A method for calculating a fatigue damage critical point of a full-thickness asphalt pavement

Abstract

This invention provides a method for calculating the critical point of fatigue damage in full-thickness asphalt pavement, relating to the field of road engineering technology. The invention first divides the full-thickness asphalt pavement into multiple sub-layers, then obtains its annual temperature field and annual axle load spectrum, determines the temperature model of the full-thickness asphalt pavement and the number of equivalent axle load applications per hour, and combines laboratory test results to obtain the dynamic modulus calculation equations and multi-temperature fatigue equations for each sub-layer. The temperature of each sub-layer is obtained using the full-thickness asphalt pavement temperature model, and the dynamic modulus value of each sub-layer is determined using the dynamic modulus calculation equations. Then, the flexural strain response of each sub-layer is calculated based on its dynamic modulus value, and its fatigue life is calculated using the multi-temperature fatigue equations for each sub-layer. Combined with the number of equivalent axle load applications per hour, the fatigue damage value of each sub-layer is calculated and accumulated to obtain the cumulative fatigue damage of each sub-layer in the full-thickness asphalt pavement, accurately obtaining the critical damage point of the full-thickness asphalt pavement.

Description

Technical Field

[0001] This invention relates to the field of road engineering technology, specifically to a method for calculating the critical point of fatigue damage in full-thickness asphalt pavement. Background Technology

[0002] Due to limitations in asphalt supply and economic conditions, the "strong base and thin surface" pavement structure has become the mainstream structure for highway pavements. In particular, asphalt pavements with semi-rigid bases have been widely used and occupy an important position in highway construction because they are economical, have good slab properties, high overall stiffness, high load-bearing capacity, strong stress diffusion capacity, certain tensile strength and fatigue strength, and good water stability.

[0003] However, semi-rigid base asphalt pavements still have some shortcomings, mainly manifested in the following ways: (1) Asphalt pavement reflective cracks of varying degrees caused by shrinkage cracking of semi-rigid base course; (2) During the service of semi-rigid base asphalt pavement, the strength and modulus of semi-rigid base materials will gradually decrease due to fatigue caused by dry-wet, freeze-thaw cycles and repeated loading. (3) Semi-rigid base asphalt pavement cannot heal after damage and is difficult to repair; (4) The overall thickness of semi-rigid base asphalt pavement is relatively large, requiring more road construction materials.

[0004] Full-thickness asphalt pavement is a type of pavement where all structural layers above the subgrade (except the base course) are constructed using asphalt mixture. Compared to other pavement structures, its total pavement thickness is reduced by more than 40%, resulting in significant savings in high-quality road construction materials. Furthermore, it offers high construction efficiency and a long service life. Given the increasing scarcity of mineral resources, growing environmental pressures, and rising stone prices, its advantages are particularly evident.

[0005] Currently, methods for calculating the critical point of fatigue damage in full-thickness asphalt pavements typically use the flexural tensile strain at the bottom of the asphalt layer as the key mechanical indicator of damage. Furthermore, the modulus of each asphalt mixture structural layer is calculated using the same value, neglecting the influence of temperature on the asphalt mixture layer modulus. Most methods also employ standard loads or a few hypothetical loads, failing to consider the impact of the actual axle load spectrum on the pavement damage state. Therefore, there is an urgent need to propose a new method for calculating the critical point of fatigue damage in full-thickness asphalt pavements to achieve accurate determination of this critical point. Summary of the Invention

[0006] To address the shortcomings of the existing technologies, this invention proposes a method for calculating the critical point of fatigue damage in full-thickness asphalt pavement. This method fully considers the influence of the actual temperature field and axle load spectrum of full-thickness asphalt pavement on the damage state of full-thickness asphalt pavement, and achieves accurate acquisition of the critical point of fatigue damage in full-thickness asphalt pavement, which is beneficial for guiding the formulation of design schemes for full-thickness asphalt pavement.

