Nano bionic super-hydrophobic modified refuse landfill anti-seepage structure layer and construction method thereof

Abstract

The invention belongs to the technical field of anti-seepage of refuse landfills, and particularly discloses a nano bionic super-hydrophobic modified refuse landfill anti-seepage structural layer and a construction method thereof. The anti-seepage structure comprises a base, a hydrophobic modified red layer soft rock main anti-seepage layer, a wax emulsion hydrophobic spraying surface layer, a non-woven geotechnical cloth protection layer, a geotechnical composite drainage net and a gravel flow guide layer which are sequentially arranged in a stacked mode from bottom to top. The hydrophobic modified red layer soft rock main impermeable layer comprises a lower impermeable layer and an upper impermeable layer; each of the lower impermeable layer and the upper impermeable layer contains a hydrophobic modifier and red-layer soft rock aggregate, and the upper impermeable layer also contains gravel; and the upper surface of the upper impermeable layer is a rough surface formed by napping treatment. Red layer soft rock is synergistically modified on the basis of various materials, a main anti-seepage layer with dewatering and densification as the core is formed, a surface hydrophobic film and a drainage diversion system are compounded, and a multi-layer and multi-barrier efficient anti-seepage system is constructed.

Description

Technical Field

[0001] This invention belongs to the field of landfill seepage prevention technology, specifically relating to a nano-biomimetic superhydrophobic modified landfill seepage prevention structural layer and its construction method. Background Technology

[0002] Landfills are one of the main methods for the final disposal of municipal solid waste, and their core environmental risk lies in the pollution of surrounding soil and groundwater caused by leachate leakage. Therefore, constructing an efficient, durable, and economical anti-seepage system is crucial for the safe operation of landfills. Currently, there are three main types of anti-seepage systems commonly used in landfills: single-layer compacted clay layer (CCL), high-density polyethylene membrane (HDPE membrane), and high-density polyethylene membrane (HDPE membrane).

[0003] Single-layer compacted clay (CCL) has low construction costs and clay has a certain degree of low permeability. However, it has high requirements for raw materials, is significantly limited by geographical location, and is prone to deterioration and cracking in long-term corrosive environments such as landfill leachate, acids, and alkalis, leading to seepage prevention failure.

[0004] Bentonite waterproof blankets (GCLs) are made by the expansion of bentonite when it comes into contact with water to form a waterproof layer. However, in environments with salt water or acidic leachate, the expansion capacity decreases, the waterproof performance weakens, and it is prone to failure due to localized cracking or pinhole defects.

[0005] High-density polyethylene (HDPE) membranes have good seepage prevention effects, but construction requirements are high. They require a very high degree of flatness of the base layer. The membrane material is easily damaged by sharp debris or construction machinery, making repair difficult. Furthermore, there is a high risk of leakage at the interface between the membrane and the soil, and long-term stress cracking is a prominent problem. Once damaged, the seepage prevention function is completely lost.

[0006] Existing technologies also include studies on using chemical agents to modify soil to improve its impermeability or stability, such as using sodium silicate solution or cement for solidification. However, these methods often suffer from problems such as limited modification effects, insufficient durability, increased brittleness leading to cracking, or poor cost-effectiveness, failing to meet the long-term safe impermeability requirements of landfills.

[0007] Therefore, developing a composite seepage-proof structure based on existing materials, with low cost, excellent seepage-proof performance, stable mechanical properties, and long-lasting hydrophobic properties to replace or partially replace traditional HDPE liners has significant engineering value and environmental significance. Summary of the Invention

[0008] In view of the above-mentioned problems, this invention provides a nano-bionic superhydrophobic modified landfill seepage prevention structure layer and its construction method. This invention is based on the synergistic modification of red bed soft rock with multiple materials to form a main seepage prevention layer with hydrophobicity and densification as its core, and incorporates a composite surface hydrophobic membrane and drainage diversion system to construct a multi-layered, multi-barrier, and highly efficient seepage prevention system.

