A method for detecting water-rich areas in asphalt layers using ground-penetrating radar

Abstract

The present invention relates to the technical field of road engineering detection, and specifically to a method for detecting water-rich areas in asphalt layers using ground-penetrating radar. S1: Select a section of the road to be tested as the test section, detect the test section using a three-dimensional ground-penetrating radar, and calculate the in-layer cumulative water-rich index of all detection points in the test section; S2: Arrange the in-layer cumulative water-rich indexes of all detection points in step S1 in a sequence according to the magnitude, and select m points at the same interval from the sequence as judgment points. Take cores to verify whether each judgment point is water-rich, and use the in-layer cumulative water-rich index of the judgment point that is water-rich and has the smallest in-layer cumulative water-rich index as the judgment value P0; S3: Detect the road surface to be tested using a three-dimensional ground-penetrating radar, calculate the in-layer cumulative water-rich index P of the road surface to be tested according to formula 1. If P≥P0, it is judged that the position is water-rich. The present invention can quantitatively evaluate the water-rich situation in the asphalt layer through the in-layer cumulative water-rich index, causes little damage to the road surface, and has high detection efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of road engineering detection, and specifically to a method for detecting water-rich areas in asphalt layers using ground-penetrating radar. Background Technique

[0002] Water damage to asphalt pavements is caused by water penetrating into the interior of the asphalt layer and being unable to drain quickly, thus eroding the interface between the asphalt and the aggregate, causing the stripping of the asphalt mixture, and thus evolving into diseases such as mixture loosening and pavement potholes, seriously endangering driving safety, comfort, and service life.

[0003] Accurately and timely detecting water damage to asphalt pavements enables decision-makers to plan effective maintenance and repair activities for in-service pavements and keep the pavement network in an acceptable state. Compared with the costs of structural repair and reconstruction activities in the case of severe damage, timely detection of water damage will extend the service life of the pavement and significantly reduce its life cycle cost.

[0004] Currently, the main methods for detecting water damage to asphalt pavements by the direct coring method are the direct coring method and the ground-penetrating radar method.

[0005] The principle of the direct coring method is simple and the calculation is accurate. However, this method is destructive, time-consuming, labor-intensive, and requires closing the lane.

[0006] The ground-penetrating radar method emits a certain intensity of ultra-high frequency (10 6 ~10 9 Hz) broadband narrow pulse electromagnetic wave into the ground through a broadband time-domain transmitting antenna. When the electromagnetic wave encounters the interface of different media during the downward propagation process, part of the electromagnetic wave will be reflected back to the ground, and part of the electromagnetic wave will continue to propagate downward after transmission. The electromagnetic wave reflected back to the ground is received by the receiving antenna ( Figure 1 ). Each received record forms a radar waveform diagram. When the electromagnetic wave propagates in the underground medium, its path, electromagnetic field strength, and waveform will change with the dielectric properties and geometric morphology of the medium it passes through. When the electromagnetic wave propagates to a position where the dielectric constant changes, a reflection signal is immediately generated. The reflection coefficient can be expressed as:

[0007]

[0008] Where ε 1 is the dielectric constant of the medium above the reflection interface, and ε 2is the dielectric constant of the medium below the reflection interface. The greater the difference in dielectric constants on both sides of the reflection interface, the greater the reflection amplitude. Some studies have shown (Zhao Jiang. Response of ground penetrating radar to fractures and water-rich zones in tunnels. [J]. Journal of Changchun Institute of Technology (Natural Science Edition), 2014, 15(3): 94-96.) that the radar waveform diagram of the water-rich zone shows: strong reflection waves, low-frequency enrichment, and relatively good continuity of the in-phase axis. Therefore, the possible water-rich areas in the asphalt pavement can be evaluated by the amplitude and period of the waveform curve in the radar waveform diagram. However, at present, the water-rich area can only be evaluated by a rough estimate with the naked eye according to the intensity of the reflection wave in the radar waveform diagram, which is not only time-consuming and laborious, but also has low evaluation accuracy. Summary of the Invention

[0009] The purpose of the present invention is to solve the above-mentioned deficiencies of the prior art, and provide a method for detecting water-rich areas in asphalt layers using ground penetrating radar. By accumulating the water-rich index within the layer, the water-rich situation in the asphalt layer can be quantitatively evaluated, with little damage to the road surface and high detection efficiency.