[0007] The present invention adopts the following technical solution: A method for calculating the fatigue damage critical point of full-thickness asphalt pavement includes the following steps: Step 1: Divide the full-thickness asphalt pavement into multiple sub-layers from top to bottom according to the preset thickness; Step 2: Obtain the annual temperature field of the full-thickness asphalt pavement and fit it to obtain the temperature model of the full-thickness asphalt pavement. The temperature model of the full-thickness asphalt pavement includes the temperature calculation model of each sub-layer, which is used to determine the temperature at each location in the full-thickness asphalt pavement. Step 3: Obtain the annual axle load spectrum of the full-thickness asphalt pavement to obtain the number of equivalent axle load applications per hour for the full-thickness asphalt pavement. Step 4: Based on the laboratory test results, obtain the dynamic modulus calculation equations and multi-temperature fatigue equations for each sublayer in the full-thickness asphalt pavement. Step 5: Obtain the internal temperature of each sublayer in the full-thickness asphalt pavement based on the temperature model of the full-thickness asphalt pavement, determine the dynamic modulus value of each sublayer in the temperature model of the full-thickness asphalt pavement based on the dynamic modulus calculation equation of each sublayer, calculate the bending tensile strain response of each sublayer based on the dynamic modulus value of each sublayer, and calculate the fatigue life of each sublayer in the full-thickness asphalt pavement based on the multi-temperature fatigue equation of each sublayer. Step 6: Calculate the fatigue damage value of each sublayer in the full-thickness asphalt pavement per hour using the equivalent axle load number of times per hour. Then, accumulate the fatigue damage values ​​of each sublayer in the full-thickness asphalt pavement per hour to obtain the cumulative fatigue damage at each location in the full-thickness asphalt pavement. Step 7: Determine the critical damage point of the full-thickness asphalt pavement based on the cumulative fatigue damage at various locations in the full-thickness asphalt pavement.

[0008] Preferably, the preset thickness is 1 cm.

[0009] Preferably, in step 1, for each sub-layer in the full-thickness asphalt pavement, a temperature calculation model for the sub-layer is obtained by performing polynomial fitting on the internal temperature of the sub-layer at different times throughout the year based on the annual temperature field. Based on the temperature calculation models of all sub-layers, a temperature model for the full-thickness asphalt pavement is obtained, and the temperature value at each depth within the full-thickness asphalt pavement is obtained in real time at each hour using the temperature model for the full-thickness asphalt pavement.

[0010] Preferably, in the polynomial fitting process, the polynomial used for fitting is selected according to the weather conditions of the full-thickness asphalt pavement. Specifically, for non-rainy or snowy weather, a quadratic equation is used to fit the temperature field data of the full-thickness asphalt pavement, and for rainy or snowy weather, a cubic equation is used to fit the temperature field data of the full-thickness asphalt pavement.

[0011] Preferably, in step 4, the asphalt mixture used in the full-thickness asphalt pavement includes SMA-13, HMAC-20, AC-20, AC-25, LSPM-25, and AC-13. For each asphalt mixture, a polynomial was used to fit the dynamic modulus of the asphalt mixture at different temperatures to obtain the relationship between the dynamic modulus of the asphalt mixture and temperature, and to obtain the dynamic modulus calculation equation for each asphalt mixture, thereby determining the dynamic modulus calculation equation for each sublayer. in, The equation for calculating the dynamic modulus of the SMA-13 ​​asphalt mixture is as follows: ; In the formula, The dynamic modulus of SMA-13 ​​asphalt mixture is expressed in MPa. Temperature, in °C; The equation for calculating the dynamic modulus of the asphalt mixture HMAC-20 is as follows: ; In the formula, The dynamic modulus of HMAC-20 asphalt mixture is expressed in MPa. The equation for calculating the dynamic modulus of the asphalt mixture AC-20 is as follows: ; In the formula, This is the dynamic modulus of asphalt mixture AC-20, expressed in MPa. The equation for calculating the dynamic modulus of the asphalt mixture AC-25 is as follows: ; In the formula, This is the dynamic modulus of asphalt mixture AC-25, expressed in MPa. The equation for calculating the dynamic modulus of the asphalt mixture LSPM-25 is as follows: ; In the formula, The dynamic modulus of LSPM-25 asphalt mixture is expressed in MPa. The equation for calculating the dynamic modulus of the asphalt mixture AC-13 is as follows: ; In the formula, This is the dynamic modulus of asphalt mixture AC-13, expressed in MPa.

