Asphalt pavement damage dynamic modulus main curve evaluation method based on disease investigation

Abstract

The invention is suitable for the technical field of road engineering, and particularly relates to an asphalt pavement damage dynamic modulus main curve evaluation method based on disease investigation. On the basis of deflection measured by a drop weight deflectometer, an indoor modulus test and a damage degree theory, a road surface field damage dynamic modulus main curve is obtained, and compared with a traditional elastic layered road surface system, viscoelasticity and damage of an asphalt material are considered in detection and evaluation of a service road, and conform to the actual service road surface condition. In addition, by taking parameters obtained by the drop weight deflectometer as a reference, the invention further provides a method for obtaining a damaged dynamic modulus main curve by calibrating crack disease investigation, and the practicability of road surface field testing is greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of road engineering, and in particular relates to a method for evaluating a main curve of a damaged dynamic modulus of an asphalt pavement based on a disease investigation. Background Art

[0002] As road projects enter the era of large-scale maintenance, a large number of existing roads in my country require efficient, fast and accurate detection and assessment methods. At present, on-site road inspections include functional characteristics such as flatness and anti-skid, as well as structural characteristics such as road surface diseases, deflection and internal water accumulation. Among them, for structural diseases, drop hammer deflectometer and crack disease survey are two commonly used methods for on-site road inspections, but the current related research on the analysis and application of such data is not in-depth, and is usually limited to direct comparison of observation parameters such as maximum deflection values ​​and road cracking percentages. Although some studies have used the measured deflection values ​​to conduct further structural assessments of roads, they are also limited to calculating the elastic modulus of the asphalt layer.

[0003] As a typical viscoelastic material, the modulus of asphalt pavement changes with temperature and load frequency. At the same time, compared with newly built pavement, the existing pavement will inevitably suffer a certain degree of damage under the repeated effects of aging, vehicle load and temperature changes. Therefore, relying on the elastic modulus to evaluate the strength of the road asphalt layer lacks scientificity and accuracy. In addition, domestic and foreign studies have confirmed that road strength is highly correlated with the rate of fatigue crack development. If the main curve of the damaged dynamic modulus of the asphalt layer of the existing road can be accurately obtained with the crack survey data as the temperature frequency changes, it will significantly reduce the cost of road inspection in my country and improve the effect and benefits.

[0004] Patent CN 116499855 A discloses a method and system for testing the dynamic elastic modulus of the asphalt structural layer of a highway. The dynamic elastic modulus of the asphalt structural layer of the highway is obtained by using the dynamic elastic modulus of each test point of each structural layer in the core sample. However, the invention is limited to the elastic modulus and does not consider the viscoelastic effect of the asphalt pavement. In addition, the efficiency of layered testing of core samples is low, and cracks may exist inside the core sample, which has a significant impact on the test results. Patent CN113626986 B discloses a method for determining the modulus gradient of an asphalt pavement. By obtaining the lateral strain value, vertical strain value and rotation angle of the pavement core sample specimen, the asphalt pavement modulus gradient model parameters and main curve are determined, and then the asphalt pavement modulus gradient under set temperature and frequency conditions is calculated. However, this method also ignores the problem of modulus reduction caused by cracking damage of the built pavement. At the same time, in the process of cutting the test specimen from the uneven pavement core sample and obtaining the strain value, the error is large, which affects the reliability of the result. Summary of the invention

[0005] The purpose of the present invention is to provide a method for evaluating the master curve of the damaged dynamic modulus of an asphalt pavement based on a disease investigation, aiming to solve the problem that in the prior art, in the process of cutting test specimens from uneven pavement core samples and obtaining strain values, errors are large, affecting the reliability of the results.

[0006] The present invention is implemented as follows: a method for evaluating a main curve of damaged dynamic modulus of an asphalt pavement based on a disease investigation, the method comprising: Select at least three test points on the road surface, conduct a drop weight deflectometer test at the test points, and record the road surface temperature and the measured deflection value; Carry out coring of the road surface at and around the test point to obtain multiple road core samples; Conduct dynamic modulus tests at multiple temperatures and frequencies indoors on the road core samples, and obtain the master curve by translating the dynamic modulus test values ​​at different temperatures; The modulus of the asphalt layer is back-calculated by the deflection measured by the drop weight deflectometer, and the pavement damage is calculated based on the difference between the modulus back-calculated by the drop weight deflectometer at 5Hz and 40Hz and the dynamic modulus indoors. Conduct a road surface disease survey and calculate the crack percentage based on the crack areas of different degrees on the lane surface; Based on the crack disease investigation results, the crack prediction equation coefficients were calibrated in combination with the pavement damage degree to obtain the calibrated crack prediction equation. Conduct disease surveys on other road sections, quickly obtain the road dynamic modulus damage degree based on the crack prediction equation, and generate the corresponding damaged dynamic modulus master curve.

