A method of predicting the life of an asphalt pavement

Abstract

The present application relates to a kind of methods for predicting asphalt pavement life, belong to road engineering technical field, main steps include: determining asphalt surface layer structure and material proportioning;Full-thickness rutting test piece is made and is carried out rutting test using full-thickness rutting tester, and test data are recorded;The relational expression of rutting deformation rate, time and temperature is established;Equation is deformed to obtain asphalt pavement life prediction model, and test data are substituted into calculation to obtain life prediction value.The present application can be used to check whether the asphalt surface layer structure selected by new pavement meets initial use requirements, and provides a new idea for the optimization and application of asphalt surface layer structure.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for predicting the service life of asphalt pavement, and belongs to the technical field of road engineering. BACKGROUND

[0002] Asphalt pavement has the advantages of driving comfort, short construction period, low noise, good anti-skid and shock absorption performance, strong drainage capacity, etc., and is the pavement form widely constructed in China at present. According to domestic public data, the total mileage of highways in China has reached 5.28 million kilometers, of which the proportion of asphalt pavement highways is more than 90%, and more than 95% of the national expressways are asphalt pavement. It can be seen that there is a huge application market for asphalt pavement in China.

[0003] At present, inorganic binder stabilizing materials are commonly used for pavement base in China, which has relatively large rigidity, so that rut deformation mainly occurs in the asphalt surface layer. The design service life of most asphalt pavements in China is generally 8-15 years, but in fact various diseases will occur in newly built asphalt pavement after being put into use for several years, and rut is one of the main diseases of various asphalt pavements in China. The degree of rut deformation of the asphalt surface layer is mainly affected by seasonal temperature, vehicle load and material performance of asphalt mixture, and the research on the service life of asphalt pavement is also mainly carried out from these aspects.

[0004] For the prediction of the service life of asphalt pavement, most of the existing methods are concentrated on the prediction of the remaining service life of asphalt pavement, and there are few methods for predicting the service life of newly built asphalt pavement. In order to more comprehensively understand the service life of a certain asphalt pavement surface layer structure and facilitate the selection and application of asphalt surface layer structure, the present application provides a method for predicting the service life of asphalt pavement. SUMMARY

[0005] The purpose of the present application is to provide a method for predicting the service life of asphalt pavement, which establishes the equation relationship among the rut deformation rate, the service time of pavement and the temperature through indoor test, and then analyzes the service life of pavement. The method can more accurately predict the service life of a certain surface layer structure applied to a certain level of road, which is beneficial to the optimization selection of pavement structure. In order to achieve the above purpose, the technical scheme of the present application is as follows:

[0006] A method for predicting the service life of asphalt pavement, comprising the following steps:

[0007] S1: According to the proportioning of each layer material of the newly built asphalt pavement, the asphalt mixture is mixed, and the full-thickness rut test piece is made layer by layer according to the requirements.

[0008] S2: Use full-thickness rutting tester to conduct rutting test under different temperature conditions and different load action times and record the corresponding values. The wheel bottom pressure is set to 0.7 MPa, the temperature conditions should take multiple values (for example: 30℃, 40℃, 50℃, 60℃, 70℃), and the load action times should take multiple values (for example: 2000-20000 times) to increase the reliability of the results.

[0009] S3: Take the permanent deformation rate of the asphalt structure layer as the index parameter to calculate the pavement rutting deformation rate ε:

[0010]

[0011] In the formula: ε - rutting deformation rate, %; R h - rutting deformation, mm; h - specimen thickness, mm.

[0012] S4: Obtain the standard equivalent axle times per hour of the road through existing data analysis and traffic investigation. The ratio of the test load action times to the standard equivalent axle times per hour is the pavement service life:

[0013]

[0014] In the formula: t - pavement service life, h; N - load action times, times; N h - standard equivalent axle times per hour, times / h.

[0015] S5: Establish the relationship between rutting deformation rate ε, time t and temperature T. The specific calculation method is:

[0016] Firstly, establish the relationship between rutting deformation rate ε and time t:

[0017] ε = Ae -kt (3)

[0018] In the formula: ε - rutting deformation rate, %; A - test parameter; k - performance change speed constant related to temperature, h -1 ; t - pavement service life, h.

[0019] Take the logarithm of both sides of equation (3):

[0020] lnε = lnA - kt (4)

[0021] Take t as the independent variable, lnε as the dependent variable, lnA as the constant term, and -k as the slope. Then use the least squares method to solve lnA and -k and determine the value of the coefficient R 2 .

[0022] Secondly, use the Arrhenius equation to establish the relationship between constant k and temperature T:

[0023]

[0024] In the formula: B - frequency factor, h -1 a - activation energy, J / mol; R - molar gas constant, J / (mol K); T - test temperature, K.

[0025] Take the logarithm of both sides of the equation of formula (5) :

[0026]

[0027] Similarly, the values of lnB and and the determination coefficient R 2 are calculated by the least square method.

