Multifunctional composite lining structure for water delivery channel in cold region and construction method thereof

Abstract

This invention discloses a multifunctional composite lining structure for water conveyance channels in cold regions and its construction method. The composite lining structure includes a phase change heat storage structure disposed between the lining plate and the channel subgrade. This phase change heat storage structure comprises a flexible layered capsule, a plastic phase change heat storage medium, and an electric heating mechanism; the phase change heat storage medium fills the closed cavity of the capsule; the electric heating mechanism is embedded within the phase change heat storage medium. The composite lining structure of this invention not only increases the temperature of the channel subgrade during the freezing period and reduces the freezing depth, but also reduces uneven deformation caused by frost heave. Furthermore, it reduces water seepage into the channel subgrade during the water flow period, lowering the moisture content of the subgrade, thus simultaneously achieving multiple functions such as heat storage, frost heave reduction, and water isolation. This composite lining structure has excellent frost heave prevention effect, and its construction method is simple and easy to operate, showing broad application prospects.

Description

Technical Field

[0001] This invention specifically relates to a multifunctional composite lining structure for water conveyance channels in cold regions and its construction method, belonging to the field of lining channel protection technology. Background Technology

[0002] Water conveyance channels are core structures in large-scale inter-regional water transfer projects, playing an irreplaceable role in ensuring agricultural irrigation, industrial water use, and ecological water replenishment. However, in cold regions, these channels face extreme and complex service challenges. Winters in cold regions last for 4-6 months, with extreme temperatures reaching -40°C. Repeated freeze-thaw cycles induce uneven frost heave deformation in the channel foundation soil. Even with frost heave-resistant foundation design, these channels are still susceptible to long-term effects of uneven frost heave in the foundation soil, ultimately leading to problems such as lining cracking, structural displacement, and even overall collapse. This not only impairs the channel's water conveyance function but also significantly shortens its service life and increases its operation and maintenance costs.

[0003] Meanwhile, to enhance the seepage prevention performance of channels and protect the channel body, a lining structure is usually installed on the channel surface. However, existing lining structures have many problems in cold environments. For example, traditional rigid linings are difficult to adapt to soil frost heave deformation and are prone to cracking and damage; flexible linings, although having a certain degree of deformation adaptability, will gradually reduce their seepage prevention performance under long-term freeze-thaw cycles, and their bonding performance with the channel soil will weaken, resulting in phenomena such as hollowing and peeling. In addition, the thermal insulation performance of channel lining structures in cold regions is insufficient, and they cannot effectively block the impact of low temperatures on the channel soil, further aggravating frost heave damage. Therefore, it is urgent to develop a channel and lining structure suitable for cold environments to solve the problems of poor durability and high maintenance costs of existing technologies under extreme climatic conditions. Summary of the Invention

[0004] The main objective of this invention is to provide a multifunctional composite lining structure and its construction method for water conveyance channels in cold regions. By using a phase change heat storage structure to increase the temperature of the foundation soil and reduce the freezing depth of the channel foundation soil, it also provides water insulation and seepage prevention. In addition, by utilizing the deformation of the phase change heat storage structure to release the frost heave deformation of the channel foundation soil, it reduces the uneven stress and displacement of the lining plate during the freezing process of the channel foundation soil, thereby overcoming the shortcomings of the prior art.

[0005] To achieve the aforementioned objectives, the technical solution adopted by this invention includes: A first aspect of this invention provides a multifunctional composite lining structure for water conveyance channels in cold regions, comprising a lining plate laid on the bottom surface of the channel; the multifunctional composite lining structure further comprises a phase change heat storage structure laid between the lining plate and the channel subgrade, the phase change heat storage structure comprising: The flexible layered capsule has a closed cavity formed by a flexible composite membrane, which can prevent water in the channel from seeping into the channel foundation soil. A plastic phase change heat storage medium is filled in the closed cavity and distributed at least along the heat conduction path between the channel and the channel subgrade, and is used to store or release heat energy through phase change. An electric heating mechanism is disposed in the enclosed cavity and is thermally connected to the phase change heat storage medium. It is used at least to generate heat for the phase change heat storage medium to store energy and to heat the channel foundation soil. The electric heating mechanism is also electrically connected to a power source.

[0006] Furthermore, the phase change temperature of the phase change heat storage medium is 2℃~5℃.

[0007] Furthermore, the phase change thermal storage medium comprises the following components by mass percentage: 58wt%~62wt% microencapsulated paraffin, 11wt%~12wt% paraffin, 9wt%~11wt% fatty acids, 10wt%~16wt% expanded graphite, 0.9wt%~1.1wt% reduced graphene oxide, and 0.9wt%~1.1wt% carbon nanotubes.

[0008] Furthermore, the phase transition temperature of the microcapsule paraffin is 2℃~5℃, and the latent heat of phase transition is greater than 100J / g.

[0009] Furthermore, the electric heating mechanism includes a resistance wire embedded in the phase change heat storage medium.

[0010] Furthermore, the power source includes a solar power system.

[0011] Furthermore, the resistance wire comprises a nickel-chromium alloy resistance wire with a diameter of 0.5 mm to 2 mm.

[0012] Furthermore, the spacing between the resistance wires distributed on the sunny slope of the channel is greater than the spacing between the resistance wires distributed on the shady slope of the channel, so that the heat released by the phase change heat storage structure on the shady slope of the channel is higher than the heat released on the sunny slope of the channel, thereby balancing the temperature and frost heave of the sunny and shady slopes of the channel.

[0013] Furthermore, the solar power supply system includes a solar panel and a battery electrically connected to the solar panel, wherein the area of ​​the solar panel is in the ratio of 1:5 to 1:10 to the area of ​​the lining plate.

[0014] Furthermore, the solar power system is also connected to a temperature control unit, which includes a temperature sensor for monitoring the temperature of the phase change thermal storage structure.

[0015] Furthermore, the flexible layered capsule includes an upper composite geomembrane and a lower composite geomembrane, with the edges of the upper and lower composite geomembranes sealed together to form the closed cavity.

[0016] Furthermore, the composite geomembrane has a fabric weight ≥ 200 g / m², a membrane thickness ≥ 0.5 mm, preferably 0.5 mm to 2 mm, and a permeability coefficient ≤ 1 × 10⁻⁶. -11 m / s.

[0017] Furthermore, the composite geomembrane comprises a PE film and a non-woven fabric bonded together, and the elongation at break of the composite geomembrane is 100% to 200%.

[0018] Furthermore, the lining slabs laid on the sunny slope of the channel are made of frost-resistant and seepage-proof concrete slabs, while the lining slabs laid on the shady slope of the channel are made of frost-resistant and seepage-proof concrete slabs mixed with steel fibers.

[0019] Furthermore, the non-woven fabric surface of the upper composite geomembrane is bonded to the lining plate, and the non-woven fabric surface of the lower composite geomembrane is in contact with the channel foundation soil.

[0020] Furthermore, the edges of the upper and lower composite geomembranes are welded and sealed, with an overlap width of ≥15cm and a peel strength of ≥10N / mm at the weld.

[0021] Furthermore, the lower composite geomembrane is laid flat on the surface of the channel foundation soil.

[0022] Furthermore, the nonwoven fabric has a weight of 100g / m² to 300g / m².

[0023] Furthermore, the non-woven fabric surface of the upper composite geomembrane is bonded to the lining plate by a modified asphalt adhesive, wherein the modified asphalt adhesive has a tensile strength ≥0.6MPa and an elongation at break ≥40%.

[0024] Furthermore, the surface flatness error of the channel foundation soil is ≤5mm, the compaction degree is ≥95%, and the moisture content is 13%~14%.

