Equivalent calculation method for quantitative evaluation of residual life of existing pavement and storage medium

Abstract

The invention discloses an equivalent calculation method for quantitative evaluation of the residual life of an existing pavement and a storage medium, and the method comprises the steps: firstly, determining a bearing threshold value of a lossless pavement structure based on a dual-modulus elastic layered system theory; secondly, a reduction coefficient of typical diseases to the structural strength is quantified through finite element simulation; thirdly, establishing a mathematical relationship model of the maximum effective stress and the fatigue life; then, actual disease information is accurately obtained by combining nondestructive testing technologies such as ground penetrating radar and three-dimensional laser scanning; then, correcting the maximum allowable equivalent stress in a lossless state according to the disease data; and finally, fusing the theoretical model and the traffic load history, and calculating the remaining service life. According to the method, three-dimensional and quantitative analysis on the influence of the diseases is realized through a mechanical response equivalence principle, the accuracy, objectivity and engineering application efficiency of residual life evaluation are remarkably improved, and a reliable basis is provided for scientifically making a road maintenance decision.

Description

Technical Field

[0001] This invention belongs to the field of road engineering technology, and specifically relates to an equivalent calculation method for quantitative evaluation of the remaining life of existing pavements. Background Technology

[0002] In the field of road engineering, with the rapid development of transportation, a large number of early-built asphalt roads are gradually entering the middle and late stages of operation. Their structural performance deteriorates due to the combined effects of long-term traffic loads and environmental factors, resulting in various defects (such as cracks, ruts, loosening, and potholes). To formulate scientific and reasonable maintenance, repair, and reconstruction plans, it is necessary to accurately assess the remaining lifespan of these roads. Accurate assessment of remaining lifespan is of great significance for extending road service life, optimizing resource allocation, and ensuring traffic safety.

[0003] However, traditional methods for assessing remaining useful life have the following shortcomings:

[0004] First, most evaluation methods ignore the synergistic effect of the coupling effect of environmental factors and load on pavement structure damage, resulting in an incomplete analysis of the damage mechanism.

[0005] Second, there is often a lack of quantitative weighting for the impact of different defects on pavement life, making it difficult to accurately reflect the relationship between the actual damage state and remaining life of existing pavements.

[0006] Third, existing evaluation models are mostly based on simplified mechanical analysis or empirical formulas, failing to fully incorporate the fatigue characteristics of asphalt materials and the three-dimensional mechanical response of pavement structures.

[0007] Fourth, traditional fatigue models typically only consider uniaxial stress states, which makes it difficult to describe the fatigue damage process of actual road surfaces under complex three-dimensional stress fields, resulting in significant deviations between evaluation results and actual conditions. Summary of the Invention

[0008] To address the above technical problems, this invention assumes that the effect of the internal health condition of the structure on the mechanical response is reflected in the modulus design parameters of the pavement material. It proposes a quantitative evaluation method for the remaining life of existing pavements that comprehensively considers the effects of load, environmental factors, and defects. This method solves the shortcomings of traditional evaluation methods in accurately quantifying the effects of multiple factors, enabling accurate quantitative evaluation of the remaining life of existing pavements and promoting the efficient integration of road maintenance decisions with actual engineering needs.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] An equivalent calculation method for quantitative evaluation of the remaining life of existing pavements includes the following steps:

[0011] S1. Determination of the load-bearing threshold under non-destructive conditions: Based on the theory of dual-modulus elastic layered systems, a non-destructive pavement structure model is constructed, and the maximum allowable equivalent stress of each structural layer under standard axle load in the non-destructive state is calculated.

[0012] S2. Calculation of fatigue strength reduction coefficient under distress conditions: Based on the aforementioned undamaged pavement structure model, a typical pavement distress model is implanted into the finite element software to calculate the actual equivalent stress at the most unfavorable point of the structure under distress conditions, and compare it with the maximum allowable equivalent stress under undamaged conditions to establish a mapping relationship between distress type, distress depth, and fatigue strength reduction coefficient to quantify the degree of weakening of structural strength by distress.

[0013] S3. Establishment of the maximum effective stress-fatigue life relationship model: By simulating the fatigue failure process of the non-destructive pavement structure model under different axle load gradients, multiple sets of maximum effective stress and fatigue life datasets are obtained, and a mathematical relationship model with maximum effective stress as the independent variable and fatigue life as the dependent variable is fitted.

