Gradient structure and design method of heavy-duty durable asphalt pavement under multi-field coupling environment

Abstract

The present application relates to the technical field of asphalt pavement structure design, and especially relates to a heavy-load durable asphalt pavement gradient structure and a design method under a multi-field coupling environment, the structure is sequentially stacked from bottom to top as a high modulus base layer, a toughness middle layer and an anti-skid surface layer; the dynamic modulus of the high modulus base layer is greater than or equal to 14,000 MPa, the thickness is 18-25 cm, the fracture energy of the toughness middle layer is greater than or equal to 1.5 kJ / m2, the thickness is 8-12 cm, the structure depth of the anti-skid surface layer is greater than or equal to 0.8 mm, the thickness is 4-6 cm, and the modulus gradient ratio of each layer is (2.8-3.5):(1.4-1.8):1; the present application realizes dynamic analysis of multi-factor synergistic degradation effects such as freeze-thaw cycles, high-temperature rutting and interlayer shear by establishing a simulation model coupling temperature field, humidity field and heavy-load stress field and a freeze-thaw damage factor quantization formula, and greatly improves the performance prediction accuracy under the coupling effect of environment and load.

Description

Technical Field

[0001] This invention relates to the field of asphalt pavement structure design technology, and in particular to gradient structures and design methods for heavy-duty durable asphalt pavements under multi-field coupling environments. Background Technology

[0002] Asphalt pavement, as the core carrier of heavy-duty transportation infrastructure, faces severe durability challenges under extreme temperature cycles, humidity infiltration, and high-intensity axle load coupling effects. Especially in areas with frequent freeze-thaw cycles and heavy-duty freight corridors, traditional pavement structures often suffer early damage due to the synergistic deterioration of multiple physical fields, thus significantly increasing maintenance costs. With the continuous increase in traffic load intensity and the intensifying trend of climate and environmental degradation, the development of durable asphalt pavement systems for multi-field coupling environments has become an urgent need in the field of road engineering. Currently, how to achieve long-term service under the synergistic effects of multiple factors such as heavy load, temperature change, and moisture damage through structural innovation and design method upgrades is a key bottleneck restricting the development of high-grade highway technology.

[0003] Traditional design methods analyze temperature, humidity, and stress fields separately, using only a single correction factor (such as temperature reduction factor or humidity adjustment factor) for compensation. This fails to quantify the synergistic amplification effect of freeze-thaw cycles and heavy-load vibration on material damage. For example, under daily temperature variations of -15℃ to 40℃, the interfacial bond strength of asphalt mixtures can decrease by up to 62% of that at room temperature. Existing models fail to couple the interaction between ice expansion stress caused by moisture migration and heavy-load shear stress, resulting in performance prediction deviations exceeding 35%. Furthermore, the high-modulus base course + flexible surface course structure commonly used in existing design methods is unstable. When the ratio of base course modulus (typically ≥12,000MPa) to surface course modulus (≤3,000MPa) exceeds 4:1, the interlayer shear strain energy density increases sharply, inducing interfacial delamination. More seriously, the intermediate layer material lacks stress buffering capacity, and the fatigue crack propagation rate accelerates under heavy-load high-frequency impact. Road surfaces with measured fracture energy less than 1.0kJ / m² have a service life shortened by more than 40% compared to the design value.

[0004] Therefore, in response to the problems mentioned above, this invention proposes a gradient structure and design method for heavy-duty durable asphalt pavement under multi-field coupling environment. Summary of the Invention

[0005] To overcome the problems of unclear multi-physics field collaborative degradation mechanism and structural stiffness gradient mismatch in existing heavy-duty asphalt pavement technology, this invention proposes a gradient structure and design method for heavy-duty durable asphalt pavement under multi-field coupling environment.

[0006] The technical solution of the present invention is: a gradient structure for heavy-duty durable asphalt pavement under multi-field coupling environment, consisting of a high-modulus base layer, a tough intermediate layer, and an anti-skid surface layer stacked sequentially from bottom to top;

[0007] Among them, the high modulus base layer has a dynamic modulus ≥14,000 MPa and a thickness of 18-25cm; the tough middle layer has a fracture energy ≥1.5kJ / m² and a thickness of 8-12cm; the anti-slip surface layer has a texture depth ≥0.8 mm and a thickness of 4-6cm; the modulus gradient ratio of each layer is base layer: middle layer: surface layer = (2.8-3.5): (1.4-1.8): 1; and the interlaminar shear strength is ≥1.2 MPa.

