A road asphalt surface layer crack evaluation method based on nondestructive testing technology

Abstract

The present application relates to a kind of road surface evaluation indexes, more particularly to a kind of road asphalt surface crack evaluation method based on nondestructive testing technology.The steps include determining the size of detection section, establishing various crack sizes by detection: the upper surface crack condition index, middle surface crack condition index, lower surface crack condition index and asphalt surface overall crack condition index are obtained by calculation in the detection section, and the indexes are evaluated according to the road asphalt surface crack classification evaluation table.The present application is based on the nondestructive testing technology of pavement, which makes up for the problem that the existing evaluation index only evaluates the surface morphology of open crack, comprehensively considers the influence of all types of cracks on the service performance of pavement, calculates the crack condition index of upper surface, middle surface and lower surface respectively, and calculates the overall crack condition index, which is more representative and improves the pertinence and scientificity of maintenance and repair measures.

Description

Technical Field

[0001] This invention relates to a road surface layer evaluation index, and more particularly to a method for evaluating cracks in road asphalt surface layers based on non-destructive testing technology. Background Technology

[0002] In the 1996 edition of the "Technical Specifications for Highway Maintenance" (JTJ 073-96) (hereinafter referred to as the 1996 evaluation standard), the 2007 edition of the "Highway Technical Condition Evaluation Standard" (JTG H20-2007) (hereinafter referred to as the 2007 evaluation standard), and the current 2018 edition of the "Highway Technical Condition Evaluation Standard" (JTG 5210-2018) (hereinafter referred to as the 2018 current evaluation standard), the crack damage area is calculated based on the surface morphology of the cracks, and is calculated together with potholes, loosening, subsidence, rutting, wave bulging, bleeding, and repair defects to calculate the pavement damage ratio (DR). In calculating the DR index, the above three versions of specifications classify surface cracks into four categories: transverse cracks, longitudinal cracks, alligator cracks, and block cracks (referred to as irregular cracks in the 1996 evaluation standard). Each type of crack is further classified into two levels (light and severe) or three levels (light, medium, and severe) based on its surface morphology, and different weights are assigned according to the type and level of the crack.

[0003] When calculating the DR value, all three versions of the specification use the method of multiplying the crack length by 0.2m for both transverse and longitudinal cracks, indicating that this measurement method basically meets the actual engineering needs. However, the current evaluation standards in the 2007 and 2018 versions significantly increased the weight of transverse and longitudinal cracks and lowered the classification standard for "severe" level. The classification standards for block cracks and alligator cracks are basically consistent in the three versions of the specification, except that the weight of light and severe block cracks was significantly increased in the current evaluation standards in the 2007 and 2018 versions, while the classification standard for "severe" level of block cracks was slightly lowered in the current standard in the 2018 version. Based on the calculated DR value, all three versions of the specification use Equation (1) to calculate the Pavement Surface Condition Index (PCI).

[0004] PCI = 100-15DR 0.412

[0005] In summary, the standards have established a relatively effective pavement crack evaluation method that has been in use for many years. This method measures various types of open cracks based on the pavement surface morphology, calculates the pavement damage rate (DR) value, and then calculates the pavement damage index (PCI) value for scoring. However, this evaluation method only assesses the pavement surface morphology of open cracks and cannot evaluate the propagation state of closed cracks in the asphalt pavement (mainly reflective cracks that do not penetrate the surface layer) based on the PCI index. Summary of the Invention

[0006] This invention addresses the aforementioned problems and shortcomings of existing road structure evaluation indicators and methods by providing a method for evaluating cracks in road asphalt pavement based on non-destructive testing technology. The evaluation method utilizes detailed crack data obtained from on-site non-destructive testing to characterize the road surface condition, exhibiting a strong positive correlation with actual service conditions. This provides a precise basis for assessing road performance degradation and subsequent maintenance decisions.