[0014] S4. Detecting road defects: Using a combination of non-destructive testing methods and manual verification, an actual database of defects in existing road surfaces is obtained;

[0015] S5. Bearing capacity correction: Based on the existing pavement defect information database actually obtained in step S4, match the mapping relationship established in step S2, and use the reduction coefficient to correct the maximum allowable equivalent stress under the undamaged state determined in step S1, thereby calculating the maximum allowable equivalent stress under the defective state that reflects the actual pavement state.

[0016] S6. Calculation of remaining life: Substitute the maximum allowable equivalent stress under the fault state calculated in step S5 as the maximum allowable stress level into the mathematical relationship model established in step S3 to calculate the total fatigue life of the pavement; then combine the consumed life obtained from historical traffic volume data statistics to calculate the number of remaining fatigue life cycles, and finally convert it into the remaining service life based on future traffic volume predictions.

[0017] Beneficial Effects: This invention proposes an equivalent calculation method for quantitatively evaluating the remaining life of existing pavements. First, based on the theory of bimodal elastic layered systems, the maximum allowable equivalent stress of the lower layer in the undamaged state is determined. Simultaneously, fatigue strength reduction coefficients under different distress conditions are obtained through finite element simulation to correct the allowable stress at the distressed location. This approach fully considers the coupling effect of environmental factors and loads, compensating for the shortcomings of most evaluation methods that neglect the synergistic effect between the two, thus making the analysis of damage mechanisms more comprehensive. Second, when establishing the stress-life relationship, the remaining life is calculated by combining the number of standard axle loads already borne and the prediction of the future daily average number of loads. This achieves a quantitative weighting of the impact of different distress conditions on pavement life, accurately reflecting the correlation between the actual damage state and the remaining life of existing pavements. Third, this method no longer relies on simplified mechanical analysis or empirical formulas but incorporates the fatigue characteristics of asphalt materials and the three-dimensional mechanical response of pavement structures, making the evaluation model more realistic. Finally, through multi-step quantitative analysis, it is no longer limited to the uniaxial stress state considered only in traditional fatigue models, but can describe the fatigue damage process of actual pavements under a complex three-dimensional stress field, making the evaluation results more consistent with reality. In summary, this method, through multi-step quantitative analysis, integrates load, environmental, and disease factors to achieve an accurate evaluation of the remaining life of existing pavements, solving the problem that traditional methods struggle to accurately quantify the effects of multiple factors.

[0018] In an optional embodiment, in step S1, the dual-modulus elastic layered system theory refers to inputting the tensile modulus and compressive modulus obtained from indoor material tests for the asphalt mixture surface layer when constructing the pavement structure model.

[0019] Beneficial effects: The use of dual-mode energy can more accurately reflect the stress characteristics of asphalt mixtures, making the non-destructive pavement structure model more realistic, and making the calculation of the maximum allowable equivalent stress under non-destructive conditions more accurate, providing a reliable basis for subsequent calculations and evaluations, and improving the accuracy and rationality of pavement fatigue life analysis.

[0020] In an optional embodiment, in step S2, the typical pavement distress includes cracks and ruts; wherein the crack distress is simulated using Cohesive elements, and different length, width, and depth gradients are set.

[0021] The rutting defects were simulated using the element stiffness attenuation method, with different depth, longitudinal length, and transverse width gradients set.

[0022] Beneficial effects: Using Cohesive elements to set multi-dimensional gradients for cracks and using the element stiffness attenuation method to set multi-dimensional gradients for ruts can accurately simulate typical defects, obtain stress responses under different parameters, make the fatigue strength reduction factor calculation more realistic, provide reliable support for the allowable stress correction of defect states, and improve the accuracy and applicability of pavement fatigue life analysis.

[0023] In an optional embodiment, step S2 involves calling the three-dimensional unified fatigue equation to calculate the three-dimensional equivalent stress of the disease model at the most unfavorable point, and forming a correspondence table of disease type, disease depth, and reduction coefficient.

[0024] Beneficial effects: By calling the three-dimensional unified fatigue equation to calculate the three-dimensional equivalent stress at the most unfavorable point of the disease model, a corresponding table of "disease type-disease depth-reduction coefficient" is formed. The fatigue strength reduction coefficient under different disease types and depths can be accurately obtained, providing an accurate basis for subsequent allowable stress correction of the disease state and improving the accuracy and efficiency of pavement fatigue life analysis.