[0008] Preferably, the high modulus base layer is made of polymer and fiber composite asphalt concrete. The damage threshold is defined as the critical stress level corresponding to the point of sudden increase in the microcrack propagation rate of the base layer in the simulation model coupled with the temperature field, humidity field and heavy load stress field. This threshold is required to be ≥0.85σmax, where σmax is the ultimate compressive strength. The high modulus and damage tolerance are synergistically improved by adding ≥6% epoxy resin and 0.3% polypropylene fiber.

[0009] Preferably, the toughness intermediate layer is made of asphalt concrete with a rubber powder content of ≥20%. The fatigue toughness index is defined as the ratio of the cumulative dissipated energy to the initial elastic strain energy when the specimen completely fails in a standard fatigue test. This index is required to be ≥8.0, so as to delay crack propagation through the elastic energy dissipation mechanism of rubber particles.

[0010] Preferably, the anti-skid surface layer is made of a mixture of basalt fiber reinforced SMA, with basalt fiber length of 6-12 mm, dosage of 0.4%, structural depth ≥0.8 mm, surface friction coefficient ≥65, and high-temperature rut depth ≤3 mm after 100,000 loading cycles at 60℃ and 0.7 MPa wheel pressure.

[0011] As a preferred approach, the design method for gradient structures of heavy-duty durable asphalt pavements under multi-field coupling environments includes the following steps:

[0012] S1. Establish a coupled simulation model of temperature field, humidity field and heavy load stress field. The input parameters include: annual temperature difference range ΔT and daily variation of temperature field, number of freeze-thaw cycles and saturation change curve of humidity field, axle load spectrum and tire pressure distribution of heavy load field. The model realizes real-time coupling of temperature conduction equation, moisture diffusion equation and stress balance equation through multi-physics iterative solver. ΔT range is -30℃ to +60℃, number of freeze-thaw cycles ≥ 10 times / year, single axle load of axle load spectrum ≥ 130kN, and tire pressure distribution range is 0.8-1.2MPa.

[0013] S2 quantifies the synergistic degradation effect of multiple factors by calculating the interlayer shear strain energy density Ws, base layer compression creep rate Cc, surface wear Aw, and freeze-thaw cycle degradation effect through a coupled model.

[0014] S3, based on the functional decomposition of layers, sets design indicators, including the base layer damage threshold Ws≤15 J / m³, the middle layer fatigue toughness index Cc≤0.035% / 10,000 cycles, and the surface layer anti-slip maintenance rate Aw≤0.2mm / year;

[0015] S4. Optimize structural parameters and adjust the combination of thickness and modulus of each layer until the index of step S3 is met.

[0016] Preferably, the coupled simulation model in step S1 is implemented using a multiphysics iterative solver, and its governing equations include the heat conduction equation:

[0017] ;

[0018] in, Thermal conductivity is a function of temperature. For the hydration heat source, For material density, For specific heat capacity, The rate of temperature change;

[0019] Moisture diffusion equation:

[0020] ;

[0021] in, This refers to the volumetric moisture content. The humidity diffusivity is... For the source of frost heave;

[0022] Dynamic stress equilibrium equation:

[0023] ;

[0024] in, This represents the contact force vector between the tire and the road surface. For displacement acceleration components;

[0025] The temperature field drives the material modulus degradation, the humidity field controls the freeze-thaw expansion force, and the stress field triggers interlaminar shear slip, thus accurately quantifying the three-field coupling effect.

[0026] Preferably, the freeze-thaw cycle degradation effect in step S2 is represented by an equivalent damage factor. Quantization, its expression is:

[0027] ;

[0028] Where N represents the number of freeze-thaw cycles per year. Let be the volumetric expansion of pore water during the k-th cycle as it freezes. The pore volume of the mixture. =35 kJ / mol is the activation energy. The gas constant is Let be the average temperature of the k-th freezing process. This model characterizes the rate of freeze-thaw damage accumulation by using a term that couples the ice expansion work with the temperature activation energy, thus overcoming the limitations of the traditional single porosity index.

[0029] Preferably, step S4 employs a genetic algorithm to optimize structural parameters, with the objective function being the minimization of the total lifecycle cost. The design variables include:

[0030] High modulus base layer thickness Polymer content (P%)

[0031] Intermediate layer thickness Rubber powder content R%

[0032] Surface thickness Fiber length .

