Subgrade and Pavement Hidden Defect Detection Method and Device Based on Electric Sensing Skin

Abstract

The present invention discloses a method and device for detecting hidden defects in roadbed pavement based on an electro-sensing skin, which relates to the field of non-destructive testing of concrete. The specific steps are as follows: using a composite film electro-sensing skin as a conductive coating for a concrete insulator, and pre-setting a concrete electrode arrangement device; injecting a continuous current into the concrete electrode arrangement device, and collecting voltage data of the concrete electrode arrangement device; using the resistance tomography technology to reconstruct an image of the composite film electro-sensing skin based on the voltage data, obtaining a real-time monitoring image of the concrete through the change of the conductivity of the composite film electro-sensing skin, and observing hidden defects in the roadbed pavement. The concrete electrodes in the present invention can be inserted and easily spliced, solving the problem that the conventional resistance tomography non-destructive testing system cannot accurately measure the change of the concrete conductivity, and meeting the requirement of observing hidden defects in the roadbed pavement without damaging the road surface structure.

Description

Technical Field

[0001] The present invention relates to the technical field of non-destructive testing of concrete, and more particularly to a method and device for detecting hidden defects in subgrade and pavement based on an electric sensing skin. Background Art

[0002] At present, the degradation of old concrete structures has become a global problem because it may threaten the structural integrity of buildings, resulting in huge losses of property and lives. Therefore, many countries have allocated a large amount of construction budget for the repair and maintenance of old structures. In the subgrade and pavement projects in our country, for the hidden concrete defects that cannot be observed by the naked eye in sections with large vehicle flow and heavy loads, methods such as truncating and excavating are often used for detection. Therefore, the accurate evaluation of hidden defects is extremely urgent. Electrical resistance tomography (ERT) technology, as a new non-destructive testing technology, has the characteristics of low cost, non-invasive, visualization, good safety performance, etc., and is widely used in the fields of geophysical exploration, groundwater detection and exploration, and non-destructive testing of concrete. Since the commonly used ERT non-destructive testing system cannot normally detect the change in the conductivity of concrete as an insulator, there is currently no set of electrical resistance tomography (ERT) non-destructive testing systems applied to concrete insulators in the world. Therefore, for those skilled in the art, how to observe the hidden defects in subgrade and pavement without damaging the road surface structure is an urgent problem to be solved. Summary of the Invention

[0003] In view of this, the present invention provides a method and device for detecting hidden defects in subgrade and pavement based on an electric sensing skin to solve the problems existing in the background art.

[0004] To achieve the above object, the present invention adopts the following technical solutions: A method for detecting hidden defects in subgrade and pavement based on an electric sensing skin, the specific steps include the following:

[0005] Using a composite film electric sensing skin as a conductive coating for the concrete insulator, and pre-installing a concrete electrode arrangement device in the monitored concrete structure;

[0006] Injecting a continuous current into the concrete electrode arrangement device, and collecting the voltage data of the concrete electrode arrangement device;

[0007] Using the resistance tomography technology to reconstruct the image of the composite film electric sensing skin with the voltage data, and obtaining a differential image of the change in conductivity before and after the damage of the monitored concrete structure;

[0008] Through the differential image, hidden defects on the roadbed and pavement are observed. Optionally, the concrete electrode arrangement device is buried inside the concrete. The specific arrangement method is as follows: when the concrete is poured to half of its thickness, the prepared aqueous polyurethane / carbon nanotube / silica fume mixed solution is sprayed onto the upper surface of the concrete to form the lower part of the aqueous polyurethane / carbon nanotube / silica fume composite film electrical sensing skin. When it reaches a certain thickness, grid copper sheet electrodes are arranged in an array on the aqueous polyurethane / carbon nanotube / silica fume composite film electrical sensing skin. One end of a silver wire is pasted on the surface of each grid copper sheet electrode with conductive silver paste. After the silver wire is led out according to the designed path, the prepared aqueous polyurethane / carbon nanotube / silica fume mixed solution is sprayed onto the surface where the grid copper sheet electrodes, conductive silver paste, and silver wire are located by a high-pressure spray gun to complete the upper part of the aqueous polyurethane / carbon nanotube / silica fume composite film electrical sensing skin. Finally, the remaining precast concrete is poured.