[0025] Furthermore, the lining plate consists of multiple pieces, and the gaps between adjacent lining plates are filled with waterproof strips and elastic sealant.

[0026] Furthermore, the thickness of the phase change heat storage structure is 5cm to 10cm.

[0027] A second aspect of this invention provides a construction method for the multifunctional composite lining structure used in cold-region water conveyance channels, comprising the following steps: S1. Level and compact the foundation soil of the channel; S2. Lay the lower composite geomembrane flat on the surface of the channel foundation soil, with the non-woven fabric side of the lower composite geomembrane facing down and in contact with the channel foundation soil, and with the lower composite geomembrane extending along the channel axis. S3. Fix resistance wires on the PE membrane surface of the lower composite geomembrane, and make the spacing between the resistance wires distributed on the sunny slope of the channel greater than the spacing between the resistance wires distributed on the shady slope of the channel, so that the heat released by the phase change heat storage structure on the shady slope of the channel is higher than the heat released on the sunny slope of the channel, thereby balancing the temperature and frost heave of the sunny and shady slopes of the channel. S4. Lay an upper composite geomembrane on the lower composite geomembrane and resistance wire, with the non-woven fabric side of the upper composite geomembrane facing upwards. Then weld and seal the edges of the upper and lower composite geomembranes, controlling the overlap width at the sealing edge to be ≥15cm and the peel strength at the weld to be ≥10N / mm, thereby forming a flexible layered capsule. S5. Fill the inner cavity of the flexible layered capsule with phase change heat storage medium through the pre-reserved opening on the flexible layered capsule. After filling, close the opening and allow the phase change heat storage medium to cool naturally to the ambient temperature. S6. Lay a lining board on the upper composite geomembrane, and use a modified asphalt adhesive to bond the non-woven fabric side of the upper composite geomembrane to the lining board, and install a solar power supply system around the channel, and electrically connect the solar power supply system to the resistance wire.

[0028] Furthermore, in step S1, when leveling the channel foundation soil, the flatness error is controlled to be ≤5mm, and a vibratory roller is used to compact it in layers, with each layer thickness controlled to be 20cm~30cm, compaction degree ≥95%, and the backfill soil moisture content controlled to be 13%~14%.

[0029] Furthermore, in step S3, a low-temperature resistant adhesive material is used to fix the resistance wire to the PE membrane surface of the lower composite geomembrane. This low-temperature resistant adhesive material can be obtained commercially and is not specifically limited here.

[0030] Furthermore, in step S4, a double-track hot-melt welding machine is used to weld and seal the edges of the upper and lower composite geomembranes, controlling the hot-melt welding temperature to be 220℃~250℃ and the speed to be 0.4m / min~0.6m / min.

[0031] Furthermore, the preparation method of the phase change thermal storage medium in step S5 includes: Graphene oxide with a monolayer ratio >95% was obtained by ultrasonically exfoliating graphite with hydrogen peroxide for 2 hours at an ultrasonic power of 400W and a temperature of 30℃. The graphene oxide was then reduced with ascorbic acid at a temperature of 60℃ for 1 hour to obtain reduced graphene oxide. The reduced graphene oxide was refluxed for 3 hours at a temperature of 80°C using a mixed acid solution. The mixed acid solution was formed by mixing concentrated nitric acid and concentrated sulfuric acid in a volume or mass ratio of 1:3 to obtain reduced graphene oxide with carboxyl groups. The reduced graphene oxide with carboxyl groups was mixed with N,N-dimethylformamide at a mass ratio of 1:1.2 and ultrasonically dispersed at 40°C for 45 minutes to obtain a reduced graphene oxide dispersion (i.e., a N,N-dimethylformamide dispersion of carboxylated reduced graphene oxide, hereinafter the same). Carbon nanotubes are mixed with the reduced graphene oxide dispersion to form a nano-dispersion. Expanded graphite was mixed with concentrated sulfuric acid and stirred at 50°C for 2 hours to complete the intercalation treatment of expanded graphite. The intercalated expanded graphite was then washed until neutral and mixed with nano-dispersion liquid. The mixture was dried at 50°C for 12 hours to form a graphene-carbon nanotube-expanded graphite composite framework. Paraffin wax and fatty acids were melted at 75°C, and the graphene-carbon nanotube-expanded graphite composite framework was added. The mixture was stirred at 600 r / min for 1.5 hours to fully expand the sheet structure. Then, the temperature was lowered to 60°C, and microcapsule paraffin wax was added. The mixture was stirred and ultrasonically assisted for 2 hours to obtain the phase change heat storage medium.

[0032] Furthermore, in step S5, the phase change heat storage medium is filled into the inner cavity of the flexible layered capsule by pumping. Every 40-50cm of filling is compacted with a vibrator for 10-15s to ensure that the density of the filled phase change heat storage medium is ≥90%, until it is filled to 5-10cm below the opening. Then, the opening is sealed with an annular hot melt gasket.

[0033] Furthermore, in step S6, when installing the solar power system, if the solar panel is installed on the sunny slope of the channel, the tilt angle of the solar panel is set to the local latitude minus (1 / 2 to 2 / 3 of the slope) to avoid an excessively large total tilt angle; if the solar panel is installed on the shady slope of the channel, the tilt angle of the solar panel is set to the local latitude plus (1 / 2 to 2 / 3 of the slope) to counteract the northward tilt of the shady slope.

[0034] Furthermore, in step S6, the lining board is laid under the condition of temperature ≥5℃.

[0035] Furthermore, in step S6, a modified asphalt adhesive is first brushed onto the non-woven fabric surface of the upper composite geomembrane, then the lining board is laid, and then the lining board is gently tapped with a rubber hammer so that the area of ​​the lower surface of the lining board bonded to the upper composite geomembrane is more than 95% of the total area of ​​the lower surface.

[0036] Compared with the prior art, the advantages of the present invention include: (1) The multifunctional composite lining structure provided for water conveyance channels in cold regions has the following properties: During the freezing period of the channel foundation soil, the solar panels absorb solar radiation during the day and convert light energy into electrical energy, which is then stored through the energy storage battery. In addition, the electric heating mechanism generates heat when energized, which stores energy in the phase change heat storage medium in the phase change heat storage structure and releases heat to increase the temperature of the channel foundation soil during the day. At night, when there is no solar radiation and the ambient temperature drops, the phase change heat storage medium in the phase change heat storage structure releases heat, the energy storage battery releases the electrical energy stored during the day, and the electric heating mechanism generates heat, which reduces the freezing depth of the channel foundation soil at night, thereby reducing uneven frost heave.

[0037] (2) The phase change heat storage structure in the multifunctional composite lining structure provided for water conveyance channels in cold regions can play a role in water isolation during the water flow period, preventing water from seeping into the foundation soil and effectively avoiding exacerbating the frost heave of the foundation soil in the following year.

[0038] (3) The multi-functional composite lining structure provided for water conveyance channels in cold regions is simple in structure, easy to construct, and has low maintenance cost. It is suitable for various channel projects in cold regions and has broad application prospects. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of a multifunctional composite lining structure for water conveyance channels in cold regions, provided by an embodiment of the present invention. Figure 2 yes Figure 1 A magnified schematic diagram of structure 8 in the middle section; Figure 3a This is a schematic diagram of the operation of a multifunctional composite lining structure for water conveyance channels in cold regions, provided by an embodiment of the present invention. Figure 3b yes Figure 3a Enlarged view of structure A in the middle; Figure 4 This is a partial structural schematic diagram of a multifunctional composite lining structure for water conveyance channels in cold regions provided by an embodiment of the present invention; Figure 5 This is a schematic diagram of the arrangement of resistance wires on the yin and yang slopes of a multifunctional composite lining structure for water conveyance channels in cold regions, provided by an embodiment of the present invention. Figure 6a , Figure 6bThese are schematic diagrams showing the operation of a multifunctional composite lining structure for water conveyance channels in cold regions during the day and at night, as provided in the embodiments of the present invention. Figure 6c This is a schematic diagram illustrating the working principle of a multifunctional composite lining structure for water conveyance channels in cold regions, provided by an embodiment of the present invention, to adapt to structural frost heave. Detailed Implementation

[0040] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate the technical solution, its implementation process, and principles in conjunction with the accompanying drawings and specific embodiments. Unless otherwise specified, the solar panels, energy storage batteries, and channel foundation soil treatment processes involved in the embodiments of this invention are all known in the art and are not specifically limited here.