[0012] Preferably, the multi-temperature fatigue equation is: ; In the formula, It is the natural logarithm function; Fatigue life is measured in cycles. The tensile strain at the bottom of the layer is expressed in units of 1. ; , , All of these are fitting coefficients for the multi-temperature fatigue equation.

[0013] Preferably, in step 6, the formula for calculating the cumulative fatigue damage of each sublayer in the full-thickness asphalt pavement is: ; In the formula, The cumulative fatigue damage of the sub-layer in a full-thickness asphalt pavement; Hourly serial number; Total number of hours throughout the year; For the first Fatigue damage in the sublayer over 2 hours; For the first The equivalent number of axle load applications per hour for a full-thickness asphalt pavement; For the first The fatigue life of the sublayer in hours.

[0014] The beneficial effects of this invention are as follows: This invention proposes a method for calculating the critical point of fatigue damage in full-thickness asphalt pavement. This method couples the pavement temperature field and traffic load on full-thickness asphalt pavement, fully considering the influence of temperature field changes on the dynamic modulus of asphalt mixture in full-thickness asphalt pavement, and taking into account the hourly distribution of traffic load on full-thickness asphalt pavement. This makes the calculation of the structural mechanical response and fatigue life prediction of full-thickness asphalt pavement more closely reflect the actual service conditions of full-thickness asphalt pavement. Compared with the traditional method of calculating fatigue damage of full-thickness asphalt pavement using constant temperature and dynamic modulus, this invention fully restores the field service state of full-thickness asphalt pavement and achieves accurate acquisition of the critical point of fatigue damage of full-thickness asphalt pavement. Attached Figure Description

[0015] Figure 1 This is a flowchart of a method for calculating the critical point of fatigue damage in full-thickness asphalt pavement according to the present invention.

[0016] Figure 2This is a schematic diagram of the structure of the full-thickness asphalt pavement of the present invention.

[0017] Figure 3 This is a schematic diagram of a temperature model for a full-thickness asphalt pavement.

[0018] Figure 4 This is a 24-hour distribution chart of the dynamic modulus of the SMA-13 ​​layer.

[0019] Figure 5 This is a 24-hour distribution chart of the dynamic modulus of the HMAC-20 layer.

[0020] Figure 6 This is a 24-hour distribution chart of the dynamic modulus of layer AC-25.

[0021] Figure 7 This is a 24-hour distribution chart of the dynamic modulus of the LSPM-25 layer.

[0022] Figure 8 This is a 24-hour distribution chart of the dynamic modulus of the HRF-13 layer.

[0023] Figure 9 This is a schematic diagram of the critical point of fatigue damage for a full-thickness asphalt pavement. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0025] Example 1 This embodiment discloses a method for calculating the fatigue damage critical point of full-thickness asphalt pavement, such as... Figure 1 As shown, it includes the following steps: Step 1: Divide the full-thickness asphalt pavement into multiple sub-layers from top to bottom according to a thickness of 1cm.

[0026] Step 2: Obtain the annual temperature field of the full-thickness asphalt pavement and fit it to obtain the temperature model of the full-thickness asphalt pavement. The temperature model of the full-thickness asphalt pavement includes temperature calculation models for each sub-layer, which are used to determine the temperature at each location within the full-thickness asphalt pavement.

[0027] Specifically, for each sub-layer in the full-thickness asphalt pavement, a temperature calculation model for the sub-layer is obtained by performing polynomial fitting on the internal temperature of the sub-layer at different times throughout the year based on the annual temperature field. Based on the temperature calculation models of all sub-layers, a temperature model for the full-thickness asphalt pavement is obtained, and the temperature value at each depth within the full-thickness asphalt pavement is obtained in real time every hour using the full-thickness asphalt pavement temperature model.

