Red clay roadbed bionic gradient water control composite structure in hot and humid areas and construction method

Abstract

The invention provides a bionic gradient water control composite structure for a red clay roadbed in a hot and humid area and a construction method. The structure comprises a root system net-shaped water blocking layer, a concrete prefabricated slab, a gravel layer, a hydrophobic layer and a blind ditch slope drainage system. The water blocking layer is formed by compounding basalt fibers and a nano-modified bentonite pH self-adaptive layer, and the surface of the water blocking layer is provided with a triangular conical convex microstructure, so that the capillary water blocking effect is enhanced; the hydrophobic layer is formed by mixing silicon dioxide aerogel and potassium methyl silicate with roadbed soil, and the hydrophobic performance is improved. During construction, humidity field changes are monitored in real time through distributed optical fibers, and intelligent water control is achieved. Blind ditches and trapezoidal permeable side ditches are arranged on the side slope, ecological protection is achieved by combining vegetation blankets, and the drainage capacity and the anti-scouring capacity are improved. According to the construction method, a'drainage-dredging-blocking 'gradient water control system is constructed, the roadbed water content is effectively stabilized, the anti-permeability and mechanical properties are improved, and the construction method is suitable for red clay roadbed construction in the hot and humid areas under the complex environment and has good engineering application value.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of road engineering drainage, in particular to a bionic gradient water control composite structure for red clay subgrade in hot and humid regions and a construction method thereof. BACKGROUND

[0002] In the hot and humid regions of southern China, the red clay subgrade has a high proportion of fine particles, and is eroded by acidic precipitation for a long time and disturbed by complex terrain conditions, resulting in obvious defects in traditional drainage technology. When using conventional geotextile for isolation, the fine particles in the red clay are prone to migration, and these fine particles gradually block the pore structure of the geotextile, forming a physical clogging phenomenon. Experimental data shows that only after 3 months, the permeability coefficient of the geotextile will decrease by about 80%, which not only seriously affects its drainage efficiency, but also causes the capillary water in the subgrade to continue to seep upwards, causing the softening of the subgrade material and reducing the stability and bearing capacity of the entire subgrade structure.

[0003] The traditional chemical improvement method, such as adding lime to improve soil properties, can improve soil strength in the short term, but in the acid rain environment with a pH value of 4.5-5.5, the improvement effect is difficult to last. Due to the influence of acidic precipitation, a reverse displacement reaction occurs between calcium ions and hydrogen ions in the lime solidification layer, which destroys the original cementation structure and further causes the internal structure to disintegrate. Research has found that under such conditions, the strength of the improved layer may decrease by more than 35% in 2 years, greatly weakening its shear resistance and overall stability.

[0004] In addition, the commonly used straight blind ditch system as a gravity drainage method is designed based on relatively flat terrain conditions. However, in the complex terrain fluctuations and dense vegetation root systems in the hot and humid regions of southern China, the actual drainage efficiency of such blind ditches is greatly reduced. On the one hand, the change of terrain limits the natural flow direction of water flow; on the other hand, the penetration of plant roots also causes additional damage to the blind ditch, leading to poor drainage and easy formation of local water accumulation areas, further increasing the risk of water damage to the subgrade. SUMMARY

[0005] The purpose of the embodiment of the present application is to provide a bionic gradient water control composite structure for red clay subgrade in hot and humid regions, to solve the problems of poor material adaptability, structural staticity and insufficient environmental erosion resistance in the prior art, and to meet the long-term service requirements of red clay subgrade in hot and humid regions.

[0006] The second purpose of the embodiment of the present application is to provide a construction method of a bionic gradient water control composite structure for red clay subgrade in hot and humid regions.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is a biomimetic gradient water control composite structure for red clay roadbed in humid and hot areas, comprising:

[0008] A water-blocking layer is laid at the bottom of the entire roadbed; the water-blocking layer has a root network structure and a pH adaptive layer on its surface.

[0009] Precast concrete slabs are laid on the water-blocking layer at the top of the roadbed; a first crushed stone layer is set on top of the precast concrete slabs.

[0010] A hydrophobic layer is set on top of the first crushed stone layer. The hydrophobic layer consists of silica hydrophobic aerogel particles with a mass fraction of 1.5% to 3.0%, potassium methylsilicate with a mass fraction of 0.3% to 1.0%, and the remainder being subgrade soil.

[0011] Blind drains are installed at the bottom of the embankment slope. Blind drain pipes are installed inside the blind drain and a second layer of crushed stone is backfilled. The top of the second layer of crushed stone and the inner wall of the blind drain are provided with a permeable concrete layer. A trapezoidal side ditch is set on the top of the blind drain.

[0012] Furthermore, the root network structure of the water-blocking layer has a thickness of 2.5–5 mm, a mesh size of 2 mm × 2 mm, a fractal dimension of 1.8–2.2, a pH adaptive layer thickness of 0.3–1 mm, and a triangular pyramidal protrusion array structure with a height of 150–300 μm and a spacing of 300–800 μm on the surface of the pH adaptive layer.