[0041] Please see Figure 1 A typical embodiment of the present invention provides a multifunctional composite lining structure for water conveyance channels in cold regions, comprising a lining plate 1 and a phase change heat storage structure 2. The phase change heat storage structure 2 is directly laid on the channel foundation soil 6, with no additional connection between the two. The lining plate 1 is laid on the phase change heat storage structure 2 and is fixedly connected to it.

[0042] It should be noted that the composite lining structure has the same cross-sectional structure as the channel. For example, the channel cross-section can be an arc-shaped structure, etc. The channel foundation soil 6 consists of an unfrozen zone 61 and a frozen zone 62 from bottom to top.

[0043] Furthermore, the phase change thermal storage structure 2 can also be referred to as a phase change thermal storage structure, phase change thermal storage layer, or phase change energy storage layer. It includes a flexible layered capsule, a plastic phase change thermal storage medium, and an electric heating mechanism 4. The flexible layered capsule has a closed cavity formed by a flexible composite membrane 5, which prevents water in the channel from seeping into the channel foundation soil 6. The phase change thermal storage medium fills the closed cavity inside the flexible layered capsule and is distributed along the heat conduction path between the channel and the channel foundation soil 6, serving to store or release heat energy through phase change. The electric heating mechanism 4 is disposed within the closed cavity inside the flexible layered capsule and is thermally connected to the phase change thermal storage medium. The electric heating mechanism 4 is connected to a power source and is used to generate heat to supply the phase change thermal storage medium for energy storage and to heat the channel foundation soil 6. It is understood that the back side of the flexible layered capsule contacts the channel foundation soil 6, and the front side is fixedly connected to the lining plate 1 (e.g., by bonding).

[0044] When the power supply is supplied to the electric heating mechanism 4, the electric heating mechanism 4 is energized and generates heat. The phase change heat storage medium absorbs and stores the heat generated by the electric heating mechanism 4, and at the same time releases the heat to the outside. When the power supply to the electric heating mechanism 4 is stopped and the external ambient temperature is lower than the phase change temperature of the phase change heat storage medium, the phase change heat storage medium in the phase change heat storage structure 2 releases the heat it stores to the outside, so as to reduce the freezing depth of the channel foundation soil 6.

[0045] The flexible composite membrane 5 comprises an upper composite geomembrane and a lower composite geomembrane, the edges of which are sealed together to form the closed chamber. Both the upper and lower composite geomembranes can be simply referred to as composite geomembranes, with a fabric weight ≥ 200 g / m², a membrane thickness ≥ 0.5 mm, preferably 0.5 mm to 2 mm, and a permeability coefficient ≤ 1 × 10⁻⁶. -11 m / s.

[0046] For example, the aforementioned composite geomembrane comprises a polymer compound film and a nonwoven fabric bonded together, with an elongation at break of 100%–200%. The polymer compound film and the nonwoven fabric are the inner and outer surfaces of the composite geomembrane, respectively. The nonwoven fabric in the upper composite geomembrane is in direct contact with and connected to the lining plate 1 (e.g., by bonding with asphalt), while the nonwoven fabric in the lower composite geomembrane has no bonding or other connection measures / structures with the channel foundation soil 6. The polymer compound film includes PE film, etc., and the unit area mass of the nonwoven fabric is 100g / m²–300g / m² to ensure that the composite geomembrane has good seepage prevention and protection performance.

[0047] Furthermore, the phase change thermal storage medium comprises the following components by mass percentage: 58wt%~62wt% microencapsulated paraffin, 11wt%~12wt% paraffin, 9wt%~11wt% fatty acids, 10wt%~16wt% expanded graphite, 0.9wt%~1.1wt% reduced graphene oxide, and 0.9wt%~1.1wt% carbon nanotubes. It should be noted that when the content of reduced graphene oxide is >1.5wt%, it is prone to stacking and agglomeration; if the content of carbon nanotubes is >1wt%, it will lead to a sharp increase in dispersion energy consumption. The total content of expanded graphite and reduced graphene oxide is ≤17wt% to ensure that the proportion of phase change material is ≥80wt%. The phase change temperature of the microencapsulated paraffin is 2℃~5℃, and the latent heat of phase change is greater than 100J / g.

[0048] The phase change heat storage medium is a six-element system, which has the following advantages compared with existing phase change heat storage media: ① Expanded graphite can enhance thermal conductivity. As a high thermal conductivity skeleton (thermal conductivity can reach 100-150W / (m・K)), expanded graphite improves the thermal conductivity efficiency of phase change material (PCM) by forming a three-dimensional network structure, reduces thermal resistance, and allows the high ambient temperature during the day to more easily penetrate the foundation soil. At night, due to the barrier of the phase change heat storage structure, the low temperature is difficult to penetrate the foundation soil. Specifically, the mass percentage of expanded graphite is 10wt%~16wt%, which can achieve the critical percolation threshold: when the content of expanded graphite is >10wt%, its lamellar structure begins to form a continuous thermal conduction path, and the thermal conductivity is significantly improved (e.g., when the content is 16wt%, the thermal conductivity of the composite material can be 40%~60% higher than that of pure fatty acids). In addition, it can avoid performance degradation: if the content of expanded graphite is >16wt%, the effective phase change volume of the phase change material may be reduced due to the agglomeration effect, and the latent heat of phase change may decrease (e.g., the latent heat loss can reach 15% when the content is 17wt%). The mass percentage of 10wt%~16wt% can balance the improvement of thermal conductivity and the retention of latent heat (latent heat retention rate >90%).

[0049] ② Paraffin wax (phase transition temperature 30℃~70℃) forms a eutectic system with fatty acids (such as stearic acid with a phase transition temperature of 69℃ and palmitic acid with a phase transition temperature of 63℃), which can adjust the phase transition temperature range and improve the formability and leakage resistance of the composite material. The mass ratio of paraffin wax is 11wt%~12wt%, which can better achieve phase transition temperature range matching: a low proportion of paraffin wax (mass ratio 11wt%~12wt%) can reduce the high phase transition temperature of fatty acids (such as stearic acid) by 5℃~10℃, making it more suitable for medium and low temperature heat storage scenarios (such as solar heating and building energy conservation); compatibility control: paraffin wax and fatty acids are similar organic materials, and a mass ratio of 11wt%~12wt% can avoid phase separation caused by polarity differences (such as the possibility of stratification when the dosage is >12wt%).

[0050] ③ Fatty acids can enhance the high latent heat characteristics of phase change thermal storage media: Fatty acids (such as stearic acid with a latent heat of 240 J / g to 250 J / g and palmitic acid with a latent heat of 210 J / g to 220 J / g) serve as the main component (with a mass ratio of 9wt% to 11wt%), ensuring the total heat storage capacity of the phase change thermal storage structure. Compared with traditional paraffin-based phase change materials (latent heat of 180 J / g to 220 J / g), the latent heat of this system is increased by 10% to 30%.