[0007] Preferably, in the step of coring the road surface at and around the test point to obtain multiple road core samples, if the asphalt layer thickness is greater than 20 cm, 3 road core samples are taken, and if the asphalt layer thickness is not greater than 20 cm, 5 road core samples are taken.

[0008] Preferably, in the step of conducting a dynamic modulus test on the road core sample, if the height of the road core sample is greater than 20 cm, the core sample is cut into a cylindrical specimen with a height of 15 cm and a diameter of 10 cm; if the road core sample is not greater than 20 cm, a cylindrical specimen with a height of 11 cm and a diameter of 3.8 cm is further obtained by transverse core drilling.

[0009] Preferably, the modulus of the asphalt layer is back-calculated using the deflection value, and in the step of calculating the pavement damage degree based on the difference between the modulus back-calculated by the drop-hammer deflectometer at 5 Hz and 40 Hz and the modulus tested indoors, if there are multiple asphalt layers on the road surface, all asphalt layers are regarded as one layer, that is, the total thickness of the asphalt layers is used to back-calculate the modulus.

[0010] Preferably, the road surface damage degree is calculated by the following formula: in, and They are the back-calculated modulus values ​​corresponding to 5Hz and 40Hz at the test temperature of the falling weight deflectometer test, and They are respectively the dynamic modulus values ​​of indoor test under the corresponding reduced frequency, For the degree of damage.

[0011] Preferably, the crack disease investigation results include at least the percentage of cracked area of ​​the road section including fatigue cracks, longitudinal cracks and reflective cracks, which is specifically calculated by the following formula: in, is the crack opening percentage, The area is slightly cracked. The crack area is medium. The severe cracking area is is the total area of ​​the lane.

[0012] Preferably, the crack prediction equation is expressed as: in, , , and is the coefficient of the equation.

[0013] Preferably, the damaged dynamic modulus master curve expression is: in, is the dynamic modulus, , , ,and is the master curve model coefficient obtained through indoor tests, To reduce the frequency.

[0014] The method for evaluating the main curve of the damaged dynamic modulus of asphalt pavement based on disease investigation provided by the present invention obtains the main curve of the damaged dynamic modulus of the pavement on site based on the deflection measured by the drop-weight deflectometer, the indoor modulus test and the damage degree theory. Compared with the traditional elastic layered pavement system, the viscoelasticity and damage of the asphalt material are considered in the detection and evaluation of the service road, which is consistent with the actual service road conditions. In addition, based on the parameters obtained by the drop-weight deflectometer, the present invention further provides a method for calibrating the crack disease investigation to obtain the main curve of the damaged dynamic modulus, which greatly improves the practicality of the pavement field test. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A flow chart of a method for evaluating a master curve of damaged dynamic modulus of an asphalt pavement based on a disease investigation provided in an embodiment of the present invention; Figure 2 A comparison chart of the lossless dynamic modulus and the damaged dynamic modulus provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0017] It is understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but unless otherwise specified, these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, without departing from the scope of this application, a first xx script may be referred to as a second xx script, and similarly, a second xx script may be referred to as a first xx script.

[0018] like Figure 1 FIG. 1 is a flowchart of a method for evaluating a main curve of a damaged dynamic modulus of an asphalt pavement based on a disease investigation according to an embodiment of the present invention. The method comprises: Select at least three test points on the road surface, conduct a drop weight deflectometer test at the test points, and record the road surface temperature and the measured deflection value; Carry out coring of the road surface at and around the test point to obtain multiple road core samples; In this step, pavement coring is performed at and around the test location of the drop weight deflectometer. If the asphalt layer is thick (greater than 20 cm), three core samples are taken; if the asphalt layer is thin (less than 20 cm), five core samples are taken.

