Method for detecting compactness of grouting in bridge prestressed duct

Abstract

The invention relates to a method for detecting the compactness of grouting in a bridge prestressed duct, which comprises the following steps of: adsorbing a wall-climbing scanner to the outer wall of a concrete beam body in the grouting process of the prestressed duct of the concrete beam body; the multi-channel array type ultrasonic excitation device transmits ultrasonic signals to the grouting prestressed duct to be detected, the multi-channel array type ultrasonic receiving device monitors elastic wave signals in real time, if an air cavity exists in the prestressed duct, total reflection and secondary wave reflection occur in ultrasonic conduction and propagation, and wave amplitude energy and sound velocity value are rapidly decreased. Therefore, the non-dense grouting part is recognized, and grouting is supplemented in time. According to the method, the bridge prestress grouting compactness is detected based on elastic waves, the integrity of an existing structure is not damaged, the grouting compactness state before solidification can be detected in real time in the grouting link, grout can be supplemented immediately once an uncompacted part is found, the stability and safety of a bridge structure are guaranteed from the source, and the construction period is shortened. And a solid foundation is laid for long-term reliable operation of the bridge.

Description

Technical Field

[0001] This invention relates to the field of bridge engineering testing technology, specifically to a method for testing the compactness of grouting in prestressed ducts of bridges. Background Technology

[0002] In bridge construction, prestressed technology is widely used, and the density of the grout in the prestressed ducts plays a crucial role in the durability and safety of the bridge structure. Inadequate grouting can lead to corrosion of the prestressing tendons, reducing the prestressing effect and consequently impacting the bridge's load-bearing capacity and service life.

[0003] Currently, there are various methods for testing the density of prestressed grout in bridges. One common method is the impact elastic wave method, which generates elastic waves by applying impact loads to the structural surface. The density is determined by the reflection and refraction of these waves as they propagate within the structure and encounter defects. However, this method has several significant drawbacks. First, the impact load may cause some damage to the structural surface during testing, especially for bridges already in service, potentially affecting their overall performance. Second, its accuracy is limited, failing to reach millimeter-level precision. In practical engineering, small, undetected areas can accumulate and lead to serious structural problems over time. Furthermore, this method has relatively low efficiency, making it unsuitable for large-scale bridge inspections, increasing costs and impacting project progress.

[0004] Other traditional testing methods, such as core drilling, while providing direct observation of grout compaction, are destructive and can cause permanent damage to the bridge structure, severely impacting its structural performance. Furthermore, core drilling can only inspect localized areas and cannot comprehensively reflect the grout compaction of the entire prestressed duct. Traditional ultrasonic testing, although non-destructive, is susceptible to interference in the complex environment of bridge structures, and point-based testing is inefficient, leading to inaccurate results.

[0005] Therefore, it is necessary to propose new measures to overcome the above-mentioned shortcomings. Summary of the Invention

[0006] The purpose of this invention is to provide a method for detecting the grout density in prestressed ducts of bridges, so as to solve the problems of structural damage, limited accuracy, and low efficiency of existing methods.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for detecting the grout density in prestressed ducts of bridges is provided, the method comprising:

[0009] During the grouting process of the prestressed ducts in the concrete beam, the wall-climbing scanner is attached to the outer wall of the concrete beam.

[0010] The coupling cavity of the wall-climbing scanner always covers the extension line of the prestressed grouting duct to be tested and proceeds in parallel.

[0011] The multi-channel array ultrasonic excitation device of the wall-climbing scanner emits ultrasonic signals to the prestressed grouting duct to be tested, and simultaneously detects multiple locations;

[0012] The multi-channel array ultrasonic receiver of the wall-climbing scanner monitors elastic wave signals in real time. If there is an air cavity in the prestressed duct, the first wave will be totally reflected when the ultrasonic wave propagates and encounters the air. It will also generate a second wave reflection after passing through the concrete interface. The amplitude energy and sound velocity of the reflected signal drop rapidly at the detection position, thereby identifying the grouting non-compacted parts. It can immediately detect the grouting non-compacted parts during the grouting process and supplement the grouting.

