Inverted asphalt pavement structure thickness optimization design method

Abstract

The invention relates to the field of road engineering and civil engineering, in particular to an inverted asphalt pavement structure thickness optimization design method which comprises the following steps: selecting thicknesses and moduli of an asphalt surface layer, a granular material transition layer and a semi-rigid layer as control variables, and taking a granular material layer stress level and surface layer fatigue performance as preliminary design targets; a D-optimal solution response surface design method is adopted to formulate a test scheme, through finite element analysis, in combination with a nonlinear constitutive model, the stress dependence characteristic of the aggregate transition layer is simulated, the influence of a variable combination on a preliminary design target is evaluated, asphalt pavement structure performance checking calculation indexes are compared, and finally an optimal design scheme is determined. According to the invention, the material consumption is effectively reduced, the construction cost is reduced, the fatigue cracking resistance and deformation resistance of the pavement are obviously improved, and the service life of the pavement is prolonged.

Description

Technical Field

[0001] The invention relates to the fields of road engineering and civil engineering, and in particular to a thickness optimization design method for an inverted asphalt pavement structure. Background Art

[0002] The thickness design of asphalt pavement structure is usually based on empirical formulas and linear elastic models, but it fails to fully consider the comprehensive impact of different layers of thickness, modulus and nonlinear stress dependence of aggregate layers on the overall performance of the pavement. The traditional linear elastic asphalt pavement thickness design method is difficult to apply to inverted pavement structures. Most existing technologies use a fixed thickness design method, and the thickness of the designed inverted pavement structure layer is generally too high, resulting in material waste or insufficient performance. In addition, traditional technologies lack accurate analysis of different loads, environmental conditions and stress dependence characteristics of aggregate materials, resulting in fatigue cracking of the inverted asphalt surface layer, permanent deformation of the aggregate transition layer, and the risk of long-term fatigue damage to the semi-rigid layer. These technical means have failed to fully optimize the thickness and modulus of each layer, resulting in insufficient durability and stability of the pavement and increased maintenance costs. Summary of the invention

[0003] In view of the many problems existing in the above-mentioned prior art, the present invention provides a method for optimizing the thickness of an inverted asphalt pavement structure. The present invention optimizes the thickness and modulus of each layer of the inverted asphalt pavement structure based on finite element analysis and nonlinear stress-dependent characteristic model, combined with the D-optimal solution response surface design method. By maximizing the volume stress of the granular transition layer and minimizing the tensile strain at the bottom of the asphalt surface layer, the overall durability and bearing capacity of the pavement are improved, and cost optimization is achieved by reducing the use of materials.

[0004] like Figure 1 As shown, a method for optimizing the thickness of an inverted asphalt pavement structure comprises the following steps:

[0005] The thickness and modulus of each layer of the inverted asphalt pavement structure were selected as control variables. The D-optimal solution response surface design method was used to develop a test plan containing multiple groups of different thickness and modulus combinations, and the significance of each group of control variables on the target response value was evaluated.

[0006] like Figure 2 As shown in the figure, by taking the thickness and modulus of each layer of the inverted asphalt pavement structure as the control variables, personalized design can be performed for different layers. For example, the thickness and modulus of the asphalt surface layer mainly affect the fatigue resistance of the pavement, while the thickness and modulus of the aggregate transition layer affect its stress-dependent characteristics, which in turn affect the structural stability of the entire pavement. At the same time, as the bearing layer in the pavement structure, the thickness and modulus of the semi-rigid layer determine the overall compressive resistance of the pavement. Therefore, in the design, optimizing the thickness and modulus of each layer can achieve the best performance of the pavement under different traffic loads and environmental conditions.

[0007] In order to find the optimal thickness and modulus combination more efficiently, the present invention adopts the D-optimal solution response surface design method. The D-optimal solution response surface design method is an experimental design method commonly used for multivariable optimization. It can achieve more accurate optimization results while reducing the number of experiments by maximizing the experimental information obtained. In the present invention, the method is used to formulate an experimental plan containing multiple groups of different thickness and modulus combinations. The control variables corresponding to each combination (i.e., the thickness and modulus of each layer) are input into the experimental design. After experimental verification under different conditions, the significance of each group of control variables to the target response value can be evaluated. For example, by evaluating the bottom tensile strain of the asphalt surface layer and the volume stress of the granular transition layer, it can be determined how these variable combinations affect the fatigue performance and stress-dependent characteristics of the pavement.

[0008] The test scheme formulated by the D-optimal solution response surface design method of the present invention can effectively evaluate the significance of each control variable combination, thereby screening out the optimal thickness and modulus combination. This method not only reduces the consumption of experimental resources, but also ensures that the test scheme has sufficient representativeness and accuracy. Finally, through a comprehensive analysis of the test results, an optimization design scheme that achieves the best balance between material use and structural performance can be determined, and the optimal thickness and modulus combination of the inverted asphalt pavement structure can be recommended.

[0009] Based on the stress-dependent nonlinear characteristics of the aggregate transition layer, the mechanical response calculation of the inverted asphalt pavement structure is carried out to obtain the bottom tensile strain of the asphalt surface layer and the volume stress of the aggregate transition layer, so as to evaluate the fatigue performance of the asphalt surface layer and the stress-dependent characteristics of the aggregate transition layer.

[0010] The granular transition layer in the inverted asphalt pavement structure has obvious stress dependence, which means that when subjected to different traffic loads, the mechanical properties of the granular transition layer (such as the modulus of resilience) will change nonlinearly with the change of stress level. Therefore, in the present invention, the stress dependence of the granular transition layer is first quantified, and the mechanical behavior of the granular transition layer under different stress conditions is simulated through finite element analysis and nonlinear constitutive model. Through this nonlinear mechanical response calculation, the present invention can accurately obtain the volume stress of the granular transition layer. This stress index reflects the load-bearing and deformation capacity of the granular transition layer in the entire structure, and directly affects the overall stability and resistance to permanent deformation of the pavement.

[0011] At the same time, the fatigue performance of the asphalt surface layer is a key indicator of the service life of the road surface. In this mechanical response calculation model, by obtaining the tensile strain at the bottom of the asphalt surface layer, the fatigue performance of the road surface under long-term load can be accurately evaluated. The tensile strain at the bottom of the asphalt surface layer is a key parameter. Excessive tensile strain will cause cracks in the asphalt surface layer, affecting the service life of the road surface. The present invention can optimize the thickness and material selection of the asphalt surface layer by accurately calculating this strain value and combining it with other parameters in the road surface design, thereby improving its fatigue resistance and extending the service life of the road surface.