[0013] The thickness of the precast concrete slab is 10-15cm;

[0014] The thickness of the hydrophobic layer is 4–8 cm;

[0015] The trapezoidal side ditch at the top of the blind drain has a depth of 30-60cm, and the inner side slope ratio is 1:1 to 1:1.5.

[0016] Furthermore, a distributed optical fiber is disposed within the water-blocking layer; the distributed optical fiber includes a pre-installed tetrafluoroethylene protective sleeve and uses a polyimide-coated high birefringence polarization-maintaining optical fiber as a sensitive element.

[0017] Furthermore, the first crushed stone layer is specifically a graded crushed stone layer with a thickness of 15-20 cm, comprising three layers; each layer is compacted to a relative density ≥93%;

[0018] The second crushed stone layer is 15-30cm thick and is laid with medium-coarse sand.

[0019] The construction method for a biomimetic gradient capillary water blocking composite structure for red clay subgrade in humid and hot regions, as described above, is carried out according to the following steps:

[0020] S1. Basalt fiber filaments with a diameter of 8-15μm are used to form a root network structure through a three-dimensional weaving process. Nano-modified bentonite slurry is sprayed onto the surface of the basalt fiber root network structure and allowed to cure naturally for 24-36 hours to form a pH adaptive layer. A triangular pyramidal protrusion array is obtained on the surface of the basalt fiber root network structure by laser etching. Distributed optical fibers are pre-embedded in an S-shape along the cross section of the roadbed at the bottom of the roadbed. Then, the naturally cured basalt fiber root network structure is laid to complete the laying of the water-blocking layer.

[0021] S2. Arrange precast concrete slabs and a drainage layer on the water-blocking layer;

[0022] S3. Lay a water-blocking layer on the roadbed slope, excavate blind drains, and backfill the roadbed slope.

[0023] Furthermore, the mass ratio of the nano-modified bentonite slurry is as follows: 79-82% bentonite, 7-9% nano silica, 1-3% nano zinc oxide, 7-10% sodium polyacrylate, and 0.5-1% sodium dodecylbenzenesulfonate.

[0024] Furthermore, the specific process of S2 is as follows:

[0025] S201. Install precast concrete slabs on the water-blocking layer. During the installation process, leave a 5-6mm gap at the horizontal splicing points.

[0026] S202. A first crushed stone layer of 15-20cm is laid on the concrete slab. The first crushed stone layer includes a bottom 5cm layer of 20-30mm crushed stone, a middle 5-10cm layer of 10-20mm crushed stone, and a top 5cm layer of 5-10mm crushed stone. Each layer is compacted with a vibratory roller to a relative density of ≥93% after it is laid.

[0027] S203. Using silica hydrophobic aerogel particles with a particle size of 3-5 mm and a hydrophobic contact angle of 150°, 1.5-3.0% by mass of silica particles and 0.3-1.0% by mass of potassium methylsilicate are mixed with the subgrade soil and laid on a 4-8 cm thick hydrophobic layer above the graded crushed stone. After laying, distributed optical fibers are deployed. The distributed optical fibers extract the strain changes caused by humidity by detecting the spectral drift of the Rayleigh backscattering signal, thereby achieving high spatial resolution distributed measurement of the humidity field.

[0028] S204. Backfill and compact the top of the roadbed in layers, with a compaction degree K≥96%, and control the moisture content of the backfill soil to ±2% of the optimum moisture content.

[0029] Furthermore, the specific process of S3 is as follows:

[0030] S301. Remove loose soil and vegetation roots from the surface of the slope, lay a water-blocking layer on the slope, and then backfill with the original soil.

[0031] S302. Excavate blind drains at the bottom of the roadbed slope and place blind drain pipes wrapped with geotextile inside the blind drains; fix the overlapping parts of the blind drain pipes with wire, and the overlapping length of the blind drain pipes shall not be less than 10cm.

[0032] S303. A second layer of crushed stone is filled above the pipeline, specifically a 15-30cm thick layer of medium-coarse sand with a particle size of not less than 15mm and a mud content of less than 3%; earthwork is backfilled on the second layer of crushed stone and compacted by vibration, with a compaction degree of not less than 60%.

[0033] S304. Trapezoidal side ditches are laid using permeable precast concrete slabs.

[0034] S305. Backfill the entire roadbed slope using a small hand-operated vibratory roller at a frequency of 35Hz, compacting twice from top to bottom along the slope to adjust the overall slope ratio to 1:1.5, ensuring the water-blocking layer adheres closely to the slope surface; and cover the outside of the backfilled roadbed slope with vegetation mat, ensuring a grass seed density greater than 60g / m². 2 .

