A method for detecting transverse cracks in semi-rigid base asphalt pavement

Abstract

The present invention relates to the technical field of road surface detection, and in particular to a method for detecting transverse cracks in a semi-rigid base asphalt road surface, comprising the following steps: S10: obtaining position information of transverse cracks in an asphalt road surface and detecting internal information of the cracks; S20: obtaining deflection change values ​​and level reading differences when passing through a road surface with transverse cracks at different vehicle speeds; S30: selecting the vehicle speed at which the deflection change value and the level reading value are the largest as the optimal driving speed; S40: obtaining the reading difference of the level at different crack types at the optimal driving speed, and determining the level reading difference range of different transverse crack types; S50: determining the transverse crack type corresponding to the subsequent level reading at the optimal driving speed according to the determined level reading difference range. After verification, the present invention can quickly and accurately obtain the type of crack only by the level reading difference during vehicle driving, thereby reducing the damage to the road surface and improving the speed and accuracy of obtaining the transverse crack type.

Description

Technical Field

[0001] The invention relates to the technical field of pavement detection, and in particular to a method for detecting transverse cracks in a semi-rigid base asphalt pavement. Background Art

[0002] Semi-rigid base asphalt pavement is the most important structural form of asphalt pavement on high-grade highways in my country. Semi-rigid base has the characteristics of high rigidity, strong structural bearing capacity, high flatness, etc., and has excellent use effect in the early stage of highway construction. However, with the increasing traffic load, semi-rigid base asphalt pavement diseases frequently occur, among which the most important and serious disease is reflection cracks. Reflection cracks are caused by the shrinkage of the semi-rigid base, and the cracks further develop upward under the action of traffic load. Generally, they exist in the form of transverse cracks. However, in addition to the above-mentioned reflection cracks, transverse cracks also include surface cracks caused by temperature stress. The causes of the two are different, and the harm to the road is also different. The base structure of the surface cracks is not damaged, while the base structure at the location of the reflection disease generally has internal defects such as cracking and looseness. Therefore, how to distinguish the above two types of transverse cracks has become an urgent problem to be solved.

[0003] In conventional technology, core sampling analysis is often used to distinguish transverse cracks. However, this method is inefficient and will cause irreversible damage to the road surface. In order to further improve the efficiency of identification, in the prior art, such as the Chinese invention patent application with publication number CN106844527A, which was disclosed on June 13, 2017, a road surface disease identification and maintenance decision-making method and system based on Internet big data is used. The method realizes the identification of road surface diseases through a big data self-learning algorithm, which includes the identification of surface cracks and reflective cracks.

[0004] However, the above-mentioned big data self-learning recognition method can only identify transverse cracks, oblique cracks and longitudinal cracks, etc., and the recognition accuracy of reflective cracks and surface cracks in transverse cracks cannot meet the requirements. Summary of the invention

[0005] In view of at least one of the above technical problems, the present invention provides a method for detecting transverse cracks in a semi-rigid base asphalt pavement, which improves the method to achieve convenience and accuracy in detecting transverse crack types in the pavement.

[0006] According to a first aspect of the present invention, a method for detecting transverse cracks in a semi-rigid base asphalt pavement is provided, comprising the following steps: S10: Obtaining location information of transverse cracks on the asphalt pavement and detecting internal information of the cracks; S20: obtaining deflection change values ​​and level reading differences when the vehicle passes through a road surface with transverse cracks at different speeds; S30: selecting the vehicle speed at which the deflection change value and the level meter reading value are the largest as the optimal driving speed; S40: obtaining the reading difference of the level meter at different crack types at the optimal driving speed, and determining the range of the reading difference of the level meter for different transverse crack types; S50: Determine, according to the determined range of the difference in the level readings, the type of transverse crack corresponding to the subsequent level readings at the optimal driving speed.

[0007] In some embodiments of the present invention, in step S10, a three-dimensional scanner is used in combination with a three-dimensional ground penetrating radar to detect the location of the transverse crack.