[0009] To address the aforementioned problems, this invention provides a nano-bionic superhydrophobic modified landfill seepage prevention structure layer, comprising a base, a hydrophobic modified red bed soft rock main seepage prevention layer, a wax emulsion hydrophobic sprayed surface layer, a non-woven geotextile protective layer, a geotextile composite drainage net, and a crushed stone diversion layer, stacked sequentially from bottom to top; the hydrophobic modified red bed soft rock main seepage prevention layer includes a lower seepage prevention layer and an upper seepage prevention layer; both the lower and upper seepage prevention layers contain hydrophobic modifiers and red bed soft rock aggregates, and the upper seepage prevention layer also contains crushed stone; the upper surface of the upper seepage prevention layer is a rough surface formed by roughening treatment.

[0010] It should be noted that the core function of the nonwoven geotextile protective layer of this invention is protection, specifically: preventing the upper gravel drainage layer from puncturing or abrading the lower wax film and impermeable layer under load. The core function of the geotextile composite drainage net of this invention is drainage, specifically: actively collecting and quickly discharging trace amounts of leachate or gas that may permeate the main impermeable layer, eliminating the hydrostatic pressure behind it. This invention significantly enhances durability through the combination of "impermeability + drainage + protection".

[0011] Through the above technical solution, the present invention significantly improves the resistance to landfill leachate corrosion, and the multi-layer hydrophobic spatial structure has regenerative capabilities.

[0012] Preferably, the nonwoven geotextile protective layer has a raised center, and its surface slope from the highest point in the center to the lowest point around the perimeter is not less than 2%.

[0013] Preferably, the geotextile drainage net is a biaxially stretched geotextile drainage net, with its core grooves having the same water-conducting direction as the slope direction. This is to ensure that leachate is rapidly guided along the slope direction, avoiding localized accumulation and improving long-term drainage efficiency.

[0014] Based on the same inventive concept, the present invention also provides a construction method for any of the above-mentioned seepage-proof structural layers, comprising the following steps:

[0015] S1. After leveling and compacting the foundation, low-permeability clay is laid using a layered compaction method to obtain the base.

[0016] S2. The hydrophobic modified mixture is spread and compacted to obtain the lower impermeable layer; the hydrophobic modified mixture and clean crushed stone are mixed evenly, spread and compacted, and then the compacted surface is roughened to obtain the upper impermeable layer; the upper and lower impermeable layers are cured and left to dry to obtain the hydrophobic modified red bed soft rock main impermeable layer; wherein, according to the mass percentage, the hydrophobic modified mixture includes: red bed soft rock 75-85%, fly ash 8-12%, sodium methylsilicate 1-2%, nano silica 0.5-1.0%, basalt fiber 0.1-0.3%, and the balance is water.

[0017] S3. A wax emulsion with a solid content of 35-45% is uniformly sprayed in multiple layers onto the hydrophobic modified red soft rock main seepage barrier layer and dried on the surface to obtain a hydrophobic sprayed surface layer of wax emulsion; a polyester filament nonwoven geotextile is laid on the hydrophobic sprayed surface layer of wax emulsion based on the manual roller laying method to obtain a nonwoven geotextile protective layer.

[0018] S4. Lay a biaxially stretched geotextile composite drainage net on the non-woven geotextile protective layer, and make its core groove consistent with the slope direction of the non-woven geotextile protective layer to obtain a geotextile composite drainage net; lay crushed stone on the geotextile composite drainage net, and use a light vibratory roller with a self-weight of no more than 10 tons to perform static compaction 1-2 times to obtain a crushed stone diversion layer.

[0019] Preferably, the compaction degree of the rolling tamping / layer rolling / compaction is not less than 95%.

[0020] Preferably, in step S1, the low-permeability clay is silty clay with a plasticity index of 15-20; and the loose thickness of each layer of the layered compaction is 20-25 cm.