[0025] In an optional embodiment, in step S3, a 30% decrease in the overall modulus of the pavement structure is used as the criterion for fatigue failure. The mathematical relationship model obtained by fitting, with the maximum effective stress as the independent variable and fatigue life as the dependent variable, is as follows:

[0026] ,

[0027] Where, σ max The maximum effective stress is given, N is the fatigue life, the coefficient of determination R² = 0.98, and the mean square error MSE = 1.2 × 10⁻⁶. 4 .

[0028] Beneficial effects: Using a 30% reduction in the overall modulus of the pavement structure as the criterion for fatigue failure, the fitted maximum effective stress-fatigue life relationship can accurately describe the relationship between the two, providing reliable model support for subsequent calculation of remaining fatigue life and improving the accuracy of pavement fatigue life assessment.

[0029] In an optional embodiment, step S4, the non-destructive testing method includes:

[0030] Ground-penetrating radar with a center frequency of 900MHz-1.5GHz was used to detect internal defects in radar maps, identifying base layer voids and interlayer cracks; and time-frequency analysis and U-Net deep learning algorithm were used to identify the radar maps.

[0031] Point cloud data of the road surface was collected using a 3D laser scanner, and geometric parameters of surface defects were extracted using elevation difference analysis and the Canny edge detection algorithm.

[0032] Beneficial effects: By using ground-penetrating radar combined with time-frequency analysis and U-Net algorithm, and a three-dimensional laser scanner combined with elevation difference and Canny algorithm for non-destructive testing, it is possible to accurately identify internal and surface defects of the pavement, obtain information such as defect type and geometric defect depth, provide accurate and comprehensive basic data for subsequent defect status analysis and remaining fatigue life calculation, and improve the accuracy and efficiency of pavement inspection and evaluation.

[0033] In one optional embodiment, the disease information database includes at least the type of disease, the geometric depth of the disease, and its distribution location.

[0034] Beneficial effects:

[0035] In an optional embodiment, in step S6, the historical traffic volume data is processed using the standard axle load equivalent conversion formula to statistically obtain the cumulative number of standard axle loads that the existing road surface has endured during operation.

[0036] Beneficial effects: By processing historical traffic volume data through the standard axle load equivalent conversion formula, the cumulative number of standard axle loads that existing pavements have endured during operation can be accurately counted. This provides a precise basis for determining the number of loads already endured in the calculation of remaining fatigue life, ensuring the accuracy of remaining fatigue life assessment, and thus helping to rationally plan pavement maintenance and service life.

[0037] The present invention further discloses a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps in the equivalent calculation method for quantitative evaluation of the remaining life of existing pavements. Attached Figure Description

[0038] Figure 1 This is a flowchart of an equivalent calculation method for quantitative evaluation of the remaining life of existing pavements, according to the present invention. Detailed Implementation

[0039] The following description, in conjunction with the accompanying drawings and specific embodiments, details an equivalent calculation method for quantitative evaluation of the remaining life of existing pavements according to the present invention.

[0040] First, let's explain the following terms used in the text:

[0041] The actual equivalent stress is the equivalent stress that the structure actually bears at the most unfavorable point under faulty working conditions;

[0042] The maximum permissible equivalent stress is the maximum equivalent stress limit that a structural layer can withstand under undamaged conditions;

[0043] Maximum effective stress is a characterization of the stress on a structure under different axial load gradients from the perspective of fatigue failure, and is used to establish a fatigue life relationship model. In this invention document, the ratio of actual equivalent stress to maximum allowable equivalent stress is the distress conversion factor. After converting the maximum allowable equivalent stress according to road distress, the converted maximum allowable equivalent stress is then used as the maximum effective stress and substituted into the relationship between maximum effective stress and remaining fatigue life to obtain the remaining fatigue life.

[0044] Effective stress: It takes into account factors such as stress transmission and interaction within the material, and focuses more on reflecting the actual stress in effect from the force mechanism of the material itself;

[0045] Equivalent stress: This transforms a complex multiaxial stress state into an equivalent uniaxial stress according to certain criteria, facilitating analysis and comparison of strength, fatigue, and other aspects. In this invention, the equivalent stress is corrected based on the defects, and then the corrected equivalent stress is used as the effective stress to calculate the remaining fatigue life.