[0008] In some embodiments of the present invention, in step S10, when detecting internal information of a crack, after background removal, noise reduction and filtering processing are performed on the signal collected by the three-dimensional ground penetrating radar, the internal information of the crack is determined by judging the signal amplitude anomaly and the continuity of the event axis.

[0009] In some embodiments of the present invention, in step S10, after determining the internal information of the cracks, coring verification is performed on some transverse crack defects.

[0010] In some embodiments of the present invention, in step S20, a laser dynamic deflection detection vehicle equipped with a vehicle-mounted level meter is used to perform multiple detections at different driving speeds.

[0011] In some embodiments of the present invention, in step S20, the vehicle-mounted level meter is leveled before detection to eliminate the influence of the transverse slope and the longitudinal slope of the road surface.

[0012] In some embodiments of the present invention, in step S30, the deflection change value and the level reading difference at the crack defect at each driving speed are detected multiple times and the results are averaged.

[0013] In some embodiments of the present invention, in step S40, the difference in level meter readings of the surface cracks is smaller than the value of the reflective cracks.

[0014] In some embodiments of the present invention, step S40 further includes obtaining a deflection change value at an optimal driving speed, wherein the deflection change value is used to evaluate the severity of the reflective crack.

[0015] In some embodiments of the present invention, step S60 is also included: using the least squares method to fit the deflection change values ​​and the level reading differences under different crack damage degrees, and determining the classification and evaluation system of the crack type through the level reading difference range of different transverse crack types.

[0016] The beneficial effects of the present invention are as follows: the present invention obtains the deflection value and the horizontal reading difference at the optimal driving speed on the road surface with known cracks according to the degree of bumps caused by vehicle driving corresponding to the transverse cracks of different semi-rigid base asphalt pavements, and determines different crack types according to the range of the horizontal reading difference. After verification, the type of crack can be quickly and accurately obtained only by the level reading difference during vehicle driving. Compared with the prior art, it will not cause damage to the road surface, and the speed and accuracy of the acquisition are guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 This is a flow chart of the steps of a method for detecting transverse cracks in a semi-rigid base asphalt pavement in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0020] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0022] In view of the problem that it is difficult to distinguish between reflected cracks and surface cracks in existing transverse cracks, the inventors found that the base structure at the location of surface cracks was not damaged, while the base structure at the location of reflective cracks generally had internal defects such as cracking and looseness. This internal structural damage is often reflected in the bearing capacity of the pavement structure. Therefore, under the premise of the same pavement structure type, the type of transverse cracks can be determined with the help of deflection measurement method.

[0023] The deflection of asphalt pavement is the total vertical deformation of the pavement at the wheel gap position under the action of standard axle load. It not only represents the overall bearing capacity of the roadbed and pavement structure, but also reflects the actual use of the asphalt pavement. Under the same asphalt pavement structure and material combination, the deflection value at the location of the transverse crack disease of the asphalt pavement is lower than the deflection value of the intact asphalt pavement due to structural damage. Similarly, the deflection at the location of the reflective crack disease of the semi-rigid base should be lower than the deflection value at the location of the crack disease only on the surface due to more serious internal structural damage. However, conventional deflection detection methods such as Beckman beam deflection measurement method and drop hammer deflectometer measurement method are inefficient, and the deflection data detected by laser high-speed dynamic detection vehicle equipment is often too large. It is not only costly, but also time-consuming and laborious to use it only to determine the type of transverse cracks in the pavement. During normal driving, when a vehicle passes through a bridge head, the vehicle will jump due to the different stiffness of the roadbed on both sides of the bridge head. Similarly, when a vehicle passes through a transverse crack disease of an asphalt pavement, the vehicle will also experience a slight "bump", which becomes more obvious as the severity of the internal structural damage of the asphalt pavement increases. The degree of jolt caused by a vehicle passing over a transverse crack defect is related to the difference between the deflection value at the defect and the deflection value of the intact asphalt pavement structure.