[0051] ④ Reduced graphene oxide forms a two-dimensional sheet-like thermally conductive network in the phase change heat storage medium, complementing the layered structure of expanded graphite and the one-dimensional structure of carbon nanotubes to construct a three-dimensional "point-line-surface" thermal conduction path, significantly reducing thermal resistance. Furthermore, together with carbon nanotubes, it serves as a "reinforcing framework," improving the brittleness of the fatty acid / paraffin matrix and preventing material cracking due to volume expansion during phase change. Then, the two-dimensional sheet structure of reduced graphene oxide can encapsulate fatty acids / paraffin, reducing their contact with oxygen and moisture, delaying oxidative degradation, and extending the material's lifespan. Finally, the chemical inertness of reduced graphene oxide can inhibit the decomposition of fatty acids at high temperatures, improving the material's thermal stability.

[0052] ⑤ The flexible structure of carbon nanotubes can be uniformly dispersed in mixtures, avoiding the agglomeration problem of reduced graphene oxide or expanded graphite. Especially in solution blending or melt processing, it can improve the fluidity and formability of materials, connect the interlayer gaps between reduced graphene oxide sheets and expanded graphite, and fill the uneven voids in the three-dimensional thermally conductive network.

[0053] ⑥ Microencapsulated paraffin contains microcapsules that encapsulate the paraffin within a polymer shell (such as melamine-formaldehyde, polyurea, etc.), forming a core-shell structure with a latent heat of phase change reaching 150 J / g~200 J / g. Furthermore, it solves the flowability problem of traditional paraffin / fatty acid during phase transitions (solid-liquid transitions), preventing liquid seepage that could lead to material failure. Finally, the microcapsule shell isolates oxygen and impurities, reducing paraffin oxidation and volatilization, thus increasing the cycle life of the phase change material.

[0054] Specifically, in addition to the above advantages, the hexa-element phase change heat storage medium used in the embodiments of the present invention also has the following synergistic effects: (1) There are synergistic effects within the phase change heat storage components (microcapsule paraffin, paraffin, fatty acids).

[0055] Increased thermal storage density: Microencapsulated paraffin is the core thermal storage unit, but there are gaps between the particles. Ordinary paraffin and fatty acids can fill these gaps, reduce the ineffective space in the system, and make the thermal storage material content per unit mass higher, thus increasing the overall thermal storage density.

[0056] Phase change temperature regulation: The phase change temperatures of the three phase change materials differ. By compounding them, the phase change temperature range of the system can be broadened to meet the temperature control requirements in different scenarios.

[0057] Leakage prevention complementarity: The wall material of the microcapsule can encapsulate the internal paraffin to prevent leakage during its phase change. Ordinary paraffin and fatty acids, after being combined with the microcapsule, can be fixed by the microcapsule particles, further reducing the flow risk of liquid phase change materials.

[0058] (2) There is a synergistic effect within the carbon-based thermally conductive components (expanded graphite, reduced graphene oxide (rGO), carbon nanotubes (CNTs)).

[0059] Thermal network construction: The three materials belong to different dimensions - expanded graphite is a macroscopic porous structure (quasi-three-dimensional), rGO is a two-dimensional sheet structure, and CNTs are a one-dimensional tubular structure. Two-dimensional rGO can be attached to the porous surface of expanded graphite, while one-dimensional CNTs can fill the gaps between rGO sheets, forming a continuous thermal conduction path of "three-dimensional skeleton - two-dimensional connection - one-dimensional bridging".

[0060] Maximizing thermal conductivity: Single thermally conductive materials are prone to problems such as "agglomeration" or "broken thermal conduction pathways". For example, CNTs are prone to entanglement and agglomeration when used alone, while the porous structure of expanded graphite can disperse CNTs; rGO sheets can combine with CNTs through van der Waals forces, fill the thermal conductivity weaknesses of the expanded graphite skeleton, and make the overall thermal conductivity much higher than the effect of adding a single material.

[0061] Specifically, to verify the advantages of the hexa-component phase change heat storage medium used in this invention, performance tests were conducted on the phase change heat storage medium (hexa-component system), the single-component phase change heat storage medium (pure paraffin), the two-component phase change heat storage medium (paraffin (80wt%) + fatty acid (20wt%)), the ternary phase change heat storage medium (paraffin (85wt%) + fatty acid (10wt%) + expanded graphite (5wt%)), the quaternary phase change heat storage medium (paraffin (83.5wt%) + fatty acid (10wt%) + expanded graphite (5wt%) + reduced graphene oxide (1.5wt%)), and the pentagonal phase change heat storage medium (paraffin (82.5wt%) + fatty acid (10wt%) + expanded graphite (5wt%) + reduced graphene oxide (1.5wt%) + carbon nanotubes (1wt%)). The test results are shown in Table 1.

[0062] Table 1 Performance test results of six phase change thermal storage media

[0063] Comparative analysis reveals that the phase change thermal storage medium of this invention constructs a three-dimensional thermally conductive network through a combination of "expanded graphite macro framework + reduced graphene oxide nanosheets + carbon nanotube bridging," achieving a pore filling rate >90% and a thermal conductivity 11-14 times higher than pure paraffin. Simultaneously, through the eutectic effect of microencapsulated paraffin (60%) and paraffin (12%), the latent heat of phase change is maintained at 190 J / g~230 J / g, significantly higher than traditional multi-component systems. Through fatty acid-reduced graphene oxide hydrogen bonding and microcapsule spherical filling, the interfacial thermal resistance is reduced by more than 30% compared to traditional multi-component systems. The microcapsule wall material (melamine-formaldehyde) isolates oxygen and moisture, and combined with the antioxidant properties of reduced graphene oxide and the mechanical reinforcement of carbon nanotubes, the cycle life is increased from 500 cycles in traditional systems to 1500-2000 cycles, with a latent heat retention rate >98%. The "micron-nano" composite framework of expanded graphite (16wt%) and reduced graphene oxide (1wt%) gives the material a compressive strength of 18MPa~22MPa. Combined with carbon nanotubes (1wt%) bridging and reduced graphene oxide sheet reinforcement, the flexural strength is increased by more than 25%, allowing for 2000 bends without breakage. This fully meets the requirements of repeated freeze-thaw deformation in water conveyance channels in seasonally frozen soil areas. Furthermore, the microcapsule wall material provides isolation, and the nanomaterials synergistically resist aging, significantly improving cycle stability. The hexa-component system rapidly absorbs heat within the 2℃~5℃ phase change range. With the help of a thermally conductive network, the temperature difference of the phase change heat storage medium can be controlled within ±1℃, preventing thermal runaway. Within a wide temperature range of -40℃~120℃, the material maintains a thermal stability rate of >95%, far superior to traditional multi-component systems (which are prone to failure above 80℃).

[0064] Verification has shown that the phase change heat storage medium (six-element system) used in the embodiments of the present invention has significantly improved performance in many aspects compared with the traditional ternary phase change heat storage medium (70wt% paraffin + 15wt% fatty acid + 15wt% expanded graphite). For example, the latent heat of phase change is increased by more than 5%, reaching 215J / g~230J / g; the thermal conductivity is increased by more than 40%, reaching 1.8W / (m·K)~2.2W / (m·K); the interfacial thermal resistance is reduced by more than 30%, reaching 0.12m²·K / W; and the compressive strength is increased by more than 20%, reaching 12MPa.