[0007] The present invention adopts the following technical solution:

[0008] The present invention discloses a method for evaluating cracks in road asphalt pavement based on non-destructive testing technology, characterized by the following steps:

[0009] Step 1: Determine the dimensions of the test section: The width of the test section is d, and the length of the test section is l0; the thicknesses of the upper asphalt surface layer, the middle asphalt surface layer, and the lower asphalt surface layer in the test section are denoted as h respectively. u ′, h m ′, h l ′;

[0010] Step 2: Establish various crack sizes through detection: Cracks in the detected road section are classified into transverse and longitudinal cracks, block cracks, and closed cracks;

[0011] Based on the results obtained from the testing of the three surface layers (upper asphalt layer, middle asphalt layer, and lower asphalt layer) in step 1:

[0012] Height of transverse and longitudinal cracks, block cracks, and closed cracks;

[0013] The length of transverse and longitudinal cracks, and closed cracks;

[0014] Integral values ​​for blocky cracks and crazing on the road surface;

[0015] Step 3: Based on Step 2, the crack rate of the upper asphalt surface layer with open cracks is UCR1, the crack rate of the middle asphalt surface layer is MCR1, and the crack rate of the lower asphalt surface layer is LCR1.

[0016] The crack rates of the upper asphalt surface layer with block cracks are UCR2, MCR2, and LCR2.

[0017] The cracking rates of the upper asphalt surface layer are UCR3, the middle asphalt surface layer is MCR3, and the lower asphalt surface layer is LCR3.

[0018] The crack rate of the upper asphalt surface layer with closed cracks is UCR4, the crack rate of the middle asphalt surface layer is MCR4, and the crack rate of the lower asphalt surface layer is LCR4.

[0019] The following formulas are used to calculate the cracking rate (UCR) of the upper asphalt surface layer, the cracking rate (MCR) of the middle asphalt surface layer, and the cracking rate (LCR) of the lower asphalt surface layer:

[0020]

[0021] Based on the above formula, the cracking rates of the upper asphalt pavement (UCR), middle asphalt pavement (MCR), and lower asphalt pavement (LCR) are obtained. The total cracking rate (TCR) of the asphalt pavement is then calculated using the following formula:

[0022]

[0023] Step 4: Calculation of layered crack evaluation index: Based on the crack rate of the upper layer UCR, the crack rate of the middle layer MCR, the crack rate of the lower layer LCR, and the total crack rate of the asphalt surface layer TCR calculated in Step 3, the crack condition index of the upper layer UPCI, the crack condition index of the middle layer MPCI, the crack condition index of the lower layer LPCI, and the total crack condition index of the asphalt surface layer TPCI are calculated by substituting them into the following formula.

[0024]

[0025] Step 5: Based on the Upper Layer Crack Condition Index (UPCI), Mid-Layer Crack Condition Index (MPCI), Surface Layer Crack Condition Index (LPCI), and Total Crack Condition Index (TPCI) of the Asphalt Surface Layer, evaluate the crack condition of the asphalt surface layer according to the classification defined in the table below:

[0026] Evaluation table for crack classification of asphalt pavement

[0027]

[0028] The present invention discloses a method for evaluating cracks in road asphalt pavement based on non-destructive testing technology.

[0029] (1) The crack rate of the upper asphalt surface layer with open cracks is obtained by the following formula: UCR1

[0030]

[0031] Medium asphalt pavement crack rate (MCR1):

[0032]

[0033] Lower asphalt surface cracking rate LCR1:

[0034]

[0035] (2) The crack rate of the asphalt surface layer with block cracks is obtained by the following formula: UCR2

[0036]

[0037] Medium asphalt pavement crack rate (MCR2):

[0038]

[0039] Lower asphalt surface cracking rate LCR2:

[0040]

[0041] (3) The crack rate of the cracked asphalt surface layer is UCR3:

[0042]

[0043] Medium asphalt pavement crack rate (MCR3):

[0044]