[0028] In this embodiment, during the polynomial fitting process, the polynomial used for fitting is selected according to the weather conditions of the full-thickness asphalt pavement. Specifically, for non-rainy or snowy weather, a quadratic equation is used to fit the temperature field data of the full-thickness asphalt pavement, and for rainy or snowy weather, a cubic equation is used to fit the temperature field data of the full-thickness asphalt pavement.

[0029] Based on the temperature calculation model of each sublayer in the full-thickness asphalt pavement, the temperature model of the full-thickness asphalt pavement is obtained. Using the temperature model of the full-thickness asphalt pavement, the hourly temperature change at each location in the full-thickness asphalt pavement can be obtained, which fully restores the internal temperature change of the full-thickness asphalt pavement during service and accurately restores the influence of temperature change on the dynamic modulus of each asphalt structural layer of the full-thickness asphalt pavement.

[0030] Step 3: Obtain the annual axle load spectrum of the full-thickness asphalt pavement. Based on the strain equivalence of the annual axle load spectrum, obtain the equivalent axle load application times per hour for the full-thickness asphalt pavement.

[0031] Step 4: Based on the laboratory test results, obtain the dynamic modulus calculation equations and multi-temperature fatigue equations for each sublayer in the full-thickness asphalt pavement.

[0032] Specifically, the asphalt mixtures used in the full-thickness asphalt pavement include SMA-13, HMAC-20, AC-20, AC-25, LSPM-25, and AC-13.

[0033] For each asphalt mixture, a polynomial was used to fit the dynamic modulus of the asphalt mixture at different temperatures to obtain the relationship between the dynamic modulus of the asphalt mixture and temperature, thus obtaining the dynamic modulus calculation equation for each asphalt mixture, and thus determining the dynamic modulus calculation equation for each sublayer.

[0034] in, The equation for calculating the dynamic modulus of the SMA-13 ​​asphalt mixture is as follows: ; In the formula, The dynamic modulus of SMA-13 ​​asphalt mixture is expressed in MPa. Temperature, in °C; The equation for calculating the dynamic modulus of the asphalt mixture HMAC-20 is as follows: ; In the formula, The dynamic modulus of HMAC-20 asphalt mixture is expressed in MPa. The equation for calculating the dynamic modulus of the asphalt mixture AC-20 is as follows: ; In the formula, This is the dynamic modulus of asphalt mixture AC-20, expressed in MPa. The equation for calculating the dynamic modulus of the asphalt mixture AC-25 is as follows: ; In the formula, This is the dynamic modulus of asphalt mixture AC-25, expressed in MPa. The equation for calculating the dynamic modulus of the asphalt mixture LSPM-25 is as follows: ; In the formula, The dynamic modulus of LSPM-25 asphalt mixture is expressed in MPa. The equation for calculating the dynamic modulus of the asphalt mixture AC-13 is as follows: ; In the formula, This is the dynamic modulus of asphalt mixture AC-13, expressed in MPa.

[0035] Specifically, multi-temperature fatigue equations are constructed for both base asphalt and modified asphalt, wherein the multi-temperature fatigue equation for base asphalt is as follows: ; The multi-temperature fatigue equation for the modified asphalt is: ; In the formula, It is the natural logarithm function; Fatigue life is measured in cycles. The tensile strain at the bottom of the layer is expressed in units of 1. ; Temperature, in °C.

[0036] Step 5: Obtain the internal temperature of each sublayer in the full-thickness asphalt pavement based on the temperature model of the full-thickness asphalt pavement. Combine the dynamic modulus calculation equation of each sublayer to determine the dynamic modulus value of each sublayer in the temperature model of the full-thickness asphalt pavement. Calculate the flexural strain response of each sublayer based on the dynamic modulus value of each sublayer. Combine the multi-temperature fatigue equation of each sublayer to calculate the fatigue life of each sublayer in the full-thickness asphalt pavement.