[0035] Compared with the prior art, the beneficial effects of the present invention include the following:

[0036] 1. This invention utilizes a novel water-blocking material composed of a basalt fiber fractal network structure and a nano-bentonite pH-adaptive layer. Compared to traditional water-blocking layers, it exhibits superior corrosion resistance and can effectively block capillary water migration paths in complex acidic or alkaline environments. Under optimal parameter conditions (80% bentonite, 9% nano-SiO2, 2.5% nano-ZnO, 8% sodium polyacrylate, and 0.5% sodium dodecylbenzenesulfonate), the nano-modified bentonite water-blocking coating shows a measured vertical permeability coefficient as low as 0.89 × 10⁻⁶. -9 The CBR exhibits a burst strength of 640 kPa and longitudinal and transverse tensile strengths of 95.2 kN / m and 48.6 kN / m, respectively, and remains structurally stable within a pH range of 3.5–9.0, fully demonstrating its impermeability, mechanical properties, and environmental stability. Furthermore, the interfacial control capability is enhanced by laser etching an array of triangular pyramidal protrusions on the surface of the basalt fiber.

[0037] 2. The present invention sets up a gradient permeable filtration layer system, which consists of a permeable precast concrete slab, a graded crushed stone layer and a hydrophobic layer, to construct a comprehensive water control mechanism of "drainage-drainage-blockage" in three parts, forming a hydraulic gradient system with step-by-step regulation capability, which significantly improves the overall drainage efficiency.

[0038] 3. Distributed fiber optic sensors protected by polytetrafluoroethylene sheaths are pre-embedded in key layers to realize real-time online monitoring of the spatial distribution of roadbed humidity field, with a monitoring accuracy of ±0.5%, providing data support for roadbed stability assessment.

[0039] This invention introduces a synergistic drainage structure combining vegetation mats and permeable side ditches, which not only improves the drainage capacity of the side ditch system but also organically combines engineering protection with vegetation restoration, enhancing the slope's erosion resistance and ecological function. This invention can effectively control lateral seepage and water evaporation processes, stabilizing the roadbed's internal moisture content within the optimal compaction moisture content range, thus ensuring the long-term service performance of the roadbed. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a flowchart illustrating the overall construction process of this implementation method;

[0042] Figure 2 This is a plan view of the distributed optical cable burial in this embodiment;

[0043] Figure 3 This is a cross-sectional view of the roadbed in this implementation method;

[0044] Figure 4 This refers to monitoring data from a roadbed-distributed fiber optic humidity sensor according to an embodiment of the present invention.

[0045] In the diagram, 1 is the hydrophobic layer; 2 is the distributed optical fiber; 3 is the first crushed stone layer; 4 is the precast concrete slab; 5 is the water-blocking layer; 6 is the blind drain; and 7 is the second crushed stone layer. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0047] like Figure 3 This embodiment provides a biomimetic gradient water control composite structure for red clay roadbed in humid and hot areas, including a hydrophobic layer 1, a first crushed stone layer 3, a precast concrete slab 4, a water-blocking layer 5, and a blind drain 6.

[0048] In some specific embodiments, the water-blocking layer 5 is formed by three-dimensional weaving of basalt fibers with a diameter of 8-15μm to form a root network structure with a thickness of 2.5-5mm, and the surface is sprayed with nano-modified bentonite slurry to form a pH adaptive layer with a thickness of 0.3-1mm. The composition is shown in Table 1.

[0049] Table 1. Composition and Proportioning of Nano-Modified Bentonite Slurry

[0050]

[0051] A triangular pyramidal protrusion array with a height of 150–300 μm and a spacing of 300–800 μm is fabricated using laser etching technology. The water-blocking layer 5 has a unit area mass of 450–600 g / m². 2 The longitudinal fracture strength is 80–100 kN / m, and the transverse fracture strength is 20–50 kN / m; the fracture elongation is 1%–4%.

[0052] In this embodiment, the water-blocking layer 5 uses basalt fiber filaments as the substrate and constructs a mesh structure through a three-dimensional weaving process, with a fractal dimension between 1.8 and 2.2. This embodiment addresses the engineering characteristics of red clay roadbeds in humid and hot regions under the combined effects of long-term high humidity, acidic precipitation, and complex terrain. The water-blocking layer is constructed using a structure with a fractal dimension between 1.8 and 2.2. This range helps optimize the microscopic topology of the water-blocking layer, thereby effectively improving its ability to block capillary water, while also enhancing the interfacial adhesion between the coating and the substrate and its long-term environmental stability. The water-blocking layer 5 simulates the branching network morphology of plant roots, possessing high spatial extensibility and interlaced interconnection characteristics. It aims to simulate the complex and dense barrier system formed by plant roots in the soil medium, thereby effectively inhibiting the upward transport path of capillary water and achieving a physical water-blocking function.

[0053] Furthermore, this embodiment uses nano-modified bentonite as a coating material to construct a pH-adaptive layer on the surface of the water-blocking layer 5. The pH-adaptive layer can adapt to changes in environmental pH between 3.5 and 9, exhibiting good chemical stability and continuous water-blocking performance. In this embodiment, the pH-adaptive layer's pH regulation function is based on the synergistic effect of various components in the modified bentonite slurry. Specifically, the modified bentonite itself has good cation exchange and adsorption properties, nano-oxides enhance structural stability and dispersion performance, and polymer thickeners impart reversible swelling behavior to the material under different pH conditions. This effectively improves the seepage prevention performance of bentonite in corrosive environments. In addition, the pH-adaptive layer possesses "swelling responsiveness," undergoing volume expansion upon contact with water, thereby enhancing the physical barrier to water penetration. This embodiment mimics the micro-protrusion configuration of plant root hairs at the cellular scale to expand the interfacial contact area and optimize drainage path regulation capabilities. This structure not only significantly improves the bond strength between the material and the surrounding soil but also enhances the system's impermeability and long-term stability.