[0046] An equivalent calculation method for quantitative evaluation of the remaining life of existing pavements includes the following steps:

[0047] S1. Based on the theory of dual-modulus elastic layered system, the bearing threshold of pavement structure under undamaged state is quantitatively determined, providing a benchmark for subsequent analysis of the impact of defects, and the maximum allowable equivalent stress of each structural layer is calculated.

[0048] S2. By finite element simulation of the weakening effect of defects on structural strength, the degree of defect impact is quantified, providing a basis for correction of remaining life calculation, and calculating the fatigue strength reduction factor under defect conditions.

[0049] S3. By simulating the fatigue failure process under non-destructive conditions, the mathematical relationship between stress and life is fitted to provide a basic model for calculating the remaining life and to establish the relationship between the maximum effective stress and fatigue life.

[0050] S4. By combining non-destructive testing with manual verification, we can accurately obtain information on existing road surface defects, provide actual data for life calculation, and detect the condition of road defects.

[0051] S5. Combining the disease detection data and reduction coefficient, correct the allowable stress under the undamaged state to reflect the actual weakening of the bearing capacity by the disease, and calculate the maximum allowable equivalent stress under the disease state.

[0052] S6. By integrating theoretical models, disease data, and historical loads, the remaining service life of existing pavements is quantitatively evaluated, and the remaining fatigue life of existing pavements is calculated.

[0053] This invention proposes an equivalent calculation method for quantitatively evaluating the remaining life of existing pavements. First, based on the theory of bimodal elastic layered systems, the maximum allowable equivalent stress of the lower layer in the undamaged state is determined. Simultaneously, fatigue strength reduction coefficients under different distress conditions are obtained through finite element simulation to correct the allowable stress at the distressed location. This approach fully considers the coupling effect of environmental factors and loads, compensating for the shortcomings of most evaluation methods that neglect the synergistic effect between the two, thus making the analysis of damage mechanisms more comprehensive. Second, when establishing the stress-life relationship, the remaining life is calculated by combining the number of standard axle loads already borne and the prediction of the future daily average number of loads. This achieves a quantitative weighting of the impact of different distresses on pavement life, accurately reflecting the correlation between the actual damage state and the remaining life of existing pavements. Third, this method no longer relies on simplified mechanical analysis or empirical formulas but incorporates the fatigue characteristics of asphalt materials and the three-dimensional mechanical response of pavement structures, making the evaluation model more realistic. Finally, through multi-step quantitative analysis, it is no longer limited to the uniaxial stress state considered only in traditional fatigue models, but can describe the fatigue damage process of actual pavements under a complex three-dimensional stress field, making the evaluation results more consistent with reality. In summary, this method, through multi-step quantitative analysis, integrates load, environmental, and disease factors to achieve an accurate evaluation of the remaining life of existing pavements, solving the problem that traditional methods struggle to accurately quantify the effects of multiple factors.

[0054] In step (1), the geometric parameters of the structural layer are determined by collecting existing pavement design drawings and geological survey reports; the tensile modulus and compressive modulus of asphalt mixture and the compressive modulus of semi-rigid base are obtained by indoor material tests, dynamic modulus tests and compressive strength tests.

[0055] In step (1), the BISAR layered system analysis software is used to construct a pavement structure model according to the bimodal elasticity theory, the interlayer contact is set to "completely continuous", and the axle load is input. Grounding pressure To simulate standard axle load, the wheel track zone in the driving direction is defined as the analysis area.

[0056] In step (1), the running model simulates the stress distribution under load, extracts the maximum equivalent stress below the wheel track of each structural layer, and determines the maximum allowable equivalent stress of the surface layer and the maximum allowable equivalent stress of the base layer.

[0057] In step (2), in Abaqus software, based on the layered system model of step 1, typical defects are implanted: crack defects: simulated using "Cohesive elements", with length gradients L=0.5m, 1m, 2m, 3m, width gradients W=2mm, 5mm, 8mm, 10mm, depth gradients D=2cm, 5cm, 8cm, 10cm, and normal stiffness Kn=5×10 4 N / m 3Rutting defects: Simulated using "element stiffness attenuation", depth gradients d=5mm, 10mm, 20mm, 30mm, longitudinal length gradients L=3m, 5m, 8m, 10m, and transverse width gradients W were set. 车 =0.5m, 1m, 1.5m, 2m, attenuation of rut modulus (30%-50%).

