A method for predicting nonlinear fatigue damage accumulation of asphalt under two-stage loading with coupled loading sequence and load interaction

Abstract

The present invention relates to the field of road engineering, and specifically to a method for predicting the accumulation of nonlinear fatigue damage of asphalt under two-stage loading with coupled loading sequence and load interaction. The method includes the following steps: 1) conducting a constant amplitude loading fatigue test on asphalt; 2) characterizing fatigue damage of asphalt; 3) determining an asphalt fatigue damage model under constant amplitude loading; 4) conducting a variable amplitude loading fatigue test on asphalt; 5) establishing an asphalt nonlinear fatigue damage accumulation model that takes into account the influence of loading sequence; 6) establishing an asphalt nonlinear fatigue damage accumulation model that couples the influence of loading sequence and load interaction; 7) determining a loading sequence factor; 8) determining a load interaction factor. The present invention more accurately simulates the fatigue damage process of asphalt pavement under actual service conditions, characterizes the accumulation of nonlinear fatigue damage under the coupled influence of loading sequence and load interaction, and has good economy and operability.

Description

Technical Field

[0001] The invention relates to the field of road engineering, and in particular to a method for predicting the accumulation of nonlinear fatigue damage of asphalt under two-stage loading of coupled loading sequence and load interaction. Background Art

[0002] The cyclic effect of vehicle loads can cause fatigue damage to asphalt mixtures, and fatigue damage is one of the main diseases of asphalt pavements. The cohesive failure of asphalt binders in the asphalt mixture structure is a common cause of fatigue damage to asphalt pavement structures. Therefore, by studying the fatigue damage characteristics of asphalt with the help of fatigue tests, a fatigue damage accumulation prediction model for asphalt is proposed, which can predict the nonlinear fatigue damage accumulation process of asphalt, thereby providing a theoretical basis for delaying the fatigue damage accumulation of roads, increasing service life, reducing construction costs, and improving economic benefits.

[0003] In response to the fatigue damage problem of viscoelastic road materials, patent CN103630450A discloses a life prediction method for asphalt mixtures that takes into account the interactive damage effects of fatigue and creep. The method includes: determining the complex modulus of the asphalt mixture under cyclic loads; determining the damage variables of the asphalt mixture; establishing creep damage equations and fatigue damage equations for the asphalt mixture respectively; and establishing a life prediction model for the asphalt mixture under the combined effects of creep damage and fatigue damage. This patent uses a fatigue test with a constant amplitude to establish a fatigue damage model, but the load amplitude of the actual running vehicle varies with time, resulting in the inability of the damage model to characterize the nonlinear fatigue damage accumulation process of the pavement under actual service conditions.

[0004] Asphalt pavement undergoes nonlinear fatigue damage accumulation under variable amplitude loading, and the accumulation process is affected by the coupling of loading sequence and load interaction. However, the traditional design method uses Miner's linear fatigue damage accumulation theory to design asphalt pavement structure, which leads to a theoretical deviation between the actual service life and the predicted life. Therefore, it is necessary to use variable amplitude loading fatigue test to establish a nonlinear fatigue damage accumulation prediction model that is affected by the coupling loading sequence and load interaction, so as to provide a theoretical basis for the reasonable characterization of the nonlinear accumulation of fatigue damage and the improvement of the fatigue life prediction accuracy. Summary of the invention

[0005] The purpose of the present invention is to provide a nonlinear fatigue damage accumulation prediction model for asphalt under two-stage loading with coupled loading sequence and load interaction, so as to solve the problem that operability, accuracy and economy cannot be well guaranteed in the prior art.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] The present invention conducts a two-stage loading variable amplitude fatigue test on asphalt, and establishes an asphalt nonlinear fatigue damage accumulation prediction model that is affected by the coupling loading sequence and load interaction. The specific steps of the prediction method are:

[0008] Step 1: Conduct fatigue testing on asphalt

[0009] 1) Conduct constant amplitude loading fatigue test on asphalt

[0010] Set the constant load amplitude to the high load amplitude ζ high and low load amplitude ζ low , a sinusoidal cyclic shear load is applied to the asphalt specimen until fatigue failure, and the fatigue life is N f , carry out constant amplitude loading fatigue test;