[0024] In order to achieve rapid detection of transverse crack types in semi-rigid asphalt pavements, it is necessary to quantify the degree of bumping when vehicles pass through transverse crack disease sites, and establish a correlation between the degree of vehicle bumping and the severity of transverse crack disease on the pavement. A spirit level is a commonly used measuring tool for measuring small angles. When placed on a certain working plane, it can measure the bumps caused by vibrations on the working plane, that is, the slope difference caused by the vibrations of the working plane. A vehicle-mounted spirit level is placed in a moving vehicle. When the vehicle is bumped during driving, the vehicle fluctuations at the driving section are reflected by recording the difference in readings of the spirit level. To this end, the present invention has developed a detection method for identifying transverse crack types in asphalt pavements based on a vehicle-mounted spirit level based on existing detection technology. Transverse cracks are currently the most important disease of semi-rigid base asphalt pavements. Rapid detection and identification of transverse crack types and evaluation of their damage levels provide efficient, scientific and convenient methods for maintenance decisions on semi-rigid base asphalt pavements. The following is a detailed introduction to the method in this application.

[0025] like Figure 1 The semi-rigid base asphalt pavement transverse crack detection method shown includes the following steps: S10: Obtain the location information of transverse cracks in the asphalt pavement and detect the internal information of the cracks; It should be pointed out here that in the embodiments of the present invention, there are multiple ways to obtain the location information of transverse cracks, and high-precision equipment, such as three-dimensional scanners and three-dimensional ground penetrating radars, can be used to detect the depth and development of the cracks. Through the setting of this step, basic data is provided for subsequent classification to ensure the accuracy of the detection data.

[0026] S20: Obtain the deflection change value and the level meter reading difference when the vehicle passes through a road surface with transverse cracks at different vehicle speeds; in an embodiment of the present invention, different vehicle speeds may affect the interaction between the vehicle and the road surface, and a more comprehensive evaluation can be obtained by testing the performance at different vehicle speeds.

[0027] S30: The vehicle speed at which the deflection change value and the level meter reading value are the largest is selected as the optimal driving speed; by comparing the data at different vehicle speeds, the most sensitive and reliable crack information during vehicle inspection can be obtained.

[0028] S40: Obtain the reading difference of the level meter at different crack types at the optimal driving speed, and determine the range of the level meter reading difference for different transverse crack types; since surface cracks and reflection cracks usually have different structural effects, the difference in their effects on deflection and bumps can be used to distinguish the two.

[0029] S50: According to the determined range of the level reading difference, determine the type of transverse crack corresponding to the subsequent level reading at the optimal driving speed. In the embodiment of the present invention, the bumpiness of the surface crack is much smaller than the bumpiness of the reflection crack. After the standard of the crack type is determined, the specific type of the transverse crack on the road surface is determined by the level reading difference.

[0030] In the above embodiment, according to the degree of bumps caused by vehicle driving corresponding to the transverse cracks in different semi-rigid base asphalt pavements, the optimal driving speed is obtained on the road surface with known cracks to obtain the deflection value and the horizontal reading difference, and different crack types are determined according to the range of the horizontal reading difference. After verification, the type of crack can be quickly and accurately obtained only by the level reading difference during vehicle driving. Compared with the existing technology, it will not cause damage to the road surface, and the speed and accuracy of acquisition are guaranteed.

[0031] On the basis of the above-mentioned embodiment, in the embodiment of the present invention, in step S10, a 3D scanner is used in combination with a 3D ground penetrating radar to detect the location of the transverse cracks. The 3D scanner can obtain the 3D spatial data of the road cracks with high precision, help locate the cracks and conduct in-depth analysis; the 3D ground penetrating radar detects the structural state of the underground layer through the reflection of the ground signal, including whether the cracks have developed to the base layer and the damage of its internal structure.

[0032] Furthermore, when detecting the internal information of the crack, the signal collected by the three-dimensional ground penetrating radar is subjected to background removal, noise reduction and filtering, and the internal information of the crack is determined by judging the signal amplitude anomaly and the continuity of the event axis. The accuracy of the signal can be ensured by background removal, noise reduction and filtering, and interference caused by factors such as the external environment and equipment failure can be eliminated. In an embodiment of the present invention, judging the signal amplitude anomaly and the continuity of the event axis can effectively determine the extension and change trend of the crack, and then judge whether it is a reflection crack or a surface crack.