[0058] To accurately obtain the fatigue strength reduction coefficients for different types and depths of pavement defects, and to provide an accurate basis for subsequent allowable stress correction of defect conditions, thereby improving the accuracy and efficiency of pavement fatigue life analysis, step (2) involves calling the three-dimensional unified fatigue equation, inputting axle loads of 50kN-150kN and loading frequencies of 10Hz-20Hz, and calculating the three-dimensional equivalent stresses at the most unfavorable point of the defect model, the crack tip, and the bottom of the rut. The allowable stress without damage is compared with the defect strength to calculate the fatigue strength reduction coefficient, forming a table corresponding to the defect type, defect depth, and reduction coefficient.

[0059] Furthermore, in order to accurately describe the relationship between the two and provide reliable model support for subsequent calculation of remaining fatigue life, thereby improving the accuracy of pavement fatigue life assessment, in step (3), a non-destructive pavement model is constructed in ABAQUS with the same parameters as in step S1. The axle load gradients P = 50kN, 80kN, 100kN, 120kN, and 150kN are set, and the load application number gradient N is set. e =1000, 3000, 5000, 7000, 10000 times; using "30% reduction in pavement structure modulus" as the fatigue failure criterion, record the maximum effective stress σ in each simulation. max And the corresponding lifespan N, the number of load applications, generating 5 or more sets (σ max Data set of N).

[0060] In step (3), the dataset is imported into Origin software, a fitting function is used for fitting, and error analysis (coefficient of determination R) is performed. 2 Mean squared error (MSE). Power function is used. The data is fitted, where x is the independent variable, representing the maximum permissible equivalent stress. Right now Let y be the dependent variable, representing fatigue life N. The fitted result is a. b is Substituting the parameters into the exponentiation function yields:

[0061] ,

[0062] Where, σ max The maximum effective stress is given, N is the fatigue life, the coefficient of determination R² = 0.98, and the mean square error MSE = 1.2 × 10⁻⁶.4 .

[0063] Furthermore, in order to accurately identify internal and surface defects of the road surface, obtain information such as defect type and geometric defect depth, and provide accurate and comprehensive basic data for subsequent defect status analysis and remaining fatigue life calculation, the accuracy and efficiency of road surface inspection and evaluation are improved. In step (4), a ground penetrating radar with a center frequency of 900MHz-1.5GHz is used to collect one survey line every 1m longitudinally and one survey line every 0.5m transversely along the existing road surface to obtain internal defect radar maps and identify base layer voids and interlayer cracks; a Leica P40 road surface three-dimensional laser scanner is used to collect surface point cloud data, generate a three-dimensional model with a resolution of 0.05m, and extract surface crack and rut geometric parameters.

[0064] In step (4), the radar map is analyzed using "time-frequency analysis + U-Net deep learning algorithm" to identify internal defects (identification accuracy > 90%); the three-dimensional point cloud is analyzed using "elevation difference analysis + Canny edge detection" to extract surface defects (crack length, width, rut depth, range); the defect type and severity are verified on-site, and the detection error is corrected; the defects are classified and stored according to "defect type - defect depth parameter - distribution location (station number, lateral offset, etc.)" to form a database containing at least 200 defect records.

[0065] In step (5), the fatigue strength reduction factor K corresponding to the existing pavement distress is matched. s Correcting the maximum allowable equivalent stress of the lower layer in the lossless state. The result will be Substitute the relation in step (3) The total fatigue life was calculated.

[0066] In step (6), traffic volume monitoring data is retrieved, and the number of standard axle loads that the existing road surface has experienced during operation is counted according to the standard axle load equivalent conversion formula.

[0067] In step (6), the remaining fatigue cycles are calculated, and combined with future traffic volume forecasts and the average daily standard axle load application count n, the remaining service life is converted to complete the quantitative evaluation of the remaining fatigue life of the existing pavement. By processing historical traffic volume data through the standard axle load equivalent conversion formula, the cumulative standard axle load application count that the existing pavement has borne during its operation can be accurately counted, providing a precise basis for determining the number of loads borne in the calculation of the remaining fatigue life, ensuring the accuracy of the remaining fatigue life assessment, and thus helping to rationally plan pavement maintenance and service life.