[0009] Optionally, the composite film electrical sensing skin is an aqueous polyurethane / carbon nanotube / silica fume composite film electrical sensing skin. The aqueous polyurethane / carbon nanotube / silica fume composite film electrical sensing skin is prepared by mixing a dispersion component obtained by mixing carbon nanotube powder and aqueous polyurethane, and a solid powder component obtained by mixing bulk cement and silica fume. The dispersion component and the solid powder component are mixed and stirred in proportion, and the prepared mixed solution is evenly sprayed onto the surface of the measured concrete by a high-pressure spray gun to obtain the aqueous polyurethane / carbon nanotube / silica fume composite film electrical sensing skin.

[0010] On the other hand, a hidden defect detection device for roadbed and pavement based on an electrical sensing skin is provided, including a precast concrete electrode arrangement module, a voltage collector, an alternating current power supply, and a data processing computer. Among them, the precast concrete electrode arrangement module is buried inside the concrete. The precast concrete electrode arrangement module is connected to the voltage collector, the alternating current power supply is connected to the voltage collector, and the voltage collector is connected to the data processing computer.

[0011] Optionally, the precast concrete electrode arrangement module includes an aqueous polyurethane / carbon nanotube / silica fume composite film electrical sensing skin, grid copper sheet electrodes, conductive silver paste, and silver wires. Among them, the aqueous polyurethane / carbon nanotube / silica fume composite film electrical sensing skin is placed inside the measured concrete, and the silver wires are pasted on the grid copper sheet electrodes through the conductive silver paste.

[0012] Optionally, it further includes an electrode converter. One end of the electrode converter is connected to the silver wire, and the other end is connected to the voltage collector.

[0013] Optionally, it further includes DuPont wire connectors, which are divided into male and female connectors. The male DuPont wire connector is connected to the silver wire conductor, and the female DuPont wire connector is connected to the electrode converter.

[0014] Optionally, the male DuPont wire connector and the female DuPont wire connector are detachably installed.

[0015] Optionally, the grid copper sheet electrodes are arranged in the precast concrete electrode arrangement module in an array form or a surrounding form.

[0016] Through the above technical solutions, compared with the prior art, the present invention discloses a method and device for detecting hidden defects in subgrade and pavement based on electric sensing skin, having the following beneficial technical effects:

[0017] 1. A waterborne polyurethane / carbon nanotube / silica powder composite film electric sensing skin with high electrical conductivity performance, current-carrying capacity and mechanical properties is studied and prepared, and is applied to the electrical resistance tomography (ERT) non-destructive testing system for detecting hidden defects in subgrade and pavement. The change in the electrical conductivity of the concrete insulator can be inversely characterized by monitoring the change in the electrical conductivity of the electric sensing skin, and finally, based on the data processing software, the electrical conductivity distribution map of the concrete is reconstructed to reflect the hidden defects that cannot be observed by the naked eye in the concrete, solving the problem that the conventional electrical resistance tomography (ERT) non-destructive testing system cannot accurately measure the change in the electrical conductivity of the concrete;

[0018] 2. A precast concrete electrode arrangement device that can be buried is prepared, greatly reducing the impact on the construction process of the concrete structure to be measured;

[0019] 3. The arrangement method of the electrode wires inside the concrete is optimized. The grid copper sheet electrodes are used to make the electrodes in close contact with the waterborne polyurethane / carbon nanotube / silica powder composite film electric sensing skin, which has a certain improvement in reducing the voltage acquisition error;

[0020] 4. An inversion formula for accurately characterizing the reconstructed image of hidden defects is established, revealing the inversion law of the reconstructed image of hidden defects in concrete; a real-time monitoring system for hidden defects in concrete is developed, providing a new solution for implementing detection and early warning control of major projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0022] Figure 1Schematic diagram of the device structure of the present invention;

[0023] Figure 2 Schematic diagram of the array arrangement of the grid copper sheet electrodes of the present invention;

[0024] Figure 3 Schematic diagram of the surrounding arrangement of the grid copper sheet electrodes of the present invention;

[0025] Figure 4 Side view of the arrangement of the grid copper sheet electrodes of the present invention;

[0026] Figure 5 Schematic diagram of the positional relationship between the device of the present invention and the concrete to be measured;

[0027] Wherein: 1 is a precast concrete electrode arrangement module, 2 is a waterborne polyurethane / carbon nanotube / silica powder composite film electrical sensing skin, 3 is a grid copper sheet electrode, 4 is a conductive silver paste, 5 is a silver wire conductor, 6 is a Dupont wire joint, 7 is an alternating current power supply, 8 is a voltage collector, 9 is an electrode converter, 10 is a data processing computer, 11 is data processing software, and 12 is a roadbed and pavement concrete structure. Specific embodiments