[0028] The specific calculation method of the least square method is as follows:

[0029] Taking formula (4) as an example, let x1=t, y1=lnε, a=lnA, b=-k, and the parameters a, b and the determination coefficient R 2 are calculated by the following formulas, respectively:

[0030]

[0031] Among them:

[0032] S6: The asphalt pavement life prediction model can be obtained by equation transformation of the formula in step (5):

[0033]

[0034] Among them, the experimental parameter A takes the average value of multiple calculation results, the rut deformation rate ε is calculated according to the maximum rut allowed to appear as a critical value, and the temperature T takes the equivalent temperature of the pavement.

[0035] Compared with the prior art, the beneficial effects of the present application are:

[0036] The present application uses a full-thickness rutting tester to measure the occurrence of different rutting conditions of a certain asphalt surface structure under different temperatures and different load action times, and then establishes the relationship among rut deformation rate, time and temperature. The life prediction model is obtained by equation transformation, and the life prediction value can be obtained by fitting calculation of the test data. The method can predict the service life of the asphalt surface structure, and check whether the surface structure meets the initial use requirements of the road, thereby providing a new idea for the selection and optimization of road structure. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is the flow chart of the present application. ​

[0038] Figure 2 is a linear fitting graph of lnε and t in the example.

[0039] Figure 3 is a linear fitting graph of lnk and 1 / T in the example. DETAILED DESCRIPTION

[0040] The application is further described below by taking a method for predicting the service life of asphalt pavement as an example.

[0041] A method for predicting the service life of asphalt pavement comprises the following steps:

[0042] S1: According to the proportioning of each layer material of the newly built asphalt pavement, the asphalt mixture is mixed, and a full-thickness rutting test piece is made layer by layer according to the requirements.

[0043] S2: The full-thickness rutting tester is used to carry out rutting test under different temperature conditions and different load action times, and the corresponding values are recorded. The wheel bottom pressure is set to 0.7 MPa, the temperature conditions should take multiple values (for example: 30℃, 40℃, 50℃, 60℃, 70℃), and the load action times should take multiple values (for example: 2000-20000 times), so as to increase the reliability of the results.

[0044] S3: Taking the rutting permanent deformation rate of the asphalt structure layer as an index parameter, the pavement rutting deformation rate ε is calculated:

[0045]

[0046] In the formula: ε is the rutting deformation rate, %; R is the rutting deformation amount, mm; h is the thickness of the test piece, mm. h

[0047] S4: The standard equivalent axle times per hour of the road are obtained through existing data analysis and traffic investigation, and the ratio of the test load action times to the standard equivalent axle times per hour is the pavement service time:

[0048]

[0049] In the formula: t is the pavement service time, h; N is the load action times, times; N is the standard equivalent axle times per hour, times / h. h

[0050] S5: The relationship formula of the rutting deformation rate ε, time t and temperature T is established, and the specific calculation method is:

[0051] Firstly, the relationship between the rutting deformation rate ε and the time t is established:

[0052] ε=Ae -kt (3) ​​

[0053] wherein: ε—rutting deformation rate, %; A—test parameter; k—performance change speed constant related to temperature, h -1 ; t—length of road service, h.

[0054] Taking logarithm on both sides of equation (3):

[0055] lnε=lnA-kt (4)

[0056] Taking t as independent variable, lnε as dependent variable, lnA as constant term, and -k as slope, then using least square method to solve lnA and -k and the value of determination coefficient R. 2

[0057] Secondly, using Arrhenius equation to establish the relationship between constant k and temperature T:

[0058]

[0059] wherein: B—frequency factor, h -1 ; E a —activation energy, J / mol; R—molar gas constant, J / (mol·K); T—test temperature, K.

[0060] Taking logarithm on both sides of equation (5):

[0061]

[0062] Similarly, using least square method to solve lnB and and the value of determination coefficient R 2 .

[0063] Among them, the specific calculation method of least square method is:

[0064] Taking equation (4) as an example, let x1=t, y1=lnε, a=lnA, b=-k, and the parameters a, b and the determination coefficient R 2 are calculated by the following formulas respectively:

[0065]

[0066] Among them:

[0067] S6: The asphalt pavement life prediction model can be obtained by equation transformation of the formula in step (5):

[0068]

[0069] ​Wherein, the experimental parameter A takes the average value of multiple calculation results, the rut deformation rate ε is calculated according to the maximum rut allowed to appear on the road as a critical value, and the temperature T takes the equivalent temperature of the road surface.

[0070] Example 1

[0071] The test section is a certain first-class highway in Tianjin, and the use requirement is that the road meets the safe driving of vehicles within 3 years and does not need to be maintained. The asphalt pavement structure material composition is shown in Table 1. According to the material ratio, the asphalt mixture is mixed, and the full-thickness rut test piece is made layer by layer according to the requirements.

[0072] Table 1 Road surface structure composition

[0073]

[0074] The test adopts a full-thickness rut tester to conduct rut tests at different temperatures and different load action times and records them. Among them, the wheel bottom pressure is set to 0.7 MPa, the temperature conditions are 30℃, 40℃, 50℃, 60℃, and 70℃, and the load action times are 2000, 4000, 6000, 8000, 10000, 12000, 14000, 16000, 18000, and 20000 times. The rut test results are shown in Table 2.