[0068] Example

[0069] A section of a provincial trunk highway, from K3+000 to K4+000, was built in 2010 and features an asphalt concrete pavement structure with a designed service life of 15 years. The pavement structure consists of: 4cm fine-grained asphalt concrete (AC-13) + 6cm medium-grained asphalt concrete (AC-20) + 20cm cement-stabilized crushed stone base course + 30cm cement-soil subbase course. In 2025, to develop a scientific maintenance plan, an equivalent calculation method based on this invention for quantitatively evaluating the remaining service life of existing pavements was used to assess the remaining service life of this section. Preliminary on-site inspection revealed transverse cracks, localized rutting, and other defects.

[0070] S1: Quantitatively determine the bearing capacity threshold of the pavement structure under undamaged conditions.

[0071] Structural layer geometric parameters: Based on the road section design drawings and geological survey report, the parameters of each structural layer are determined as follows: total surface layer thickness 10cm (AC-13 layer 4cm, AC-20 layer 6cm), base layer thickness 20cm, subbase layer thickness 30cm, and total road width 12m. Material parameters: obtained through indoor material testing, specifically: AC-13 tensile modulus 4600MPa, compressive modulus 6100MPa; AC-20 tensile modulus 3900MPa, compressive modulus 5300MPa; cement-stabilized crushed stone base layer compressive modulus 3100MPa.

[0072] The BISAR layered system analysis software was used to construct a pavement structure model based on the bimodal elasticity theory. The interlayer contact was set to "completely continuous". The standard axle load was 100kN and the ground pressure was 0.7MPa. The wheel track zone in the driving direction (within 2-4m from the edge of the pavement) was defined as the analysis area.

[0073] The running model simulates the stress distribution under load, extracts the maximum equivalent stress below the wheel track zone of each structural layer, and applies the formula... (σ) x， σ y， σ z For normal stress, τ xy Calculations were performed to determine the maximum allowable equivalent stress of the surface layer (σ1) as 1.85 MPa and the maximum allowable equivalent stress of the base layer (σ2) as 3.4 MPa.

[0074] S2: Calculate the fatigue strength reduction factor under faulty working conditions.

[0075] In Abaqus software, typical defects are implanted based on the layered system model from step S1. Crack defects: Transverse cracks are simulated using "Cohesive elements," with a length L=2m, width W=5mm, depth D=5cm, and a defined normal stiffness K. n =5×10 4N / m³; Rutting damage: Simulated using "element stiffness attenuation", with a depth d=15mm, longitudinal length L=6m, and transverse width W. 车 =1.2m.

[0076] The three-dimensional unified fatigue equation is invoked, and the axle load is 100kN and the loading frequency is 15Hz. The three-dimensional equivalent stress at the most unfavorable point (crack tip, rut bottom) of the disease model is calculated.

[0077]

[0078] in, , , To calculate the intermediate coefficients, Uniaxial compressive strength, For direct tensile strength, For indirect tensile strength, It is the Rhodes angle;

[0079] Where a, b, and m are the parameters of the three-dimensional strength model;

[0080] in, To allow stress, To determine the three-dimensional strength under the failure state corresponding to the triaxial stress working conditions at the design point, This is the fatigue strength reduction factor; To the ultimate stress along the meridian, This represents the ultimate stress along the meridian;

[0081] By comparing the non-destructive allowable stress with the damage intensity, the fatigue strength reduction factor under the action of the most unfavorable part of the road section tested—the transverse reflective crack—is calculated and shown in Table 1.

[0082] Table 1 Summary of Reduction Coefficients for Different Disease Depths

[0083] Crack depth 0mm 93mm 226mm upper layer 100.00% 60.85% 62.47% Lower layer 100.00% 28.81% 28.33% grassroots 100.00% 23.71% 25.68% Subbase 100.00% 13.17% 23.6%

[0084] S3: Establish the relationship between maximum effective stress and fatigue life

[0085] Construct a non-destructive pavement model in ABAQUS with the same parameters as in step S1. Set the axle load gradients P = 50kN, 80kN, 100kN, 120kN, and 150kN, and the load application number gradients N = 1000, 3000, 5000, 7000, and 10000 times. Use "30% reduction in pavement structure modulus" as the fatigue failure criterion, and record the maximum effective stress σ in each simulation. max And the corresponding fatigue life N, generating 5 sets (σ max Datasets (N):

[0086] Axle load (kN) <![CDATA[Maximum effective stress σ max (MPa)]]> Fatigue life N (times) 50 0.92 860000 80 1.32 440000 100 1.85 215000 120 2.15 125000 150 2.55 78000

[0087] Import the dataset into Origin software, perform function fitting, and obtain the relational expression: (Coefficient of determination R² = 0.98, Mean squared error MSE = 1.2 × 10⁻⁶) 4 ).