[0054] In some possible implementations, distributed optical fibers 2, pre-sheathed with polytetrafluoroethylene (PTFE), are installed within the water-blocking layer 5 at the bottom of the roadbed, with a spacing of 3-8m between the distributed optical fibers 2. After the vibration compaction process is completed, the water-blocking layer 5 is laid throughout the entire roadbed area to achieve efficient waterproofing and structural stability. Subsequently, a gradient permeable layer is laid. The first layer is a 10-15cm thick precast concrete slab 4 laid on the water-blocking layer 5 at the top of the roadbed to guide lateral drainage. The second layer is a 15-20cm thick first crushed stone layer 3, specifically a graded crushed stone layer, compacted in three layers, each compacted to a relative density ≥93%. The third layer is a 4-8cm thick hydrophobic layer 1, which uses the subgrade soil as the base material and adds 1.5-3.0wt% silica hydrophobic aerogel particles and 0.3-1.0wt% potassium methylsilicate to enhance its hydrophobic properties. Subsequently, distributed optical fibers 2 with pre-insulated polytetrafluoroethylene (PTFE) sheaths are installed inside the hydrophobic layer 1, with a spacing of 3-8m between the distributed optical fibers 2. After completion, the roadbed soil is backfilled in layers.

[0055] In some specific embodiments, the distributed optical fiber 2 uses a polyimide-clad high-birefringence polarization-maintaining fiber as the sensing element. The polyimide coating has good hygroscopic properties; changes in ambient relative humidity (RH) will cause it to expand or contract, resulting in strain along the fiber axis. This strain will cause a change in the optical path length between Rayleigh scattering centers within the fiber. By detecting the spectral shift of the Rayleigh backscattering signal, the strain change caused by humidity is extracted, achieving high spatial resolution distributed measurement of the humidity field. The specific humidity measurement process is as follows: first, the effective strain Δε is determined. eff:

[0056]

[0057] Where, ζ L Where ε is the optical path length, Pe is the photoelastic coefficient, ζ is the thermo-optical coefficient, and Δε RH , Δε T The strains caused by humidity and temperature are respectively, where ΔT is the temperature change; and the optical path length change Δζ is the strain caused by humidity and temperature, respectively. L P is extracted in real time by Rayleigh spectral shift using an optical frequency domain reflectance (OFDR) system. e (Photoelastic coefficient) and ξ (thermo-optic coefficient) are inherent parameters of polarization-maintaining fiber materials; Δε RH , Δε T The spectral drift was independently calibrated through controlled temperature and humidity gradient experiments, and then decoupled and inverted using a spectral drift curve fitting method. A linear matrix model of spectral drift and temperature / humidity changes was further established as follows:

[0058]

[0059] Δv a Δv c The Rayleigh spectral shifts for channels a and c are represented by these values. The spectral drift sensitivity of channels a and c to temperature changes; ΔT represents the spectral drift sensitivity of channels a and c to humidity changes; ΔT represents the temperature change at the measurement point (relative to the initial state); ΔRH represents the relative humidity change at the measurement point (relative to the initial state); Δv a,0 The initial frequency shift baseline deviation of channel a.

[0060] Distributed humidity field measurement results can be obtained by solving the matrix inversion.

[0061] A blind ditch 6, 0.8–1.5m deep, is installed at the bottom of the roadbed slope. A Φ150mm blind ditch pipe is installed inside the blind ditch 6, and the outside is wrapped with permeable geotextile to achieve integrated filtration and drainage functions. A second crushed stone layer 7, 15–30cm thick, is backfilled inside the blind ditch 6, using medium-coarse sand to ensure good permeability and structural support.

[0062] A permeable concrete layer is provided on the second crushed stone layer 7 and the inner wall of the blind drain 6. The permeable concrete layer is made of C20 strength grade permeable concrete and is cast on site. The side wall of the blind drain 6 and the second crushed stone layer 7 are uniformly cast with a thickness of 8-15cm to enhance the overall stability and impermeability of the drainage system.

[0063] Blind drain 6 and its slope surface are covered with backfill soil. A trapezoidal side ditch with a depth of 30–60 cm is reserved at the top of blind drain 6, with an inner slope ratio of 1:1 to 1:1.5. At the same time, the slope ratio of the backfill soil layer of the roadbed slope is uniformly adjusted to 1:1.5 to meet the requirements of slope stability and drainage function.