[0013] Furthermore, the wall-climbing scanner includes a multi-channel array ultrasonic excitation device, a multi-channel array ultrasonic receiving device, a coupling cavity, a gas / liquid negative pressure cavity, a travel wheel, and a main battery pack.

[0014] A multi-channel array ultrasonic excitation device is used to transmit ultrasonic signals to the prestressed grouting duct to be tested;

[0015] A multi-channel array ultrasonic receiver is used to receive elastic wave signals reflected from the prestressed grouting duct under test.

[0016] The coupling cavity, filled with a coupling agent, provides a conductive medium for ultrasonic wave transmission.

[0017] The gas / liquid negative pressure chamber is used to attach the wall-climbing scanner to the outer wall of the concrete beam.

[0018] Travel wheels are used for the wall-climbing scanner to travel on the outer wall of the concrete beam.

[0019] The main battery pack powers the wall-climbing scanner.

[0020] Furthermore, the multi-channel array ultrasonic receiver is equipped with signal amplification and filtering circuits, which perform preliminary amplification and filtering on the elastic wave signal after receiving it.

[0021] Furthermore, the wall-climbing scanner also includes a data processing module and a data transmission and storage module;

[0022] The data processing module is used to perform analog-to-digital conversion on elastic wave signals, as well as denoising, feature extraction, and comparative analysis.

[0023] The data transmission and storage module is used to transmit the elastic wave signal to the data processing module and store the converted data.

[0024] Furthermore, feature extraction is performed through spectral analysis or time-domain analysis, including the extraction of propagation time, amplitude, and frequency;

[0025] By comparing the characteristics of elastic wave signals at different locations and times, the density distribution of the grouting body can be determined.

[0026] Furthermore, a relationship model between grouting density and elastic wave signal characteristics is established in advance. The elastic wave signal characteristics acquired in real time are input into the relationship model to obtain the grouting density.

[0027] Furthermore, the wall-climbing scanner is also equipped with a multi-functional inspection module, including an additional power supply and a coupling agent storage tank;

[0028] Additional power units are used to supplement the main power battery pack;

[0029] The coupling agent reservoir is used to introduce coupling agent into the coupling cavity.

[0030] Furthermore, the wall-climbing scanner also includes a distance encoder for labeling distance data.

[0031] Furthermore, the multi-functional inspection module also includes a marking tool for marking cross-sectional distances on the outer wall of concrete beams.

[0032] Furthermore, the method also includes:

[0033] For prestressed ducts in concrete beams with large burial depths, a multi-channel array ultrasonic excitation device uses low-frequency ultrasonic waves for detection.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] This invention provides a method for detecting the grout density in prestressed ducts of bridges. Based on elastic wave detection, it assesses the density of prestressed grout without compromising the integrity of the existing structure. It allows for real-time monitoring of the grout density before solidification during the grouting process, enabling immediate replenishment of any loose sections. This ensures the stability and safety of the bridge structure from the source, laying a solid foundation for its long-term reliable operation. Because it accurately detects and promptly addresses loose grout, it provides a good protective barrier for the prestressed steel reinforcement, significantly reducing the risk of corrosion. Furthermore, this invention achieves high-frequency, millimeter-level precision detection using ultrasonic waves, providing more accurate data support for bridge quality assessment and enabling more accurate prediction of potential risks to the bridge structure. The use of an array-type ultrasonic excitation and receiving device and intelligent detection path planning greatly shortens the detection time. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained from these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the ultrasonic detection principle of the present invention.

[0038] Figure 2 This is a schematic diagram of the ultrasonic array detection principle for a 3D model of a pipeline according to the present invention.

[0039] Figure 3 This is a diagram of the components of a wall-climbing scanner.