[0011] 2) Conduct variable amplitude loading fatigue test on asphalt

[0012] Select two loading sequences, low-high and high-low, to carry out variable amplitude loading fatigue test. The first-level load amplitude of the low-high loading sequence is ζ 1 and the secondary load amplitude ζ 2 , respectively, for the low load amplitude ζ low and high load amplitude ζ high , the first-order load amplitude ζ of the high-low loading sequence 1 and the secondary load amplitude ζ 2 They are high and low In theory, the load amplitude of the constant amplitude loading fatigue test is ζ 1 and 2 When the corresponding constant amplitude loading fatigue life is N f1 and N f2 ;

[0013] According to the first-level fatigue life fraction N 1 / N f1 , determine the number of primary loading times N of the variable amplitude fatigue test 1 =N 1 / N f1 *N f1 ; Adopt ζ 1 The specimen was subjected to N 1 The first level of loading is then adopted 2 Perform N 2 The secondary loading is repeated until fatigue failure. The primary loading life fraction, secondary loading life fraction and fatigue life of the variable amplitude loading fatigue test are N respectively. 1 / N f1 、N 2 / N f2 、N 1 +N 2 ;

[0014] Step 2: Determine the asphalt fatigue damage model under constant amplitude loading

[0015] 1) Characterization of fatigue damage of asphalt

[0016] Substituting the data of the constant amplitude loading fatigue test into equation (1), the dissipated pseudo strain energy DPSE in the entire sample volume is determined c ,

[0017]

[0018] Where, t N is the loading end time; V is the sample volume; t 0 is the initial moment; ω is the angular velocity; t 0 is the initial time; τ(t 0 ,r) is t 0 At time r, shear stress at radius; γ R (t,r) pseudostrain at time t and radius r in a single cycle,

[0019] Due to the evolution of asphalt fatigue damage, accompanied by DPSE c Therefore, the Nth and Nth f DPSE of cycles c The ratio of , characterizes the fatigue damage of asphalt, as shown in formula (2):

[0020]

[0021] In the formula: DPSE c,N and DPSE c,Nf The Nth and Nth f DPSE of cycles c ; N f is the fatigue life;

[0022] 2) Determine the asphalt fatigue damage model under constant amplitude loading

[0023] The Chaboche damage model is selected to characterize the evolution law of asphalt fatigue damage under constant amplitude loading, as shown in formula (3):

[0024] D=1-[1-(N / N f ) 1 / (1-α) ] 1 / (1+β) (3)

[0025] Where: D is the asphalt damage variable; N is the number of load cycles; β is the model parameter that depends on temperature; α is the model parameter that depends on temperature and load amplitude;

[0026] Step 3: Nonlinear fatigue damage accumulation model of asphalt with coupled loading sequence and load interaction

[0027] 1) Establish a nonlinear fatigue damage accumulation model for asphalt considering the effect of loading sequence

[0028] When only the effect of loading sequence on asphalt fatigue damage accumulation is considered, based on the damage equivalence criterion, σ 1 Function 1 The fatigue damage accumulation path AP1 generated by the second is equivalent to σ 2 Function 2 'The fatigue damage accumulation path AP1', and N 2 '+N 2 =N f2 , as shown in formula (4), then σ 1 and σ 2 Respectively act N 1 and N 2 The fatigue damage accumulation path generated by this is equivalent to σ 2 Function 2 '+N 2 The fatigue damage accumulation path generated by

[0029] D(σ 1 ,N 1 / N f1 )=D(σ 2 ,N' 2 / N f2 ) (4)

[0030] Substituting formula (3) into formula (4), we can obtain the asphalt nonlinear fatigue damage accumulation model that only considers the influence of loading sequence, as shown in formula (5):

[0031]

[0032] Where: α 1 The load amplitude is ζ 1 α of constant amplitude loading fatigue test; α 2 The load amplitude is ζ 2 α of constant amplitude loading fatigue test; N 1 / N f1 and N 2 / N f2 are the first-level loading life fraction and the second-level loading life fraction respectively; γ is the loading order factor, γ=(1-α 2 ) / (1-α 1 ), which reflects the dependence of asphalt fatigue damage accumulation on loading sequence;