[0064] After the backfill layer was completed, a small road roller with a vibration frequency of 35Hz was used for two passes of compaction to improve soil density and ensure the overall stability of the slope structure. Finally, a vegetation mat was laid on the slope surface, with the grass seeding density controlled at 50–80 g / m². 2 Within the scope, the aim is to achieve rapid greening, soil stabilization and slope protection, and ecological restoration.

[0065] This embodiment provides a specific construction method for a biomimetic gradient capillary water blocking composite structure for red clay roadbeds in humid and hot regions, which is carried out according to the following steps:

[0066] S11. Basalt fibers with a diameter of 8-15μm are used to form a root network structure with a fractal dimension of 1.8-2.2 through a three-dimensional weaving process. The fiber tensile strength is ≥2100MPa, the mesh size is 2mm×2mm, and the mesh layer thickness is 2.5-5mm. To effectively isolate external water, a nano-modified bentonite slurry is sprayed onto the surface of the basalt fiber biomimetic plant root water-blocking layer 5. After natural curing for 24-36 hours, a pH adaptive layer with a pH adaptation range of 3.5-9 and an expansion ratio of 120% is formed.

[0067] S12. A triangular pyramidal protrusion array with a height of 150–300 μm and a spacing of 300–800 μm is formed on the surface of the root network structure using laser etching technology.

[0068] S13. Distributed PTFE-sheathed optical fibers 2 are pre-embedded at S-shaped intervals of 3-8m along the cross-section of the roadbed at the bottom of the subgrade. To verify the monitoring accuracy of the humidity sensor in the distributed optical fiber 2, a TDR-3 type moisture sensor is buried every 2-3m. Figure 2 As shown.

[0069] S14. Lay the water-blocking layer 5 along the full width of the roadbed cross section. During the laying process, the water-blocking layer 5 needs to be straightened so that the lower surface is closely attached to the underlying layer to avoid twisting and wrinkling. When splicing, the overlap length in the middle of the roadbed should not be less than 20cm, and Φ6 basalt fiber rods should be used to fix the overlap. Sufficient width should be reserved on both sides to meet the needs of slope edging.

[0070] Experimental Example

[0071] This embodiment systematically evaluates the application effects of water-blocking layers 5 with different fractal dimensions, studies their specific impact on permeability coefficient, CBR puncture strength, and pH stability, clarifies the influence law of different fractal dimensions on the performance of water-blocking layers 5, and then determines the optimal combination of fractal dimensions in the engineering application of water-blocking layers 5 in this embodiment. Specific formulation details are shown in Table 2.

[0072] Table 2 Experimental design of water-blocking layers with different fractal dimensions

[0073]

[0074] Experimental steps:

[0075] (1) Sampling and determination of fractal dimension: Box-counting was used on optical micrographs, and the average value of 5 fields of view for each group was taken as the fractal dimension of that group.

[0076] (2) Performance testing: Vertical permeability coefficient: determined according to the requirements of the "Test Procedure for Geosynthetics" (SL235-2012), describing the ability of geotextile to permeate water in the vertical direction; CBR puncture strength: the test uses a universal testing machine to fix the sample in the specified ring clamp, according to the "Static Puncture Test (CBR Method) of Geosynthetics" (GB / T14800-2010); Chemical stability: soaked in acidic solutions of pH=3.5 and 5.0 for 48h, observe the structural stability, and measure the percentage of weight loss under different conditions.

[0077] Table 3 Experimental Results

[0078]

[0079]

[0080] As shown in Tables 2 and 3, the groups with lower fractal dimensions (D = 1.4 and 1.6) performed poorly, exhibiting high permeability coefficients, low CBR puncture strength, and significant weight loss under acidic conditions, indicating a loose structure and weak resistance to chemical corrosion. With increasing fractal dimension, the permeability coefficient of the water-blocking layer 5 gradually decreased, while its mechanical strength and chemical stability significantly improved. In summary, this embodiment suggests that, without coating, a fractal dimension of 1.8–2.2 represents the optimal range for the structure of the water-blocking layer 5, achieving the best balance between permeability, mechanical properties, and chemical stability.

[0081] Example

[0082] This embodiment systematically evaluates the application effect of nano-modified bentonite with different ratios in the treatment of water-blocking layer 5, studies its specific influence on vertical permeability coefficient, horizontal permeability coefficient and pH stability, and thus clarifies the effect of nano-modified bentonite slurry ratio on the performance improvement of water-blocking layer 5.

[0083] This embodiment uses multiple groups of nano-modified bentonite with different ratios for experiments. The effects of each component on the material's permeability, expansion performance, and pH stability are comprehensively analyzed to determine the optimal ratio combination for the water-blocking layer 5 engineering application. Specific ratio details of the embodiments are shown in Table 4.