[0045] Lower asphalt surface cracking rate (LCR3):

[0046]

[0047] (4) The crack rate of the asphalt surface layer with closed cracks is UCR4:

[0048]

[0049] Medium asphalt pavement crack rate MCR4;

[0050]

[0051] Lower asphalt surface cracking rate (LCR4):

[0052]

[0053] In the above formula: h represents the transverse and longitudinal cracks in the asphalt surface layer. ui transverse and longitudinal cracks in the medium asphalt surface layer h mi transverse and longitudinal cracks in the lower asphalt surface layer h li Blocky cracks in the asphalt surface layer h uj Blocky cracks in the medium asphalt pavement h mj Blocky cracks in the lower asphalt surface layer h lj Closed cracks h in the asphalt surface layer up Closed cracks in medium asphalt pavement h mp Closed cracks in the lower asphalt surface layer h lp The lengths of transverse and longitudinal cracks, closed cracks, and the surface integral S of blocky cracks. j Cracked road surface integral S k The total number of transverse and longitudinal cracks N1, the total number of block cracks N2, the total number of alligator cracks N3, and the total number of closed cracks N4 in the measured road section, and the weight of transverse and longitudinal crack severity ω. i(0.6 for width ≤ 3mm, 1.0 for width > 3mm), weight ω for the severity of blocky cracks. j (0.6 for block size > 1m and width 1-2mm, 0.8 for block size 0.5-1m and width > 2mm), weight ω for the severity of closed cracks. p (No grading, always take 0.8).

[0054] The evaluation results from step 4, based on the UPCI (Upper Layer Crack Condition Index), MPCI (Middle Layer Crack Condition Index), LPCI (Lower Layer Crack Condition Index), and TPCI (Total Crack Condition Index of Asphalt Pavement), combined with the road asphalt pavement crack classification evaluation table from step 5, are determined as follows:

[0055] Based on this standard, when any of the following indices is rated as substandard or poor: UPCI (upper layer crack condition index), MPCI (middle layer crack condition index), LPCI (lower layer crack condition index), or TPCI (total crack condition index of asphalt surface layer), it is determined that: repair measures must be taken for the entire asphalt surface layer.

[0056] When the Total Crack Index (TPCI) of the asphalt pavement is rated as medium, it is determined that: repair measures should be taken for the entire asphalt pavement.

[0057] When the Total Crack Condition Index (TPCI) of asphalt pavement is rated as good, it is determined that: repair measures can be taken for the asphalt pavement as a whole.

[0058] When the Total Crack Condition Index (TPCI) of the asphalt pavement is rated as excellent, it is determined that the asphalt pavement is in good service condition and does not require repair.

[0059] When any one of the three crack conditions indexes (UPCI, MPCI, LPCI) is rated as medium, it is determined that necessary repair measures should be taken for that layer and above.

[0060] When any one of the three crack conditions indexes (UPCI, MPCI, LPCI) is rated as good, it is determined that necessary repair measures can be taken for that layer and above.

[0061] When the crack condition index UPCI of the upper layer, the crack condition index MPCI of the middle layer, and the crack condition index LPCI of the lower layer are all excellent, it is determined that the service condition of each layer of the asphalt surface is healthy and does not require repair.

[0062] Beneficial effects

[0063] The beneficial effects of this invention are that the proposed evaluation index fully considers all cracks in the asphalt pavement, and based on the results of non-destructive testing of the pavement, it can make accurate quantitative evaluations of the upper layer, middle layer, lower layer and the overall surface layer, respectively. It can provide scientific guidance for asphalt pavement maintenance based on the evaluation results, and can effectively reduce the maintenance cost of road asphalt pavement. It has certain beneficial effects in terms of technology, theory and application. Detailed Implementation

[0064] To make the objectives and technical solutions of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0065] A method for evaluating the bearing capacity of highway structures in-situ based on measured crack and modulus includes the following steps:

