period, and significantly reduces project costs. Simultaneously, it ensures the simultaneous sealing of deep bedrock fissures and seepage channels in the loose layer, achieving long-term control of complex pollution.

[0018] Compared to traditional methods like "full-section milling and replacement" or "high-pressure grouting of the entire borehole," this invention treats two typical leakage scenarios—"entering the entire bedrock" and "soil above rock"—separately. For pure bedrock sections, only one high-pressure grouting is performed after drilling, with the borehole plug sealed. For the upper loose layer, on-site mixing is used, and a guide sleeve is left in the center. After initial setting, the sleeve is pulled out to form a coaxial guide hole. Drilling continues into the bedrock, and grouting is completed in the same hole, achieving "one hole for two uses and connection between upper and lower layers." The entire process does not require large milling machines or large amounts of wall-protecting mud. The equipment is conventional, the amount of waste grout is small, the construction period is short, and the cost is significantly reduced. At the same time, it avoids the defects of traditional replacement methods in hard rock, such as rapid tool wear and easy "hanging" of the trench wall, as well as the defects of single grouting methods, such as "grout flowing through the upper part and not being able to be injected into the lower part." It ensures that the leakage channels of deep bedrock fissures and loose layers are simultaneously sealed by a continuous curtain, thereby achieving the goal of long-term control of complex pollution. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the steps in the first working condition of the present invention. Figure 1 Drilling, cleaning holes.

[0020] Figure 2 This is a schematic diagram of the steps in the first working condition of the present invention. Figure 2 : Grouting of bedrock fissures.

[0021] Figure 3 This is a schematic diagram of the steps in the first working condition of the present invention. Figure 3 : Filling the cavity.

[0022] Figure 4 This is a schematic diagram of the steps in the second working condition of the present invention. Figure 4 : Upper mixing to the required depth (single-axis, multi-axis or milling mixing).

[0023] Figure 5 This is a schematic diagram of the steps in the second working condition of the present invention. Figure 2 Insert the guide sleeve into the mixing layer as required.

[0024] Figure 6 This is a schematic diagram of the steps in the second working condition of the present invention. Figure 3 Remove the guide sleeve before initial setting.

[0025] Figure 7 This is a schematic diagram of the steps in the second working condition of the present invention. Figure 4 Drill the pilot hole to the required depth in the bedrock and clean the hole.

[0026] Figure 8 This is a schematic diagram of the steps in the second working condition of the present invention. Figure 5 : Grouting of bedrock fissures.

[0027] Figure 9 This is a schematic diagram of the steps in the second working condition of the present invention. Figure 6 : Filling the cavity. Figure 10 To invent a construction sequence diagram. Detailed Implementation

[0028] This implementation provides two typical geological conditions, offering two curtain-forming paths: "full rock penetration" and "soil above rock." All operations involve continuous construction of several unit sections along the perimeter axis of the landfill, with adjacent unit sections overlapping to form a continuous vertical barrier curtain perpendicular to the groundwater flow direction. The construction equipment only requires conventional mixing pile machines and geological drilling rigs, without the need for large trenching machines or additional mud systems.

[0029] The specific implementation process is as follows: 1. Geological Exploration: Using a combination of drilling and geophysical exploration, the depth of the bedrock surface, the orientation of fault zones, and the distribution of karst caves will be determined, and the appropriate method (I) or (II) will be adopted for each unit section. Specifically, (a) Geological conditions where drilling directly enters the rock: a) Drill holes along the design axis to the control depth using a drilling rig; b) Clean the bottom and walls of the hole; c) After installing the grouting plug at the borehole and sealing it with pressure, high-pressure grouting is injected into the bedrock fissures to form a grouting curtain; d) After grouting is completed, the cavity is filled to finish a single curtain wall; (II) Geological conditions of the upper loose strata and the lower bedrock: a) Along the design axis, cement-based curing agent is first mixed in situ in the upper loose layer using a mixing process to form a mixing curtain, with the mixing depth extending below the bedrock surface; b) Before the initial setting of the mixing curtain, insert a removable guide sleeve at its center, with the lower end of the sleeve extending below the bedrock surface; c) After the stirring curtain has initially solidified, pull out the guide sleeve to obtain continuous guide holes; d) Drill down through the pilot hole into the bedrock to the designed resistance depth, and clean the bottom and walls of the hole; e) After installing a grouting plug at the borehole opening in the bedrock and applying pressure to seal the borehole, high-pressure grouting forms a grouting curtain; f) After grouting is completed, the cavity is filled, and a composite pollution barrier curtain consisting of "mixing curtain + grouting curtain" is finally obtained in the upper loose layer and the lower bedrock. Adjacent unit sections are constructed in accordance with method (i) or (ii) above and overlap each other to form a continuous deep-seepage composite pollution barrier curtain along the perimeter of the landfill. 2. Equipment preparation: Mixing pile machine: Equipped with single-shaft, multi-shaft or milling mixing functions, it can mix cement-based curing agents in situ; Geological drilling rig: capable of drilling into bedrock, equipped with high-pressure grouting plugs and grouting pumps; Guide sleeve: Seamless steel pipe with an outer diameter matching the diameter of the mixing pile and a tapered seal at the lower end.