[0084] Table 4. Formulation ratios (by mass) for different embodiments

[0085] Bentonite nano-SiO2 Nano-ZnO Sodium polyacrylate Sodium dodecyl benzene sulfonate Example 1 79％ 9％ 1％ 10％ 1％ Example 2 80％ 9％ 2.5％ 8％ 0.5％ Example 3 81％ 8％ 3％ 7％ 1％ Example 4 82％ 7％ 2.5％ 8％ 0.5％ Comparative Example 1 0％ 0％ 0％ 0％ 0％

[0086] S1. Slurry preparation: Weigh each solid component according to the mass ratio; mix evenly and add deionized water, controlling the water-cement ratio to be 1:1.2; stir with a high-speed mixer for 10 minutes, let stand for 12 hours to mature, and form a stable slurry; coat the slurry onto the surface of basalt fiber woven fabric, controlling the coating thickness to be 0.5 mm; cure naturally at room temperature for 24 hours to obtain the test sample.

[0087] Performance Testing: Vertical Permeability Coefficient: Determined according to the requirements of "Test Procedure for Geosynthetics" (SL235-2012), describing the ability of geotextile to transmit water in the vertical direction; CBR Bursting Strength: The test uses a universal testing machine to fix the sample in a specified annular clamp, according to "Static Bursting Test (CBR Method) of Geosynthetics" (GB / T14800—2010); Longitudinal and Transverse Tensile Strength: First, according to the requirements of "Determination of Trapezoidal Tear Strength of Geosynthetics" (GB / T13763-2010): the curing temperature is 20℃, the relative humidity is 65%, and the condition is adjusted for 24 hours before measurement; Chemical Stability: Immersed in solutions with pH=3.5, 5.0, 7.0, and 9.0 for 48 hours, the stability of the coating structure is observed, and the percentage of weight loss under different conditions is measured.

[0088] Experimental results:

[0089] Table 5 Experimental Results

[0090]

[0091] Table 6 Results of Chemical Stability Experiments

[0092]

[0093] As shown in Tables 5 and 6, the comparative examples performed the worst, with low strength. Example 2 showed the best overall performance among all indicators. Its nano-SiO2 and sodium polyacrylate compounded to form a dense three-dimensional network structure, effectively improving water-blocking performance. The appropriate introduction of nano-ZnO significantly enhanced the structural stability of the coating in a strong acid environment. In summary, the formulation of Example 2 (80% bentonite, 9% nano-SiO2, 2.5% nano-ZnO, 8% sodium polyacrylate, and 0.5% sodium dodecylbenzenesulfonate) is the optimal formulation for the nano-modified bentonite water-blocking coating of this embodiment.

[0094] S2. A precast concrete slab and a drainage layer are arranged on the biomimetic root system water-blocking layer 5. The specific construction process of step S2 is as follows:

[0095] S21. Install a 10-15cm thick precast concrete slab 4 on the water-blocking layer 5 of S14, leaving a 5-6mm gap at the transverse joints during installation. In some possible embodiments, the precast concrete slab 4 is specifically a permeable precast concrete slab 4.

[0096] S22. A first crushed stone layer 3, 15-20cm thick, is laid on the concrete slab. The first crushed stone layer 3 consists of a bottom 5cm layer of 20-30mm crushed stone, a middle 5-10cm layer of 10-20mm crushed stone, and a top 5cm layer of 5-10mm crushed stone. After each layer is laid, it is compacted with a vibratory roller to a relative density ≥93%.

[0097] S23. Using silica hydrophobic aerogel particles with a particle size of 3-5 mm and a hydrophobic contact angle of 150°, mix 1.5-3.0% silica particles and 0.3-1.0% potassium methylsilicate with the subgrade soil, and lay a 4-8 cm thick hydrophobic layer 1 on top of the graded crushed stone to form a continuous water vapor barrier interface. After laying, deploy distributed optical fibers 2 and TDR-3 type moisture sensors as follows. Figure 2 .

[0098] After the gradient permeable layer is laid, the top of the roadbed is backfilled and compacted in layers, with a compaction degree K≥96%, and the moisture content of the backfill soil is controlled at about ±2% of the optimum moisture content.

[0099] S3. After the roadbed filling is completed, continue construction according to the following process:

[0100] S31. Remove the loose soil and vegetation roots from the surface of the slope, lay the water-blocking layer 5 reserved in S14 on the remaining slope, and backfill the slope with the original soil.

[0101] S32. Excavate blind drains at the bottom of the roadbed slope, selecting plastic blind drain pipes with a porosity of 88.82% and a diameter of 150 mm, using water-permeable materials with a density of 100 g / cm³. 2The geotextile is wrapped around the pipe and placed inside the blind drain. At the overlap of the pipe in the blind drain, it is fixed with wire to prevent the pipe joint from slipping or misaligning. The overlap length of the pipe in the blind drain should not be less than 10cm.

[0102] S33. Fill a 15-30cm thick layer of medium-coarse sand with a particle size of not less than 15mm and a mud content of less than 3% above the pipeline. Finally, backfill the soil above the second crushed stone layer 7 and compact it with vibration. The compaction degree should not be less than 60%.

[0103] S34. Trapezoidal side ditches are laid using 10cm C20 permeable concrete precast slabs, with an inner slope ratio of 1:1 to 1:1.5.