[0012] On this basis, the entire mechanical response calculation model comprehensively evaluates the performance of the pavement structure by combining the bottom tensile strain of the asphalt surface layer and the volume stress of the granular transition layer. The fatigue performance of the asphalt surface layer determines the pavement's crack resistance, while the stress-dependent characteristics of the granular transition layer determine the stability and deformation resistance of the structure. This evaluation method enables the present invention to design the optimal pavement structure thickness combination according to actual working conditions such as different traffic loads and climatic conditions, which can not only ensure the overall performance of the pavement structure, but also maximize the reduction of material costs.

[0013] According to the fatigue performance of the asphalt surface layer and the stress-dependent characteristics of the granular transition layer, the optimal design range of the inverted asphalt pavement structure is determined, the optimal solution is determined based on the satisfaction theory, and other pavement structure mechanical verification indicators are compared to recommend the optimal thickness and modulus combination of the inverted asphalt pavement structure.

[0014] In the process of optimizing the design, the fatigue performance of the asphalt surface layer is measured by the tensile strain at the bottom of the layer, which reflects the deformation of the asphalt surface layer under the action of external loads. If the tensile strain exceeds a certain critical value, fatigue cracks are likely to occur in the asphalt surface layer, thereby affecting the overall service life of the road surface. To this end, the present invention accurately obtains the tensile strain data of the asphalt surface layer through mechanical response calculation in the design to ensure that the thickness and modulus of the surface layer meet the fatigue performance requirements while minimizing material waste.

[0015] On the other hand, the stress-dependent characteristics of the granular transition layer have an important influence on its compression and deformation resistance. The modulus of the granular transition layer shows nonlinear characteristics as the stress level changes, which makes it impossible for the traditional linear mechanical model to accurately describe its performance. Therefore, the present invention accurately calculates the volume stress of the granular transition layer through a nonlinear mechanical model to ensure that it can maintain good mechanical properties under different load conditions.

[0016] After determining the fatigue performance of the asphalt surface layer and the stress-dependent characteristics of the aggregate transition layer, the present invention uses the satisfaction theory to further optimize the design solution. The satisfaction theory is a method for selecting the optimal solution by maximizing the consistency between the design results and the target expected value. This method has significant advantages in multivariable optimization, and can balance multiple design objectives to ensure that the final design solution not only meets the requirements of structural performance, but also minimizes material costs. In the present invention, the application of the satisfaction theory aims to find the optimal thickness and modulus combination that can simultaneously meet the fatigue performance of the asphalt surface layer and the stress-dependent characteristics of the aggregate transition layer through multiple iterative calculations.

[0017] Preferably, Figure 3 As shown, the D-optimal solution response surface design method is implemented by Design-expert software, which is used to determine the optimal combination of asphalt surface layer thickness, asphalt surface layer modulus, granular transition layer thickness, granular transition layer modulus, semi-rigid layer thickness, semi-rigid layer modulus and roadbed modulus.

[0018] In the present invention, the D-optimal solution response surface design method is implemented by Design-expert software to determine the optimal combination of asphalt surface layer thickness, asphalt surface layer modulus, granular transition layer thickness, granular transition layer modulus, semi-rigid layer thickness, semi-rigid layer modulus and roadbed modulus. The core of this method is to maximize the acquisition of experimental information while minimizing the number of experiments by designing the optimal experimental plan, thereby effectively improving the design efficiency and accuracy.

[0019] D-optimal solution response surface design is an experimental design method for dealing with multi-factor optimization problems. It is particularly suitable for systems with many variables and complex interactions, such as the optimization of the thickness and modulus of each layer in an inverted asphalt pavement structure. In the present invention, the thickness and modulus of the asphalt surface layer, the granular transition layer and the semi-rigid layer are all key design variables. The thickness and modulus of the asphalt surface layer determine the fatigue resistance of the pavement structure, while the thickness and modulus of the granular transition layer and the semi-rigid layer have a crucial influence on the compressive resistance and long-term stability of the pavement. Therefore, by rationally selecting and optimizing these variable combinations, the durability and structural stability of the pavement can be greatly improved.

[0020] In the specific implementation process, Design-expert software was used to implement the D-optimal solution response surface design method. The software provides powerful experimental design and analysis functions, which can screen out the optimal experimental scheme in multi-dimensional space. In the optimization process, the thickness and modulus of the asphalt surface layer, granular transition layer, semi-rigid layer and roadbed are first used as input variables, and experimental points with multiple groups of variable combinations are generated through experimental scheme design. Each experimental point represents a different combination of thickness and modulus. Then, based on these experimental points, the effects of different combinations on pavement performance are evaluated through finite element simulation or actual measurement.

[0021] The D-optimal solution function of the Design-expert software can ensure that the maximum amount of information is obtained within the minimum number of experiments. This feature is particularly suitable for the design of inverted asphalt pavement structures, because in actual engineering, conducting a large number of experiments is both time-consuming and laborious. By reducing unnecessary experimental steps, the present invention can obtain sufficient data under limited experimental resources to comprehensively analyze the effects of different thickness and modulus combinations.

[0022] After all the experimental results were summarized, the Design-expert software performed a regression analysis on the response values ​​of each experimental point and calculated the significance of the impact of each design variable on the pavement performance. Finally, the D-optimal solution algorithm was used to screen out the optimal thickness and modulus combination that can minimize the use of materials while ensuring the durability of the pavement structure. This combination scheme can not only improve the fatigue resistance and long-term stability of the pavement, but also significantly reduce construction and material costs.

[0023] Preferably, the response surface design method is generated based on multiple sets of experimental data and evaluates the effects of different thickness and modulus combinations on the fatigue performance of the asphalt pavement and the stress-dependent characteristics of the granular transition layer.