[0030] Materials: Cement-based curing agent (P·O 42.5 ordinary Portland cement), water-cement ratio determined by on-site test; grouting slurry is cement-based slurry, no specific ratio is specified, adjusted according to injectability test.

[0031] 3. Implementation Method (I) - Full Rock Penetration Condition Drilling: A geological drilling rig is used to drill along the axis, with a drill bit diameter of 42 mm to 150 mm, until the designed resistance control depth is reached.

[0032] Hole cleaning: Use high-pressure water to flush the bottom and walls of the hole until the water returning to the surface is free of mud and sand.

[0033] Grouting curtain: Grouting plugs are installed at the borehole opening, and after pressure sealing, high-pressure grouting is performed. The grout diffuses in the bedrock fissures or karst caves, and adjacent unit diffusers overlap to form a continuous grouting curtain.

[0034] Sealing: After grouting is completed, cement-based grout is used to fill the cavity up to the opening, completing a single curtain wall.

[0035] 4. Implementation Method (II) – Soil Above Rock Below Working Condition Stirring Curtain: A cement-based curing agent is mixed in situ in the upper loose layer using a mixing pile machine, with the mixing depth extending below the bedrock surface; The mixing, sinking, and lifting are completed in one step, without repeated spraying, to prevent over-cutting; The pile diameter is 0.6 m to 1.0 m, and adjacent unit sections interlock with each other.

[0036] Indwelling guide cannula: Before the initial setting of the mixing pile, a guide sleeve is inserted at the center position, with the lower end extending below the bedrock surface; The casing is pressed in using the winch system of the mixing pile machine, eliminating the need for additional drilling.

[0037] Remove the cannula: After initial setting, the sleeve is pulled out 0.5 h to 1.5 h to form a continuous guide hole with a verticality deviation ≤ 1 / 200.

[0038] Bedrock drilling: Continue drilling along the center of the pilot hole, drilling through the bedrock to the designed resistance depth; Clean the hole with high-pressure water until the return water is clear.

[0039] Grouting curtain: A grouting plug is installed at the borehole opening, and after pressure sealing, high-pressure grouting is performed. The grout diffuses within the bedrock fissures and overlaps with the diffuser body of the adjacent unit to form a continuous grouting curtain.

[0040] Sealing: After grouting is completed, cement-based grout is used to fill the cavity up to the opening, completing a single curtain wall.

[0041] 5. Overlap and Continuity The center-to-center distance between adjacent unit sections is 0.8 m to 1.2 m, ensuring that the mixing curtains interlock ≥200 mm and the grouting curtains overlap horizontally ≥100 mm; Each piece is constructed using the same method (I) or (II) to avoid mixing methods that could lead to joint failure. The top of the curtain is more than 0.5 m above the highest groundwater level, and the bottom is more than 2 m below the bottom lining or the bottom boundary of pollutant diffusion.

[0042] 6. Key Points of Quality Control Coaxiality: The center of the guide sleeve is aligned with the center of the mixing pile, and the deviation of the center of the guide hole after the sleeve is pulled out is ≤1 / 200; Grouting pressure: gradually increase to 0.8 MPa to 10 MPa (with the grout intake rate ≤ 1 L / min for 10 min as the termination condition). Sealing reliability: The grouting plug at the orifice maintains pressure until the grouting is completed to prevent grout backflow; Continuity: The construction interval between adjacent unit sections shall not exceed the initial setting time to ensure that the grout or mixture at the joints is mutually integrated.

[0043] 7. Comparison with traditional solutions Compared to the full-section milling replacement method: it eliminates the need for large milling machines and large amounts of wall-protecting slurry, reduces tool wear, decreases slurry waste, and reduces costs by ≥30%; Compared to the single high-pressure grouting method: the upper loose layer is sealed with a mixing curtain first to avoid the phenomenon of "grout crossing in the upper part and not being able to be injected in the lower part", and the overall uniformity and impermeability of the curtain are significantly improved. The mixing, pipe pulling, drilling, grouting, and filling are all completed at the same vertical hole position, making the process compact and shortening the construction period.