[0021] Preferably, in step S2, the preparation method of the hydrophobic modifier includes the following steps: placing nano-silica and fly ash in a high-speed mixer and mixing them evenly; then adding sodium methylsilicate and water, and mixing them evenly to form a slurry; then adding basalt fiber, and mixing until the basalt fiber is evenly dispersed to obtain the hydrophobic modifier; wherein the basalt fiber is 3-7mm short-cut basalt fiber.

[0022] Preferably, in step S2, the mass of the hydrophobic modifier is 11-20% of the mass of the red bed soft rock aggregate; the maximum particle size of the red bed soft rock aggregate does not exceed 50mm; the water content in the mixture of the upper and lower impermeable layers is 1-4wt%; the particle size of the clean crushed stone is 5-10mm, and the volumetric content of the clean crushed stone is 5-10% of the red bed soft rock aggregate.

[0023] Preferably, in step S3, the two spraying directions are perpendicular to each other, and after each spraying, the surface is allowed to dry before the next spraying is performed; the areal density of the polyester filament nonwoven geotextile is not less than 600 g / m².2 Adjacent polyester filament nonwoven geotextiles are connected by an overlapping method, with an overlap width of 30-50cm.

[0024] Preferably, the overlap width of adjacent biaxially stretched geotextile drainage nets is not less than 10cm; the crushed stone has a particle size of 20-40mm.

[0025] The synergistic effect and hydrophobication mechanism of nano-SiO2 and sodium methylsilicate in the hydrophobic modifier of this invention:

[0026] Sodium methylsilicate (CH3NaO3Si) hydrolyzes to generate active silanol (Si-OH), and the surface of nano-SiO2 itself also has abundant hydroxyl groups. Through a condensation reaction, the two form a dense silicon-oxygen bond network on the particle surface. Nano-SiO2 can act as a nucleation center, promoting the polymerization and gelation of silicic acid. This polymerization reaction can form a strong Si-O-Si covalent bond network structure between particles and on the particle surface. This structure can effectively block the penetration of water molecules, thereby improving the hydrophobic properties of the material.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) The nano-SiO2 of the present invention has a high specific surface area and an active surface. The large number of silanols on its surface provide abundant reaction sites for the hydrolysis products (silanols) of sodium methylsilicate. This not only promotes the formation of the Si-O-Si network and significantly accelerates the hydrophobic reaction process, but also makes the formed gel network structure more compact and uniform. This structure can reduce the exposure of hydrophilic functional groups on the surface of red bed soft rock materials and further improve the hydrophobic properties.

[0029] (2) The sodium methylsilicate of the present invention provides a stable alkaline environment for the system, effectively activating the active SiO2 and Al2O3 in fly ash. These active components undergo a pozzolanic reaction and react with Ca in the system. 2+ (From the soft rock itself or external sources) hydration products such as hydrated calcium silicate (CSH) gel and hydrated calcium aluminate (CAH) are generated through reactions. These products interpenetrate with organic-inorganic hybrid networks, forming interpenetrating polymer-cement structure, which improves compactness and mechanical properties. Fly ash, as an excellent fine-particle material, has spherical, fine-grained particles. These smooth spherical particles have a physical filling effect in the mixture, which can effectively improve the uneven particle size distribution of coarse particles, make the packing structure more compact, improve compaction, and further reduce porosity.

[0030] (3) The uniformly dispersed short-cut basalt fibers of the present invention form a three-dimensional random reinforcing network in the compacted modified soft rock. When the soft rock is subjected to tension or compression and microcracks are generated, the high tensile strength fibers can cross the two ends of the crack and transfer and disperse the stress through the interfacial bonding force between them and the soft rock, thus consuming the fracture energy. This process effectively inhibits the initiation, propagation and penetration of cracks, transforming the brittle failure before modification into the ductile failure after modification, thereby enhancing the crack resistance and overall stability of the impermeable layer under the condition of uneven settlement in the landfill.