[0024] The thickness optimization design method of the inverted asphalt pavement structure of the present invention generates a specific optimization model based on multiple sets of experimental data through the response surface design method, and comprehensively evaluates the influence of different thickness and modulus combinations on the fatigue performance of the asphalt surface layer and the stress dependence characteristics of the granular transition layer. In this process, the role of the response surface design method is to find the optimal solution for the pavement performance of different thickness and modulus combinations through experimental design and data analysis, so as to ensure the stability and durability of the pavement structure under various working conditions.

[0025] The present invention has collected a large amount of performance data on different thickness and modulus combinations through experiments and finite element simulations, including the fatigue performance of the asphalt surface layer and the stress-dependent characteristics of the granular transition layer. The fatigue performance of the asphalt surface layer is mainly measured by the tensile strain at the bottom of the layer. The greater the tensile strain at the bottom of the layer, the more likely the asphalt surface layer is to crack under long-term traffic loads, and the shorter the fatigue life. Therefore, by adjusting the thickness and modulus combination of the asphalt surface layer, the tensile strain value can be reduced, thereby improving the fatigue performance and service life of the surface layer. The stress-dependent characteristics of the granular transition layer refer to the nonlinear characteristics of its modulus changing with stress, which is crucial to the bearing capacity and deformation resistance of the pavement structure. The behavior of the granular transition layer under different stress states determines whether it can effectively disperse the traffic load and prevent excessive deformation or failure of the pavement.

[0026] The present invention uses the response surface design method to generate a multidimensional optimization model based on multiple sets of experimental data. In this model, the thickness and modulus of the asphalt surface layer and the granular transition layer are used as input variables, and the fatigue performance and stress-dependent characteristics are used as output responses. By designing experiments, the software automatically generates different variable combinations and performs data analysis on each set of experimental results. The advantage of the response surface design method is that it can generate a wide range of experimental schemes containing different thickness and modulus combinations through a small number of experiments, and can accurately evaluate the significance of the impact of each combination on pavement performance.

[0027] Through the calculation and analysis of the model, the optimal thickness and modulus configuration under different combinations can be determined. Specifically, when the thickness and modulus of the asphalt surface layer are adjusted to the appropriate range, the tensile strain at the bottom of the layer will be minimized and the fatigue performance will be maximized; and when the thickness and modulus combination of the granular transition layer is optimal, its stress-dependent characteristics are fully utilized, and it can maintain stability and compressive resistance under traffic loads. In this way, the design method of the present invention not only ensures the durability and fatigue resistance of the overall structure of the pavement, but also reduces the engineering cost by reducing the thickness and material usage.

[0028] Preferably, Figure 4 As shown, the mechanical response calculation is based on the finite element analysis method, using the compiled UMAT subroutine to give the granular transition layer stress-dependent nonlinear characteristics, and accurately simulate the stress response of the granular transition layer through the constitutive model.

[0029] In the present invention, the mechanical response calculation adopts the finite element analysis method, and combines the compiled UMAT subroutine to give the granular transition layer stress-dependent nonlinear characteristics, and realizes the accurate simulation of the stress response of the granular transition layer through the nonlinear constitutive model. The core of this process is that the mechanical properties of the granular transition layer do not change linearly, but show complex nonlinear behavior with the change of stress level. In order to accurately describe this stress dependence, the traditional linear elastic model cannot meet the accuracy requirements, so the present invention introduces a more complex nonlinear constitutive model.

[0030] In practical applications, the aggregate transition layer of the inverted asphalt pavement structure assumes the load transfer function between the upper asphalt surface layer and the lower semi-rigid layer. Due to the repeated action of traffic loads, the aggregate transition layer needs to have a certain degree of compression and deformation resistance, and these mechanical properties are greatly affected by the stress level. Under different load conditions, the modulus of the aggregate layer changes nonlinearly, and this change will significantly affect the structural stability of the entire pavement. Therefore, the mechanical response calculation must not only take into account the geometric and material properties of each layer, but also accurately simulate the stress response characteristics of the aggregate transition layer.

[0031] The finite element analysis method is an effective tool for simulating the mechanical behavior of complex structures. It solves mechanical responses such as stress, strain and displacement by discretizing the complex structure into finite units. In the present invention, the finite element analysis can not only accurately simulate the stress distribution in the asphalt pavement structure, but also realize the nonlinear stress response simulation of the granular transition layer through the UMAT subroutine. UMAT (UserMaterial Subroutine) is a user material subroutine in the finite element software, which allows researchers to customize the constitutive model of the material. In the present invention, the UMAT subroutine is compiled into a nonlinear constitutive model specifically for the stress-dependent characteristics of the granular transition layer, so that the finite element model can accurately reflect the stress-strain relationship of the granular layer under different load conditions.

[0032] The constitutive model is the core part of the mechanical response calculation, which is used to describe the stress-strain relationship of the material under the action of external force. In the present invention, the constitutive model of the granular transition layer combines the stress-dependent nonlinear characteristics, that is, its modulus changes with the change of stress level. This model is implemented in the finite element analysis through the UMAT subroutine, so that the simulation results can more accurately reflect the mechanical behavior in reality. In this way, the simulated granular transition layer volume stress can not only reflect the performance of the road surface under static conditions, but also reveal its long-term mechanical performance under dynamic loads.

[0033] Preferably, the fatigue performance of the asphalt surface layer is determined by evaluating the maximum principal strain at the bottom of the asphalt surface layer, and the upper limit of the maximum principal strain at the bottom of the asphalt surface layer is 120με.

[0034] In the present invention, the fatigue performance of the asphalt surface layer is determined by evaluating the maximum principal strain at the bottom of the asphalt surface layer. The fatigue performance of the asphalt surface layer is a key factor affecting the long-term service life of the pavement, especially under repeated traffic loads, cracks will gradually appear in the asphalt surface layer, leading to structural failure. In order to accurately evaluate and optimize the fatigue resistance of the asphalt surface layer, the present invention quantifies the fatigue performance by calculating the maximum principal strain at the bottom of the asphalt surface layer, wherein the upper limit of the maximum principal strain is set to 120με.

[0035] Asphalt surface layers will experience repeated stretching and compression under the long-term action of traffic loads. If the strain at the bottom of the layer is too large, the cracks in the surface layer will accelerate and expand, leading to premature failure of the road surface. Therefore, controlling the tensile strain at the bottom of the layer within a reasonable range is the key to extending the service life of the road surface. In the present invention, the evaluation of the maximum principal strain is obtained by finite element analysis and calculation, which reflects the maximum tensile strain state of the asphalt surface layer under external loads. Setting 120με as the upper limit is based on a large amount of engineering experience and test results to ensure that the surface layer will not fail quickly due to excessive tensile strain.