[0033] 2) Establish a nonlinear fatigue damage accumulation model for asphalt that takes into account the effects of coupled loading sequence and load interaction

[0034] When the effects of loading sequence and load interaction on asphalt fatigue damage accumulation are considered simultaneously, the influence of load interaction on asphalt fatigue damage accumulation is analyzed by taking the low-high loading sequence as an example. During the first-level loading period, asphalt is subjected to low amplitude load ζ low The slow-growing crack core produced by the primary loading will reduce the high-amplitude load ζ during the secondary loading. high The crack nucleus growth rate generated causes the fatigue damage accumulation path to deviate from the equivalent path AP1' obtained by considering only the loading sequence. This phenomenon is called load interaction.

[0035] Under the coupled influence of loading sequence and load interaction, σ 1 Function 1 The AP1 generated is equivalent to σ 2 Function 2 ” (Not equal to N 2 ') times the fatigue damage accumulation path AP1", and N 2 ”+N 2 =N f2 , as shown in formula (6),

[0036] D(σ 1 ,N 1 / N f1 )=D(σ 2 ,N” 2 / N f2 ) (6)

[0037] By introducing the load interaction factor ω=(σ 1 / σ 2 ) λ , describes the effect of load interaction on damage accumulation, assuming that N 2 ” / N f2 =(N 2 ' / N f2 ) ω , then:

[0038] D(σ 1 ,N 1 / N f )=D(σ 2 ,N” 2 / N f2 )=D[σ 2 ,(N' 2 / N f2 ) ω ] (7)

[0039] Substituting formula (3) into formula (7), we can obtain the asphalt nonlinear fatigue damage accumulation model affected by the coupled loading sequence and load interaction, as shown in formula (8):

[0040]

[0041] Where: κ is the nonlinear fatigue damage accumulation factor that couples the loading order and load interaction, which is numerically equal to the product of the loading order factor γ and the load interaction factor ω, that is, κ = γω;

[0042] 3) Determine the loading order factor

[0043] First, the high load amplitude ζ high and low load amplitude ζ low Substituting the corresponding constant amplitude loading data into equation (2), we can obtain ζ high and low The corresponding fatigue damage curve; then, the two damage curves are fitted using formula (3) to obtain ζ high and low The corresponding α parameter, α high and α low ; Finally, according to γ=(1-α 2 ) / (1-α 1 ), calculate the loading order factor γ, the γ of low-high and high-low loading order are (1-α high ) / (1-α low ) and (1-α low ) / (1-α high );

[0044] 4) Determine the load interaction factor

[0045] First, the N of the variable amplitude loading fatigue test is fitted using formula (8) when the low-high and high-low loading sequences are respectively: 1 / N f1 -N 2 / N f2 The nonlinear fatigue damage accumulation factor κ, which is coupled with the loading sequence and load interaction under different loading sequences, is obtained by using κ(1-α low ) / (1-α high ) and κ(1-α high ) / (1-α low ), calculate the load interaction factor ω for low-high and high-low loading sequences.

[0046] In the above technical solution, further, when γ and ω are both 1, κ is 1, and the model cannot characterize the nonlinearity of fatigue damage accumulation, and degenerates into a linear damage accumulation model.

[0047] The beneficial effects of the present invention are:

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] (1) It can accurately simulate the fatigue damage process of asphalt pavement under actual service conditions and provide a theoretical basis for designing reasonable fatigue tests.

[0050] (2) It can more accurately characterize the nonlinear fatigue damage accumulation process of asphalt under the coupled influence of loading sequence and load interaction, providing a theoretical basis for improving the service life of asphalt pavement.