[0033] In order to further ensure the accuracy of the detection, in step S10, after determining the internal information of the cracks, some transverse crack diseases are cored for verification. By coring some cracks, the internal information of the cracks provided by the ground penetrating radar or the three-dimensional scanner can be verified, and by comparing with the actual pavement structure, the accuracy of the detection is ensured to avoid misjudgment of the crack type. According to the core sampling results, the bubble offset in the level meter at the surface cracking only and the base reflection crack is compared, and the critical value of the bubble offset in the level meter at these two different transverse crack types is taken as the basis for the subsequent use of the level meter to distinguish the transverse crack types.

[0034] Specifically, in an embodiment of the present invention, in step S20, a laser dynamic deflection detection vehicle equipped with a vehicle-mounted level meter is used to perform multiple tests at different driving speeds. This type of equipment is a common means of evaluating the bearing capacity of a road. By using it together with the vehicle-mounted level meter, the road deformation and the degree of bumpiness during vehicle driving can be obtained synchronously. When placing the level meter, (1) first establish a constant horizontal working platform for the level meter in a common detection vehicle to avoid the bubbles in the level meter from generating offsets that are irrelevant to the detection of transverse cracks due to the vehicle passing through the transverse slope, longitudinal slope, super-high section and other areas of the road during driving. The main method is to select a metal container, and use the hot pressing method to hot press the polytetrafluoroethylene material onto the metal surface. At the same time, propylene glycol and a thicker lightweight floating plate are added to the metal container. The edge of the lightweight floating plate can slide on the inner wall of the metal container, and then the universal level meter is placed. On the lightweight floating plate, the purpose of using propylene glycol is not only to keep the level gauge in a horizontal state, but also because of its high viscosity and density, it can prevent the vehicle from bumping and causing the floating plate to produce sudden oscillations that affect the level gauge reading. The purpose of spraying a polytetrafluoroethylene coating on the metal surface is to prevent propylene glycol from adhering to the wall of the container, which causes a lag effect in the movement of bubbles. (2) Secondly, a universal level with the largest range specification is selected for testing. The universal level is placed in the above device and in a road maintenance vehicle. The vehicle is driven at speeds of 70, 80, 90, 100, and 110 km / s, and the maximum value of the bubble displacement of the level gauge when the vehicle passes through the transverse crack disease is recorded. The maximum value of the bubble displacement of the level gauge when the vehicle passes through each crack is averaged, and the speed with the largest average value is selected as the subsequent optimal detection speed, that is, the speed at which the vehicle is most bumpy when driving through the transverse crack. The range specification of the universal level is selected based on the maximum value of the bubble displacement of the level gauge at all speeds.

[0035] In the embodiment of the present invention, in step S20, the vehicle-mounted level meter is leveled before detection to eliminate the influence of the transverse slope and the longitudinal slope of the road surface. Since the transverse slope and the longitudinal slope have a significant invisible effect on the bumps generated when the vehicle is driving, eliminating such errors by leveling is a prerequisite for ensuring accurate measurement results.

[0036] In the embodiment of the present invention, in step S30, the deflection change value and the level reading difference at the crack defect at each driving speed are tested multiple times and the results are averaged. By testing multiple times and taking the average value, accidental errors can be reduced and the reliability of data can be improved. This design method is helpful to further improve the optimal driving speed and the accuracy of detection.

[0037] In an embodiment of the present invention, in step S40, the difference in the level reading of the surface crack is smaller than the value of the reflection crack. The influence of the surface crack is small, while the reflection crack has a greater influence due to the serious damage to the base layer, and the vehicle bump caused will be more obvious.

[0038] In an embodiment of the present invention, in order to further detect the damage severity of the reflective cracks, step S40 further includes obtaining a deflection change value at an optimal driving speed, wherein the deflection change value is used to evaluate the severity of the reflective cracks.