[0066] (1) Determine the dimensions of the test section. The width and length of the test section are denoted as d and l0, respectively. For a common asphalt pavement consisting of three layers (upper, middle, and lower), the thicknesses of the upper, middle, and lower asphalt pavement layers of the test section are denoted as h, respectively. u ′, h m ′, h l ′;

[0067] (2) Detection of various crack sizes: For transverse and longitudinal cracks, block cracks, and closed cracks in the inspected road section, their average internal depth or average burial depth can be measured by Rayleigh wave detector and road surface image recognition. The height occupied by transverse and longitudinal cracks, block cracks, and closed cracks in the upper / middle / lower layers is denoted as h. ui / h mi / h li h uj / h mj / h lj h up / h mp / h lp The lengths of transverse and longitudinal cracks can be directly measured from the road surface, while the lengths of closed cracks can be measured using ground-penetrating radar. The lengths of each transverse, longitudinal, and closed crack are denoted as l. i and l p The areas of blocky cracks and alligator cracks can be directly measured from the road surface, and the surface areas of blocky cracks and alligator cracks at each location are denoted as S. j and S kThe cracks in the crater are relatively densely distributed, making it difficult to detect their depth using Rayleigh wave detectors or ground penetrating radar. Therefore, based on the crack severity, light / moderate / severe cratering is approximated as surface layer / upper-middle surface layer / upper-middle-lower surface layer penetrating disease, respectively.

[0068] (3) Calculation of layered crack ratio: According to Appendix 1 and Equation (2), the three indicators of upper / middle / lower surface crack ratio (UCR), middle / lower surface crack ratio (MCR), and lower surface crack ratio (LCR) are calculated respectively. Based on this, according to the thickness of the upper, middle and lower layers, the total crack ratio (TCR) of the asphalt surface layer is calculated by weighting according to Equation (3). In the table, N1, N2, N3 and N4 are the total number of transverse and longitudinal cracks, block cracks, alligator cracks and closed cracks in the measured road section, respectively. The severity of transverse and longitudinal cracks is weighted by ω. i (0.6 for width ≤ 3mm, 1.0 for width > 3mm), weight ω for the severity of blocky cracks. j (0.6 for block size > 1m and width 1-2mm, 0.8 for block size 0.5-1m and width > 2mm), weight ω for the severity of closed cracks. p (No grading, always take 0.8).

[0069] Table 1. Classification standards and measurement methods for various types of cracks when calculating UCR, MCR, and LCR indices.

[0070]

[0071]

[0072]

[0073]

[0074] (4) Calculation of layered crack evaluation index: Based on the UCR, MCR, LCR, TCR (Asphalt Surface Total Crack Ratio) values ​​calculated in step (3), the upper layer crack condition index UPCI, middle layer crack condition index MPCI, lower layer crack condition index LPCI (Upper / Middle / Lower Pavement Surface Crack Index) and the asphalt surface layer total crack condition index TPCI (Total Asphalt Pavement Surface Crack Index) are calculated by formula (4). If the longitudinal cracks caused by uneven settlement of the subgrade extend to the asphalt surface layer, the UPCI, MPCI, LPCI and TPCI values ​​of this evaluated road section are all rated as 0 points.

[0075]

[0076] (5) Based on the crack condition index UPCI of the upper layer, crack condition index MPCI of the middle layer, crack condition index LPCI of the lower layer and crack condition index TPCI of the asphalt surface layer, the crack condition of the upper, middle and lower asphalt surface layers is graded and evaluated according to Table 2.