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0029] Embodiment 1 of the present invention discloses a method for detecting hidden defects in roadbeds and pavements based on an electrical sensing skin. The specific steps are as follows:

[0030] Use a waterborne polyurethane / carbon nanotube / silica powder composite film electrical sensing skin as a conductive coating for concrete insulators, and preset a concrete electrode arrangement device;

[0031] Inject a continuous current into the concrete electrode arrangement device and collect the voltage data of the concrete electrode arrangement device;

[0032] Use electrical impedance tomography technology to reconstruct the image of the waterborne polyurethane / carbon nanotube / silica powder composite film electrical sensing skin with the voltage data,

[0033] Obtain a real-time monitoring image of the concrete through the conductivity change of the waterborne polyurethane / carbon nanotube / silica powder composite film electrical sensing skin, and observe hidden defects in the roadbed and pavement.

[0034] The main difference between Electrical Resistance Tomography (ERT) and other traditional non-destructive testing methods is that ERT is an electrical means. ERT mainly studies and reconstructs images of the electrical properties (mainly resistivity and conductivity) of the object to be measured. It arranges electrodes on the surface of the object to be measured, then injects a certain current (usually a low-frequency alternating current) at the electrode positions, and collects the corresponding voltage data at the remaining electrodes. Finally, using a certain image reconstruction algorithm, it inversely calculates the distribution of the electrical parameters of the object to be measured from the voltage data and presents it in the form of a visualized image.

[0035] According to the different image reconstruction methods, ERT technology can be divided into two categories: absolute ERT imaging and differential ERT imaging (hereinafter referred to as absolute imaging and differential imaging). Among them, differential imaging is globally linearized, and its calculation process is relatively simple, requiring at least two sets of voltage data corresponding to the same target in two states. The method of the present invention aims to reconstruct the change in the conductivity distribution of the object to be measured in the initial state (before damage) and the final state (after damage). By performing ERT measurements on the object to be measured in the two states and using a specific differential imaging algorithm to calculate the difference in the conductivity distribution of the object to be measured in the two states, a differential image that can reflect the change in conductivity before and after the object to be measured is damaged is finally reconstructed. Therefore, when the initial conductivity distribution of the object to be measured is available, the linearized difference can provide an effective method for quickly locating the position of the conductivity change.

[0036] Before and after the deformation of the electrically sensitive skin, the voltage data in the initial state (before deformation) and the final state (after deformation) of the electrically sensitive skin can be measured respectively, and a specific differential imaging algorithm is used to calculate the difference in the conductivity distribution of the electrically sensitive skin in the initial state and the final state, and a differential image that can reflect the change in conductivity before and after the object to be measured is damaged is reconstructed. This differential image can reflect the deformation or defect distribution of the electrically sensitive skin. And the waterborne polyurethane / carbon nanotube / silica powder composite film electrically sensitive skin is in close contact with the concrete and deforms synergistically, so the hidden defect distribution inside the concrete can be reflected by the deformation or defect distribution of the electrically sensitive skin.

[0037] Import the voltage data into the data processing computer. Using the forward and inverse problem calculation models established in the data processing software for ERT, the electrical conductivity distribution of the waterborne polyurethane / carbon nanotube / silica powder composite film electro-sensing skin in the initial state (before deformation) and the final state (after deformation) is obtained based on the electrical resistance tomography technology of the equipotential line back-projection method. A differential image of the change in electrical conductivity before and after damage is reconstructed. This image can reflect the deformation or defect distribution of the electro-sensing skin. Since the electro-sensing skin is in close contact with the concrete and deforms synergistically, the deformation or defect distribution of the electro-sensing skin can be used to reflect the hidden defect distribution inside the concrete, so as to obtain a real-time monitoring image of the inside of the concrete.

[0038] Furthermore, bury the concrete electrode arrangement device inside the concrete. The specific arrangement method is as follows: When the concrete is poured to half of its thickness, spray the prepared waterborne polyurethane / carbon nanotube / silica powder mixed solution onto the upper surface of the concrete to form the lower part of the waterborne polyurethane / carbon nanotube / silica powder composite film electro-sensing skin. When it reaches a certain thickness, arrange the grid copper sheet electrodes in an array on the waterborne polyurethane / carbon nanotube / silica powder composite film electro-sensing skin. Paste one end of the silver wire to the surface of each grid copper sheet electrode with conductive silver paste. After leading out the silver wire according to the designed path, then spray the prepared waterborne polyurethane / carbon nanotube / silica powder mixed solution onto the surface where the grid copper sheet electrodes, conductive silver paste, and silver wire are located to complete the upper part of the waterborne polyurethane / carbon nanotube / silica powder composite film electro-sensing skin. Finally, pour the remaining precast concrete.