[0051] (3) It can improve the design theory of asphalt pavement to a certain extent, provide a reasonable theoretical basis for the scientific management of asphalt pavement, and create good economic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 Schematic diagram of loading for the linear amplitude sweep test in Example 1;

[0053] Figure 2 1 is the G* and δ change curve of the linear amplitude sweep test in Example 1, a is the G* change curve, and b is the ζ-ε curve;

[0054] Figure 3 Schematic diagram of loading for the constant amplitude loading fatigue test in Example 1;

[0055] Figure 4 is a loading schematic diagram of the variable amplitude loading fatigue test in Example 1, where a is low-high (ζ low -ζ high ) loading order, b is high-low (ζ high -ζ low ) Loading order;

[0056] Figure 5 is the fitting result of fatigue damage curve under horizontal loading in Example 1, a is low load amplitude, b is high load amplitude;

[0057] Figure 6 N in Example 1 1 / N f1 -N 2 / N f2 Curve fitting results;

[0058] Figure 7 This is the prediction result of the nonlinear fatigue damage accumulation model in Example 1. DETAILED DESCRIPTION

[0059] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0060] Example 1

[0061] (1) Conduct fatigue tests on asphalt

[0062] A dynamic shear rheometer was selected as the loading device. The test temperature and frequency were 20°C and 10 Hz, respectively. The number of parallel tests was 3, and the test results were averaged.

[0063] 1) Materials and specimen preparation

[0064] SBS modified asphalt was selected as the test material, and its basic technical indicators are shown in Table 1. The asphalt sample was heated by DSR, and the excess asphalt was scraped off with a scraper, and finally a cylindrical asphalt sample with a height of 2 mm and a diameter of 8 mm was formed.

[0065] Table 1 Asphalt technical indicators

[0066]

[0067] 2) Linear amplitude sweep test

[0068] By carrying out the loading diagram as Figure 1 The linear amplitude sweep test shown in the figure determines the nonlinear viscoelastic critical stress ζ corresponding to the critical point of the asphalt sample in the non-destructive stage and the damaged stage cri According to the results of shear strain ε, shear stress ζ, and shear modulus G*, the variation curves of G* and ζ are obtained, as shown in Figure 2 By analyzing the curvature of the curve of G* changing with lgε, the intersection point ε of the two stages of G* linear stability and rapid decay is determined. cri , respectively take the intersection point ε cri The corresponding load amplitude is taken as ζ cri . SBS modified asphalt cri The result is 105 kPa.

[0069] 3) Constant amplitude loading fatigue test of asphalt

[0070] By carrying out the loading diagram as Figure 3 The constant amplitude fatigue test shown above determines the non-destructive shear modulus G* of the asphalt material. T And the fatigue life under constant amplitude loading N f The selected low load amplitude ζ low and high load amplitude ζ high The test steps are as follows: First, the load amplitude and loading time are ζ criand 100s nondestructive constant amplitude fatigue test to obtain G* T Then, after the 300 s recovery period, the same sample was subjected to loads with amplitudes of ζ low and high The results of the fatigue life of asphalt under constant amplitude loading are shown in Table 2.

[0071] Table 2 Constant amplitude loading fatigue life of asphalt

[0072]

[0073] 4) Variable amplitude loading fatigue test of asphalt

[0074] Select as Figure 4 The high-low (ζ high -ζ low ) and low-high (ζ low -ζ high ) two loading sequences, and conduct variable amplitude loading fatigue test. The test steps are: 1 / N f1 Set to 0, 0.2, 0.4, 1 to determine the number of primary loading times N for the variable amplitude fatigue test 1 =N 1 / N f1 *N f1 ;Use the first level load amplitude ζ 1 The specimen was subjected to N 1 The first level loading is then performed with the first level load amplitude ζ 2 Perform N 2 Secondary loading is performed until fatigue failure, and the primary loading life fraction N is recorded. 1 / N f1 , Secondary loading life fraction N 2 / N f2 , fatigue life N 1 +N 2 ζ high -ζ low The primary and secondary load amplitudes corresponding to the loading sequence are ζ high and low , low -ζ high The primary and secondary load amplitudes corresponding to the loading sequence are ζ low and high .

[0075] (2) Determine the asphalt fatigue damage model under constant amplitude loading

[0076] 1) Characterization of fatigue damage of asphalt

[0077] Substituting the data of the constant amplitude loading fatigue test into equation (1), the dissipated pseudo strain energy DPSE in the entire sample volume is determined c .

[0078]

[0079] Where, t N is the loading end time; V is the sample volume; t 0 is the initial moment; ω is the angular velocity; t 0 is the initial time; τ(t 0 ,r) is t 0 At time r, shear stress at radius; γ R (t,r) Pseudostrain at time t and radius r within a single cycle.