[0033] Preferably, the gradient stiffness matching verification method in step S4 optimization includes:

[0034] Calculate the modulus ratio of each layer:

[0035] / ;

[0036] when When ∈[1.8,2.2], interlayer strengthening measures are activated by spraying emulsified asphalt binder into the interlayer and laying fiberglass grid.

[0037] As a preferred option, on-site verification of layer functional indicators is carried out during the construction phase: for the base layer damage threshold verification, a mobile pulse load tester is used to detect the critical load point for crack initiation within 72 hours after paving; for the intermediate layer fatigue toughness verification, core samples are drilled for dynamic shear rheological tests, and the standard is met when the phase angle δ≤65° and the rutting factor G* / sinδ≥2.5kPa; for the surface layer anti-skid retention rate verification, a laser profiler is used to scan the structural depth distribution, and the coefficient of variation is required to be ≤0.15.

[0038] The beneficial effects of this invention are:

[0039] 1. This invention establishes a simulation model coupling temperature field, humidity field and heavy load stress field and a quantitative formula for freeze-thaw damage factor, realizing the dynamic analysis of the synergistic degradation effect of multiple factors such as freeze-thaw cycle, high temperature rutting and interlayer shear, which greatly improves the performance prediction accuracy under the coupled effect of environment and load, and solves the prediction deviation problem caused by field effect decoupling in traditional methods.

[0040] 2. This invention employs a gradient structure of "high-modulus base layer + tough intermediate layer + anti-slip surface layer" and limits the modulus gradient ratio of base layer: intermediate layer: surface layer = (2.8-3.5):(1.4-1.8):1, while also incorporating a modulus compatibility coefficient. The quantitative control improves the interlaminar shear strength, thereby avoiding the interface peeling caused by abrupt changes in stiffness in traditional binary structures. Attached Figure Description

[0041] Figure 1 The diagram shown is a schematic representation of the design method of this invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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 some embodiments of the present invention, but 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.

[0043] This invention provides an embodiment: a gradient structure for heavy-duty durable asphalt pavement under multi-field coupling environment, comprising a high-modulus base layer, a tough intermediate layer, and an anti-skid surface layer stacked sequentially from bottom to top;

[0044] Among them, the high modulus base layer has a dynamic modulus ≥14,000 MPa and a thickness of 18-25cm; the tough middle layer has a fracture energy ≥1.5kJ / m² and a thickness of 8-12cm; the anti-slip surface layer has a texture depth ≥0.8 mm and a thickness of 4-6cm; the modulus gradient ratio of each layer is base layer: middle layer: surface layer = (2.8-3.5): (1.4-1.8): 1; and the interlaminar shear strength is ≥1.2 MPa.

[0045] Furthermore, this structure allows for a smooth transition in the modulus between adjacent layers (e.g., the modulus ratio of the base layer to the middle layer is ≤3.5:1.8≈1.94), thereby avoiding the interlaminar shear failure problem caused by abrupt changes in stiffness (modulus ratio >4:1) in traditional structures. Under the coupled effect of heavy axial load (≥130kN) and environmental temperature change (-30℃~+60℃), the overall lifespan of the structure can be increased to more than 15 years, and the interlaminar delamination rate approaches zero.

[0046] Furthermore, the high-modulus base course uses polymer-fiber composite asphalt concrete, with a polymer modifier (such as SBS) dosage ≥4.5% and fiber (such as polyester fiber) length 6-12mm and dosage 0.3-0.5%. The damage threshold is defined as the critical stress level corresponding to the point of sudden increase in the microcrack propagation rate of the base course in the simulation model coupled with the temperature field, humidity field and heavy load stress field. This threshold is required to be ≥0.85σmax, where σmax is the ultimate compressive strength. The high modulus and damage tolerance are synergistically improved by adding ≥6% epoxy resin and 0.3% polypropylene fiber.

[0047] Polymer modifiers (such as SBS) can form an elastic network structure, enhancing the resilience of asphalt mastic and reducing residual strain accumulation in heavy-load stress fields. When the temperature field rises from -15℃ to 40℃, the penetration index of SBS-modified asphalt changes by only ±10%, while that of base asphalt reaches ±35%, fundamentally inhibiting the initiation of microcracks caused by temperature changes. Fibers block the crack propagation path through bridging effects, reducing crack propagation energy. By designing fiber lengths of 6-12mm, they form a three-dimensional network in concrete, significantly reducing the local stress concentration factor and directly addressing the high stress penetration risk in heavy-load fields.