[0031] (4) In this invention, crushed stone aggregate with a particle size of 5–10 mm is incorporated into the modified material of the upper impermeable layer during mixing. After compaction, the surface is roughened to form a rough, hard surface structure rich in micro-protrusions. While maintaining impermeability, this layer constructs a structure that facilitates the mechanical bonding and penetration of the wax emulsion, thereby improving the adhesion and durability of the surface film. The wax emulsion partially fills the pits between the micro-protrusions on the surface, thus naturally forming a series of stable transverse micro-channels embedded in the impermeable layer body.

[0032] (5) The hydrophobic groups (long-chain alkyl groups) in the wax emulsion of this invention can combine with the hydroxyl groups on the surface of red bed soft rock minerals through physical adsorption or chemical reaction to form a stable hydrophobic film, significantly reducing surface energy and water absorption. The wax emulsion can penetrate into the micropores and microcracks on the surface of red bed soft rock to form a continuous and dense film layer, blocking water penetration. The wax emulsion film has low surface energy and is not easy to adsorb pollutants such as organic matter and heavy metals in landfill leachate, reducing the risk of pollutant accumulation and penetration on the surface. After the surface is treated with wax emulsion, the resistance to microbial erosion is significantly improved, extending the life of the impermeable layer. At the same time, the surface smoothness is improved, promoting leachate drainage. The wax emulsion coated on the surface forms a low surface energy film layer, which combines with the rough interface in the next step to form a hydrophobic-drainage integrated composite surface layer. This provides a solid and stable construction base for the multi-layer structure (geotextile, drainage net) above it. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the nano-bionic superhydrophobic modified landfill seepage prevention structure layer described in Embodiment 1 of the present invention;

[0034] Figure 2 for Figure 1 Enlarged view of part A in the middle

[0035] Figure 3 This is a SEM image of the lower impermeable layer prepared before and after modification of the red bed soft rock aggregate in Example 2 of the present invention.

[0036] Explanation of reference numerals in the attached figures:

[0037] 1. Substrate; 2. Lower impermeable layer; 3. Upper impermeable layer; 4. Hydrophobic wax emulsion spray coating; 5. Non-woven geotextile protective layer; 6. Geocomposite drainage net; 7. Crushed stone diversion layer. Detailed Implementation

[0038] To make the present invention easier to understand, specific embodiments are described below to further illustrate the invention. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical terms used below have the same meaning as understood by those skilled in the art; unless otherwise specified, the raw materials and reagents involved herein can be purchased commercially or obtained by known methods.

[0039] In order to develop a composite seepage-proof structure based on existing materials, with low cost, excellent seepage-proof performance, stable mechanical properties, and long-lasting hydrophobic properties, to replace or partially replace traditional HDPE liners, this invention provides a seepage-proof structure for landfills made of hydrophobically modified red soft rock and its construction method.

[0040] The following examples and comparative models further illustrate this point.

[0041] Example 1

[0042] A nano-biomimetic superhydrophobic modified landfill seepage-proof structural layer, such as Figure 1-2 As shown, the structure includes, in ascending order, a base 1, a hydrophobic modified red bed soft rock main impermeable layer, a wax emulsion hydrophobic sprayed surface layer 4, a non-woven geotextile protective layer 5, a geosynthetic drainage net 6, and a gravel drainage layer 7; the hydrophobic modified red bed soft rock main impermeable layer includes a lower impermeable layer 2 and an upper impermeable layer 3; both the lower and upper impermeable layers contain hydrophobic modifiers and red bed soft rock aggregates, and the upper impermeable layer also contains gravel; the upper surface of the upper impermeable layer is a rough surface formed by roughening. The non-woven geotextile protective layer has a raised center, and its surface slope from the highest point in the center to the lowest point around the perimeter is 2%. The geosynthetic drainage net is a biaxially stretched geosynthetic drainage net, whose core groove ( Figure 2 The direction of water flow is consistent with the direction of the slope.