[0077] Table 2 Evaluation Indicators for Crack Classification of Road Asphalt Surface Layer

[0078]

[0079] (6) When any one of the TPCI or UPCI / MPCI / LPCI indicators is rated as substandard or poor, this standard considers that overall repair measures must be taken for the asphalt pavement; when the TPCI indicator is rated as moderate, this standard recommends overall repair measures for the asphalt pavement; when the TPCI indicator is rated as good, this standard considers that overall repair measures can be taken for the asphalt pavement; when the TPCI indicator is rated as excellent, this standard considers that the asphalt pavement is in good service condition and does not require repair. When any one of the UPCI / MPCI / LPCI indicators is rated as moderate, this standard recommends that necessary repair measures be taken for the layer and above; when any one of the three indicators is rated as good, this standard considers that necessary repair measures can be taken for the layer and above; when all three are excellent, this standard considers that the service condition of each layer of the asphalt pavement is healthy and does not require repair. When the repair recommendations derived from the overall score conflict with the repair recommendations derived from the local score, this standard considers that the more unfavorable situation should be considered when formulating the maintenance and repair plan.

[0080] Example 1

[0081] A method for evaluating cracks in road asphalt pavement based on non-destructive testing technology is adopted, and the specific operation is as follows:

[0082] (1) Select a test section with a length l0 = 2 meters and a width d = 2 meters according to the requirements. Conduct a preliminary investigation of the design documents to obtain the asphalt surface layer thickness of the test section as follows: upper layer h′ u = 4 cm, middle layer h′ m =6 cm, lower layer h′ l = 8 centimeters.

[0083] (2) The dimensions of various cracks were obtained by field non-destructive testing methods such as ground penetrating radar or Rayleigh wave detection, as shown in Table 1 below:

[0084] Table 1. Crack Sizes Obtained Through On-Site Non-Destructive Testing Methods

[0085] crack <![CDATA[h u ]]> <![CDATA[h m ]]> <![CDATA[h l ]]> <![CDATA[l i / l p ]]> <![CDATA[S i / S k ]]> transverse crack 1 2 6 3 5 Longitudinal crack 1 0 6 2 5 Blocky crack 1 1 5 0 / 5 Closed crack 1 2 2 0 5 Cracks / / / / 5

[0086] The cracks in the crater are relatively densely distributed, making it difficult to detect their depth. Therefore, based on the crack grade, light / moderate / severe cracks are approximated as surface layer / upper middle layer / upper middle lower layer penetrating disease, respectively.

[0087] (3) Calculate the three indicators of crack rate UCR of the upper layer, crack rate MCR of the middle layer, and crack rate LCR of the lower layer according to Appendix 2 and Formula (1). Based on this, calculate the total crack rate TCR of the asphalt surface layer according to the thickness of the upper, middle and lower layers according to Formula (2). In the table, N1, N2, N3 and N4 are the total number of transverse and longitudinal cracks, block cracks, alligator cracks and closed cracks in the measured road section, respectively. The severity of transverse and longitudinal cracks is weighted by ω. i (0.6 for width ≤ 3mm, 1.0 for width > 3mm), weight ω for the severity of blocky cracks. j (0.6 for block size > 1m and width 1-2mm, 0.8 for block size 0.5-1m and width > 2mm), weight ω for the severity of closed cracks. p (No grading, always take 0.8).

[0088] Table 2. Classification standards and measurement methods for various types of cracks when calculating UCR, MCR, and LCR indices.

[0089]

[0090]

[0091]

[0092]

[0093] The results were: UCR = 0.31, MCR = 0.47, LCR = 0.28, LCR = 0.35.

[0094] (4) Based on the UCR, MCR, LCR and TCR values ​​calculated in step (3), the crack condition index UPCI of the upper layer, crack condition index MPCI of the middle layer, crack condition index LPCI of the lower layer and crack condition index TPCI of the asphalt surface layer are calculated by the following formula (3). If the longitudinal cracks caused by uneven settlement of the subgrade extend to the asphalt surface layer, the UPCI, MPCI, LPCI and TPCI values ​​of this evaluated road section are all rated as 0 points.

[0095]

[0096] The results are: UPCI = 90.74, MPCI = 89.01, LPCI = 91.12, TPCI = 90.27.