[0037] Step 6: Calculate the fatigue damage value of each sublayer in the full-thickness asphalt pavement per hour using the equivalent axle load application times per hour, and accumulate the fatigue damage values ​​of each sublayer in the full-thickness asphalt pavement per hour to obtain the cumulative fatigue damage at each location in the full-thickness asphalt pavement.

[0038] Specifically, the formula for calculating the cumulative fatigue damage of each sublayer in the full-thickness asphalt pavement is as follows: ; In the formula, The cumulative fatigue damage of the sub-layer in a full-thickness asphalt pavement; Hourly serial number; In this embodiment, the total number of hours throughout the year is used. Set it to 8760, which is the total number of hours throughout the year; For the first Fatigue damage in the sublayer over 2 hours; For the first The equivalent number of axle load applications per hour for a full-thickness asphalt pavement; For the first The fatigue life of the sublayer in hours.

[0039] Step 7: Determine the critical damage point of the full-thickness asphalt pavement based on the cumulative fatigue damage at various locations in the full-thickness asphalt pavement.

[0040] Example 2 This embodiment applies the fatigue damage critical point calculation method for full-thickness asphalt pavement described in Embodiment 1 to a certain expressway. The expressway has a design speed of 120 km / h, a total length of 89 km, a design life of 15 years, an average daily traffic volume of 16,820 vehicles / day, a traffic volume growth rate of 3.2%, a lane coefficient of 0.5, and a directional coefficient of 0.55. Some sections of this expressway use full-thickness asphalt pavement. Based on meeting the design requirements of the current asphalt pavement design specifications, the fatigue damage critical point is determined using the fatigue damage critical point calculation method for full-thickness asphalt pavement described in Embodiment 1.

[0041] In this embodiment, the preliminary pavement structure design scheme of the full-thickness asphalt pavement is shown in Table 1.

[0042] Table 1 Preliminary Design Scheme for Full-Thickness Asphalt Pavement As shown in Table 1, the full-thickness asphalt pavement consists of a surface layer, a base layer, and a subgrade from top to bottom. Figure 2As shown, the surface layer comprises multiple structural layers, arranged from top to bottom as a top layer, a middle layer, and a bottom layer. The top layer has a thickness of 40 mm, a dynamic modulus of 12000 MPa, a Poisson's ratio of 0.25, and is paved with asphalt mastic aggregate mixture-13 (SMA-13). The middle layer has a thickness of 60 mm, a dynamic modulus of 14000 MPa, a Poisson's ratio of 0.25, and is paved with dense-graded asphalt concrete-20 (HMAC-20). The bottom layer has a thickness of 80 mm, a dynamic modulus of 11500 MPa, a Poisson's ratio of 0.25, and is paved with dense-graded asphalt concrete-25 (AC-25). The roadbed is constructed as follows: Multiple structural layers are provided within the base course, consisting of an upper base course, a lower base course, and a subbase course from top to bottom. The upper base course has a thickness of 80mm, a dynamic modulus of 11500MPa, a Poisson's ratio of 0.25, and is paved with dense-graded asphalt concrete-25 (AC-25). The lower base course has a thickness of 80mm, a dynamic modulus of 9500MPa, a Poisson's ratio of 0.25, and is paved with large-particle-size permeable asphalt mixture-25 (LSPM-25). The subbase course has a thickness of 40mm, a dynamic modulus of 11000MPa, a Poisson's ratio of 0.25, and a design standard of 13 million axle passes. The subgrade is a soil subgrade with a dynamic modulus of 160MPa and a Poisson's ratio of 0.4.

[0043] The measured annual temperature field data at various depths of the full-thickness asphalt pavement were obtained, and a temperature model for the full-thickness asphalt pavement was fitted, as follows: Figure 3 As shown, this is used to determine the temperature at different locations in the full-thickness asphalt pavement temperature model per hour, and to realistically reproduce the internal temperature field of the full-thickness asphalt pavement temperature model during its service.

[0044] Analysis of traffic load parameters shows that, within the design service life, the cumulative equivalent axle fatigue cycles of the asphalt layer in the temperature model of the full-thickness asphalt pavement are 15001303.