[0040] Figure 4 This is a diagram showing the components of a multi-functional inspection module. Detailed Implementation

[0041] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0042] In the description of this invention, it should be understood that all components or modules utilize commercially available existing equipment. Any existing equipment capable of performing the corresponding functions can be used to implement the method of this invention. This invention does not modify these existing devices, and therefore their structures are not described in detail. Similarly, all algorithms or data processing methods utilize existing methods. Any existing method capable of implementing the corresponding means can be used to implement the method of this invention. This invention does not modify these existing methods.

[0043] It should also be noted that although the order of steps is mentioned in the method description, in some cases, steps may be performed in a different order than that described here, and this should not be interpreted as a restriction on the order of steps.

[0044] Existing methods for testing the density of prestressed grout in bridges have many shortcomings in terms of non-destructive testing, accuracy, and efficiency, making it difficult to meet the requirements of modern bridge construction and maintenance for testing technology. To address this, this invention provides a method for testing the density of grouting in prestressed ducts of bridges. This method does not damage the bridge structure and can accurately and efficiently test the density of grouting in prestressed ducts. It can promptly identify areas with insufficient grouting and perform grouting repairs, thereby improving the durability and safety of the bridge structure and meeting the stringent requirements of modern bridge construction and maintenance for testing technology.

[0045] Specifically, the method includes the following steps:

[0046] S1: During the grouting process of the prestressed ducts in the concrete beam, the wall-climbing scanner is attached to the outer wall of the concrete beam.

[0047] Most existing testing methods are designed for testing after concrete has solidified, and cannot detect the density of prestressed ducts before grouting solidifies. This prevents timely detection and re-grouting during the grouting process, hindering timely control of construction quality. The method of this invention, however, is implemented during the grouting process of prestressed ducts in concrete beams. It can promptly identify areas of insufficient grouting and replenish the grout, controlling bridge construction quality from the source and avoiding a series of problems caused by insufficient grouting later. Before solidification, the grout is in a fluid or semi-fluid state, and the propagation characteristics of ultrasonic waves in this state differ from those in the solidified state. Therefore, the method of this invention is designed with a testing procedure suitable for grout before solidification.

[0048] like Figure 1 and Figure 3 The wall-climbing scanner used in this method includes a multi-channel array ultrasonic excitation device, a multi-channel array ultrasonic receiving device, a coupling cavity, a gas / liquid negative pressure cavity, a travel wheel, a main power battery pack, and a distance encoder.

[0049] in:

[0050] A multi-channel array-type ultrasonic excitation device is used to transmit ultrasonic signals to the prestressed grouting ducts under test. An exciter capable of generating broadband ultrasonic waves is selected, and the frequency and energy output of the exciter can be flexibly adjusted according to different testing scenarios. For example, when testing grout before solidification, a lower frequency and moderate energy ultrasonic excitation method is used to allow the ultrasonic waves to propagate better in the fluid or semi-fluid state of the grout. The exciter is equipped with a high-precision triggering system to ensure high consistency and stability of the elastic waves generated each time, providing a foundation for accurate subsequent signal analysis.

[0051] A multi-channel array ultrasonic receiver is used to receive elastic wave signals reflected from the prestressed grouting ducts under test. A multi-channel, high-sensitivity sensor array is employed as the elastic wave receiver. The sensors possess wideband response characteristics, enabling accurate capture of elastic wave signals with different frequency components. Each sensor is equipped with signal amplification and filtering circuitry. After receiving the elastic wave signal, it undergoes preliminary amplification and filtering to remove noise interference and improve signal quality. The sensor array layout is optimized based on the shape and location of the prestressed duct to ensure comprehensive and accurate reception of the elastic wave signals propagating within the grouting body and surrounding structure.