[0104] S35. Backfill the entire roadbed slope using a small hand-operated vibratory roller at a frequency of 35Hz, compacting twice from top to bottom along the slope to adjust the overall slope ratio to 1:1.5, ensuring the water-blocking layer 5 is in close contact with the slope surface. Cover the outside of the backfilled slope with a vegetation mat, ensuring a grass seed density greater than 60g / m². 2 .

[0105] S36. After construction is completed, simulated rainfall will be conducted on the roadbed, and the humidity of the roadbed with distributed optical fiber 2 will be continuously monitored simultaneously. Figure 4 The test results show that the accuracy of the distributed optical fiber 2 humidity monitoring is only ±0.5% different from that of the TDR-3 moisture sensor.

[0106] Overall cross-sectional profile as shown Figure 3 As shown.

[0107] This embodiment aims to verify the effect of the biomimetic gradient capillary water blocking composite structure on the regulation of the humidity field in red clay subgrade engineering. By selecting representative field test sections, three working conditions were constructed, including the structure of this invention, the traditional geotextile laying structure, and the unlaid waterproof material. The variation characteristics of the subgrade humidity field under the same environmental conditions were compared and analyzed, thereby evaluating the performance advantages of the structure of this invention in practical engineering applications and providing technical basis for subsequent engineering promotion.

[0108] Specifically, three typical test sections, each 15 meters in length, were selected. The geotextile placement, structural layer thickness, compaction degree, and slope treatment methods remained consistent across all test sections. The test structure design parameters are detailed in Table 7. In each test section, TDR-3 humidity sensors were installed at depths of 0.3 m and 0.7 m (below the geotextile) to continuously monitor changes in the internal humidity field of the roadbed over 30 days. To simulate natural rainfall conditions, a uniform spraying system was used to humidify the entire test area, ensuring uniform rainwater infiltration. The simulated rainfall duration was 4 hours, with a rainfall intensity controlled at 30 mm / h, to reproduce the ability of each structure to block and regulate moisture migration under typical rainfall conditions.

[0109] Table 7 Structural Design

[0110] Structure of water blocking layer 5 Example 4 Bionic gradient capillary water blocking composite structure Comparative Example 2 Common geotextile Comparative Example 3 Without geotextile

[0111] The experimental results are shown in Table 8.

[0112] Table 8. Results of soil moisture content experiments at different experimental days and depths.

[0113]

[0114] As shown in Table 8, in the blank control example 3, rainwater rapidly infiltrated into the lower structure, and the overall humidity increased significantly, reaching a maximum of 33.8%, remaining moist for a long time and posing a risk of water collapse; Example 2 could play a certain role in preventing seepage, but the effect was limited due to micro-cracks and uneven tension at the interface; Example 4 clearly formed a boundary between the water-blocking layer 5 and the water storage zone, and the moisture content of the 0.3m layer was significantly lower than that of other groups, decreasing rapidly and recovering to stability; the overall trend shows that this implementation method can effectively slow down the infiltration rate of rainwater, inhibit the diffusion of saturated areas, and form a durable and stable humidity gradient barrier.

[0115] The results of simulated rainfall field tests show that the composite water-blocking structure proposed in this invention can significantly slow down the moisture infiltration process after heavy rainfall, keep the upper part of the structural layer dry, and prevent the red clay from softening, deforming, and becoming unstable. It has excellent engineering applicability and environmental stability.

[0116] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0117] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A biomimetic gradient water-control composite structure for red clay roadbed in humid and hot regions, characterized in that, include: A water-blocking layer (5) is laid at the bottom of the entire roadbed; the water-blocking layer (5) is a root network structure with a pH adaptive layer on its surface; A precast concrete slab (4) is laid on the water-blocking layer (5) on top of the roadbed; a first crushed stone layer (3) is set on top of the precast concrete slab (4); A hydrophobic layer (1) is set on top of the first crushed stone layer (3). The hydrophobic layer (1) is composed of silica hydrophobic aerogel particles with a mass fraction of 1.5% to 3.0%, potassium methylsilicate with a mass fraction of 0.3% to 1.0%, and the remainder being subgrade soil. Blind drain (6) is set at the bottom of the embankment slope. The blind drain (6) is filled with a pipe and backfilled with a second crushed stone layer (7). The top of the second crushed stone layer (7) and the inner wall of the blind drain (6) are provided with a permeable concrete layer. A trapezoidal side ditch is set on the top of the blind drain (6).

2. The biomimetic gradient water control composite structure for red clay roadbed in humid and hot regions according to claim 1, characterized in that, The root network structure of the water-blocking layer (5) has a thickness of 2.5-5 mm, a mesh size of 2 mm × 2 mm, a fractal dimension of 1.8-2.2, a pH adaptive layer thickness of 0.3-1 mm, and a triangular pyramidal protrusion array structure with a height of 150-300 μm and a spacing of 300-800 μm on the surface of the pH adaptive layer. The thickness of the precast concrete slab (4) is 10-15 cm; The thickness of the hydrophobic layer (1) is 4-8 cm; The depth of the trapezoidal side ditch at the top of the blind ditch (6) is 30-60cm, and the slope ratio of the inner side slope is 1:1 to 1:1.