[0080] Due to the evolution of asphalt fatigue damage, accompanied by DPSE c Therefore, the Nth and Nth f DPSE of cycles c The ratio of , characterizes the fatigue damage of asphalt, as shown in formula (2).

[0081]

[0082] In the formula: DPSE c,N and DPSE c,Nf The Nth and Nth f DPSE of cycles c ; N f is the fatigue life.

[0083] 2) Determine the asphalt fatigue damage model under constant amplitude loading

[0084] The Chaboche damage model is selected to characterize the evolution law of asphalt fatigue damage under constant amplitude loading, as shown in formula (3).

[0085] D=1-[1-(N / N f ) 1 / (1-α) ] 1 / (1+β) (3)

[0086] Where: D is the asphalt damage variable; N is the number of load cycles; N f is the fatigue life; β is the model parameter that depends on temperature; α is the model parameter that depends on temperature and load amplitude.

[0087] (3) Nonlinear fatigue damage accumulation model of asphalt considering the effects of coupled loading sequence and load interaction

[0088] 1) Establish a nonlinear fatigue damage accumulation model for asphalt considering the effect of loading sequence

[0089] When only the effect of loading sequence on asphalt fatigue damage accumulation is considered, based on the damage equivalence criterion, σ 1 Function 1 The fatigue damage accumulation path AP1 generated by the second is equivalent to σ 2 Function 2 'The fatigue damage accumulation path AP1', and N 2 '+N 2 =N f2 , as shown in formula (4). Then σ 1 and σ 2 Respectively act N 1 and N 2 The fatigue damage accumulation path generated by this is equivalent to σ 2 Function 2 '+N 2 The fatigue damage accumulation path generated by this process.

[0090] D(σ 1 ,N 1 / N f1 )=D(σ 2 ,N' 2 / N f2 ) (4)

[0091] Substituting formula (3) into formula (4), we can obtain the asphalt nonlinear fatigue damage accumulation model that only considers the influence of loading sequence, as shown in formula (5).

[0092]

[0093] Where: α 1 The load amplitude is ζ 1 α of constant amplitude loading fatigue test; α 2 The load amplitude is ζ 2 α of constant amplitude loading fatigue test; N 1 / N f1 and N 2 / N f2 are the first-level loading life fraction and the second-level loading life fraction respectively; γ is the loading order factor, γ=(1-α 2 ) / (1-α 1 ), which reflects the dependence of asphalt fatigue damage accumulation on the loading sequence.

[0094] 2) Establish a nonlinear fatigue damage accumulation model for asphalt that takes into account the effects of coupled loading sequence and load interaction

[0095] When the effects of loading sequence and load interaction on asphalt fatigue damage accumulation are considered simultaneously, the influence of load interaction on asphalt fatigue damage accumulation is analyzed by taking the low-high loading sequence as an example. During the first-level loading period, asphalt is subjected to low amplitude load ζ low The slow-growing crack core produced by the primary loading will reduce the high-amplitude load ζ during the secondary loading. high The crack nucleus growth rate generated causes the fatigue damage accumulation path to deviate from the equivalent path AP1' obtained by considering only the loading sequence. This phenomenon is called load interaction.

[0096] Under the coupled influence of loading sequence and load interaction, σ 1 Function 1 The AP1 generated is equivalent to σ 2 Function 2 ” (Not equal to N 2 ') times the fatigue damage accumulation path AP1", and N 2 ”+N 2 =N f2 , as shown in formula (6).

[0097] D(σ 1 ,N 1 / N f1 )=D(σ 2 ,N” 2 / N f2 ) (6)

[0098] By introducing the load interaction factor ω=(σ 1 / σ 2 ) λ , describes the effect of load interaction on damage accumulation. Assume that N 2 ” / N f2 =(N 2 ' / N f2 ) ω , then:

[0099] D(σ 1 ,N 1 / N f )=D(σ 2 ,N” 2 / N f2 )=D[σ 2 ,(N' 2 / N f2 ) ω ] (7)

[0100] Substituting formula (3) into formula (7), we can obtain the asphalt nonlinear fatigue damage accumulation model affected by coupled loading sequence and load interaction, as shown in formula (8).