[0039] The waterborne polyurethane / carbon nanotube / silica powder composite film electro-sensing skin is prepared by mixing carbon nanotube powder with waterborne polyurethane to prepare the dispersion liquid component, and grinding bulk cement and silica powder to obtain the solid powder component. Mix and stir the dispersion liquid component and the solid powder component in proportion, and use a high-pressure spray gun to evenly spray the prepared mixed liquid onto the surface of the measured concrete to obtain the waterborne polyurethane / carbon nanotube / silica powder composite film electro-sensing skin.

[0040] Embodiment 2 of the present invention discloses a device for detecting hidden defects in subgrade and pavement based on an electro-sensing skin, as Figure 1 shown, including a precast concrete electrode arrangement module 1, a voltage collector 8, an alternating current power supply 7, and a data processing computer 10; among them, the precast concrete electrode arrangement module 1 is buried inside the concrete, the precast concrete electrode arrangement module 1 is connected to the voltage collector 8, the alternating current power supply 7 is connected to the voltage collector 8, and the voltage collector 8 is connected to the data processing computer 10.

[0041] The alternating current power supply 7 uses the KEITHLEY 6221 type alternating and direct current current source of the American Keithley Corporation. The alternating current power supply 7 can provide continuous and stable constant current for the voltage collector 8, and the alternating current power supply 7 is connected to the voltage collector 8.

[0042] In the embodiment of the present invention, the voltage collector 8 uses the AGILENT 34970A high-performance data acquisition and switch mainframe of Keysight Technologies, Inc. The voltage collector is very suitable for data recording, data acquisition, and general switching and control applications.

[0043] Furthermore, the precast concrete electrode arrangement module 1 includes a waterborne polyurethane / carbon nanotube / silica powder composite film electro-sensing skin 2, a grid copper sheet electrode 3, a conductive silver paste 4, and a silver wire 5; wherein, the waterborne polyurethane / carbon nanotube / silica powder composite film electro-sensing skin 2 is placed inside the concrete to be measured, and the silver wire 5 is attached to the grid copper sheet electrode 3 through the conductive silver paste 4.

[0044] In this embodiment, the size of the precast concrete electrode arrangement device module 1 is 50 cm × 50 cm × 10 cm, which can be used to realize the integrated installation, arrangement, and embedding of the waterborne polyurethane / silica powder / carbon nanotube composite film electro-sensing skin 2, the grid copper sheet electrode 3, the conductive silver paste 4, and the silver wire 5.

[0045] It further includes an electrode converter 9. The electrode converter 9 realizes electrode switching by using a programmable electrode switching model. One end of the electrode converter 9 is connected to the silver wire 5, and the other end of the electrode converter 9 is connected to the voltage collector 8.

[0046] It further includes a DuPont wire connector 6. The DuPont wire connector is divided into a male head and a female head. The male head of the DuPont wire connector is connected to the silver wire, and the female head of the DuPont wire connector is connected to the electrode converter.

[0047] The male head of the DuPont wire connector and the female head of the DuPont wire connector are detachably installed.

[0048] Such as Figure 2 、 Figure 3 、 Figure 4 As shown, the grid copper sheet electrodes 3 are arranged in an array form or a surrounding form inside the precast concrete electrode arrangement module.

[0049] The data processing software 11 is mainly based on the open-source software EIDORS of ERT and MATLAB. The data processing software is installed in the data processing computer 10.

[0050] Such as Figure 5The figure shows the positional relationship diagram between the device of the present invention and the concrete to be measured. The present invention prefabricates a precast concrete electrode arrangement device that can be buried and easily spliced by using a composite film electro-sensing skin of waterborne polyurethane / carbon nanotube / silica powder as a conductive coating for concrete insulators, designs a resistance tomography imaging system to perform differential resistance tomography imaging on hidden defects that cannot be detected by the naked eye in subgrade and pavement engineering, can invert and characterize the conductivity change of the concrete insulator through the conductivity change of the electro-sensing skin, and finally reconstructs the conductivity distribution map of the concrete based on data processing software to reflect the hidden defects existing in the concrete that cannot be observed by the naked eye, solving the problem that the conventional electrical resistance tomography (ERT) non-destructive testing system cannot accurately measure the conductivity change of concrete, meeting the requirement of being able to observe the hidden defects of subgrade and pavement without damaging the pavement structure, so as to meet the needs of subgrade and pavement structure engineering detection and early warning for sections with large vehicle flow and large load.