5.

3. The biomimetic gradient water control composite structure for red clay roadbed in humid and hot regions according to claim 1, characterized in that, Distributed optical fiber (2) is installed inside the water-blocking layer (5); the distributed optical fiber (2) includes a pre-installed tetrafluoroethylene protective sleeve and uses polyimide-coated high birefringence polarization-maintaining optical fiber as a sensitive element.

4. The biomimetic gradient water control composite structure for red clay roadbed in humid and hot regions according to claim 1, characterized in that, The first crushed stone layer (3) is specifically a graded crushed stone layer with a thickness of 15-20cm, consisting of three layers; each layer is compacted to a relative density ≥93%; The second crushed stone layer (7) is 15-30cm thick and is laid with medium-coarse sand.

5. The construction method of a biomimetic gradient water control composite structure for red clay roadbed in humid and hot areas as described in claim 1, characterized in that, Please follow these steps: S1. Basalt fibers with a diameter of 8-15μm are used to form a root network structure through a three-dimensional weaving process. Nano-modified bentonite slurry is sprayed onto the surface of the basalt fiber root network structure and naturally cured for 24-36 hours to form a pH adaptive layer. A triangular pyramidal protrusion array is obtained on the surface of the basalt fiber root network structure by laser etching. Distributed optical fibers (2) are pre-embedded in an S-shape along the cross section of the roadbed at the bottom of the roadbed; then, a natural-cured basalt fiber root network structure is laid to complete the laying of the water-blocking layer (5); S2. A precast concrete slab (4) and a drainage layer (1) are arranged on the water-blocking layer (5); S3. Lay a water-blocking layer (5) on the roadbed slope, excavate blind drains (6), and backfill the roadbed slope.

6. The construction method of a biomimetic gradient water control composite structure for red clay roadbed in humid and hot areas according to claim 5, characterized in that, The mass ratio of the nano-modified bentonite slurry is as follows: 79-82% bentonite, 7-9% nano silica, 1-3% nano zinc oxide, 7-10% sodium polyacrylate, and 0.5-1% sodium dodecylbenzenesulfonate.

7. The construction method of a biomimetic gradient water control composite structure for red clay roadbed in humid and hot areas according to claim 5, characterized in that, The specific process of S2 is as follows: S201. Install precast concrete slabs (4) on the water-blocking layer (5). During the installation process, leave a gap of 5-6 mm at the horizontal splicing point. S202, The first crushed stone layer (3) of 15-20cm is laid on the concrete slab; The first crushed stone layer (3) includes a lower layer of 5cm of 20-30mm crushed stone, a middle layer of 5-10cm of 10-20mm crushed stone, and an upper layer of 5cm of 5-10mm crushed stone. After each layer is laid, it is compacted with a vibratory roller to a relative density of ≥93%. S203. Using silica hydrophobic aerogel particles with a particle size of 3-5 mm and a hydrophobic contact angle of 150°, 1.5-3.0% by mass of silica particles and 0.3-1.0% by mass of potassium methylsilicate are mixed with the subgrade soil and laid on a hydrophobic layer with a thickness of 4-8 cm above the graded crushed stone (1). After laying, distributed optical fibers (2) are arranged. The distributed optical fibers (2) extract the strain changes caused by humidity by detecting the spectral drift of the Rayleigh backscattering signal, thereby realizing high-resolution distributed measurement of the humidity field. S204. Backfill and compact the top of the roadbed in layers, with a compaction degree K≥96%, and control the moisture content of the backfill soil to ±2% of the optimum moisture content.

8. The construction method of a biomimetic gradient water control composite structure for red clay roadbed in humid and hot areas according to claim 5, characterized in that, The specific process of S3 is as follows: S301. Remove loose soil and vegetation roots from the surface of the slope, and lay a water-blocking layer on the slope (5); then backfill with the original soil. S302. Excavate a blind ditch (6) at the bottom of the roadbed slope and place a blind ditch (6) pipe wrapped with geotextile inside the blind ditch (6); fix the overlapping position of the blind ditch (6) pipe with iron wire, and the overlapping length of the blind ditch (6) pipe shall not be less than 10cm. S303. A second crushed stone layer (7) is filled above the pipeline. Specifically, a medium-coarse sand with a thickness of 15-30cm and a particle size of not less than 15mm and a mud content of less than 3% is filled. Backfilling is carried out on the second crushed stone layer (7) and compaction is carried out by vibration. The compaction degree is not less than 60%. S304. Trapezoidal side ditches are laid using permeable precast concrete slabs (4). S305. Backfill the entire roadbed slope using a small hand-held vibratory roller with a vibration frequency of 35Hz, rolling twice from top to bottom along the slope to adjust the overall slope ratio of the roadbed slope to 1:1.5, and ensuring that the water-blocking layer (5) is in close contact with the slope surface; and cover the outside of the backfilled roadbed slope with a vegetation mat to ensure that the grass seed density is greater than 60g / m². 2 .

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