[0048] Furthermore, the toughness intermediate layer is made of asphalt concrete with a rubber powder content of ≥20%. The fatigue toughness index is defined as the ratio of the cumulative dissipated energy to the initial elastic strain energy when the specimen completely fails in a standard fatigue test. This index is required to be ≥8.0, which delays crack propagation through the elastic energy dissipation mechanism of rubber particles.

[0049] Rubber powder can form an elastic microparticle phase in asphalt, with a glass transition temperature as low as -60℃, which enables the mixture to maintain high deformation capacity in the temperature range of -30℃ to 60℃. When the rubber powder content is <20%, the elastic network is discontinuous and cannot effectively dissipate energy, while >22% leads to a sharp increase in viscosity, affecting construction and workability.

[0050] Furthermore, the anti-skid surface layer is made of a mixture of basalt fiber reinforced SMA, with basalt fiber length of 6-12 mm, dosage of 0.4%, structural depth ≥0.8 mm, surface friction coefficient ≥65, and high-temperature rut depth ≤3 mm after 100,000 loading cycles at 60℃ and 0.7 MPa wheel pressure.

[0051] Among them, basalt fiber can form a three-dimensional network to anchor the aggregate in the SMA skeleton, increasing the pull resistance of coarse aggregate to ≥800 N, thereby directly resisting the wear and shear of heavy-duty tires. The fiber melting point is ≥1600℃, and the modulus retention rate is >95% at a high temperature of 60℃.

[0052] Please see Figure 1Furthermore, the design method for gradient structures of heavy-duty durable asphalt pavements under multi-field coupling environments includes the following steps:

[0053] S1. Establish a coupled simulation model of temperature field, humidity field, and heavy load stress field. Input parameters include: annual temperature difference range ΔT and daily variation of temperature field, number of freeze-thaw cycles and saturation change curve of humidity field, and axle load spectrum and tire pressure distribution of heavy load field. The model realizes real-time coupling of temperature conduction equation, moisture diffusion equation and stress balance equation through multiphysics iterative solver. ΔT range is -30℃ to +60℃, number of freeze-thaw cycles ≥ 10 times / year, single axle load of axle spectrum ≥ 130kN, and tire pressure distribution range is 0.8-1.2MPa. Solve the coupled control equations through multiphysics iterative solver.

[0054] Temperature field: calculated using the heat conduction equation. ;

[0055] in, Thermal conductivity is a function of temperature. For the hydration heat source, For material density, For specific heat capacity, The rate of temperature change;

[0056] Humidity field: calculated using the moisture diffusion equation. ;

[0057] in, This refers to the volumetric moisture content. Where is the humidity diffusion coefficient, and Sw is the frost heave source term;

[0058] Stress field: calculated using dynamic stress equilibrium equations. ;

[0059] in, This represents the contact force vector between the tire and the road surface. For displacement acceleration components;

[0060] Output spatiotemporal distribution cloud maps of the temperature gradient, moisture migration flux, and stress tensor of the entire subgrade section over a 15-year period.

[0061] S2, Calculate the freeze-thaw damage factor Df based on the output of the coupled model. Interlayer shear strain energy density Ws, base layer compressive creep rate Cc, and surface wear Aw; where Df quantifies the ice body expansion volume. With pore volume The ratio of Ws to Ws represents the cumulative damage to the microstructure of the material, and Ws characterizes the failure risk of the interlayer interface under the coupled action of heavy shear and temperature and humidity deformation.

[0062] S3 defines design thresholds based on the division of labor among structural layers. The damage threshold for the base layer is limited to Ws≤15 J / m³ to suppress interlayer delamination. The fatigue toughness index of the middle layer is required to be Cc≤0.035% / 10,000 cycles to control heavy-load creep. The surface layer anti-slip retention rate is limited to Aw≤0.2 mm / year to ensure long-term anti-slip performance. The boundary values ​​of each index are determined by inversion through a coupled model.

[0063] S4 sets design variables with the goal of minimizing the total life cycle cost, where the base layer thickness h1 is 18-25cm and the polymer content P% is 4.5-6%; the middle layer thickness h2 is 8-12cm and the rubber powder content R% is 20-22%; the surface layer thickness h3 is 4-6cm and the fiber length Lf is 6-12mm.

[0064] Calculate the modulus ratio of each layer:

[0065] / ;

[0066] when When the interlayer reinforcement measures are activated in the range of [1.8,2.2], 0.8 kg / m² emulsified asphalt binder is sprayed and a fiberglass grid with a tensile strength ≥50 kN / m is laid to ensure that the interlayer shear strength is stable at ≥1.2 MPa.