[0039] (1) In order to obtain more comprehensive detection results, in an embodiment of the present invention, step S60 is also included: using the least squares method to fit the deflection change value and the level reading difference under different crack disease degrees, and determining the classification and evaluation system of the crack type through the level reading difference range of different transverse crack types. Through the fitting of the least squares method, a mathematical model can be established for crack types of different severity, so that the relationship between the level reading difference and the deflection change value is clearer, which provides a theoretical basis for subsequent automated detection and crack evaluation. In an embodiment of the present invention, since the bumps generated by the vehicle come from the sudden change of road deformation during the vehicle driving process, the maximum value of the bubble offset of the level at different transverse crack types measured is linearly fitted with the deflection difference between the disease center and the intact part of the corresponding transverse crack, and the optimization algorithm is used to optimize the fitting parameters. The corresponding theoretical equation and objective function in the parameter optimization process are as follows, which can be used for the subsequent level to detect the degree of transverse disease type, predict the deflection difference according to the maximum value of the bubble offset of the level, and then evaluate the severity of the transverse crack disease of the asphalt pavement. In an embodiment of the present invention, the fitting function is: Where Y is the theoretical value of deflection, X is the maximum value of the bubble displacement of the level, t1 and t2 are fitting parameters, is the objective function. When the fitting parameters t1 and t2 reach the optimal value, the objective function is maximum.

[0040] Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for detecting transverse cracks in a semi-rigid base asphalt pavement, characterized in that: The following steps are involved: S10: Obtaining location information of transverse cracks on the asphalt pavement and detecting internal information of the cracks; S20: obtaining deflection change values ​​and level reading differences when the vehicle passes through a road surface with transverse cracks at different speeds; S30: selecting the vehicle speed at which the deflection change value and the level meter reading value are the largest as the optimal driving speed; S40: obtaining the reading difference of the level meter at different crack types at the optimal driving speed, and determining the range of the reading difference of the level meter for different transverse crack types; S50: Determine, according to the determined range of the difference in the level readings, the type of transverse crack corresponding to the subsequent level readings at the optimal driving speed.

2. The method for detecting transverse cracks in a semi-rigid base asphalt pavement according to claim 1 is characterized in that: In step S10, a three-dimensional scanner combined with a three-dimensional ground penetrating radar is used to detect the location of the transverse crack.

3. The method for detecting transverse cracks in a semi-rigid base asphalt pavement according to claim 2 is characterized in that: In step S10, when detecting the internal information of the crack, after background removal, noise reduction and filtering processing are performed on the signal collected by the three-dimensional ground penetrating radar, the internal information of the crack is determined by judging the signal amplitude anomaly and the continuity of the event axis.

4. The method for detecting transverse cracks in a semi-rigid base asphalt pavement according to claim 3 is characterized in that: In step S10, after determining the internal information of the cracks, coring verification is performed on some transverse crack defects.

5. The method for detecting transverse cracks in a semi-rigid base asphalt pavement according to claim 1 is characterized in that: In step S20, a laser dynamic deflection detection vehicle equipped with a vehicle-mounted level meter is used to perform multiple detections at different driving speeds.

6. The method for detecting transverse cracks in a semi-rigid base asphalt pavement according to claim 5 is characterized in that: In step S20, the vehicle-mounted level gauge is leveled before detection to eliminate the influence of the transverse slope and the longitudinal slope of the road surface.

7. The method for detecting transverse cracks in a semi-rigid base asphalt pavement according to claim 1 is characterized in that: In step S30, the deflection change value and the level reading difference at the crack defect at each driving speed are detected multiple times and the results are averaged.

8. The method for detecting transverse cracks in a semi-rigid base asphalt pavement according to claim 1 is characterized in that: In step S40, the difference in the level meter readings of the surface cracks is smaller than the value of the reflective cracks.

9. The method for detecting transverse cracks in a semi-rigid base asphalt pavement according to claim 1, characterized in that: In step S40, it also includes obtaining a deflection change value at an optimal driving speed, wherein the deflection change value is used to evaluate the severity of the reflective crack.

10. The method for detecting transverse cracks in a semi-rigid base asphalt pavement according to claim 9, characterized in that: The step S60 is also included: using the least square method to fit the deflection change values ​​and the level reading differences under different crack damage degrees, and determining the classification and evaluation system of the crack type through the level reading difference ranges of different transverse crack types.

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