[0065] Furthermore, the electric heating mechanism 4 can be embedded within the phase change heat storage medium. For example, the electric heating mechanism 4 may include a resistance wire embedded within the phase change heat storage medium, and the resistance wire may be in a zigzag shape (e.g.,...). Figure 5(As shown). Preferably, the density of the resistance wires distributed on the sunny slope of the channel is less than that distributed on the shady slope (e.g., the spacing between resistance wires on the shady slope is ≤20cm, and the spacing between resistance wires on the sunny slope is ≤30cm). This can better compensate for uneven solar radiation, reduce the temperature difference between the soil on the sunny and shady slopes, and avoid uneven frost heave deformation caused by temperature differences. This ensures that the heat released by the phase change heat storage structure on the shady slope of the channel is higher than that released on the sunny slope, thereby balancing the temperature and degree of frost heave on the sunny and shady slopes. Specifically, the distribution density of the resistance wires can be changed by altering the spacing between them. Specifically, the resistance wires are nickel-chromium alloy resistance wires with a diameter of 0.5mm to 2mm. This design enables uniform heat distribution and improves the heating effect of the phase change heat storage structure 2.

[0066] It should be noted that the sunny slopes of the canal receive more solar radiation and have relatively higher temperatures, while the shady slopes receive less solar radiation and have relatively lower temperatures. This results in the soil temperature on the shady slopes being lower than on the sunny slopes. Consequently, the shady slopes experience greater frost depth and frost heave, while the sunny slopes experience less frost heave. This leads to asymmetrical deformation and stress on the canal structure due to the difference between the sunny and shady slopes. For the structure, uneven deformation and stress are key causes of structural failure. Therefore, by unevenly arranging resistance wires on the sunny and shady slopes of the canal, on the one hand, the soil foundation can be heated, increasing its temperature and reducing the frost depth. On the other hand, the smaller spacing of the resistance wires on the shady slopes allows the phase change heat storage structure to release more heat on the shady slopes, thereby regulating the temperature difference between the sunny and shady slopes. This reduces the temperature difference, frost depth difference, and frost heave deformation differences between the sunny and shady slopes, minimizing uneven frost heave deformation on the structure.

[0067] Furthermore, the power source can be a solar power system, which may include a solar panel 3 and an energy storage battery 7. The solar panel 3 can be fixed to the top of the channel and electrically connected to the energy storage battery 7, which is electrically connected to the electric heating mechanism 4.

[0068] Specifically, the solar panel 3 can be fixedly installed on the channel foundation soil 6, located on one side of the sunny or shady slope. The area ratio of the solar panel 3 to the lining plate 1 is preferably 1:5 to 1:10, which can meet the heating needs of the electric heating mechanism 4 during the day without excessively occupying the channel's surface area. The solar panel 3 can be a monocrystalline silicon solar panel, etc. In some cases, if the solar panel 3 is installed on the sunny slope of the channel, the tilt angle of the solar panel 3 is set to [local latitude - (1 / 2 to 2 / 3 of the slope gradient)] to avoid an excessively large total tilt angle; if the solar panel 3 is installed on the shady slope of the channel, the tilt angle of the solar panel 3 is set to [local latitude + (1 / 2 to 2 / 3 of the slope gradient)] to counteract the northward tilt of the shady slope. When the solar panel 3 is installed on the sunny slope, "slope gradient" specifically refers to the slope of the sunny slope itself, that is, the angle between the surface of the sunny slope and the horizontal plane. When solar panel 3 is installed on a shady slope, "slope gradient" specifically refers to the slope of the shady slope itself, that is, the angle between the surface of the shady slope and the horizontal plane.

[0069] Furthermore, the lining slab 1 can be made of frost-resistant concrete slab, such as C30~C35 concrete slab. As a preferred option, the lining slab 1 laid on the sunny slope of the channel is made of frost-resistant and seepage-proof concrete slab, while the lining slab 1 laid on the shady slope of the channel is made of frost-resistant and seepage-proof concrete slab mixed with steel fibers.

[0070] The working principle of the multifunctional composite lining structure provided in this embodiment will be explained in detail below.

[0071] Firstly, such as Figure 3a , Figure 3b As shown, the multifunctional composite lining structure separates the lining plate 1 from the channel foundation soil 6 through the phase change heat storage structure 2. During the daytime, when there is solar radiation, the solar panel 3 converts solar energy into electrical energy, which powers the electric heating mechanism 4 to generate heat. The heat is transferred to the phase change heat storage medium inside the phase change heat storage structure 2, allowing it to store energy (such as...). Figure 6a (As shown), this simultaneously increases the daytime temperature of the channel foundation soil 6, slowing down its freezing rate. At night, when there is no solar radiation and the ambient temperature decreases, the phase change heat storage medium within the phase change heat storage structure 2 begins to release heat. Simultaneously, the battery can release electrical energy to heat the resistance wire, preventing external negative temperatures from entering the foundation soil (such as...). Figure 6b As shown in the figure, reducing the freezing depth of the channel foundation soil 6 at night effectively reduces the occurrence of frost heave in the foundation soil.

[0072] Secondly, the unevenness of the channel foundation soil 6 in contact with the phase change heat storage structure 2 is mainly due to the uneven distribution of the moisture content of the channel foundation soil 6 from top to bottom, the bidirectional freezing process at the top of the channel with a higher freezing rate than the middle and lower parts of the channel, and the varying degrees of constraint of the lining plate 1 on the frost heave of the channel foundation soil 6 at different locations. Therefore, the frost heave deformation of the channel foundation soil is different at different locations, resulting in uneven deformation.

[0073] like Figure 6c As shown, firstly, the surface layer of the phase change heat storage structure 2 provided in this embodiment of the invention is a composite geomembrane with an elongation rate ≥10%, and its interior is filled with a plastic phase change heat storage medium, making the phase change heat storage structure 2 as a whole a flexible structure. The phase change heat storage structure 2 is directly laid on the channel foundation soil 6, in contact with but not connected to the channel foundation soil 6, and is only fixedly connected to the upper lining plate 1 through the composite geomembrane, thus relieving the rigid constraint between the lining plate 1 and the channel foundation soil 6. Secondly, the phase change heat storage structure 2 can release heat and reduce the thickness of the frozen zone below the lining plate 1, reducing uneven frost heave, thereby effectively preventing material damage to the lining plate 1 caused by uneven frost heave, avoiding cracks caused by stress concentration in the lining plate 1, and reducing the structural crack incidence rate to below 5%, thus significantly reducing the risk of cracking of the lining plate 1. Meanwhile, because the composite geomembrane has a good seepage prevention effect, it can prevent water leakage from the canal and reduce the moisture content of the canal foundation soil 6, thereby reducing the degree of frost heave of the canal foundation soil 6 in the second year and extending the service life of the lining plate 1.

[0074] More specifically, when the channel foundation soil freezes, the water between soil particles expands upon freezing, resulting in frost heave and frost heave displacement. The frost heave displacement primarily originates from the temperature gradient difference between the frozen and unfrozen layers of the foundation soil, causing shear displacement of the upper soil layer towards the slope crest (in traditional structures, the temperature difference between the convex and convex slopes can reach 15℃, triggering lateral displacement of the lining slab). In this invention, the phase change heat storage structure 2 controls the freezing depth of the channel foundation soil 6 to ≤0.5m through the electric heating mechanism 4 and the phase change heat storage medium, reducing the temperature gradient between the frozen and unfrozen layers and decreasing the driving force for tangential displacement. Simultaneously, the phase change heat storage structure 2 is not connected to the channel foundation soil 6, but is only bonded to the lining slab through a composite geomembrane. When the channel foundation soil 6 experiences tangential displacement, the composite geomembrane can slide along the tangential direction. Combined with the plastic flow of the phase change heat storage medium, this releases tangential stress and prevents the lining slab from following the displacement.