[0067] S5. Within 72 hours after the base course is laid, the damage threshold of the base course is verified by using a mobile pulse load tester to detect the critical load point for crack initiation; the fatigue toughness of the intermediate layer is verified by drilling core samples for dynamic shear rheological tests, and the standard is met when the phase angle δ≤65° and the rutting factor G* / sinδ≥2.5kPa; the surface anti-skid retention rate is verified by scanning the structural depth distribution with a laser profiler, and the coefficient of variation is required to be ≤0.15.

[0068] Furthermore, the present invention provides an embodiment:

[0069] In heavy-load highway sections in freeze-thaw-prone areas with ≥15 freeze-thaw cycles per year, a 20cm thick high-modulus base course (dynamic modulus 15,000MPa, polymer and fiber composite asphalt concrete) is laid, followed by a 10cm thick tough intermediate course (fracture energy 1.8kJ / m², rubber asphalt concrete with 20% rubber powder content), and a 5cm thick anti-skid surface course (structural depth 0.85mm, basalt fiber SMA mixture). The modulus gradient ratio is controlled at 3.0:1.6:1 (base course 15GPa: intermediate course 8GPa: surface course 5GPa). Emulsified asphalt is sprayed between the layers to achieve a shear strength of 1.5MPa. After 3 years of heavy traffic (average 130kN axle load >2000 times per day), there is no delamination between the layers, the rut depth is only 2.1mm, and the entire structure is in good working order.

[0070] Furthermore, the present invention provides an embodiment:

[0071] A base material composed of polymer (5% SBS content) and polyester fiber (12mm length, 0.4% content) was used. The ultimate compressive strength σ_max = 13.8MPa was measured. In the coupled simulation model, the point of sudden increase in microcrack propagation rate was determined to be 11.7MPa, which meets the damage threshold requirement. At the same time, the critical load for crack initiation of the core specimen under pulsed load reached 145kN (>130kN), and the crack depth stabilized at 3.8mm (<5mm), which significantly improved the service life compared with the untreated base material.

[0072] Furthermore, the present invention provides an embodiment:

[0073] Forty-eight hours after the base course was laid, the critical load of the crack was measured to be 148 kN (>130 kN) using a pulse load tester. The DSR test of the middle core sample (60℃, 10Hz) showed a phase angle δ=63° (≤65°) and G* / sinδ=2.7 kPa (≥2.5 kPa). The coefficient of variation of the surface laser scanning texture depth was 0.12 (≤0.15). All indicators met the standards.

[0074] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A design method for gradient structures of heavy-duty durable asphalt pavements under multi-field coupling environments, characterized in that, It includes the following steps: S1. Establish a coupled simulation model of temperature field, humidity field and heavy load stress field. The input parameters include: annual temperature difference range ΔT and daily variation of temperature field, number of freeze-thaw cycles and saturation change curve of humidity field, axle load spectrum and tire pressure distribution of heavy load field. The model realizes real-time coupling of temperature conduction equation, moisture diffusion equation and stress balance equation through multi-physics iterative solver. ΔT range is -30℃ to +60℃, number of freeze-thaw cycles ≥ 10 times / year, single axle load of axle load spectrum ≥ 130kN, and tire pressure distribution range is 0.8-1.2MPa. S2 quantifies the synergistic degradation effect of multiple factors by calculating the interlayer shear strain energy density Ws, base layer compression creep rate Cc, surface wear Aw, and freeze-thaw cycle degradation effect through a coupled model. S3, based on the functional decomposition of layers, sets design indicators, including the base layer damage threshold Ws≤15 J / m³, the middle layer fatigue toughness index Cc≤0.035% / 10,000 cycles, and the surface layer anti-slip maintenance rate Aw≤0.2mm / year; S4. Optimize structural parameters and adjust the combination of thickness and modulus of each layer until the index of step S3 is met. The coupled simulation model in step S1 is implemented using a multiphysics iterative solver, and its governing equations include the heat conduction equation: ； in, Thermal conductivity is a function of temperature. For the hydration heat source, For material density, For specific heat capacity, The rate of temperature change; Moisture diffusion equation: ； in, This refers to the volumetric water content. Where is the humidity diffusion coefficient, and Sw is the frost heave source term; Dynamic stress equilibrium equation: ； in, This represents the contact force vector between the tire and the road surface. For displacement acceleration components; Among them, the temperature field drives the material modulus degradation, the humidity field controls the freeze-thaw expansion force, and the stress field triggers interlayer shear slip, thereby accurately quantifying the three-field coupling effect; In step S2, the freeze-thaw cycle degradation effect is represented by an equivalent damage factor. Quantization, its expression is: ； Where N represents the number of freeze-thaw cycles per year. Let be the volumetric expansion of pore water during the k-th cycle as it freezes. The pore volume of the mixture. =35 kJ / mol is the activation energy. The gas constant is... Let be the average temperature of the k-th freezing process. This model characterizes the rate of freeze-thaw damage accumulation by using a term that couples the ice expansion work with the temperature activation energy, thus overcoming the limitations of the traditional single porosity index.