[0010] The technical problems to be solved are achieved by the following technical solutions:

[0011] A method for detecting water-rich areas in asphalt layers using ground penetrating radar includes the following steps:

[0012] S1. Select a section of the road to be measured as the test section, detect the test section through a three-dimensional ground penetrating radar, and calculate the in-layer cumulative water-rich index of all detection points in the test section according to Equation 1 through the radar waveform diagram:

[0013]

[0014] In Equation 1, P is the in-layer cumulative water-rich index, S i represents the area enclosed by the positive part of the amplitude in the i-th wave between the reflection wave on the surface of the asphalt layer and the reflection wave at the bottom of the asphalt layer and the time axis, and S 0 is the area enclosed by the positive part of the amplitude of the reflection wave on the surface of the asphalt layer and the time axis, and n is the number of positive parts of the amplitude between the reflection wave on the surface of the asphalt layer and the reflection wave at the bottom of the asphalt layer;

[0015] S2. Arrange the in-layer cumulative water-rich indexes of all detection points in step S1 in a sequence according to the size order, select m points at the same interval from the sequence as judgment points, take cores to verify whether the m judgment points are water-rich, and according to the core-taking verification situation, take the in-layer cumulative water-rich index of the judgment point with the smallest in-layer cumulative water-rich index among the water-rich judgment points as the judgment value P 0 ;

[0016] S3. Detect the road surface to be measured through a three-dimensional ground penetrating radar, calculate the in-layer cumulative water-rich index P of the road surface to be measured according to Equation 1. If P ≥ P0 , it is determined that the position is water-rich.

[0017] Compared with the prior art, the beneficial effects of the method for detecting water-rich areas in asphalt layers using ground-penetrating radar according to the present invention are as follows: (1) The ratio of the sum of the areas enclosed by the positive-amplitude part between the surface reflection wave and the bottom reflection wave of the asphalt layer in the radar waveform diagram to the time axis to the area enclosed by the positive-amplitude part of the surface reflection wave of the asphalt layer and the time axis is used as the in-layer cumulative water-rich index, which can quantitatively evaluate the water-rich situation in the asphalt layer. That is, the larger the in-layer cumulative water-rich index, the greater the possibility of water-richness, so that the water-rich areas in the asphalt layer can be accurately detected. Moreover, since the transmission frequencies of the radar antennas are sometimes different, there will be a large difference in the amplitude intensity levels of the received reflection signals, and the results calculated in this way will vary greatly. The in-layer cumulative water-rich index in the present invention is a dimensionless quantity, which can minimize the influence caused by different transmission frequencies; (3) Only a small number of core samplings are needed to verify and obtain the judgment value P 0 , and by comparing the in-layer cumulative water-rich index of the road surface to be measured with P 0 , the water-rich areas in the asphalt layer can be detected, with little damage to the road surface and high detection efficiency.

[0018] Another technical solution of the present invention is that the calculation method of the area S enclosed by the positive-amplitude part of the reflection wave and the time axis is as follows:

[0019] The positive-amplitude part of the reflection wave is discretized into N points and calculated according to Equation 2:

[0020]

[0021] In Equation 2, y j is the amplitude intensity of the jth discrete point of the positive-amplitude part of the reflection wave, and Δt is the time interval between two adjacent discrete points.

[0022] Another technical solution of the present invention is that the length of the test section is 1000 meters.

[0023] Another technical solution of the present invention is that m = 9. Description of the Drawings

[0024] Figure 1 It is a schematic diagram of the reflection principle of a three-dimensional ground-penetrating radar.

[0025] Figure 2 It is the radar waveform diagram in Example 1.

[0026] In the figure: 1, asphalt layer; 2, water-rich area; 3, reflection wave on the surface of the asphalt layer; 4, bottom reflection wave of the asphalt layer. Detailed Embodiments

[0027] To make the objectives, technical solutions, and advantages of the technical solutions of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings of specific embodiments of the present disclosure. The same reference numerals in the drawings represent the same components. It should be noted that the described embodiments are some, but not all, of the embodiments of the present disclosure. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present disclosure without creative efforts fall within the scope of protection of the present disclosure.

[0028] Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meanings as understood by those of ordinary skill in the art to which the present disclosure pertains. The "first", "second", and similar terms used in the specification and claims of the present patent application do not denote any order, quantity, or importance, but are only used to distinguish different components. Similarly, terms such as "a" or "an" do not necessarily denote a quantity limitation. The terms "comprising" or "including" and similar terms mean that the elements or items appearing before the term cover the elements or items listed after the term and their equivalents, without excluding other elements or items. The terms "connected" or "coupled" and similar terms are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right", etc. are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0029] Embodiment 1

[0030] This embodiment provides a method for detecting water-rich areas in asphalt layers using ground-penetrating radar, including the following steps:

[0031] S1. Select a section of the road section to be measured as the test section. In this embodiment, the length of the test section is 1000 meters, and the test section is detected by a three-dimensional ground-penetrating radar. Refer to Figure 2 , and through the radar waveform diagram, calculate the in-layer cumulative water-rich index of all detection points in the test section according to Equation 1:

[0032]

[0033] In Equation 1, P is the in-layer cumulative water-rich index, and S i represents the area enclosed by the positive-amplitude part of the i-th wave between the asphalt layer surface reflection wave 3 and the asphalt layer bottom reflection wave 4 and the time axis ( Figure 2 the black area in), and S 0 is the area enclosed by the positive-amplitude part of the asphalt layer surface reflection wave 3 and the time axis, and n is the number of positive-amplitude parts between the asphalt layer surface reflection wave 3 and the asphalt layer bottom reflection wave 4;

[0034] According to the reflection principle of electromagnetic waves between different media and the amplitude and phase of waves in the radar waveform diagram, the surface reflection wave and the bottom reflection wave of the asphalt layer in the radar waveform diagram are judged. The specific judgment method is well-known technology in this field and will not be elaborated here.

[0035] The three-dimensional ground penetrating radar in this embodiment is an air-coupled radar, and the radar waveform diagram is a single-channel waveform. As Figure 2 shown, the wave between the surface reflection wave 3 of the asphalt layer and the bottom reflection wave 4 of the asphalt layer can be considered as the reflection wave of the water-rich area.

[0036] The calculation method of the area S enclosed by the positive part of the reflection wave amplitude and the time axis is:

[0037] Discretize the positive part of the reflection wave amplitude into N points and calculate according to Equation 2:

[0038]

[0039] In Equation 2, y j is the amplitude intensity of the jth discrete point of the positive part of the reflection wave amplitude, and Δt is the time interval between two adjacent discrete points.

[0040] S2. Arrange the in-layer cumulative water-rich indexes of all detection points in step S1 in ascending order, and select 9 points as judgment points at the same interval from the sequence. Core test whether the 9 judgment points are water-rich. According to the core test situation, take the in-layer cumulative water-rich index of the judgment point that is water-rich and has the smallest in-layer cumulative water-rich index as the judgment value P 0 ;

[0041] S3. Detect the road surface to be measured through a three-dimensional ground penetrating radar, calculate the in-layer cumulative water-rich index P of the road surface to be measured according to Equation 1. If P≥P 0 , it is judged that the position is water-rich.

[0042] The above is only the specific implementation manner of the present disclosure, but the protection scope of the embodiments of the present disclosure is not limited thereto. Any person skilled in the art can easily think of changes, substitutions or combinations within the technical scope disclosed by the embodiments of the present disclosure or under the idea disclosed by the embodiments of the present disclosure, and all should be covered by the protection scope of the embodiments of the present disclosure.

Claims

1. A method for detecting water-rich areas in asphalt layers using ground penetrating radar, comprising the following steps: S1. Select a section in the road section to be measured as the test section, detect the test section using a three-dimensional ground penetrating radar, and calculate the in-layer cumulative water-rich index of all detection points in the test section according to Equation 1 through the radar waveform diagram: In Equation 1, P is the cumulative water-rich index within the layer, and S i represents the area enclosed by the positive amplitude part of the i-th wave between the asphalt layer surface reflection wave (3) and the asphalt layer bottom reflection wave (4) and the time axis. S 0 is the area enclosed by the positive amplitude part of the asphalt layer surface reflection wave (3) and the time axis. n is the number of positive amplitude parts between the asphalt layer surface reflection wave (3) and the asphalt layer bottom reflection wave (4); S2. Arrange the in-layer cumulative water-rich indexes of all detection points in step S1 in ascending order to form a sequence, select m points from the sequence at the same interval as judgment points, take cores to verify whether the m judgment points are water-rich, and according to the core-taking verification results, use the in-layer cumulative water-rich index of the judgment point that is water-rich and has the smallest in-layer cumulative water-rich index as the judgment value P 0 ; S3. Detect the road surface to be measured by three-dimensional ground penetrating radar, calculate the in-layer cumulative water-rich index P of the road surface to be measured according to Equation 1. If P ≥ P 0 , it is determined that the position is water-rich.

2. The method for detecting water-rich areas in asphalt layers using ground penetrating radar according to claim 1, characterized in that the calculation method of the area S enclosed by the positive part of the reflected wave amplitude and the time axis is: discretize the positive part of the reflected wave amplitude into N points and calculate according to Equation 2: In Equation 2, y j is the amplitude intensity of the j-th discrete point where the amplitude of the reflected wave is positive, and Δt is the time interval between two adjacent discrete points.

3. The method for detecting water-rich areas in asphalt layers using ground penetrating radar according to claim 1, characterized in that the length of the test section is 1000 meters.

4. The method for detecting water-rich areas in asphalt layers using ground penetrating radar according to claim 1, characterized in that m＝9。

Images