[0101]

[0102] Where: κ is the nonlinear fatigue damage accumulation factor that couples the loading order and load interaction, which is numerically equal to the product of the loading order factor γ and the load interaction factor ω, that is, κ = γω.

[0103] When γ and ω are both 1, κ is 1, and the model cannot represent the nonlinearity of fatigue damage accumulation, and it degenerates into a linear damage accumulation model.

[0104] 3) Determine the loading order factor

[0105] First, the high load amplitude ζ high and low load amplitude ζ low Substituting the corresponding constant amplitude loading data into equation (2), we can obtain ζ high and low The corresponding fatigue damage curve; then, the two damage curves are fitted using formula (3) to obtain ζ high and low The corresponding α parameter, α high and α low ; Finally, according to γ=(1-α 2 ) / (1-α 1 ), calculate the loading order factor γ, the γ of low-high and high-low loading order are (1-α high ) / (1-α low ) and (1-α low ) / (1-α high ). The damage curve fitting results under constant amplitude loading are shown in Figure 5 The γ of different loading orders is shown in Table 3.

[0106] Table 3 Model parameter results

[0107]

[0108] 4) Determine the load interaction factor

[0109] First, the N of the variable amplitude loading fatigue test is fitted using formula (8) when the low-high and high-low loading sequences are respectively: 1 / N f1 -N 2 / N f2 The nonlinear fatigue damage accumulation factor κ, which is coupled with the loading sequence and load interaction under different loading sequences, is obtained by using κ(1-α low ) / (1-α high ) and κ(1-α high ) / (1-α low), calculate the load interaction factor ω, N for low-high and high-low loading sequences 1 / N f1 -N 2 / N f2 The curve fitting results are as follows Figure 6 The κ and ω of different loading orders are shown in Table 3.

[0110] 5) Model Validation

[0111] Keeping the loading condition unchanged and setting the primary loading life fraction to 0.6, we conducted variable amplitude loading fatigue tests on asphalt in low-high and high-low loading sequences, and compared the predicted results with the test results to verify the effectiveness of the established asphalt nonlinear fatigue damage accumulation model. Figure 7 As shown by Figure 7 It can be seen that the established asphalt nonlinear fatigue damage accumulation model can accurately predict the nonlinear fatigue damage accumulation process of asphalt under the coupling influence of loading sequence and load interaction.