2. The design method for gradient structures of heavy-duty durable asphalt pavement under multi-field coupling environment according to claim 1, characterized in that, Step S4 employs a genetic algorithm to optimize structural parameters, with the objective function being the minimization of the total lifecycle cost. The design variables include: High modulus base layer thickness Polymer content (P%) Intermediate layer thickness Rubber powder content R% Surface thickness Fiber length .

3. The design method for gradient structure of heavy-duty durable asphalt pavement under multi-field coupling environment according to claim 1, characterized in that: The gradient stiffness matching verification method in step S4 optimization includes: Calculate the modulus ratio of each layer: / ； when When ∈[1.8,2.2], interlayer strengthening measures are activated by spraying emulsified asphalt binder into the interlayer and laying fiberglass grid.

4. The design method for gradient structure of heavy-duty durable asphalt pavement under multi-field coupling environment according to claim 1, characterized in that, During the construction phase, on-site verification of layer functional indicators was conducted: For the base layer damage threshold verification, a mobile pulse load tester was used to detect the critical load point for crack initiation within 72 hours after paving; for the intermediate layer fatigue toughness verification, core samples were drilled for dynamic shear rheological tests, and the test was conducted when the phase angle δ≤65° and the rutting factor G... The standard is met when sinδ≥2.5kPa; for the verification of surface anti-slip retention rate, the depth distribution of the structure is scanned using a laser profiler, and the coefficient of variation is required to be ≤0.

15.

5. The gradient structure in the design method of heavy-duty durable asphalt pavement gradient structure under multi-field coupling environment as described in claim 1, characterized in that, The high-modulus base layer, tough intermediate layer, and anti-slip surface layer are stacked sequentially from bottom to top. Among them, the high-modulus base layer has a dynamic modulus ≥14,000 MPa and a thickness of 18-25cm; the tough middle layer has a fracture energy ≥1.5 kJ / m² and a thickness of 8-12cm; the anti-slip surface layer has a texture depth ≥0.8 mm and a thickness of 4-6cm; the modulus gradient ratio of each layer is base layer: middle layer: surface layer = (2.8-3.5): (1.4-1.8): 1; and the interlaminar shear strength is ≥1.2 MPa.

6. The gradient structure for heavy-duty durable asphalt pavement under multi-field coupling environment according to claim 5, characterized in that: The high-modulus base course is made of polymer and fiber composite asphalt concrete. The damage threshold is defined as the critical stress level corresponding to the point of sudden increase in the microcrack propagation rate of the base course in the simulation model coupled with temperature field, humidity field and heavy load stress field. The threshold requirement is ≥0.85σmax, where σmax is the ultimate compressive strength. The high modulus and damage tolerance are synergistically improved by adding ≥6% epoxy resin and 0.3% polypropylene fiber.

7. The gradient structure for heavy-duty durable asphalt pavement under multi-field coupling environment according to claim 5, characterized in that: The toughness intermediate layer uses asphalt concrete with a rubber powder content of ≥20%. The fatigue toughness index is defined as the ratio of the cumulative dissipated energy to the initial elastic strain energy when the specimen completely fails in a standard fatigue test. The index is required to be ≥8.

0. The elastic energy dissipation mechanism of the rubber particles delays crack propagation.

8. The gradient structure for heavy-duty durable asphalt pavement under multi-field coupling environment according to claim 5, characterized in that: The anti-skid surface layer is made of a mixture of basalt fiber reinforced SMA, with basalt fiber length of 6-12mm, dosage of 0.4%, structural depth ≥0.8mm, surface friction coefficient ≥65, and high-temperature rutting depth ≤3mm after 100,000 loading cycles at 60℃ and 0.7MPa wheel pressure.

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