[0052] The coupling cavity is filled with a coupling agent to provide a conductive medium for ultrasonic wave transmission. The coupling agent can be water or hydrogel. When the beam is in a water curing tank, it is not necessary to add a coupling agent; the coupling cavity can be kept full of water by utilizing the principle of water pressure equalization.

[0053] The gas / liquid negative pressure chamber is used to attach the wall-climbing scanner to the outer wall of the concrete beam.

[0054] Travel wheels are used for the wall-climbing scanner to travel on the outer wall of the concrete beam.

[0055] The main battery pack powers the wall-climbing scanner. The distance encoder is used for distance data annotation.

[0056] The wall-climbing scanner also includes a data processing module and a data transmission and storage module.

[0057] in:

[0058] The data processing module performs analog-to-digital conversion on the elastic wave signal, transforming the analog signal into a digital signal. It then uses wavelet transform algorithms to denoise the signal, preserving its effective feature information. Feature extraction is performed through spectral analysis or time-domain analysis, including extraction of propagation time, amplitude, and frequency. By comparing the elastic wave signal characteristics at different locations and times, the density distribution of the grouting body is determined. Furthermore, this method pre-establishes a relationship model between grout density and elastic wave signal characteristics. Inputting the real-time acquired elastic wave signal characteristics into this model yields the grout density. When the elastic wave signal characteristics at a certain location indicate insufficient grout density, an alarm is immediately issued, and the location information is fed back to construction personnel for timely grouting repair. Finally, a detailed inspection report is generated based on the analysis results, providing a comprehensive assessment of the density status of the bridge's prestressed grouting and offering a basis for bridge quality acceptance and subsequent maintenance.

[0059] The data transmission and storage module is used to transmit the elastic wave signal to the data processing module and store the converted data.

[0060] In other embodiments, the data processing module may have a data visualization module that presents the AI ​​analysis results to the testing personnel in an intuitive graphical or chart format.

[0061] In addition, such as Figure 4 The wall-climbing scanner is also equipped with a multi-functional inspection module, including an auxiliary power supply unit, a coupling agent reservoir, and a marking device. Other optional components can be added to the multi-functional inspection module depending on actual needs. The auxiliary power supply unit replenishes the main battery pack. The coupling agent reservoir is used to introduce coupling agent into the coupling cavity, which can be done via a peristaltic pump through pipelines. The marking device is used to mark cross-sectional distances on the outer wall of the concrete beam.

[0062] S2: The coupling cavity of the wall-climbing scanner always covers the extension line of the prestressed grouting duct to be tested and proceeds in parallel.

[0063] The detection path and parameter settings for the wall-climbing scanner can be planned according to the characteristics of the bridge structure and the distribution of prestressed ducts. During the movement, distance data can be automatically marked by a distance encoder, and cross-sectional distance markings can be made on the surface of the concrete beam at the same time.

[0064] S3: The multi-channel array ultrasonic excitation device of the wall-climbing scanner emits ultrasonic signals to the prestressed grouting ducts under test, simultaneously detecting multiple locations. Compared to traditional ultrasonic methods that can only detect one point or a small area at a time, this significantly reduces the detection time.

[0065] S4: The wall-climbing scanner's multi-channel array ultrasonic receiver monitors elastic wave signals in real time, such as... Figure 2 If there is an air cavity in the prestressed duct, the first wave will be totally reflected when the ultrasonic wave propagates and encounters the air. It will also be reflected by a second wave through the concrete interface. The amplitude energy and sound velocity of the reflected signal will drop rapidly at the detection position, thereby identifying the part of the grout that is not dense. This allows for the immediate detection of the part of the grout that is not dense during the grouting process and the supplementary grouting.

[0066] This invention employs an ultrasonic testing method, the core of which lies in utilizing the principle that ultrasonic waves exhibit different propagation characteristics due to the varying properties of different media, thereby accurately determining the compactness of prestressed duct grouting. Unlike the traditional impact elastic wave method, this method optimizes aspects such as ultrasonic excitation, propagation path design, and signal reception analysis to avoid damage to the bridge under test.