[0043] Example 2

[0044] A nano-bionic superhydrophobic modified landfill seepage-proof structural layer ( Figure 1 The preparation method of ) includes the following steps:

[0045] (1) Level, clean and compact the site to a compaction degree of 95%; lay silty clay with a plasticity index of 18, compact in layers, each layer with a loose thickness of 22cm, and compact 6 times with a 20t vibratory roller to a compaction degree of 0.95 to obtain the base.

[0046] (2) According to the mass percentage, 0.8% nano-silica and 12% fly ash were placed in a high-speed mixer and dry-mixed for 5 minutes. Then, 2% sodium methylsilicate and 10% water were added, and the mixture was stirred for 30 minutes to form a uniform slurry. Finally, 0.2% short-cut basalt fibers with a length of 6 mm were added, and the mixture was stirred for 5 minutes until the fibers were evenly dispersed to obtain a hydrophobic modifier.

[0047] (3) The above-mentioned hydrophobic modifier and 75% of air-dried red bed soft rock aggregate (maximum particle size 50mm, 1t) are placed in a mixer and stirred for 8 minutes until the mixture is uniform and free of white flocs; it is then transported to the working surface (base), spread and leveled, and the loose layer thickness is controlled to be 25cm; static compaction is performed using a vibratory roller, with a compaction degree of 95%, to obtain the lower impermeable layer; wherein, the mass of the hydrophobic modifier is 20% of the mass of the red bed soft rock aggregate;

[0048] (4) Put the above-mentioned hydrophobic modifier, crushed stone (particle size 5-10mm) and 1t of air-dried red bed soft rock aggregate (maximum particle size 50mm) into a mixer and mix for 8 minutes until they are evenly mixed; transport it to the working surface (lower impermeable layer), spread it evenly and control the loose layer thickness to 10cm; use a vibratory roller for static compaction with a compaction degree of 95%; avoid over-vibration during rolling to prevent the upper crushed stone aggregate from being pressed into the lower compacted layer; after compaction, use a special roughening equipment to roughen the compacted surface to form a rough interface with a depth of about 5mm to enhance the interlayer bonding and obtain the upper impermeable layer; wherein, the volume of crushed stone is 8% of the red bed soft rock aggregate, and the mass of hydrophobic modifier is 20% of the mass of red bed soft rock aggregate;

[0049] (5) The upper and lower impermeable layers are uniformly cured and left to dry for no less than 24 hours. During this period, avoid rain and sun exposure to obtain the hydrophobic modified red soft rock main impermeable layer.

[0050] (6) A wax emulsion with a solid content of 40% is uniformly sprayed onto the hydrophobically modified red soft rock main seepage barrier layer using a high-pressure spray system (output pressure 0.6 MPa). The emulsion is applied in three coats, with each coat applied at a rate of 5 kg / m². 2 The spraying directions are perpendicular to each other, with each coat allowed to dry naturally for 1 hour, ultimately forming a hydrophobic wax emulsion spray coating layer with a thickness of approximately 0.3 mm. A surface density of 600 g / m² is then laid on top of this hydrophobic wax emulsion spray coating layer using a manual roller application method. 2A nonwoven geotextile protective layer with a slope (slope from the highest point in the center to the lowest point around the perimeter) of 2% is obtained by using polyester filament nonwoven geotextile (overlap width 30cm).

[0051] (7) Lay a biaxially stretched geotextile composite drainage net (water conductivity ≥ 0.5 cm) on the nonwoven geotextile protective layer. 2 / s), and make its core slot ( Figure 2 The slope direction is consistent with that of the non-woven geotextile protective layer to obtain a geotextile composite drainage net (overlap width is 15cm); crushed stone (particle size 20-40mm, thickness 30cm) is laid on the geotextile composite drainage net, and static compaction is carried out once using a light vibratory roller with a self-weight of 8 tons to obtain a crushed stone diversion layer with a diversion slope of 2%.

[0052] Example 3

[0053] The difference between this comparative example and Example 2 is that the content of sodium methylsilicate in silica is different (the content of sodium methylsilicate is 1.0%). Other steps and parameters are the same as in Example 2.