[0019] Conduct dynamic modulus tests on road core samples at multiple temperatures and frequencies indoors, and obtain the master curve by translating the dynamic modulus test values ​​of core samples at different temperatures; In this step, for the dynamic modulus test, if the asphalt layer is thick (greater than 20 cm), the core sample is cut into cylindrical specimens with a height of 15 cm and a diameter of 10 cm. If the asphalt layer is thin (less than 20 cm), a cylindrical specimen with a height of 11 cm and a diameter of 3.8 cm is obtained by transverse core drilling.

[0020] The modulus of the asphalt layer is back-calculated by the deflection value measured by the drop weight deflectometer, and the pavement damage degree is calculated based on the difference between the back-calculated modulus at 5Hz and 40Hz at the drop weight deflectometer test temperature and the indoor dynamic modulus; In this step, if there are multiple asphalt layers on the road surface, all asphalt layers are regarded as one layer, and the road surface damage degree is calculated by the following formula: in, and They are the back-calculated modulus values ​​corresponding to 5Hz and 40Hz at the test temperature of the falling weight deflectometer test, and They are respectively the dynamic modulus values ​​of indoor test under the corresponding reduced frequency, For the degree of damage.

[0021] Conduct a road surface disease survey and calculate the crack percentage based on the crack areas of different degrees on the lane surface; In this step, the crack disease investigation results include at least the percentage of cracked area of ​​the road section including fatigue cracks, longitudinal cracks and reflective cracks, which is specifically calculated by the following formula: in, is the crack opening percentage, The area is slightly cracked. The crack area is medium. The severe cracking area is is the total area of ​​the lane.

[0022] Based on the crack disease investigation results, the crack prediction equation coefficients were calibrated in combination with the pavement damage degree to obtain the calibrated crack prediction equation. In this step, the crack prediction equation is as follows: in, , , and is the coefficient of the equation.

[0023] Based on the investigated pavement cracking area percentage and calculated pavement damage degree Calibrate the coefficients of the crack prediction equation, that is, adjust , , and One or more parameters in the crack prediction equation make the left and right sides equal; if no targeted calibration is performed, the master curve obtained from the crack disease investigation may have a large error compared with the master curve obtained by the deflection back calculation, such as Figure 2 As shown; Conduct disease surveys on other road sections, quickly obtain the road dynamic modulus damage degree based on the crack prediction equation, and generate the corresponding damaged dynamic modulus master curve.

[0024] In this step, the calibrated crack prediction equation is used to conduct a disease investigation on cracks in other road sections in the area. The road dynamic modulus damage degree is assessed based on the calibrated crack prediction equation, and the damaged dynamic modulus master curve is obtained using the following formula: in, is the dynamic modulus, , , ,and is the master curve model coefficient obtained through indoor tests, To reduce the frequency.

[0025] In the present invention, drop weight deflectometer tests and disease investigations were conducted at three different road locations and the temperature was recorded. At the corresponding test locations, pavement core samples were extracted and it was found that the core samples were composed of multiple layers of asphalt mixtures. All asphalt layers were considered as a whole, the total thickness of the core samples was tested, and the extracted core samples were used in the laboratory to conduct dynamic modulus tests to obtain the indoor dynamic modulus master curve. The corresponding reduction frequency was obtained according to the road surface temperature during the drop weight deflectometer test, and the corresponding modulus value was determined according to the master curve, as shown in Table 1.

[0026] Table 1 Damage degree corresponding to the drop weight deflectometer and crack disease investigation

[0027] The modulus of the asphalt layer is calculated based on the deflection measured by the drop weight deflectometer. The modulus measured indoors and the damaged modulus calculated by the drop weight deflectometer are substituted into formula (1) to calculate the damage degree. The damage degrees corresponding to positions A, B and C are 0.179, 0.147 and 0.361, respectively. The percentage of crack opening obtained by formula (2) from the crack disease survey is substituted into formula (3) to calculate the damage degree. The damage degrees corresponding to positions A, B and C are 0.07, 0.03 and 0.02, respectively. Comparing the damage degrees obtained by the two methods, it can be seen that the damage degree calculated based on the crack disease survey has a large error. Therefore, formula (3) was recalibrated and it was found that a 2 is adjusted to 0.11 to make the damage degrees obtained by the two methods match.