[0097] (5) Based on the crack condition index UPCI of the upper layer, crack condition index MPCI of the middle layer, crack condition index LPCI of the lower layer and crack condition index TPCI of the asphalt surface layer, the crack condition of the upper, middle and lower asphalt surface layers is graded and evaluated according to Table 3.

[0098] Table 3 Evaluation Indicators for Crack Classification of Road Asphalt Surface Layer

[0099]

[0100] The evaluation results are as follows: top layer grade "Excellent"; middle layer grade "Good"; bottom layer grade "Excellent"; overall surface grade "Excellent".

[0101] (6) Based on the evaluation results, the repair recommendations given in this standard are as follows: the overall service condition of the surface layer is healthy and does not require repair. Simple repair measures can be taken for the middle surface layer and above. Based on the principle of considering the worst-case scenario, the final recommendation is that repair measures can be taken for the middle surface layer and above.

[0102] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for evaluating cracks in road asphalt pavement based on non-destructive testing technology, characterized in that: The steps are as follows: Step 1: Determine the dimensions of the inspection section: The width of the inspection section is... The length of the road section to be inspected is In the tested road section: the thicknesses of the upper asphalt surface layer, the middle asphalt surface layer, and the lower asphalt surface layer are respectively recorded as follows: , , ; Step 2: Establish various crack sizes through detection: Cracks in the road section are divided into open cracks and closed cracks. Open cracks include transverse and longitudinal cracks, block cracks, and alligator cracks. Based on the results obtained from the testing of the three surface layers (upper asphalt layer, middle asphalt layer, and lower asphalt layer) in step 1: Height of transverse and longitudinal cracks, block cracks, and closed cracks; The length of transverse and longitudinal cracks, and closed cracks; Integral values ​​for blocky cracks and crazing on the road surface; Step 3: Based on Step 2, calculate the crack rates of the upper asphalt surface layer (UCR1), the middle asphalt surface layer (MCR1), and the lower asphalt surface layer (LCR1) for transverse and longitudinal cracks. Based on step 2, the crack rates of the upper asphalt surface layer (UCR2), the middle asphalt surface layer (MCR2), and the lower asphalt surface layer (LCR2) for blocky cracks are calculated. Based on step 2, the crack rates of the upper asphalt surface layer (UCR3), the middle asphalt surface layer (MCR3), and the lower asphalt surface layer (LCR3) were calculated. Based on step 2, the crack rates of the upper asphalt surface layer with closed cracks are calculated as UCR4, the crack rates of the middle asphalt surface layer asphalt ... The following formulas are used to calculate the cracking rate (UCR) of the upper asphalt surface layer, the cracking rate (MCR) of the middle asphalt surface layer, and the cracking rate (LCR) of the lower asphalt surface layer: ； Based on the above formula, the cracking rates of the upper asphalt pavement (UCR), middle asphalt pavement (MCR), and lower asphalt pavement (LCR) are obtained. The total cracking rate (TCR) of the asphalt pavement is then calculated using the following formula: ； Step 4: Calculation of layered crack evaluation index: Based on the crack rate of upper asphalt surface layer UCR, crack rate of middle asphalt surface layer MCR, crack rate of lower asphalt surface layer LCR, and total crack rate of asphalt surface layer TCR calculated in Step 3, the crack condition index of upper layer UPCI, crack condition index of middle layer MPCI, crack condition index of lower layer LPCI, and total crack condition index of asphalt surface layer TPCI are calculated by substituting them into the following formula. ； Step 5: Based on the UPCI (Upper Layer Crack Condition Index), MPCI (Middle Layer Crack Condition Index), LPCI (Lower Layer Crack Condition Index), and TPCI (Total Crack Condition Index of Asphalt Pavement), evaluate the crack condition using the road asphalt pavement crack classification evaluation table defined in the table below: 。 2. The method for evaluating cracks in road asphalt surface layers based on non-destructive testing technology according to claim 1, characterized in that: (1) The crack rate of the upper asphalt surface layer with transverse and longitudinal cracks is obtained by the following formula: UCR1 ； Medium asphalt pavement crack rate (MCR1): ； Lower asphalt surface cracking rate LCR1: ； (2) The crack rate of the upper asphalt surface layer with blocky cracks is obtained by the following formula: UCR2 ； Medium asphalt pavement crack rate (MCR2): ； Lower asphalt surface cracking rate LCR2: ； (3) The crack rate of the cracked asphalt surface layer is UCR3: ； Medium asphalt pavement crack rate (MCR3): ； Lower asphalt surface cracking rate (LCR3): ； (4) The crack rate of the asphalt surface layer with closed cracks is UCR4: ； Medium asphalt pavement crack rate (MCR4): ； Lower asphalt surface cracking rate LCR4: ； In the above formula: transverse and longitudinal cracks in the asphalt surface layer transverse and longitudinal cracks in medium asphalt surface layer transverse and longitudinal cracks in the lower asphalt surface layer Blocky cracks in the asphalt surface layer Blocky cracks in medium asphalt pavement Blocky cracks in the lower asphalt surface layer Closed cracks in the asphalt surface layer Closed cracks in medium asphalt pavement Closed cracks in the underlying asphalt surface layer Length of transverse and longitudinal cracks Length of closed crack Blocky crack road surface integral Integral of cracked road surface The total number of transverse and longitudinal cracks in the measured road section Total number of blocky cracks Total number of cracks Total number of closed cracks Weighting of the severity of transverse and longitudinal cracks Severity weight of blocky cracks Severity weight of closed cracks .