[0054] Example 4

[0055] The difference between this embodiment and Embodiment 2 is that the fly ash content is different (the fly ash content is 12%). Other steps and parameters are the same as in Embodiment 2.

[0056] Comparative Example 1

[0057] The difference between this comparative example and Example 2 is that the hydrophobic modifier contains only 2% sodium methylsilicate and 98% water. Other steps and parameters are the same as in Example 2.

[0058] Comparative Example 2

[0059] The difference between this comparative example and Example 2 is that the hydrophobic modifier contains only 2% sodium methylsilicate, 0.8% nano-silica, and 97.8% water. Other steps and parameters are the same as in Example 2.

[0060] Comparative Example 3

[0061] The difference between this comparative example and Example 2 is that the hydrophobic modifier contains only 2% sodium methylsilicate, 12% fly ash, and 86% water. Other steps and parameters are the same as in Example 2.

[0062] Comparative Example 4

[0063] The difference between this comparative example and Example 2 is that the hydrophobic modifier contains only 2% sodium methylsilicate, 0.8% nano silica, 12% fly ash, and 86% water. Other steps and parameters are the same as in Example 2.

[0064] Comparative Example 5

[0065] The difference between this comparative example and Example 2 is that the hydrophobic modified red soft rock main impermeable layer is replaced with an HDPE membrane. Other steps and parameters are the same as in Example 2.

[0066] Comparative Example 6

[0067] The difference between this comparative example and Example 2 is that the upper and lower impermeable layers have the same composition (i.e., no crushed stone is added to the upper impermeable layer). Other steps and parameters are the same as in Example 2.

[0068] Performance testing and results analysis:

[0069] The microstructure images of the lower impermeable layer prepared from the air-dried red bed soft rock aggregate of Example 2 before and after modification with a hydrophobic modifier are shown below. Figure 3 As shown. By Figure 3 It can be seen that the lower impermeable layer prepared before the modification of the red bed soft rock aggregate still has a large number of interconnected pores and microcracks between the sheet-like structures on a microscopic scale; the lower impermeable layer prepared after the modification of the red bed soft rock aggregate has the original macroscopic pores and microcracks filled with a large number of products, and the CSH gel generated by the fly ash hydration products forms bridging between particles, and a capping layer formed by the deposition of hydrophobic groups can also be seen in some areas.

[0070] The permeability coefficient (k), contact angle, and unconfined compressive strength of the composite seepage-proof structures prepared in Examples 2-4 and Comparative Examples 1-6 are shown in Table 1.

[0071] Table 1: ; Note: In the table above, " "Indicates that the permeability coefficient is extremely low when initially intact (k = 1.0 × 10⁻⁶)" -12 (cm / s), but k increases significantly after being punctured by a sharp object or stress cracking, causing hydrophobicity to fail and making it very sensitive to defects / damage; "This indicates that when HDPE film is replaced, the main load-bearing capacity is borne by the underlying soil. The measured unconfined compressive strength is 1.44 MPa, which is only used as a reference for engineering comparison."

[0072] As shown in Table 1, comparing Example 2 and Comparative Example 1, the permeability coefficient k of Example 2 is two orders of magnitude lower than that of Comparative Example 1, the contact angle is much higher, and the unconfined compressive strength is significantly higher than that of Comparative Example 1 (1.6 MPa). This indicates that using sodium methylsilicate alone (Comparative Example 1) can only form a small amount of hydrophobic film on the particle surface, lacking filling and cementing effects, resulting in ineffective densification of the pore structure and insufficient hydrophobicity and mechanical strength. In contrast, Example 2 generates an organic-inorganic network through the condensation reaction of nano-SiO2–sodium methylsilicate, with the pozzolanic reaction products of fly ash filling the pores. Combined with the bridging effect of fibers, a dense and tough structure is constructed, thereby achieving superhydrophobicity and high strength.