[0112] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may be modified and changed. Any changes, variations or equivalent substitutions made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for predicting the accumulation of nonlinear fatigue damage of asphalt under two-stage loading with coupled loading sequence and load interaction, characterized by: The prediction method comprises the following steps: Step 1: Conduct fatigue testing on asphalt 1) Conduct constant amplitude loading fatigue test on asphalt Set the constant load amplitude to the high load amplitude σ high and low load amplitude σ low , a sinusoidal cyclic shear load was applied to the asphalt specimen until fatigue failure; 2) Conduct variable amplitude loading fatigue test on asphalt Select two loading sequences, low-high and high-low, and carry out variable amplitude loading fatigue tests. The specimen is subjected to primary loading N1 times with the primary load amplitude σ1, and then the specimen is subjected to secondary loading N2 times with the secondary load amplitude σ2 until fatigue failure. Step 2: Determine the asphalt fatigue damage model under constant amplitude loading 1) Characterization of fatigue damage of asphalt Substituting the data of the constant amplitude loading fatigue test into equation (1), the dissipated pseudo strain energy DPSE in the entire sample volume is determined c , In the formula, t N is the end time of loading; V is the sample volume; t0 is the initial time; ω is the angular velocity; t0 is the initial time; τ(t0,r) is the shear stress at the radius r at the time t0; γ R (t, r) pseudostrain at time t and radius r in a single cycle, Asphalt fatigue cracks are mainly caused by DPSE c The accumulation of the Nth and Nth f DPSE of cycles c The ratio of , characterizes the fatigue damage of asphalt, as shown in formula (2): In the formula: DPSE c,N and DPSE c,Nf The Nth and Nth f DPSE of cycles c ; N f is the fatigue life; 2) Determine the asphalt fatigue damage model under constant amplitude loading The Chaboche damage model is selected to characterize the evolution law of asphalt fatigue damage under constant amplitude loading, as shown in formula (3): D=1-[1-(N / N f ) 1 / (1-α) ] 1 / (1+β) (3) Where: D is the asphalt damage variable; N is the number of load cycles; β is the model parameter that depends on temperature; α is the model parameter that depends on temperature and load amplitude; Step 3: Nonlinear fatigue damage accumulation model for asphalt with coupled loading sequence and load interaction 1) Establish a nonlinear fatigue damage accumulation model for asphalt considering the effect of loading sequence When only the effect of loading sequence on asphalt fatigue damage accumulation is considered, based on the damage equivalence criterion, the fatigue damage accumulation path AP1 generated by σ1 acting N1 times is equivalent to the fatigue damage accumulation path AP1' generated by σ2 acting N2' times, and N2'+N2=N f2 , as shown in formula (4), D(σ1,N1 / N f1 )=D(σ2,N'2 / N f2 ) (4) Substituting formula (3) into formula (4), we can obtain the asphalt nonlinear fatigue damage accumulation model that only considers the effect of loading sequence, as shown in formula (5): Where: α1 and N f1 They are the parameter α and fatigue life N corresponding to the constant amplitude loading fatigue test when the load amplitude is σ1. f ; α2 and N f2 They are the parameter α and fatigue life N corresponding to the constant amplitude loading fatigue test when the load amplitude is σ2. f ; N1 / N f1 and N2 / N f2 are the first-level loading life fraction and the second-level loading life fraction, respectively; γ is the loading order factor, γ = (1-α2) / (1-α1), which reflects the dependence of asphalt fatigue damage accumulation on the loading order; 2) Establish a nonlinear fatigue damage accumulation model for asphalt that takes into account the effects of coupled loading sequence and load interaction When the effects of loading sequence and load interaction on asphalt fatigue damage accumulation are considered simultaneously, AP1 generated by σ1 acting N1 times is equivalent to the fatigue damage accumulation path AP1” generated by σ2 acting N2” times, and N2”+N2=N f2 , as shown in formula (6), D(σ1,N1 / N f1 )=D(σ2,N”2 / N f2 ) (6) By introducing the load interaction factor ω=(σ1 / σ2) λ , describes the effect of load interaction on damage accumulation, assuming that N2” / N f2 =(N2' / N f2 ) ω , then: D(σ1,N1 / N f )=D(σ2,N”2 / N f2 )=D[σ2,(N'2 / N f2 ) ω ] (7) Substituting formula (3) into formula (7), we can obtain the asphalt nonlinear fatigue damage accumulation model affected by the coupled loading sequence and load interaction, as shown in formula (8): Where: κ is the nonlinear fatigue damage accumulation factor that couples the loading order and load interaction, which is numerically equal to the product of the loading order factor γ and the load interaction factor ω, that is, κ = γω; 3) Determine the loading order factor First, the high load amplitude σ high and low load amplitude σ low Substituting the corresponding constant amplitude loading data into equation (2), we can obtain σ high and σ low The corresponding fatigue damage curve; then, the two damage curves are fitted using formula (3) to obtain σ high and σ low The corresponding α parameter, α high and α low Finally, according to γ ​​= (1-α2) / (1-α1), the loading order factor γ is calculated. The γ of low-high and high-low loading orders are (1-α high ) / (1-α low ) and (1-α low ) / (1-α high ); 4) Determine the load interaction factor First, formula (8) is used to fit the N1 / N of the variable amplitude loading fatigue test when the low-high and high-low loading sequences are respectively f1 -N2 / N f2 The nonlinear fatigue damage accumulation factor κ, which is coupled with the loading sequence and load interaction under different loading sequences, is obtained by using κ(1-α low ) / (1-α high ) and κ(1-α high ) / (1-α low ), calculate the load interaction factor ω for low-high and high-low loading sequences.

2. The prediction method according to claim 1, characterized in that: When γ and ω are both 1, κ is 1, and the model cannot represent the nonlinearity of fatigue damage accumulation, and it degenerates into a linear damage accumulation model.

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