[0067] In other embodiments, when an abnormality in the sound velocity amplitude is detected during the detection process, the defect location can be marked in real time, and the AI ​​agent can be used to interpret the abnormality to quickly assess the defect before the grout solidifies. At the same time, after the detection is completed, the cross-sectional detection data can be used by the AI ​​agent to perform CT overlay inversion to obtain a 3D intuitive model of the grouting density of the entire prestressed pipe, which can intuitively reflect the area and degree of insufficient grouting density of the prestressed pipe.

[0068] To address the absorption and scattering characteristics of ultrasonic waves by the grout before solidification, the excitation frequency and energy of the elastic wave can be adjusted. For prestressed ducts in concrete beams with large burial depths, a multi-channel array ultrasonic excitation device uses low-frequency ultrasonic waves for detection, enabling the ultrasonic waves to effectively penetrate the liquid cementitious grout and carry information reflecting its density to be acquired by the receiving device.

[0069] The method of the present invention can also be used to detect the density of grout after solidification. The detection steps differ from those before solidification as follows:

[0070] Preliminary Preparation: After the grout has solidified and reached a certain strength, the area of ​​the bridge to be tested should be cleaned to ensure that the surface is flat and free of debris. Based on the bridge structural drawings and prestressed duct layout information, a plan for the placement of the ultrasonic climbing scanner should be developed. During the placement process, the propagation characteristics of ultrasound in concrete structures must be fully considered to avoid signal interference or blind spots due to improper device placement.

[0071] The first step is to determine the signal characteristics of the solid grout by calibrating the wave velocity and amplitude of the defect-free solid grout, based on the significant differences in propagation velocity and wave impedance between the elastic wave in the solid grout and the surrounding concrete medium compared to the liquid grout.

[0072] The second step, to improve detection accuracy to the millimeter level, requires ultrasonic signal acquisition equipment and advanced signal processing algorithms to determine defects based on the actual material wave velocity and amplitude characteristics, preventing interface signals from being misidentified as defect signals. The signal processing algorithm performs noise reduction and feature extraction on the acquired signals, enhancing the defect-related feature information within the signal, thereby achieving precise location and identification of millimeter-level non-dense areas.

[0073] Third, since solid slurry testing may be carried out on existing bridges, it is necessary to select a multi-functional inspection module with wall-mounted or cable-mounted functions for assistance. This can be achieved simply by replacing the inspection module's walking system.

[0074] The method of the present invention has the following technical advantages:

[0075] 1. Precision applications of ultrasound:

[0076] Accurate detection is achieved by precisely adjusting the excitation frequency, energy, and reception and analysis methods of elastic waves, taking into account their different states before and after grouting solidification. For example, before solidification, the excitation parameters of elastic waves are optimized based on the absorption and scattering characteristics of ultrasonic waves by the fluid or semi-fluid grout; after solidification, the elastic wave signal is accurately analyzed by utilizing the difference in wave impedance between the solid grout and the concrete medium.

[0077] 2. Multi-device collaboration and parameter optimization:

[0078] The coordinated operation of the ultrasonic excitation device, the receiving device, and the multi-functional inspection module for auxiliary detection, as well as the optimized settings of key parameters of each device, such as the ultrasonic coupling and triggering accuracy of the exciter, the sensitivity and frequency response of the sensor, and the selection of data processing algorithms, together ensure high accuracy and high efficiency of the detection.

[0079] 3. Real-time detection and feedback mechanism:

[0080] The mechanism of real-time detection and immediate feedback of information on locations of non-compact grouting during the grouting process, enabling timely replenishment of grout, is crucial for controlling construction quality.