3. The method for evaluating cracks in road asphalt surface layers based on non-destructive testing technology according to claim 1, characterized in that: The evaluation results of the upper layer crack condition index (UPCI), middle layer crack condition index (MPCI), lower layer crack condition index (LPCI), and overall asphalt surface layer crack condition index (TPCI) from step 4, combined with those from the road asphalt surface layer crack classification evaluation table in step 5, are determined as follows: When any of the following indices is rated as substandard or poor: UPCI (upper layer crack condition index), MPCI (middle layer crack condition index), LPCI (lower layer crack condition index), or TPCI (total crack condition index of asphalt surface layer), it is determined that: repair measures must be taken for the entire asphalt surface layer. When the Total Crack Index (TPCI) of the asphalt pavement is rated as medium, it is determined that: repair measures should be taken for the entire asphalt pavement. When the Total Crack Index (TPCI) of asphalt pavement is rated as good, it is determined that: repair measures can be taken for the asphalt pavement as a whole. When the Total Crack Condition Index (TPCI) of the asphalt pavement is rated as excellent, it is determined that the asphalt pavement is in good service condition and does not require repair. When any one of the three crack conditions indexes (UPCI, MPCI, LPCI) is rated as medium, it is determined that necessary repair measures should be taken for that layer and above. When any one of the three crack conditions indexes (UPCI, MPCI, LPCI) is rated as good, it is determined that necessary repair measures can be taken for that layer and above. When the crack condition index UPCI of the upper layer, the crack condition index MPCI of the middle layer, and the crack condition index LPCI of the lower layer are all excellent, it is determined that the service condition of each layer of the asphalt surface is healthy and does not require repair.

4. The method for evaluating cracks in road asphalt surface layers based on non-destructive testing technology according to claim 2, characterized in that: Weighting of transverse and longitudinal crack severity When the width of the transverse and longitudinal cracks is ≤3mm, Take 0.6; when the width of the transverse and longitudinal cracks is >3mm, Set the value to 1.0; Weighting of the severity of block cracks When the size of the blocky crack is >1m and the width is between 1-2mm, Take 0.6; when the size of the blocky cracks is between 0.5-1m and the width is >2mm, Take 0.8; Weighting of the severity of closed cracks Take 0.8.

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