[0073] As shown in Table 1, comparing Example 2 and Comparative Example 2, the permeability coefficient of Example 2 is an order of magnitude lower than that of Comparative Example 2, the contact angle is significantly higher, and the unconfined compressive strength is also higher. This indicates that Comparative Example 2, containing sodium methylsilicate and nano-SiO2, can undergo a condensation reaction to form a certain network structure. However, due to the lack of secondary hydration reaction of fly ash, the pores are not fully filled, resulting in insufficient overall density, leading to a higher permeability coefficient and limited hydrophobicity. In Example 2, the addition of fly ash generates a large amount of C–S–H gel that interpenetrates with the network structure, significantly improving both density and strength.

[0074] As can be seen from the comparison between Example 2 and Comparative Example 3 in Table 1, the permeability coefficient of Example 2 is lower than that of Comparative Example 3, the contact angle is higher than that of Comparative Example 3, and the unconfined compressive strength is higher than that of Comparative Example 3. Note: Comparative Example 3 contains fly ash and sodium methylsilicate, which can produce a certain degree of cementation, but lacks the participation of nano-SiO2, resulting in insufficient condensation reaction. The hydrophobic groups are difficult to firmly anchor on the framework, and the formed hydrophobic film is unstable.

[0075] As shown in Table 1, comparing Example 2 and Comparative Example 4, Example 2 has a lower permeability coefficient, a higher contact angle, and a higher unconfined compressive strength than Comparative Example 4. This indicates that Comparative Example 4, which contains sodium methylsilicate, nano-SiO2, and fly ash, can form a certain composite structure, but lacks the reinforcing and bridging effect of basalt fibers, making crack propagation easier and resulting in insufficient mechanical properties. In Example 2, the fibers cross the microcracks, changing the failure mode to ductile failure, and significantly improving both strength and durability.

[0076] As shown in Table 1, comparing Example 2 and Comparative Example 5, the HDPE membrane (Comparative Example 5) exhibits an extremely low bulk permeability coefficient in its intact state, superior to Example 2. However, after being punctured or stress-cracking, it immediately loses its seepage-proof function, with a contact angle of approximately 95°, lower than the 124° of Example 2. Referring to the unconfined compressive strength data of the HDPE membrane, it is clear that the system's bearing capacity is largely borne by the underlying soil, and the unconfined compressive strength is significantly lower than that of Example 2. This indicates that although the HDPE membrane has extremely strong initial seepage-proof capability, it is extremely sensitive to defects. Once damaged, its performance drops sharply, and its mechanical bearing capacity becomes insufficient.

[0077] As shown in Table 1, comparing Example 2 and Comparative Example 6, Example 2 has a lower permeability coefficient, a higher contact angle, and a higher unconfined compressive strength than Comparative Example 6. This indicates that the upper and lower impermeable layers in Comparative Example 6 have the same composition, lacking the upper rough-aggregate composite design, resulting in insufficient surface reinforcement, easily interconnected pore structures, and insufficient mechanical strength. Example 2, through layered design and a rough interface to enhance interlayer bonding, and by introducing crushed stone aggregate, constructs a composite structure with both superhydrophobic and drainage functions, thus exhibiting superior impermeability and mechanical properties compared to Comparative Example 6.

[0078] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A nano-biomimetic superhydrophobic modified landfill seepage-proof structural layer, characterized in that, The system comprises, in ascending order, a base layer, a hydrophobic modified red bed soft rock main impermeable layer, a wax emulsion hydrophobic sprayed surface layer, a non-woven geotextile protective layer, a geotextile composite drainage net, and a crushed stone diversion layer; the hydrophobic modified red bed soft rock main impermeable layer includes a lower impermeable layer and an upper impermeable layer; both the lower and upper impermeable layers contain hydrophobic modifiers and red bed soft rock aggregates, and the upper impermeable layer also contains crushed stone; the upper surface of the upper impermeable layer is a rough surface formed by roughening treatment.