[0045] Based on the asphalt mixture type of each sublayer in the full-thickness asphalt pavement temperature model, the dynamic modulus calculation equations for each sublayer in the full-thickness asphalt pavement temperature model are obtained, such as... Figures 4-8 As shown.

[0046] Based on the dynamic modulus of each sublayer in a full-thickness asphalt pavement, and combined with the multi-temperature fatigue equation, the fatigue life of each sublayer is determined.

[0047] Step 5: Obtain the internal temperature of each sublayer in the full-thickness asphalt pavement based on the temperature model of the full-thickness asphalt pavement. Combine the dynamic modulus calculation equation of each sublayer to determine the dynamic modulus value of each sublayer in the temperature model of the full-thickness asphalt pavement. Calculate the flexural strain response of each sublayer based on the dynamic modulus value of each sublayer. Combine the multi-temperature fatigue equation of each sublayer to calculate the fatigue life of each sublayer in the full-thickness asphalt pavement.

[0048] Step 6: Calculate the fatigue damage value of each sublayer in the full-thickness asphalt pavement per hour using the equivalent axle load application times per hour, and accumulate the fatigue damage values ​​of each sublayer in the full-thickness asphalt pavement per hour to obtain the cumulative fatigue damage at each location in the full-thickness asphalt pavement.

[0049] Step 7: Based on the cumulative fatigue damage at various locations in the full-thickness asphalt pavement, determine the critical damage point of the full-thickness asphalt pavement, such as... Figure 9 As shown.

[0050] Depend on Figure 9 It can be seen that as the depth of the full-thickness asphalt pavement increases, the fatigue damage of each sublayer of the full-thickness asphalt pavement gradually increases, and the fatigue damage reaches its maximum at 35cm. Therefore, the critical point of fatigue damage for the full-thickness asphalt pavement is determined to be 35cm.

[0051] In summary, the method of this invention couples the actual traffic load and temperature effects of full-thickness asphalt pavement, realistically reproducing the mechanical response of full-thickness asphalt pavement. By accurately reproducing the fatigue damage at various depths of full-thickness asphalt pavement during service, it achieves accurate acquisition of the fatigue damage critical point of full-thickness asphalt pavement.

[0052] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for calculating the critical point of fatigue damage in full-thickness asphalt pavement, characterized in that, Includes the following steps: Step 1: Divide the full-thickness asphalt pavement into multiple sub-layers from top to bottom according to the preset thickness; Step 2: Obtain the annual temperature field of the full-thickness asphalt pavement and fit it to obtain the temperature model of the full-thickness asphalt pavement. The temperature model of the full-thickness asphalt pavement includes the temperature calculation model of each sub-layer, which is used to determine the temperature at each location in the full-thickness asphalt pavement. Step 3: Obtain the annual axle load spectrum of the full-thickness asphalt pavement to obtain the number of equivalent axle load applications per hour for the full-thickness asphalt pavement. Step 4: Based on the laboratory test results, obtain the dynamic modulus calculation equations and multi-temperature fatigue equations for each sublayer in the full-thickness asphalt pavement. Step 5: Obtain the internal temperature of each sublayer in the full-thickness asphalt pavement based on the temperature model of the full-thickness asphalt pavement, determine the dynamic modulus value of each sublayer in the temperature model of the full-thickness asphalt pavement based on the dynamic modulus calculation equation of each sublayer, calculate the bending tensile strain response of each sublayer based on the dynamic modulus value of each sublayer, and calculate the fatigue life of each sublayer in the full-thickness asphalt pavement based on the multi-temperature fatigue equation of each sublayer. Step 6: Calculate the fatigue damage value of each sublayer in the full-thickness asphalt pavement per hour using the equivalent axle load number of times per hour. Then, accumulate the fatigue damage values ​​of each sublayer in the full-thickness asphalt pavement per hour to obtain the cumulative fatigue damage at each location in the full-thickness asphalt pavement. Step 7: Determine the critical damage point of the full-thickness asphalt pavement based on the cumulative fatigue damage at various locations in the full-thickness asphalt pavement.