[0036] During the design process, the thickness and modulus of the asphalt surface layer are two key variables that directly affect the maximum principal strain. A larger thickness can effectively reduce the tensile strain of the surface layer, because a thicker asphalt surface layer can more evenly disperse the external load, thereby reducing strain concentration. The modulus affects the rigidity of the material. The larger the modulus, the less likely the material is to deform significantly, thereby reducing the tensile strain at the bottom of the layer. In the present invention, by optimizing the thickness and modulus of the asphalt surface layer, the maximum principal strain can be controlled within 120με, thereby improving the fatigue resistance of the surface layer.

[0037] By evaluating the maximum principal strain, the present invention can accurately control the fatigue performance of the asphalt surface layer, so that the surface layer maintains good crack resistance under long-term load. This optimization not only improves the durability of the pavement, but also extends the service life of the pavement, reducing the subsequent maintenance and repair costs. At the same time, by setting an upper limit value of 120με, the present invention ensures the safety of the design and avoids fatigue damage caused by excessive strain. By combining the control of the maximum principal strain at the bottom of the layer with the optimization of materials, the present invention provides a more scientific and reasonable design method for asphalt pavement structures, which can optimize material costs while ensuring structural performance.

[0038] Preferably, the volume stress of the granular transition layer is used to characterize the stress-dependent characteristics of the granular transition layer, and the lower limit of the volume stress level is 150 kPa.

[0039] In the thickness optimization design of the inverted asphalt pavement structure of the present invention, the volume stress of the granular transition layer is used to characterize its stress dependence characteristics. Specifically, the volume stress is a key indicator reflecting the comprehensive stress state borne inside the granular transition layer. The granular transition layer is located between the asphalt surface layer and the semi-rigid layer, and plays the role of load transfer and stress dispersion. When subjected to traffic loads, the stress characteristics of the granular transition layer are not linear, but show obvious stress dependence. Therefore, accurate calculation and evaluation of the volume stress level can help to better understand the mechanical behavior of the granular transition layer under different loads, thereby optimizing its thickness and modulus design. In the present invention, the lower limit of the volume stress level of the granular transition layer is set to 150kPa. This critical value is used to ensure that its stress characteristics maintain reasonable responsiveness under load.

[0040] Volumetric stress is represented by the sum of the principal stresses, and the stress-dependent property means that the modulus of the aggregate transition layer changes as the stress it is subjected to changes. Specifically, the modulus of the aggregate transition layer exhibits a nonlinear change as the volumetric stress increases. This property is very important for the long-term stability of the pavement because it determines the bearing capacity and deformation behavior of the aggregate layer at different stress levels. If the volumetric stress is below the set lower limit of 150 kPa, the stress response of the aggregate transition layer may be insufficient, resulting in premature failure of the material or large deformation, which in turn affects the overall mechanical properties and durability of the pavement.

[0041] In order to accurately capture this stress-dependent characteristic, the present invention accurately simulates the volume stress of the granular transition layer through finite element analysis and stress-dependent nonlinear constitutive model. In this model, the mechanical properties of the granular transition layer under different stress conditions are quantified, so that its performance under long-term load can be evaluated. The lower limit of volume stress of 150kPa is determined through a large number of experiments and simulation results, which represents a critical value of the granular transition layer in terms of bearing capacity and deformation capacity. Below this value, the granular layer may not be able to effectively bear the external load, thereby increasing the risk of pavement structure failure.

[0042] By setting the lower limit of the volume stress of the granular transition layer to 150 kPa, the present invention ensures that this layer in the pavement structure can maintain sufficient strength and stability when subjected to load. Reasonable control of the volume stress level can not only improve the compressive capacity of the granular layer, but also prevent excessive deformation, making the pavement structure more durable and stable. This setting also provides a scientific basis for optimizing the thickness and modulus of the granular transition layer, and can achieve the rational use of materials and cost optimization in practical applications. Finally, the present invention ensures the long-term performance and safety of the inverted asphalt pavement structure through the control of volume stress, reduces maintenance frequency and material waste, and improves the overall efficiency of the pavement system.

[0043] Preferably, the goal of the optimization design is to reduce the thickness of the asphalt surface layer and improve the durability of the asphalt pavement by minimizing the tensile strain at the bottom of the asphalt surface layer and maximizing the volume stress of the aggregate transition layer.

[0044] The core goal of the thickness optimization design of the inverted asphalt pavement structure of the present invention is to achieve the purpose of reducing the thickness of the asphalt surface layer and improving the overall durability of the asphalt pavement by minimizing the tensile strain at the bottom of the asphalt surface layer and maximizing the volume stress of the granular transition layer. In the optimization design process, the tensile strain of the asphalt surface layer and the volume stress of the granular transition layer are two key mechanical parameters that directly determine the fatigue resistance and stability of the pavement structure.

[0045] The tensile strain at the bottom of the asphalt surface layer is one of the main causes of fatigue damage to the road surface under long-term traffic loads. Excessive tensile strain will lead to rapid expansion of cracks in the surface layer, thus affecting the life of the road surface. Therefore, controlling the tensile strain at the bottom of the surface layer within a reasonable range can effectively improve its crack resistance and extend the service life of the road surface. In the optimization design, by accurately calculating and analyzing the thickness and modulus of the asphalt surface layer, a combination that minimizes the tensile strain at the bottom of the layer can be found, thereby achieving better fatigue resistance. At the same time, thinning the thickness of the surface layer is also one of the important goals of the present invention. Through optimized design, while ensuring the fatigue resistance of the surface layer, the amount of asphalt material used can be significantly reduced, thereby reducing construction costs.

[0046] On the other hand, the volume stress of the aggregate transition layer is a key indicator to measure the structural stability of this layer. The aggregate transition layer is located between the asphalt surface layer and the underlying structure, and plays a role in dispersing and transferring stress. When the volume stress is large, the aggregate layer can better disperse the traffic load, prevent stress concentration, and maintain the stability of the road surface. Therefore, in the optimization design, maximizing the volume stress of the aggregate transition layer can enhance its bearing capacity and anti-deformation ability, ensuring the stability and durability of the entire pavement structure under long-term load.