[0051] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple. For the relevant parts, reference can be made to the description in the method part.

[0052] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting hidden defects in subgrade and pavement based on electric sensing skin, characterized in that, The specific steps are as follows: Use a composite film electro-sensing skin as the conductive coating of the concrete insulator, and preset a concrete electrode arrangement device in the monitored concrete structure; Inject a continuous current into the concrete electrode arrangement device, and collect the voltage data of the concrete electrode arrangement device; Use electrical resistance tomography technology to reconstruct the image of the composite film electro-sensing skin from the voltage data, and obtain a differential image of the change in conductivity before and after the damage of the monitored concrete structure; Observe the hidden defects of the roadbed and pavement through the differential image; Bury the concrete electrode arrangement device into the concrete. The specific arrangement method is as follows: when the concrete is poured to half of its thickness, spray the prepared mixed solution on the upper surface of the concrete to form the lower half of the composite film electro-sensing skin. When it reaches a certain thickness, arrange the grid copper sheet electrodes in an array on the composite film electro-sensing skin. Use conductive silver paste to paste one end of the silver wire on the surface of each grid copper sheet electrode. After leading out the silver wire according to the designed path, spray the prepared mixed solution on the surface where the grid copper sheet electrode, conductive silver paste, and silver wire are located by using a high-pressure spray gun to complete the upper half of the composite film electro-sensing skin. Finally, pour the remaining precast concrete to complete the concrete electrode arrangement device; The composite film electro-sensing skin is a waterborne polyurethane / carbon nanotube / silica powder composite film electro-sensing skin. Prepare a dispersion component by mixing carbon nanotube powder and waterborne polyurethane, and obtain a solid powder component by mixing and grinding bulk cement and silica powder. Mix and stir the dispersion component and the solid powder component in proportion, and use a high-pressure spray gun to evenly spray the prepared mixed solution on the surface of the measured concrete to obtain the waterborne polyurethane / carbon nanotube / silica powder composite film electro-sensing skin.

2. A subgrade and pavement concealed defect detection device based on an electrically sensitive skin, which is used to implement a subgrade and pavement concealed defect detection method based on an electrically sensitive skin as described in claim 1, and is characterized in that, It includes a precast concrete electrode arrangement module, a voltage collector, an alternating current power supply, and a data processing computer; among them, the precast concrete electrode arrangement module is buried inside the concrete, the precast concrete electrode arrangement module is connected to the voltage collector, the alternating current power supply is connected to the voltage collector, and the voltage collector is connected to the data processing computer.

3. The concealed defect detection device for roadbed pavement based on electric sensing skin according to claim 2, wherein, The precast concrete electrode arrangement module includes a waterborne polyurethane / carbon nanotube / silica powder composite film electro-sensing skin, grid copper sheet electrodes, conductive silver paste, and silver wires; among them, the waterborne polyurethane / carbon nanotube / silica powder composite film electro-sensing skin is placed inside the measured concrete, and the silver wires are pasted on the grid copper sheet electrodes through the conductive silver paste.

4. The concealed defect detection device for roadbed pavement based on electric sensing skin according to claim 3, wherein It also includes an electrode converter, one end of the electrode converter is connected to the silver wire, and the other end of the electrode converter is connected to the voltage collector.

5. The concealed defect detection device for roadbed pavement based on electric sensing skin according to claim 4, characterized in that It also includes a DuPont line connector. The DuPont line connector is divided into a male head and a female head. The male head of the DuPont line connector is connected to the silver wire, and the female head of the DuPont line connector is connected to the electrode converter.

6. The concealed defect detection device for subgrade pavement based on electric sensing skin according to claim 5, wherein, The male head and the female head of the DuPont line connector are detachably installed.

7. The concealed defect detection device for roadbed pavement based on electric sensing skin according to claim 3, wherein, The grid copper sheet electrodes are arranged in an array or in a surrounding form inside the precast concrete electrode arrangement module.

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