[0075] When the channel foundation soil experiences frost heave, due to spatial differences in freezing rate and frost heave amount (such as inconsistent freezing depth at different locations in the channel cross-section), the bottom of the lining plate will be subjected to uneven frost heave force, leading to local stress concentration, misalignment, or even fracture of the lining plate. In this invention, the phase change heat storage structure 2, based on the three-dimensional heat-conducting network formed by the electric heating mechanism 4 and the phase change heat storage medium, can achieve uniform heat release. The expanded graphite, reduced graphene oxide, and carbon nanotubes in the phase change heat storage medium form a heat-conducting network, making the heat distribution uniform (temperature difference ≤1℃), reducing uneven frost heave of the channel foundation soil. At the same time, the phase change heat storage medium releases latent heat (>100J / g) in the phase change range of 2~5℃, slowing down the freezing rate of the channel foundation soil. Meanwhile, its plasticity can disperse local stress, reducing the peak freezing force by more than 40%. In summary, the phase change heat storage structure 2 of the present invention offsets / releases the uneven deformation of the channel foundation soil 6, reduces the uneven force of the channel foundation soil on the lining plate, and eliminates the uneven deformation and displacement of the lining plate in the normal and tangential directions.

[0076] This typical embodiment of the invention also provides a construction method for the multifunctional composite lining structure. The process mainly involves: first, laying a composite geomembrane on the channel foundation soil 6; then, processing the composite geomembrane into a semi-closed state through hot melting, leaving only the phase change heat storage medium filling hole and the channel for the electric heating mechanism 4 to enter. Next, the phase change heat storage medium is filled into the semi-closed composite geomembrane, and the electric heating mechanism 4 is embedded, forming a phase change heat storage structure 2. Subsequently, solar panels 3 are installed on the channel foundation soil 6, and the solar panels 3 and the electric heating mechanism 4 are connected through an energy storage battery 7 and wires. Finally, a lining plate 1 is laid on the phase change heat storage structure 2, and the composite geomembrane of the phase change heat storage structure 2 is bonded and fixed to the lining plate 1.

[0077] Furthermore, the construction method specifically includes the following steps: (1) Leveling and compacting the foundation soil of the channel. Use a bulldozer / grader to level the foundation soil, control the flatness error to ≤5mm, and use a vibratory roller to compact it in layers (each layer 20~30cm, compaction degree ≥95%), and test the rebound modulus to ≥30MPa.

[0078] With a flatness error of ≤5mm, compaction degree of ≥95%, and resilience modulus of ≥30MPa, a uniform and stable foundation is provided for the composite lining structure, avoiding cracking of the lining plate 1 due to the settlement of the foundation soil (the proportion of cracks caused by the settlement of the foundation soil 6 in traditional channels reaches 30%). The dense foundation soil can act as a channel for the migration of pore water, reducing the possibility of water accumulating at the bottom of the lining plate 1 in winter, thus weakening the conditions for frost heave from the source (frost heave damage often begins with uneven frost heave of the foundation soil), solving the problems of uneven settlement of the foundation soil and frost heave sensitivity, and ensuring the long-term uniformity of stress of the lining structure.

[0079] In this step, the thickness of each layer of compaction should be controlled (20~30cm). If it is too thick, the compaction of the bottom layer may be insufficient. The moisture content of the backfill soil should be controlled at the optimum moisture content ±2% to avoid drying and cracking or excessive moisture and softening.

[0080] (2) Laying composite geomembrane A layer of composite geomembrane is laid on the channel foundation soil 6 along the channel axis as the lower composite geomembrane. The non-woven side of the composite geomembrane is in contact with the channel foundation soil 6, and the PE film side is pasted with resistance wire and filled with phase change heat storage medium.

[0081] (3) Embedding resistance wire Considering the asymmetrical solar radiation received by the sunny and shady slopes, with the sunny slope having a higher temperature than the shady slope, the spacing / density of the resistance wires on the sunny slope is less than that on the shady slope when installing the resistance wires. For example, the spacing of the resistance wires on the sunny slope is 30cm, and the spacing on the shady slope is 20cm. The resistance wires are fixed to one side of the PE membrane of the composite geomembrane using tape or glue to ensure that the heat released by the sunny and shady slopes tends to be consistent at night.

[0082] In this step, it is preferable to fix the resistance wire with low-temperature resistant tape (which remains sticky at -40℃) to prevent displacement when filling with phase change material; when laying the composite geomembrane, a longitudinal slack of 1% to 2% should be reserved to accommodate the frost heave deformation of the channel (the elongation rate should be ≥10%).

[0083] (4) Seal the edges of the composite geomembrane Based on step (3), another layer of composite geomembrane is laid on top of the lower composite geomembrane and the resistance wire as the upper composite geomembrane. The non-woven fabric side of the upper geomembrane faces upward and is used to bond with the lining plate 1, while the PE film side faces downward and is in contact with the resistance wire and the phase change heat storage medium.

[0084] The edges of the two layers of composite geomembrane are sealed, with an overlap width of ≥15cm. The sealing is welded using a double-track hot melt welding machine, and the peel strength at the weld is ≥10N / mm. Then, the sealed composite geomembrane is perforated by drilling a 60mm diameter circular hole at the corresponding hole position in the membrane material. The perforation position is at the top of the channel slope, i.e., at the channel embankment.

[0085] A seepage-proof layer (permeability coefficient ≤ 1×10⁻⁶) is formed by using a composite geomembrane structure consisting of a fabric layer and a membrane layer (fabric weight 400g / m², membrane thickness 0.5mm). -11 (m / s), preventing water in the channel foundation soil 6 from seeping upwards to the phase change heat storage structure 2, avoiding corrosion of the resistance wire (the circuit failure rate caused by water seepage in traditional channels reaches 25%); the resistance wire is pasted on the PE film surface, and the non-woven fabric surface is in contact with the channel foundation soil 6, realizing the functional separation of "seepage prevention layer - heating layer - foundation soil layer" and improving the system durability.

[0086] In this step, the perforation positioning should avoid the joint of the lining plate 1 to prevent stress concentration from tearing the membrane material later; the hot melt welding should be controlled at a temperature of 220~250℃ and a speed of 0.5m / min to avoid scorching of the membrane material or incomplete welding.

[0087] (5) Fill with phase change heat storage medium First, the phase change thermal storage medium is prepared, and the process includes: S1. Graphene oxide with a single-layer ratio >95% was obtained by ultrasonically exfoliating graphite with 5wt% hydrogen peroxide for 2 hours at an ultrasonic power of 400W and a temperature of 30℃. Then, graphene oxide was reduced by ascorbic acid to obtain reduced graphene oxide. The concentration of ascorbic acid in the reduction reaction system was 1wt%, the reduction temperature was 60℃, and the holding time was 1 hour.

[0088] S2. The reduced graphene oxide is refluxed for 3 hours with a mixed acid at a temperature of 80°C. The mixed acid is formed by mixing concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 1:3 to obtain reduced graphene oxide with carboxyl groups.

[0089] S3. Reduced graphene oxide with carboxyl groups is mixed with N,N-dimethylformamide at a mass ratio of 1:1.2 and ultrasonically dispersed at 40°C for 45 minutes to obtain a reduced graphene oxide dispersion.

[0090] S4. Mix carbon nanotubes with the reduced graphene oxide dispersion to form a nano-dispersion.

[0091] S5. The expanded graphite is mixed with concentrated sulfuric acid and stirred at 50°C for 2 hours to complete the intercalation treatment of the expanded graphite. The intercalated expanded graphite is then washed until neutral and mixed with the nano-dispersion. After that, it is dried at 50°C for 12 hours to form a graphene-carbon nanotube-expanded graphite composite framework.

[0092] S6. Melt paraffin and fatty acid at 75°C, add the graphene-carbon nanotube-expanded graphite composite framework, stir at 600 r / min for 1.5 hours to fully expand the sheet structure, then cool to 60°C, add microcapsule paraffin, stir and ultrasonically assisted for 2 hours to obtain phase change heat storage medium.