[0047] The present invention determines the best combination of thickness and modulus by comprehensively considering these two key parameters, using experimental data and finite element simulation analysis. In the specific implementation process, the asphalt surface layer and the granular transition layer are iterated multiple times to gradually optimize the design scheme and find the optimal solution that can minimize the tensile strain at the bottom of the layer and maximize the volume stress. Using the D-optimal solution response surface design method, the effects of various thickness and modulus combinations can be quickly evaluated without increasing a large amount of experimental resources, thereby obtaining an optimal solution that balances pavement performance and economy.

[0048] Through this optimization design method, the present invention can not only significantly reduce the thickness of the asphalt surface layer and reduce material costs, but also ensure the high durability and stability of the pavement structure in long-term use. Specifically, minimizing the tensile strain at the bottom of the asphalt surface layer can reduce the occurrence of fatigue cracks and improve the fatigue resistance of the pavement; maximizing the volume stress of the granular transition layer enhances the bearing capacity and deformation resistance of the pavement, ensuring that the pavement does not deform or damage prematurely under long-term loads. In addition, thinning the surface layer while ensuring structural performance can make the pavement design more economical and feasible, and meet the cost and performance requirements in engineering practice. Finally, the present invention provides an efficient, reliable and economical pavement structure optimization design solution by optimizing the combination of thickness and modulus, which extends the service life of the pavement, reduces the subsequent maintenance costs, and improves the performance of the overall structure.

[0049] Preferably, the thickness of the asphalt surface layer ranges from 8 cm to 18 cm, the thickness of the granular transition layer ranges from 10 cm to 30 cm, and the thickness of the semi-rigid layer ranges from 15 cm to 40 cm.

[0050] In the present invention, the thickness ranges of the asphalt surface layer, the granular transition layer and the semi-rigid layer are set to 8cm to 18cm, 10cm to 30cm and 15cm to 40cm respectively. These thickness ranges are set based on a large amount of experimental data, engineering experience and a comprehensive analysis of the mechanical properties of the pavement structure, and are intended to achieve economical material use while satisfying durability and stability by adjusting the thickness of each layer.

[0051] The asphalt surface layer, granular transition layer and semi-rigid layer each have different functions in the inverted asphalt pavement structure. The asphalt surface layer is mainly responsible for bearing the fatigue stress caused by traffic load and providing sufficient wear resistance. The granular transition layer plays a role in stress transmission, which reduces the stress concentration on the lower semi-rigid layer by relieving the load on the upper surface layer. The semi-rigid layer provides support for the entire road surface, ensuring that the road surface maintains sufficient structural strength and deformation resistance under long-term heavy-load traffic.

[0052] In the design, the thickness of the asphalt surface layer directly affects its anti-fatigue performance. A thicker surface layer can better disperse the traffic load, thereby reducing tensile strain and extending the life of the road surface. However, too thick a surface layer will lead to material waste, so within the thickness range of 8cm to 18cm, the optimized design can achieve effective use of materials while meeting the anti-fatigue performance. 8cm is the lower limit to ensure basic anti-fatigue performance, while the upper limit of 18cm takes into account the enhanced durability required under special traffic conditions.

[0053] The thickness of the aggregate transition layer is set in the range of 10cm to 30cm, mainly based on its stress buffering role in the structure. By adjusting the thickness of the aggregate layer, its volume stress can be adjusted so that it has sufficient stress dispersion capacity under load. A thinner aggregate layer (such as 10cm) is suitable for lighter traffic loads, while increasing the thickness of the aggregate transition layer (such as 30cm) can effectively prevent excessive deformation of the pavement structure under heavy traffic flow or heavy load conditions.

[0054] The thickness of the semi-rigid layer ranges from 15cm to 40cm, mainly to provide the overall bearing capacity of the pavement. When the semi-rigid layer is thicker, it can better bear the load transferred from the superstructure, prevent the road base from deforming, and increase the overall stiffness of the pavement structure. 15cm is the minimum thickness of the semi-rigid layer to ensure that it has basic bearing capacity, while in heavy traffic or poor foundation conditions, a thickness of 40cm can significantly enhance the overall bearing capacity of the pavement.

[0055] By setting the thickness range of the asphalt surface layer, the granular transition layer and the semi-rigid layer, the present invention can perform flexible pavement structure design under a variety of traffic conditions and environments. The combination of different thicknesses can not only ensure the durability and stability of the pavement structure, but also optimize the use of materials according to specific engineering requirements and reduce construction costs. The optimized design within the range of the asphalt surface layer can improve its fatigue resistance and reduce the probability of cracks; the thickness optimization of the granular transition layer ensures a reasonable distribution of stress and reduces the deformation of the pavement structure; and the thickness optimization of the semi-rigid layer enhances the bearing capacity and long-term stability of the entire pavement. Through these reasonable thickness settings, the present invention provides a scientific and efficient optimization solution for the design of inverted asphalt pavements.

[0056] Preferably, Figure 5 As shown, the dynamic modulus of the asphalt surface layer is determined by the actual traffic parameters, temperature conditions and roadbed soil properties, and the dynamic modulus under different environmental conditions is calculated based on the design formula.

[0057] In the present invention, the dynamic modulus of the asphalt surface layer is an important parameter affecting the performance of the pavement, which directly affects the fatigue resistance, crack resistance and bearing capacity of the pavement. The dynamic modulus represents the deformation ability of the material under repeated loads, and the dynamic modulus of the asphalt surface layer is affected by many factors, including actual traffic parameters, temperature conditions and the properties of the roadbed soil. By comprehensively considering these variables, the present invention can accurately calculate the dynamic modulus under different environmental conditions, thereby optimizing the pavement structure design.

[0058] The dynamic modulus of the asphalt surface layer changes with the frequency and temperature of the traffic load. At higher load frequencies, the asphalt material exhibits a higher modulus, that is, the material becomes more rigid, while at lower frequencies, its modulus decreases and the material's deformation capacity increases. At the same time, changes in temperature also have a significant impact on the dynamic modulus. Higher temperatures will reduce the rigidity of asphalt, causing the material's modulus to decrease, resulting in greater deformation; while lower temperatures will increase the rigidity of the material and increase the dynamic modulus. The properties of the subgrade soil also affect the dynamic modulus of the surface layer. The rigidity and stability of different soils will produce a certain force feedback on the mechanical behavior of the asphalt surface layer. Therefore, when designing the pavement structure, these variables must be considered comprehensively to ensure that the dynamic modulus of the asphalt surface layer can meet the requirements under actual use conditions.