[0028] In this section, the calibrated formula (3) combined with the crack disease survey data can be used to quickly and accurately calculate the road damage degree and obtain the main curve of the damaged dynamic modulus through formula (4), thus achieving an efficient assessment of the damage condition of the built road surface.

[0029] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

[0030] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for evaluating the main curve of damaged dynamic modulus of asphalt pavement based on disease investigation, characterized in that: The method comprises: Select at least three test points on the road surface, conduct a drop weight deflectometer test at the test points, and record the road surface temperature and the measured deflection value; Carry out coring of the road surface at and around the test point to obtain multiple road core samples; Conduct dynamic modulus tests at multiple temperatures and frequencies indoors on the road core samples, and obtain the master curve by translating the dynamic modulus test values ​​at different temperatures; The modulus of the asphalt layer is back-calculated by the deflection measured by the drop weight deflectometer, and the pavement damage is calculated based on the difference between the modulus back-calculated by the drop weight deflectometer at 5Hz and 40Hz and the dynamic modulus indoors. Conduct a road surface disease survey and calculate the crack percentage based on the crack areas of different degrees on the lane surface; Based on the crack disease investigation results, the crack prediction equation coefficients were calibrated in combination with the pavement damage degree to obtain the calibrated crack prediction equation. Conduct disease surveys on other road sections, quickly obtain the road dynamic modulus damage degree based on the crack prediction equation, and generate the corresponding damaged dynamic modulus master curve.

2. The method for evaluating the main curve of damaged dynamic modulus of asphalt pavement based on disease investigation according to claim 1 is characterized in that: In the step of coring the road surface at and around the test point to obtain multiple road core samples, if the asphalt layer thickness is greater than 20 cm, 3 road core samples are taken; if the asphalt layer thickness is not greater than 20 cm, 5 road core samples are taken.

3. The method for evaluating the main curve of damaged dynamic modulus of asphalt pavement based on disease investigation according to claim 1 is characterized in that: In the step of conducting a dynamic modulus test on the road core sample, if the road core sample height is greater than 20 cm, the core sample will be cut into a cylindrical specimen with a height of 15 cm and a diameter of 10 cm. If the road core sample is not greater than 20 cm, a cylindrical specimen with a height of 11 cm and a diameter of 3.8 cm will be further obtained by transverse core drilling.

4. The method for evaluating the main curve of damaged dynamic modulus of asphalt pavement based on disease investigation according to claim 1 is characterized in that: The modulus of the asphalt layer is back-calculated using the deflection value. In the step of calculating the pavement damage degree based on the difference between the modulus calculated by the drop-hammer deflectometer at 5 Hz and 40 Hz and the modulus tested indoors, if there are multiple asphalt layers on the road surface, all asphalt layers are regarded as one layer, that is, the total thickness of the asphalt layer is used to back-calculate the modulus.

5. The method for evaluating the main curve of damaged dynamic modulus of asphalt pavement based on disease investigation according to claim 1 is characterized in that: The road surface damage degree is calculated by the following formula: in, and They are the back-calculated modulus values ​​corresponding to 5Hz and 40Hz at the test temperature of the falling weight deflectometer test, and They are respectively the dynamic modulus values ​​of indoor test under the corresponding reduced frequency, For the degree of damage.

6. The method for evaluating the main curve of damaged dynamic modulus of asphalt pavement based on disease investigation according to claim 1 is characterized in that: The crack disease investigation results include at least the percentage of cracked area of ​​the road section, including fatigue cracks, longitudinal cracks and reflective cracks, which can be calculated by the following formula: in, is the crack opening percentage, The area is slightly cracked. The crack area is medium. The severe cracking area is is the total area of ​​the lane.

7. The method for evaluating the main curve of damaged dynamic modulus of asphalt pavement based on disease investigation according to claim 1 is characterized in that: The crack prediction equation is expressed as: in, , , and is the coefficient of the equation.

8. The method for evaluating the main curve of damaged dynamic modulus of asphalt pavement based on disease investigation according to claim 1 is characterized in that: The expression of the damaged dynamic modulus master curve is: in, is the dynamic modulus, , , ,and is the master curve model coefficient obtained through indoor tests, To reduce the frequency.

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