[0093] Secondly, at the perforations of the composite geomembrane, a funnel and hose pump are used to fill the phase change heat storage medium. Every 40-50cm of filling, a micro-vibrator (φ30mm) is used for 10-15 seconds to ensure a compaction degree ≥90%, until the filling reaches 5cm below the perforation. A ring-shaped hot-melt gasket (100mm diameter) is welded to the membrane to seal the perforation holes (round holes), ensuring no leakage at the junction of the holes and the membrane, and ensuring no gaps at the contact point between the resistance wire and the hot-melt gasket. After pouring in the phase change heat storage medium, it is allowed to cool naturally to ambient temperature to eliminate internal stress and improve the strength of the heat storage medium.

[0094] This step utilizes two layers of composite geomembrane to form a "phase change material sealed chamber," coupled with ≥15cm hot-melt welded edges (peel strength ≥10N / mm) to prevent the phase change heat storage medium from becoming damp and failing, while also preventing the resistance wire from contacting external moisture, extending the insulation life to over 10 years. The perforation is located at the top of the canal slope, utilizing gravity and pumping to fill the phase change material, avoiding the dead corners caused by traditional side perforations, increasing the filling density from 75% to 90%. A ring-shaped hot-melt gasket seals the perforation opening, solving the problem of "resistance wire and membrane perforation leakage," reducing the leakage rate from 15% in traditional processes to below 2%.

[0095] The phase change heat storage medium needs to be filled in a molten state at 20℃ to avoid low-temperature solidification and delamination; during vibration, it needs to be inserted vertically into the center of the channel to avoid touching the resistance wire; the vibrator is preferably made of non-metallic material.

[0096] This step solves the problems of insufficient density of phase change thermal storage medium and membrane perforation and leakage, and constructs a waterproof-insulating-fillable composite structure layer. In addition, it also solves the problem of low thermal efficiency caused by incomplete filling of phase change material, and effectively protects the resistance wire from mechanical damage.

[0097] (6) Integration of solar panels and resistance wires The tilt angle of the solar panels can be adjusted according to their installation location, as described above. Polycrystalline silicon solar panels are used on the sunny slopes to prioritize the conversion of solar energy into heat for storage. Thin-film solar panels (approximately 2mm thick) are used on the shady slopes, primarily for resistance wire power supply to compensate for insufficient heat on the shady slopes. The circuit control employs a dual-loop temperature control system, using thermocouples to monitor the phase change layer temperature in real time (one measuring point is placed every 20m), achieving temperature uniformity in the lining plate 1 through intelligent temperature control.

[0098] (7) Laying of lining board 1 and bonding of interface Board selection: C30 frost-resistant concrete board (6cm thick, frost resistance grade F200) can be used on sunny slopes, while C25 fiber concrete board with 1% steel fiber can be used on shady slopes to improve crack resistance and match the different stress conditions of sunny and shady slopes (frost heave stress on shady slopes is greater than that on sunny slopes).

[0099] Bonding process: A modified asphalt adhesive (such as composite modified emulsified asphalt with a tensile strength ≥0.6MPa and elongation at break ≥40%) is applied to the surface of the composite geomembrane as a 2mm thick bonding layer. After the slabs are laid, they are gently tapped with a rubber mallet to ensure a bonding area ≥95%. The joints between the slabs are filled with elastic sealant (5mm wide). The modified asphalt adhesive can withstand the relative deformation between the lining slab 1 and the composite geomembrane, avoiding the slab detachment caused by brittle fracture due to traditional adhesives. The probability of bonding failure can be reduced from 20% to below 5%.

[0100] Lining slab 1 must be laid at an ambient temperature above 5℃, and load disturbance is prohibited during the curing period of the adhesive; the sealant for the slab joints must be a silicone weather-resistant type (displacement capacity ±25%) to adapt to the freezing and deformation of the channel.

[0101] This step creates a highly tough and deformable interfacial bonding system, solving the cracking and detachment problem caused by the limited material selection in traditional lining panels.

[0102] In summary, compared with the traditional construction method, which involves laying a geomembrane directly on the channel foundation soil and then casting concrete lining on the geomembrane, the construction method provided by the above embodiments of the present invention can effectively overcome problems such as lining cracking caused by temperature differences between sunny and shady slopes, leakage and failure of phase change material filling, resistance wire being susceptible to mechanical damage and corrosion, delamination between the lining plate and the foundation soil interface, and low efficiency of solar panels in winter. For example, the cracking rate of the lining plate can be reduced to below 5%, the lifespan of the phase change material can be increased to 1500-2000 cycles, the circuit failure rate and interface delamination damage rate can be significantly reduced, and the power supply stability of the resistance wire can be greatly improved in winter.

[0103] The multifunctional composite lining structure for water conveyance channels in cold regions provided in this invention is applicable to various water conveyance channel projects in cold regions. It can effectively solve the problems of frost heave damage and water leakage in channels, and has broad application prospects. By reducing the freezing depth of the foundation soil (heat storage function), reducing frost heave deformation, and reducing water leakage, the service life and operational stability of the channel are significantly improved, maintenance costs are reduced, and reliable technical support is provided for the construction of water conservancy projects in cold regions.

[0104] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A multi-functional composite lining structure for water channel in cold region, comprising a lining plate (1) laid on the bottom surface of the channel; characterized in that, The multifunctional composite lining structure also includes a phase change heat storage structure laid between the lining plate (1) and the channel foundation soil (6), the phase change heat storage structure comprising: The flexible layered capsule has a closed cavity formed by a flexible composite membrane (5) and can prevent water in the channel from seeping into the channel foundation soil (6). A plastic phase change heat storage medium is filled in the closed cavity and distributed at least in the heat conduction path between the channel and the channel foundation soil (6), and is used to store or release heat energy through phase change; An electric heating mechanism is disposed in the closed chamber and is thermally connected to the phase change heat storage medium. It is used at least to generate heat for the phase change heat storage medium to store energy and heat the channel foundation soil (6). The electric heating mechanism is also electrically connected to a power source.

2. The multifunctional composite lining structure for water conveyance channels in cold regions according to claim 1, characterized in that: The phase change temperature of the phase change heat storage medium is 2℃~5℃; And / or, the phase change thermal storage medium comprises the following components by mass percentage: 58wt%~62wt% microencapsulated paraffin, 11wt%~12wt% paraffin, 9wt%~11wt% fatty acids, 10wt%~16wt% expanded graphite, 0.9wt%~1.1wt% reduced graphene oxide and 0.9wt%~1.1wt% carbon nanotubes.

3. The multifunctional composite lining structure for water conveyance channels in cold regions according to claim 2, characterized in that: The phase transition temperature of the microcapsule paraffin is 2℃~5℃, and the latent heat of phase transition is greater than 100J / g.

4. The multifunctional composite lining structure for water conveyance channels in cold regions according to claim 1, characterized in that: The electric heating mechanism includes a resistance wire embedded in the phase change heat storage medium; And / or, the power source includes a solar power system.

5. The multifunctional composite lining structure for water conveyance channels in cold regions according to claim 4, characterized in that: The resistance wire comprises a nickel-chromium alloy resistance wire with a diameter of 0.5 mm to 2 mm; And / or, the spacing between the resistance wires distributed on the sunny slope of the channel is greater than the spacing between the resistance wires distributed on the shady slope of the channel, so that the heat released by the phase change heat storage structure on the shady slope of the channel is higher than the heat released on the sunny slope of the channel, thereby balancing the temperature and frost heave of the sunny and shady slopes of the channel. And / or, the solar power supply system includes a solar panel (3) and a battery electrically connected to the solar panel (3), wherein the area of ​​the solar panel (3) is in the ratio of the area of ​​the lining plate (1) to the area of ​​the lining plate (1) to 1:5 to 1:10; And / or, the solar power system is also connected to a temperature control unit, which includes a temperature sensor for monitoring the temperature of the phase change thermal storage structure.