[0059] The present invention incorporates factors such as traffic load, temperature and roadbed soil into the calculation formula of dynamic modulus through a specific design formula. The formula is fitted through multiple sets of experimental data and simulation analysis, and can be adjusted according to specific traffic conditions, temperature environment and roadbed conditions. In the calculation process, the frequency of actual traffic load, vehicle type and driving speed are included in the calculation model to reflect the performance of the asphalt surface layer under various dynamic loads. At the same time, the impact of ambient temperature changes on the rigidity of asphalt materials is also quantified, and combined with different roadbed soil types, a dynamic modulus calculation model that adapts to various conditions is formed.

[0060] Through this design formula, the present invention can flexibly adjust the thickness and modulus of the asphalt surface layer to adapt to different environmental conditions. For example, in areas with higher temperatures, the dynamic modulus may be lower, so it is necessary to increase the thickness of the asphalt surface layer or select a material with a higher modulus to resist excessive deformation caused by softening. In cold areas, the asphalt surface layer may become too rigid, increasing the risk of cracks, so the adjustment of the dynamic modulus can help optimize the thickness and material properties of the surface layer and prevent brittle failure.

[0061] By combining traffic parameters, temperature conditions and subgrade soil properties, the present invention achieves accurate calculation of the dynamic modulus of the asphalt surface layer. This design method that comprehensively considers multiple variables can effectively improve the structural performance of the pavement, enabling it to maintain good mechanical behavior under different environments and traffic conditions. At the same time, the calculation of the dynamic modulus combined with thickness optimization can effectively reduce material waste and reduce construction costs. Ultimately, the present invention not only improves the durability and fatigue resistance of the pavement through the optimized calculation of the dynamic modulus, but also maintains stability in various complex environments, extending the service life of the pavement and reducing the frequency and cost of subsequent maintenance.

[0062] Preferably, the fatigue cracking resistance of the asphalt surface layer, the fatigue performance of the semi-rigid layer and the permanent deformation resistance of the granular transition layer are simultaneously considered in the optimization design to ensure the overall structural performance and economic benefits of the inverted asphalt pavement.

[0063] In the present invention, the optimization design not only considers the fatigue cracking resistance of the asphalt surface layer, but also comprehensively considers the fatigue performance of the semi-rigid layer and the permanent deformation resistance of the granular transition layer to ensure the performance and economic benefits of the entire pavement structure. This all-round design method allows the pavement structure to maintain high durability and stability during long-term use by finely adjusting the thickness and modulus of each layer, while controlling the use of materials and reducing construction costs.

[0064] The fatigue cracking resistance of asphalt surface layer is one of the key indicators of long-term traffic load bearing of pavement. As time goes by, fatigue cracks are prone to occur in asphalt surface layer under repeated loads. The gradual expansion of such cracks will affect the integrity of the overall structure of the pavement. In order to improve the fatigue cracking resistance of asphalt surface layer, the present invention optimizes the thickness and modulus of the surface layer and reduces the tensile strain at the bottom of the layer, thereby slowing down the formation and expansion of cracks. This optimization process combines finite element analysis with experimental data to accurately control stress concentration points and improve the durability of asphalt surface layer.

[0065] At the same time, the fatigue performance of the semi-rigid layer also plays an important role in the entire pavement structure. As the load-bearing core of the pavement structure, the semi-rigid layer needs to maintain good fatigue resistance under long-term loads. Since the semi-rigid layer mainly bears compressive stress and shear stress, optimizing its thickness and material modulus can effectively disperse the upper layer load and prevent the accumulation of fatigue damage in the layer. The present invention reasonably adjusts the thickness of the semi-rigid layer to ensure that the layer is not prone to fatigue damage under long-term traffic, thereby extending the service life of the pavement.

[0066] The granular transition layer is the key transition layer connecting the asphalt surface layer and the semi-rigid layer. Its ability to resist permanent deformation determines the stability of the entire road surface. Due to the nonlinear stress-dependent characteristics of the granular layer, its deformation capacity is closely related to the stress level under the action of traffic load. In order to ensure that the granular transition layer will not be permanently deformed during long-term use, the present invention adopts a stress-dependent nonlinear constitutive model, combined with experimental data, to optimize the thickness and modulus of the granular layer, so that it can still maintain good bearing capacity and deformation stability when subjected to high stress.

[0067] By simultaneously optimizing the fatigue cracking resistance of the asphalt surface layer, the fatigue performance of the semi-rigid layer, and the permanent deformation resistance of the granular transition layer, the present invention provides a comprehensive pavement thickness design solution. This optimized design can ensure that the pavement structure maintains high durability and stability under different traffic conditions and environments, and effectively reduces the risk of pavement cracking, fatigue damage, and permanent deformation. At the same time, a reasonable thickness design can reduce the amount of materials used, reduce construction costs, and improve economic benefits. In addition, the improvement of the long-term stability and fatigue resistance of the pavement also reduces the frequency and cost of subsequent maintenance, further improving the overall benefits of the project. Therefore, while optimizing the pavement performance, the present invention maximizes the structural economy and long-term benefits.

[0068] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0069] Through finite element analysis combined with nonlinear constitutive model technology, the thickness and modulus of the asphalt surface layer, granular transition layer and semi-rigid layer were accurately optimized, effectively controlling the fatigue cracking of the asphalt surface layer and the permanent deformation of the granular transition layer, thereby improving the stability of the overall pavement structure.

[0070] Through the D-optimal solution response surface design method, a reasonable distribution of thickness and modulus of each layer was achieved, which not only reduced the use of materials but also ensured the long-term durability of the pavement under different load and environmental conditions.