[0075] Table 2 Rut test results

[0076]

[0077] According to the investigation, the original road equivalent temperature is 22.4℃, the hourly standard equivalent axle number of the road is 23.41 times / h, the values of ε and t are calculated by using formula (1) and formula (2) respectively, and the value of lnε is calculated. The results are shown in Table 3.

[0078]

[0079]

[0080] Table 3 Calculation results of index parameters

[0081]

[0082] The values of -k and lnA are calculated by using formula (3) and formula (4), the results are shown in Table 4, and the linear fitting results are shown in Figure 1 .

[0083] ε=Ae -kt (3)

[0084] lnε=lnA-kt (4)

[0085] Table 4 k and A values at different temperatures

[0086]

[0087]

[0088] According to the data in Table 5, the relevant parameter values are calculated by using formula (5) and formula (6), and the results are shown in Table 6, and the linear fitting results are shown in Figure 2

[0089]

[0090]

[0091] Table 5 Parameter values at different temperatures

[0092]

[0093] Table 6 Fitting results of lnk and 1 / T

[0094]

[0095] The parameter A takes the average value of multiple calculation results:

[0096]

[0097] The maximum rut 15mm of the pavement is taken as the critical value, so the calculation result of the rut deformation rate ε is:

[0098]

[0099] The temperature is converted into Kelvin temperature 295.55K, and the parameter values are substituted, and the predicted value t of the asphalt pavement life is obtained:

[0100]

[0101] From the above calculation results, it can be known that the estimated service life of the pavement is greater than 3 years, so the asphalt surface structure under normal use conditions meets the initial use requirements of the road section. After 3 years, whether to carry out a certain degree of maintenance according to the pavement damage condition (especially at the wheel trace) can be considered, so as to ensure the normal use of the pavement.

[0102] The unmentioned part of the application is applicable to the prior art.

[0103] Although the embodiments of the application have been shown and described, it can be understood by those of ordinary skill in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the application, and the scope of the application is defined by the appended claims and their equivalents.​

Claims

1. A method of predicting the life of an asphalt pavement, characterized by: The method comprises the following steps: S1, according to the composition of the new asphalt pavement structure, material proportioning is carried out and a full-thickness rutting test piece is prepared; S2, a full-thickness rutting tester is used to measure the rutting deformation of the test piece under different temperatures and different load action times; S3, the rutting deformation rate is calculated according to the experimental data; S4, the pavement service time is calculated according to the test conditions and road traffic investigation; S5, a relationship among the rutting deformation rate, time and temperature is established; S6, a prediction model of the service life of the asphalt pavement is obtained by solving the equation, and the prediction model is substituted into the calculation to obtain the predicted service life of the pavement; In the step S4, the standard equivalent axle times per hour of the road are obtained through existing data analysis and traffic investigation, and the ratio of the test load action times to the standard equivalent axle times per hour is the pavement service time: In the formula: t - the length of time of using the road surface, h; N - the number of load actions, times; N h - the standard equivalent number of axles per hour, times / h; The step S5 specifically comprises: The relationship between the rutting deformation rate ε and the service time t is established: ε = Ae -kt (3) In the formula, ε is the rutting deformation rate, %, A is a test parameter, k is a performance change speed constant related to temperature, h-1, and t is the pavement service time, h; The logarithm of both sides of the equation (3) is taken: lnε=lnA-kt (4) With t as independent variable, lnε as dependent variable, lnA as constant term, -k as slope, then use least square method to find lnA and -k and determine the value of coefficient R 2 ; The Arrhenius equation is used to establish the relationship between the constant k and the temperature T: where: B - frequency factor, h-1; E a - activation energy, J / mol; R - molar gas constant, J / (mol K); T - test temperature, K; The logarithm of both sides of the equation (5) is taken: The values of lnB and and the determination coefficient R 2 are determined using the least squares method. The specific calculation method of the least square method is: With formula (4), let x1 = t, y1 = lnε, a = lnA, b = -k, parameters a, b and its determination coefficient R 2 are calculated by the following formulas, respectively: wherein:

2. The method of predicting the life of an asphalt pavement of claim 1, wherein: In the step S1, the asphalt mixture is mixed according to the proportioning of the materials of each layer of the pavement, and the test piece is prepared layer by layer according to the requirements.

3. The method of predicting the life of an asphalt pavement of claim 1, wherein: In the step S2, the full-thickness rutting test is carried out under different temperatures and different load action times by using the full-thickness rutting tester.

4. The method of predicting the life of an asphalt pavement of claim 1, wherein: In the step S6, the prediction model of the service life of the asphalt pavement is: In the formula, the experimental parameter A is the average value of multiple calculation results, the rutting deformation rate ε is calculated according to the maximum rutting depth allowed on the road as the critical value, and the temperature T is the equivalent temperature of the pavement.

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