[0088] S4: Inspect road defects

[0089] Using a ground-penetrating radar with a center frequency of 1.0 GHz, one survey line was collected every 1 m longitudinally and one survey line was collected every 0.5 m laterally along the existing road surface to obtain radar maps of internal defects; a Leica P40 road surface 3D laser scanner was used to collect surface point cloud data and generate a 3D model with a resolution of 0.05 m.

[0090] Internal defects were identified using a combination of time-frequency analysis and U-Net deep learning algorithm on radar images, achieving an accuracy of 92%. Surface defect parameters were extracted from the 3D point cloud using elevation difference analysis and Canny edge detection. After on-site verification and correction, typical defect data are as follows: a transverse crack at K3+500, 2.05m long, 5.1mm wide, and 4.9cm deep, located 2.5m from the road edge; and ruts with an average depth of 14.9mm, a longitudinal length of 6.1m, and a transverse width of 1.15m, located in the wheel track area. Defect records were categorized and stored according to "defect type - defect depth parameters - distribution location, station number, transverse offset, etc.," forming a database containing 210 defect records.

[0091] S5: Calculate the maximum permissible equivalent stress under diseased conditions.

[0092] From the "Disease Type - Disease Depth - Reduction Coefficient" correspondence table in step S2, match the reduction coefficient corresponding to the existing pavement defects, and interpolate the fatigue strength reduction coefficient Ks=0.71 at the most unfavorable location with severe defects to correct the maximum allowable equivalent stress of the lower layer in the undamaged state: .

[0093] S6: Calculate the remaining fatigue life of the existing pavement

[0094] Substitute the maximum allowable equivalent stress under the faulty state obtained in step S5 into the relationship in step S3 to calculate the total fatigue life:

[0095] The total lifespan at the crack is N = 4.5 × 10⁻⁶. 6 ×(1.3135)⁻ 3.9 ≈6.0×10 5 Second-rate;

[0096] By retrieving traffic volume monitoring data and applying the standard axle load equivalent conversion formula, the number of standard axle loads that the road section has experienced during its operation period was calculated. =3.3×10 5 Second-rate.

[0097] Remaining number of attempts at the rut: =N- =6.0×10 5 -3.3×10 5 =2.7×10 5 Second-rate.

[0098] Based on future traffic volume forecasts, (N) i P represents the actual number of axle load applications. i (Based on the actual axle load), the average daily standard axle load application frequency for this road section is n=300 times. Therefore, the remaining service life at the crack is 2.7×10⁻⁶. 5 ÷300 = 30 years.

[0099] This invention proposes an equivalent calculation method for quantitatively evaluating the remaining life of existing pavements. Through multi-step quantitative analysis, it achieves accurate evaluation of the remaining life of existing pavements. For example, in a provincial trunk highway case, based on the theory of bimodal elastic layered systems, the maximum allowable equivalent stress of the lower layer in its undamaged state is first determined to be 1.85 MPa, and that of the base layer is 3.4 MPa. Then, through finite element simulation, fatigue strength reduction coefficients under different defects are obtained, and the allowable stress at the corresponding defect location is corrected to 1.3135 MPa. Finally, a stress-life relationship is established, combined with the number of standard axle loads already borne (3.3 × 10⁻⁶). 5 Based on 300 predictions per day and the next few days, the remaining lifespan is calculated to be 30 years. This fully demonstrates the quantitative advantages of this method in comprehensively considering load, environmental and disease factors, and solves the problem that traditional methods are unable to accurately quantify the effects of multiple factors.