[0071] The present invention also solves the problem of neglecting the stress-dependent characteristics of granular materials in traditional methods, and significantly improves the structural performance and economic benefits of the road surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 It is a schematic diagram of the process of the present invention;

[0073] Figure 2 It is a schematic diagram of the structure of the asphalt surface layer, the granular material transition layer and the semi-rigid layer in the present invention;

[0074] Figure 3 Schematic diagram of the experimental scheme of the D-optimal solution response surface design method in the present invention;

[0075] Figure 4 It is a flow chart of the inverted asphalt pavement structure analysis based on the nonlinear characteristics of the granular layer in the present invention;

[0076] Figure 5 This is a schematic diagram of the preliminary design of the response target interval range in the present invention. DETAILED DESCRIPTION

[0077] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is obvious that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0078] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0079] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0080] Step 1: Using the D-optimal solution response surface design method, the thickness and modulus of each structural layer of the inverted asphalt pavement are selected as the control factor variables, and a test scheme with a good spatial distribution state is designed, such as Figure 5 As shown, the significance of the impact of each control variable on the target response value is evaluated.

[0081] According to the research results of the engineering application of inverted asphalt pavement structure layer at home and abroad, as well as the actual traffic parameters (medium load level), temperature conditions (the lowest temperature can reach -15.2℃, the highest temperature can reach 31.0℃) and the properties of the roadbed soil, the thickness and modulus range of the inverted asphalt pavement structure layer are determined as discrete variables. The thickness of the asphalt surface layer (AC layer) is 8cm, 10cm, 12cm, 15cm and 18cm, the thickness of the aggregate transition layer (UAB layer) is 10cm, 15cm, 20cm, 25cm and 30cm, and the thickness of the semi-rigid subbase (CTB layer) is 15cm, 20cm, 32cm, 36cm and 40cm; the modulus value of the AC layer under summer conditions is 3000MPa, 5000MPa and 7000MPa, and the UAB layer is 2000MPa, 3000MPa and 4000MPa. The nonlinear modulus parameters are Eu1 (k1=5.43, k2=0.32, k3=0.11), Eu2 (k1=4.09, k2=0.41, k3=0.17) and Eu3 (k1=2.64, k2=0.45, k3=0.15), the CTB layer modulus is 10000MPa, 12000MPa and 14000MPa, and the subgrade (SUB) modulus is 40MPa, 60MPa and 80MPa.

[0082] Based on the D-optimal design principle, five repeated test points and five missing fitting points are allowed, and five blocks are used to estimate the experimental design error. Among them, setting repeated points is conducive to reducing experimental errors and improving the reliability of the experimental design. The designed test points have a good spatial distribution state, and a total of 50 experimental scheme combinations are designed.

[0083] Step 2: Calculate the mechanical response of the inverted asphalt pavement structure based on the nonlinear characteristics of the aggregate, and evaluate the fatigue performance of the asphalt surface layer of the inverted asphalt pavement structure and the stress-force dependence nonlinearity of the aggregate transition layer under different test schemes.

[0084] The calculation of mechanical response of inverted asphalt pavement structure should be based on the theory of layered elastic system, and the finite element analysis method of inverted asphalt pavement structure based on nonlinear characteristics of granular materials should be adopted. By compiling UMAT subroutine, the stress-dependent nonlinear constitutive model of granular transition layer should be given to realize the calculation.

[0085] A standard axle load of 100KN is applied to the elastic layered system with a double-wheel set, and the converted load is 0.7MPa; a double rectangular uniform load is converted with equal area using a double circular uniform load, the load length is 22.5cm, the width is 15.5cm, and the inner distance of the double rectangular load is 16.4cm;

[0086] When selecting material parameters, the dynamic modulus of the asphalt surface layer is predicted by the constitutive model shown in formulas (1) and (2), the rebound modulus of the granular transition layer is predicted by formula (3), and the modulus of the semi-rigid layer and the roadbed are selected based on experience;

[0087] Wherein, the formula (1) is:

[0088]

[0089] The formula (2) is:

[0090]

[0091] The formula (3) is:

[0092]

[0093] In the formula, E * represents the dynamic modulus; max represents the maximum value of the dynamic modulus; f is the load frequency at the test temperature; α(T) is the displacement factor at temperature T; β and γ are fitting parameters respectively; ΔE a represents the activation energy, which is also a regression coefficient; T is the test temperature, T r is the reference temperature; M r represents the rebound modulus; k1, k2, k3 are regression parameters; confining pressure P a =100kPa.

[0094] The finite element method is used to calculate the structural mechanical response, and the calculated stress, strain and vertical displacement response results are output; according to the selected structural design control index, the structural design index value is output; the calculation point position is selected as the maximum mechanical response at the bottom of the structural layer.

[0095] Fatigue performance evaluation of asphalt surface layer of inverted asphalt pavement structure: the maximum temperature reaches 31.0℃, at which time the dynamic modulus of the asphalt surface layer is 3000MPa; and the modulus of the granular transition layer is relatively low, which is greatly different from the modulus of the surface layer. In summer, the tensile strain at the bottom of the inverted asphalt surface layer is large. The maximum principal strain (MPS) at the bottom of the asphalt mixture layer is selected as the response variable to evaluate its anti-fatigue performance.

[0096] Evaluation of stress-dependent nonlinear characteristics of aggregate transition layer in inverted asphalt pavement structure: The increase of volume stress can lead to an increase in the stress-dependent rebound modulus of the aggregate transition layer. Fully utilizing the stress-dependent effect of the aggregate transition layer can improve its own stress-dependent rebound modulus. The average volume stress (BS) of the aggregate transition layer is selected as the response variable.

[0097] Furthermore, the mechanical response variables of the inverted asphalt pavement structure were calculated, and the significance of the influence of each control variable on the response value was independently evaluated. The F value and P value were used to determine whether there was a significant relationship between the response variable and each control variable: when the P value was less than 0.05, it indicated that there was a significant relationship between the two, otherwise, there was no significant relationship; the F value was the ratio of the average effect term to the error term, which could not be negative, and the higher the value, the greater the degree of influence. The significance analysis results of the nonlinear dependence of the stress of the granular transition layer are shown in Table 1, and the significance analysis results of the fatigue performance of the asphalt surface layer are shown in Table 2.

[0098]

[0099] Table 2 Results of significance analysis of maximum principal strain

[0100]

[0101] According to the results of single factor significance analysis, four variables, namely, AC layer thickness and modulus, UAB layer thickness and modulus, were selected for combined optimization design of inverted asphalt pavement structure.