[0044] Construction using the above-described method can create a continuous vertical barrier curtain in one go under two typical geological conditions, effectively cutting off deep seepage channels, reducing the migration and diffusion flux of pollutants, and achieving long-term control of complex groundwater pollution in landfill sites with complex geology.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preventing complex pollution from deep seepage in landfills, characterized in that, Based on the geological conditions revealed by the boreholes, the following two methods are used to form a continuous vertical barrier curtain: (a) Geological conditions where drilling directly enters the rock: a) Drill holes along the design axis to the control depth using a drilling rig; b) Clean the bottom and walls of the hole; c) After installing the grouting plug at the borehole and sealing it with pressure, high-pressure grouting is injected into the bedrock fissures to form a grouting curtain; d) After grouting is completed, the cavity is filled to finish a single curtain wall; (II) Geological conditions of the upper loose strata and the lower bedrock: a) Along the design axis, cement-based curing agent is first mixed in situ in the upper loose layer using a mixing process to form a mixing curtain. The mixing depth is embedded into the bedrock surface by 0.2-1 meters, depending on the test results. b) Before the initial setting of the mixing curtain, insert a removable guide sleeve at its center, with the lower end of the sleeve extending below the bedrock surface; c) After the stirring curtain has initially solidified, pull out the guide sleeve to obtain continuous guide holes; d) Drill down through the pilot hole into the bedrock to the designed resistance depth, and clean the bottom and walls of the hole; e) After installing a grouting plug at the borehole opening in the bedrock and applying pressure to seal the borehole, high-pressure grouting forms a grouting curtain; f) After grouting is completed, the cavity is filled, and a composite pollution barrier curtain consisting of "mixing curtain + grouting curtain" is finally obtained in the upper loose layer and the lower bedrock. Adjacent unit sections are constructed in accordance with method (i) or (ii) above and overlap each other to form a continuous deep-seepage composite pollution barrier curtain along the perimeter of the landfill.

2. The method for preventing complex pollution from deep seepage in landfills according to claim 1, characterized in that, In method (ii), the bottom of the mixing curtain extends below the bedrock surface to ensure that the mixing section and the subsequent grouting section are connected at the bedrock surface.

3. The method for preventing complex pollution from deep seepage in landfills according to claim 1, characterized in that, In method (ii), the lower end of the guide sleeve enters below the bedrock surface to ensure that the center of the guide hole is aligned with the center of the mixing curtain.

4. The method for preventing complex pollution from deep seepage in landfills according to claim 1, characterized in that, In both Method (I) and Method (II), after the grouting plug is installed, "pressure sealing" is performed, and the sealing pressure is maintained until the grouting is completed to prevent the grout from flowing back along the borehole wall.

5. The method for preventing complex pollution from deep seepage in landfills according to claim 1, characterized in that, In method (ii), the guide sleeve is pulled out after the stirring curtain has initially set to ensure that the guide hole wall stands upright and does not collapse.

6. The method for preventing complex pollution from deep seepage in landfills according to claim 1, characterized in that, Adjacent unit panels are constructed in the same manner (I) or (II) to ensure continuous overlap of the curtain in the axial direction.

7. The method for preventing complex pollution from deep seepage in landfills according to claim 1, characterized in that, In step b) of method (ii), the guide sleeve is inserted "before initial setting" and removed "after initial setting", and both insertion and removal are completed using the original winch system of the mixing pile machine, without the need for additional drilling.

8. The method for preventing complex pollution from deep seepage in landfills according to claim 1, characterized in that, In step d) of method (ii), continue drilling along the center of the guide hole to ensure that the bedrock borehole is coaxial with the upper mixing curtain and avoid curtain misalignment.

9. The method for preventing complex pollution from deep seepage in landfills according to claim 1, characterized in that, In both methods (I) and (II), high-pressure grouting is carried out after "installing a grouting plug at the bedrock borehole and applying pressure to seal the borehole", so that the grouting pressure acts directly on the bedrock fissures and reduces the backflow of grout along the borehole.

10. The method for preventing complex pollution from deep seepage in landfills according to claim 1, characterized in that, In method (ii), the stirring curtain adopts one of "single-axis, multi-axis or milling stirring", and the stirring sinking and lifting are completed in one go without repeated spraying to prevent excessive cutting that leads to diameter expansion.

Images