2. The method for calculating the critical point of fatigue damage in full-thickness asphalt pavement according to claim 1, characterized in that, The preset thickness is 1cm.

3. The method for calculating the critical point of fatigue damage in full-thickness asphalt pavement according to claim 1, characterized in that, In step 1, for each sub-layer in the full-thickness asphalt pavement, a temperature calculation model for the sub-layer is obtained by performing polynomial fitting on the internal temperature of the sub-layer at different times throughout the year based on the annual temperature field. Based on the temperature calculation models of all sub-layers, a temperature model for the full-thickness asphalt pavement is obtained, and the temperature value at each depth within the full-thickness asphalt pavement is obtained in real time every hour using the temperature model for the full-thickness asphalt pavement.

4. The method for calculating the critical point of fatigue damage in full-thickness asphalt pavement according to claim 3, characterized in that, In the polynomial fitting process, the polynomial used for fitting is selected according to the weather conditions of the full-thickness asphalt pavement. Specifically, for non-rainy or snowy weather, a quadratic equation is used to fit the temperature field data of the full-thickness asphalt pavement, and for rainy or snowy weather, a cubic equation is used to fit the temperature field data of the full-thickness asphalt pavement.

5. The method for calculating the critical point of fatigue damage in full-thickness asphalt pavement according to claim 1, characterized in that, In step 4, the asphalt mixture used in the full-thickness asphalt pavement includes SMA-13, HMAC-20, AC-20, AC-25, LSPM-25, and AC-13. For each asphalt mixture, a polynomial was used to fit the dynamic modulus of the asphalt mixture at different temperatures to obtain the relationship between the dynamic modulus of the asphalt mixture and temperature, and to obtain the dynamic modulus calculation equation for each asphalt mixture, thereby determining the dynamic modulus calculation equation for each sublayer. in, The equation for calculating the dynamic modulus of the SMA-13 ​​asphalt mixture is as follows: ； In the formula, The dynamic modulus of SMA-13 ​​asphalt mixture is expressed in MPa. Temperature, in °C; The equation for calculating the dynamic modulus of the asphalt mixture HMAC-20 is as follows: ； In the formula, The dynamic modulus of HMAC-20 asphalt mixture is expressed in MPa. The equation for calculating the dynamic modulus of the asphalt mixture AC-20 is as follows: ； In the formula, This is the dynamic modulus of asphalt mixture AC-20, expressed in MPa. The equation for calculating the dynamic modulus of the asphalt mixture AC-25 is as follows: ； In the formula, This is the dynamic modulus of asphalt mixture AC-25, expressed in MPa. The equation for calculating the dynamic modulus of the asphalt mixture LSPM-25 is as follows: ； In the formula, The dynamic modulus of LSPM-25 asphalt mixture is expressed in MPa. The equation for calculating the dynamic modulus of the asphalt mixture AC-13 is as follows: ； In the formula, This is the dynamic modulus of asphalt mixture AC-13, expressed in MPa.

6. The method for calculating the critical point of fatigue damage in full-thickness asphalt pavement according to claim 1, characterized in that, The multi-temperature fatigue equation is as follows: ； In the formula, It is the natural logarithm function; Fatigue life is measured in cycles. The tensile strain at the bottom of the layer is expressed in units of 1. ; , , All of these are fitting coefficients for the multi-temperature fatigue equation.

7. The method for calculating the critical point of fatigue damage in full-thickness asphalt pavement according to claim 1, characterized in that, In step 6, the formula for calculating the cumulative fatigue damage of each sublayer in the full-thickness asphalt pavement is as follows: ； In the formula, The cumulative fatigue damage of the sub-layer in a full-thickness asphalt pavement; Hourly serial number; Total number of hours throughout the year; For the first Fatigue damage in the sublayer over 2 hours; For the first The equivalent number of axle load applications per hour for a full-thickness asphalt pavement; For the first The fatigue life of the sublayer in hours.

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