[0102] Step 3: Taking the fatigue performance of the asphalt surface layer and the stress-dependent characteristics of the aggregate transition layer as the balanced design principle, determine the optimal design range of the pavement structure combination, determine the optimal solution based on the satisfaction theory, conduct comparative verification of other pavement structure mechanical indicators, and finally recommend the pavement structure combination optimization plan.

[0103] The smaller the maximum principal strain (MPS) value of the asphalt surface layer bottom, the better the fatigue cracking resistance of the asphalt surface layer (AC layer); the larger the volume stress (BS), the stronger the stress dependence of the aggregate transition layer (UAB), which helps to improve the resilience modulus of the UAB layer. 120με is used as the MPS limit design value, and 150kPa is selected as the lower limit value of the volume stress level optimization design.

[0104] Furthermore, according to the 50 test combinations designed in step 1, the structural mechanics response variables were calculated, and the results are shown in Table 3.

[0105] Table 3 Response surface methodology design scheme

[0106]

[0107]

[0108] Furthermore, two cases were considered in the optimization design calculation process: one was to consider the stress-dependent nonlinear characteristics of the granular transition layer and the other was not. Case 1: Considering the stress-dependent characteristics of the granular transition layer: the design target was the MPS value of the asphalt surface layer (target: minimization, upper limit: 120με) and the volume stress level of the granular transition layer (target: maximization, lower limit: 150kPa); Case 2: The stress-dependent characteristics of the granular transition layer were not considered, and the design targets were the MPS value (target: minimization, upper limit: 120με) and the volume stress level (target: none). In the optimal function, the mathematical indicator "desirability" is used to evaluate the accuracy of the solution. The larger the "desirability" value, the closer the calculated solution is to the target value.

[0109] As shown in Table 4. Design case 2, NS1, NS2 and NS3 are the top three solutions with the highest "desirability" values, and the designed structural combinations have thicker AC and UAB layers. In contrast, in design case 1, YS1, YS2 and YS3 are the top three solutions with the highest "desirability" values, and the MPS values ​​obtained are only 1.8% different from those obtained by NS1, NS2 and NS3 solutions, while the volume stress value of the granular layer is 30% higher, indicating that according to the structural thickness and modulus parameters in the optimized solutions YS1, YS2 and YS3, the designed inverted asphalt pavement has both good fatigue performance and stronger stress dependence characteristics.

[0110] Table 4 Optimization design solution

[0111]

[0112] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems or computer program products. Therefore, the present application may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware.

[0113] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A method for optimizing the thickness of an inverted asphalt pavement structure, characterized in that: The following steps are involved: The thickness and modulus of each layer of the inverted asphalt pavement structure were selected as control variables. The D-optimal solution response surface design method was used to develop a test plan containing multiple groups of different thickness and modulus combinations, and the significance of each group of control variables on the target response value was evaluated. Based on the stress-dependent nonlinear characteristics of the aggregate transition layer, the mechanical response calculation of the inverted asphalt pavement structure is carried out to obtain the bottom tensile strain of the asphalt surface layer and the volume stress of the aggregate transition layer, so as to evaluate the fatigue performance of the asphalt surface layer and the stress-dependent characteristics of the aggregate transition layer. According to the fatigue performance of the asphalt surface layer and the stress-dependent characteristics of the granular transition layer, the optimal design range of the inverted asphalt pavement structure is determined, the optimal solution is determined based on the satisfaction theory, and other pavement structure mechanical verification indicators are compared to recommend the optimal thickness and modulus combination of the inverted asphalt pavement structure.

2. The thickness optimization design method of inverted asphalt pavement structure according to claim 1 is characterized in that: The D-optimal solution response surface design method is implemented by Design-expert software, and is used to determine the optimal combination of asphalt surface layer thickness, asphalt surface layer modulus, granular transition layer thickness, granular transition layer modulus, semi-rigid layer thickness, semi-rigid layer modulus and roadbed modulus.

3. The thickness optimization design method of inverted asphalt pavement structure according to claim 1 is characterized in that: The response surface design methodology is generated based on multiple sets of experimental data and evaluates the effects of different thickness and modulus combinations on the fatigue performance of the asphalt pavement and the stress-dependent characteristics of the aggregate transition layer.

4. The thickness optimization design method of inverted asphalt pavement structure according to claim 1 is characterized in that: The mechanical response calculation is based on the finite element analysis method, using the compiled UMAT subroutine to give the granular transition layer stress-dependent nonlinear characteristics, and achieve accurate simulation of the granular transition layer stress response through the constitutive model.

5. The thickness optimization design method of inverted asphalt pavement structure according to claim 1 is characterized in that: The fatigue performance of the asphalt surface layer is determined by evaluating the maximum principal strain at the bottom of the asphalt surface layer, and the upper limit of the maximum principal strain at the bottom of the asphalt surface layer is 120με.

6. The thickness optimization design method of inverted asphalt pavement structure according to claim 1 is characterized in that: The volume stress of the granular transition layer is used to characterize the stress-dependent characteristics of the granular transition layer, and the lower limit of the volume stress level is 150 kPa.

7. The thickness optimization design method of inverted asphalt pavement structure according to claim 1 is characterized in that: The goal of the optimization design is to reduce the thickness of the asphalt surface layer and improve the durability of the asphalt pavement by minimizing the tensile strain at the bottom of the asphalt surface layer and maximizing the volume stress of the aggregate transition layer.

8. The thickness optimization design method of inverted asphalt pavement structure according to claim 7 is characterized in that: The thickness of the asphalt surface layer ranges from 8cm to 18cm, the thickness of the granular transition layer ranges from 10cm to 30cm, and the thickness of the semi-rigid layer ranges from 15cm to 40cm.

9. The thickness optimization design method of inverted asphalt pavement structure according to claim 1 is characterized in that: The dynamic modulus of the asphalt surface layer is determined by the actual traffic parameters, temperature conditions and the properties of the roadbed soil, and the dynamic modulus under different environmental conditions is calculated based on the design formula.

10. The thickness optimization design method of inverted asphalt pavement structure according to claim 1, characterized in that: The optimization design takes into account the fatigue cracking resistance of the asphalt surface layer, the fatigue performance of the semi-rigid layer and the permanent deformation resistance of the granular transition layer to ensure the overall structural performance and economic benefits of the inverted asphalt pavement.

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