6. The multifunctional composite lining structure for water conveyance channels in cold regions according to claim 1, characterized in that: The flexible layered capsule includes an upper composite geomembrane and a lower composite geomembrane, with the edges of the upper and lower composite geomembranes sealed together to form the closed chamber. And / or, the composite geomembrane has a fabric weight ≥200g / m², a membrane thickness ≥0.5mm, preferably 0.5mm~2mm, and a permeability coefficient ≤1×10⁻¹¹m / s; And / or, the composite geomembrane comprises mutually bonded PE film and non-woven fabric, and the elongation at break of the composite geomembrane is 100% to 200%; And / or, the lining slabs (1) laid on the sunny slope of the channel are made of frost-resistant and seepage-proof concrete slabs, and the lining slabs (1) laid on the shady slope of the channel are made of frost-resistant and seepage-proof concrete slabs mixed with steel fibers.

7. The multifunctional composite lining structure for water conveyance channels in cold regions according to claim 6, characterized in that: The non-woven fabric surface of the upper composite geomembrane is bonded to the lining plate (1), and the non-woven fabric surface of the lower composite geomembrane is in contact with the channel foundation soil (6). And / or, the edges of the upper composite geomembrane and the lower composite geomembrane are welded and sealed, with an overlap width of ≥15cm and a peel strength of ≥10N / mm at the weld. And / or, the lower composite geomembrane is laid flat on the surface of the channel foundation soil (6); And / or, the nonwoven fabric has a fabric weight of 100g / m² to 300g / m²; And / or, the non-woven fabric surface of the upper composite geomembrane is bonded to the lining plate (1) by a modified asphalt adhesive, wherein the modified asphalt adhesive has a tensile strength ≥0.6MPa and an elongation at break ≥40%.

8. The multifunctional composite lining structure for water conveyance channels in cold regions according to claim 1, characterized in that: The surface flatness error of the channel foundation soil (6) is ≤5mm, the compaction degree is ≥95%, and the moisture content is 13%~14%; And / or, the lining plate (1) is made of multiple pieces, and the gaps between adjacent lining plates (1) are filled with water-proof strips and elastic sealant; And / or, the thickness of the phase change heat storage structure is 5cm to 10cm.

9. The construction method of the multifunctional composite lining structure for water conveyance channels in cold regions as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Level and compact the channel foundation soil (6); S2. Lay the lower composite geomembrane flat on the surface of the channel foundation soil (6), so that the non-woven fabric side of the lower composite geomembrane faces downward and contacts the channel foundation soil (6), and the lower composite geomembrane extends along the channel axis. S3. Fix resistance wires on the PE membrane surface of the lower composite geomembrane, and make the spacing between the resistance wires distributed on the sunny slope of the channel greater than the spacing between the resistance wires distributed on the shady slope of the channel, so that the heat released by the phase change heat storage structure on the shady slope of the channel is higher than the heat released on the sunny slope of the channel, thereby balancing the temperature and frost heave of the sunny and shady slopes of the channel. S4. Lay an upper composite geomembrane on the lower composite geomembrane and resistance wire, with the non-woven fabric side of the upper composite geomembrane facing upwards. Then weld and seal the edges of the upper and lower composite geomembranes, controlling the overlap width at the sealing edge to be ≥15cm and the peel strength at the weld to be ≥10N / mm, thereby forming a flexible layered capsule. S5. Fill the inner cavity of the flexible layered capsule with phase change heat storage medium through the pre-reserved opening on the flexible layered capsule. After filling, close the opening and allow the phase change heat storage medium to cool naturally to the ambient temperature. S6. Lay a lining board (1) on the upper composite geomembrane, and use a modified asphalt adhesive to bond the non-woven fabric surface of the upper composite geomembrane to the lining board (1), and install a solar power supply system around the channel and connect the solar power supply system to the resistance wire.

10. The construction method according to claim 9, characterized in that, In step S1, when leveling the channel foundation soil (6), the flatness error is controlled to be ≤5mm, and a vibratory roller is used to compact it in layers, with each layer thickness controlled to be 20cm~30cm, compaction degree ≥95%, and the backfill soil moisture content controlled to be 13%~14%; And / or, in step S3, a low-temperature resistant adhesive material is used to fix the resistance wire to the PE membrane surface of the lower composite geomembrane; And / or, in step S4, a double-track hot melt welding machine is used to weld and seal the edges of the upper and lower composite geomembrane, controlling the hot melt welding temperature to be 220℃~250℃ and the speed to be 0.4m / min~0.6m / min; And / or, the method for preparing the phase change thermal storage medium in step S5 includes: Graphene oxide with a monolayer ratio >95% was obtained by ultrasonically exfoliating graphite with hydrogen peroxide for 2 hours at an ultrasonic power of 400W and a temperature of 30℃. The graphene oxide was then reduced with ascorbic acid at a temperature of 60℃ for 1 hour to obtain reduced graphene oxide. Reduced graphene oxide was refluxed for 3 hours at a temperature of 80°C using a mixed acid solution. The mixed acid solution was formed by mixing concentrated nitric acid and concentrated sulfuric acid in a volume or mass ratio of 1:3 to obtain reduced graphene oxide with carboxyl groups. The reduced graphene oxide with carboxyl groups was mixed with N,N-dimethylformamide at a mass ratio of 1:1.2 and ultrasonically dispersed at 40°C for 45 minutes to obtain a reduced graphene oxide dispersion. Carbon nanotubes are mixed with the reduced graphene oxide dispersion to form a nano-dispersion. Expanded graphite was mixed with concentrated sulfuric acid and stirred at 50°C for 2 hours to complete the intercalation treatment of expanded graphite. The intercalated expanded graphite was then washed until neutral and mixed with the nano-dispersion. After that, it was dried at 50°C for 12 hours to form a graphene-carbon nanotube-expanded graphite composite framework. Paraffin wax and fatty acids were melted at 75°C and added to the graphene-carbon nanotube-expanded graphite composite framework. The mixture was stirred at 600 r / min for 1.5 hours to fully expand the sheet structure. Then the temperature was lowered to 60°C, microcapsule paraffin wax was added, and the mixture was stirred and ultrasonically assisted for 2 hours to obtain the phase change heat storage medium. And / or, in step S5, the phase change heat storage medium is filled into the inner cavity of the flexible layered capsule by pumping. Every 40-50cm of filling is compacted with a vibrator for 10-15s to ensure that the density of the filled phase change heat storage medium is ≥90%, until it is filled to 5-10cm below the opening. Then, the opening is sealed with an annular hot melt gasket. And / or, in step S6, when installing the solar power system, if the solar panel (3) is installed on the sunny slope of the channel, the tilt angle of the solar panel (3) is set to [local latitude - (1 / 2 to 2 / 3 of the slope)], and if the solar panel (3) is installed on the shady slope of the channel, the tilt angle of the solar panel (3) is set to [local latitude + (1 / 2 to 2 / 3 of the slope)]; And / or, in step S6, the lining board is laid under the condition of temperature ≥ 5℃ (1). And / or, in step S6, a modified asphalt adhesive is first brushed onto the non-woven fabric surface of the upper composite geomembrane, and then the lining plate (1) is laid. After that, the lining plate (1) is gently tapped with a rubber hammer so that the area of ​​the lower surface of the lining plate (1) bonded to the upper composite geomembrane is more than 95% of the total area of ​​the lower surface.

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