Claims

1. An equivalent calculation method for quantitative evaluation of the remaining life of existing pavements, characterized in that, Includes the following steps: S1. Determination of the bearing capacity threshold in the undamaged state: Construct an undamaged pavement structure model and calculate the maximum allowable equivalent stress of each structural layer in the undamaged state under standard axle load; S2. Calculation of fatigue strength reduction coefficient under distress conditions: Based on the aforementioned undamaged pavement structure model, a typical pavement distress model is implanted into the finite element software. The actual equivalent stress at the most unfavorable point of the structure under distress conditions is calculated and compared with the maximum allowable equivalent stress under undamaged conditions. A mapping relationship table of distress type-distress depth-fatigue strength reduction coefficient is established to quantify the degree of weakening of structural strength by distress. S3. Establishment of the maximum effective stress-fatigue life relationship model: By simulating the fatigue failure process of the non-destructive pavement structure model under different axle load gradients, multiple sets of maximum effective stress and fatigue life datasets are obtained, and a mathematical relationship model with maximum effective stress as the independent variable and fatigue life as the dependent variable is fitted. S4. Detect road defects: Use non-destructive testing methods to obtain a database of defects in existing road surfaces; S5. Bearing capacity correction: Based on the existing pavement distress information database actually obtained in step S4, match the mapping relationship table established in step S2 to obtain the fatigue strength reduction coefficient, and use the fatigue strength reduction coefficient to correct the maximum allowable equivalent stress under the undamaged state determined in step S1, thereby calculating the maximum allowable equivalent stress reflecting the actual pavement distress state. S6. Calculation of remaining life: Substitute the maximum allowable equivalent stress under the fault state calculated in step S5 as the maximum allowable stress level into the mathematical relationship model established in step S3 to calculate the total fatigue life of the road surface; then combine the consumed life obtained from historical traffic volume data statistics to calculate the number of remaining fatigue life cycles, and finally convert the remaining life based on future traffic volume predictions.

2. The equivalent calculation method for quantitative evaluation of the remaining life of existing pavements according to claim 1, characterized in that, In step S1, the construction of the non-destructive pavement structure model is based on the theory of dual-modulus elastic layered system. When constructing the pavement structure model, the tensile modulus and compressive modulus of the asphalt mixture surface layer obtained from indoor material tests are used.

3. The equivalent calculation method for quantitative evaluation of the remaining life of existing pavements according to claim 1, characterized in that, In step S2, the typical pavement defects include cracks and ruts; wherein, The cracks were simulated using Cohesive elements, with different length, width, and depth gradients set. The rutting defects were simulated using the element stiffness attenuation method, with different depth, longitudinal length, and transverse width gradients set.

4. The equivalent calculation method for quantitative evaluation of the remaining life of existing pavements according to claim 3, characterized in that, In step S2, the three-dimensional unified fatigue equation is called to calculate the three-dimensional equivalent stress of the disease model at the most unfavorable point, and a corresponding table of disease type, disease depth and reduction coefficient is formed.

5. The equivalent calculation method for quantitative evaluation of the remaining life of existing pavements according to claim 1, characterized in that, In step S3, a 30% decrease in the overall modulus of the pavement structure is used as the criterion for fatigue failure. The mathematical relationship model obtained through fitting, with the maximum effective stress as the independent variable and fatigue life as the dependent variable, is as follows: ， Where, σ max The maximum effective stress is given, N is the fatigue life, the coefficient of determination R² = 0.98, and the mean square error MSE = 1.2 × 10⁻⁶. 4 .

6. The equivalent calculation method for quantitative evaluation of the remaining life of existing pavements according to claim 1, characterized in that, In step S4, the non-destructive testing method includes: Ground-penetrating radar with a center frequency of 900MHz-1.5GHz was used to detect internal defects in radar maps, identifying base layer voids and interlayer cracks; and time-frequency analysis and U-Net deep learning algorithm were used to identify the radar maps. Point cloud data of the road surface was collected using a 3D laser scanner, and geometric parameters of surface defects were extracted using elevation difference analysis and the Canny edge detection algorithm.

7. The equivalent calculation method for quantitative evaluation of the remaining life of existing pavements according to claim 1, characterized in that, The disease information database includes at least the type of disease, the geometric depth of the disease, and its distribution location.

8. The equivalent calculation method for quantitative evaluation of the remaining life of existing pavements according to claim 1, characterized in that, In step S6, the historical traffic volume data is processed using the standard axle load equivalent conversion formula to obtain the cumulative number of standard axle loads that the existing road surface has experienced during operation.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps in the equivalent calculation method for quantitative evaluation of the remaining life of existing pavements as described in any one of claims 1 to 8.

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