2. The nano-biomimetic superhydrophobic modified landfill seepage-proof structural layer according to claim 1, characterized in that, The nonwoven geotextile protective layer has a raised center, and its surface slope from the highest point in the center to the lowest point around the perimeter is not less than 2%.

3. The nano-biomimetic superhydrophobic modified landfill seepage-proof structural layer according to claim 2, characterized in that, The geotextile composite drainage net is a biaxial tensile geotextile composite drainage net, and the water guiding direction of its core groove is consistent with the slope direction.

4. The construction method of the seepage-proof structural layer according to any one of claims 1-3, characterized in that, Includes the following steps: S1. After leveling and compacting the foundation, low-permeability clay is laid using a layered compaction method to obtain the base. S2. The hydrophobic modified mixture is spread and compacted to obtain the lower impermeable layer; the hydrophobic modified mixture and clean crushed stone are mixed evenly, spread and compacted, and then the compacted surface is roughened to obtain the upper impermeable layer; the upper and lower impermeable layers are cured and left to dry to obtain the hydrophobic modified red bed soft rock main impermeable layer; wherein, according to the mass percentage, the hydrophobic modified mixture includes: red bed soft rock 75-85%, fly ash 8-12%, sodium methylsilicate 1-2%, nano silica 0.5-1.0%, basalt fiber 0.1-0.3%, and the balance is water; S3. A wax emulsion with a solid content of 35-45% is uniformly sprayed in multiple layers onto the hydrophobic modified red soft rock main seepage barrier layer and dried on the surface to obtain a hydrophobic sprayed surface layer of wax emulsion; a polyester filament nonwoven geotextile is laid on the hydrophobic sprayed surface layer of wax emulsion based on the manual roller laying method to obtain a nonwoven geotextile protective layer. S4. Lay a biaxially stretched geotextile composite drainage net on the non-woven geotextile protective layer, and make its core groove consistent with the slope direction of the non-woven geotextile protective layer to obtain a geotextile composite drainage net; lay crushed stone on the geotextile composite drainage net, and use a light vibratory roller with a self-weight of no more than 10 tons to perform static compaction 1-2 times to obtain a crushed stone diversion layer.

5. The construction method according to claim 4, characterized in that, The compaction degree of the rolling tamping / layer rolling / compaction shall not be less than 95%.

6. The construction method according to claim 4, characterized in that, In step S1, the low-permeability clay is silty clay with a plasticity index of 15-20; the loose thickness of each layer of the layered compaction is 20-25cm.

7. The construction method according to claim 4, characterized in that, In step S2, the preparation method of the hydrophobic modifier includes the following steps: placing nano-silica and fly ash in a high-speed mixer and mixing them evenly; then adding sodium methylsilicate and water, and mixing them evenly to form a slurry; then adding basalt fiber, and stirring until the basalt fiber is evenly dispersed to obtain the hydrophobic modifier; wherein the basalt fiber is 3-7mm short-cut basalt fiber.

8. The construction method according to claim 4, characterized in that, In step S2, the mass of the hydrophobic modifier is 11-20% of the mass of the red bed soft rock aggregate; the maximum particle size of the red bed soft rock aggregate does not exceed 50mm; the water content in the mixture of the upper and lower impermeable layers is 1-4wt%; the particle size of the clean crushed stone is 5-10mm, and the volumetric content of the clean crushed stone is 5-10% of the red bed soft rock aggregate.

9. The construction method according to claim 4, characterized in that, In step S3, the two spraying directions are perpendicular to each other. After each spraying, the surface is allowed to dry before the next spraying is performed. The areal density of the polyester filament nonwoven geotextile is not less than 600 g / m². 2 Adjacent polyester filament nonwoven geotextiles are connected by an overlapping method, with an overlap width of 30-50cm.

10. The construction method according to claim 4, characterized in that, In step S4, the overlap width of adjacent biaxial tensile geotextile drainage nets shall not be less than 10cm; the crushed stone shall have a particle size of 20-40mm.

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