[0081] From the perspective of quality control during construction, this invention can detect the density of grout before solidification in real time during the grouting process. If any areas are found to be not dense enough, grout can be added immediately. This feature greatly improves the first-time success rate of prestressed grouting construction for bridges, effectively avoiding rework. Traditional detection methods often fail to detect problems in time during the grouting process, only discovering incomplete grouting later. Rework at this stage not only incurs significant additional manpower, material resources, and time costs, but may also cause new damage to the bridge structure. This invention ensures the uniformity and density of grout within the prestressed ducts through timely grout addition, guaranteeing the stability and safety of the bridge structure from the source and laying a solid foundation for the long-term reliable operation of the bridge.

[0082] In ensuring the durability of bridge structures, this invention accurately detects and promptly addresses issues of inadequate grouting, significantly reducing the risk of prestressed steel reinforcement corrosion. When the prestressed duct grouting is not tight, external corrosive media such as moisture and oxygen can easily penetrate and contact with the prestressed steel reinforcement, causing corrosion. Corrosion reduces the cross-sectional area of ​​the steel reinforcement, lowering its load-bearing capacity and consequently affecting the overall structural performance of the bridge. This invention, by ensuring tight grouting, provides a strong protective barrier for the prestressed steel reinforcement, effectively delaying or preventing corrosion, extending the service life of the prestressed steel reinforcement, and ensuring the long-term safety of the bridge structure.

[0083] Meanwhile, reducing instances of incomplete grouting also helps lower the risk of cracking in the concrete cover. Areas of incomplete grouting can lead to localized stress concentration. Under the influence of vehicle loads, temperature changes, and other factors, this stress concentration can be transmitted to the concrete cover, causing cracking. Cracks in the concrete cover not only affect the bridge's appearance but, more importantly, expose the internal reinforcing steel directly to the external environment, accelerating steel corrosion. This invention, by ensuring the density of the grouting, allows for a uniform distribution of stress within the structure, reducing the likelihood of cracking in the concrete cover due to stress concentration, and further maintaining the integrity and durability of the bridge structure.

[0084] In terms of detection accuracy, this invention achieves high-precision detection at the millimeter level using high-frequency ultrasonic waves. This means that extremely small areas of grouting insufficiency can be accurately identified, and these minute defects are easily overlooked under traditional detection methods. The high-precision detection results provide more accurate data support for bridge quality assessment, enabling engineers to more accurately predict potential risks to bridge structures. For example, for some important large bridges, millimeter-sized insufficiency areas, if they persist for a long time, may gradually expand under the influence of vehicle loads, environmental erosion, and other factors, ultimately affecting the bridge's load-bearing capacity. This invention can detect these hidden dangers in a timely manner, facilitating targeted reinforcement measures and extending the service life of the bridge.

[0085] The improved detection efficiency also brings numerous advantages. Compared to existing shock elastic wave methods, this invention employs an array-type ultrasonic excitation and receiving device and intelligent detection path planning, significantly shortening the detection time. In large-scale bridge construction or periodic inspections of existing bridges, efficient detection methods can significantly improve work efficiency and reduce detection costs. For example, when inspecting a long-distance bridge, traditional methods may require several days or even weeks to complete, while the method of this invention may only take a few days or even hours. This not only reduces the workload of inspection personnel but also allows the detection results to be applied to engineering decisions more quickly, accelerating the project progress.

[0086] Furthermore, the ultrasonic testing method used in this invention is a non-destructive testing method, which will not cause any damage to the bridge structure under test. This is particularly important for the inspection of existing bridges, as they may have been in service for many years and their structures are relatively fragile. Traditional destructive testing methods may further weaken the structural performance of the bridge. Non-destructive testing ensures the integrity of the bridge during the inspection process, does not affect its normal use function, and also meets the requirements of modern engineering for green and environmentally friendly testing technologies.

[0087] In summary, this invention comprehensively improves the level of prestressed grout density testing for bridges through its advantages in construction quality control, structural durability enhancement, testing accuracy, testing efficiency, and non-destructive testing. This has significant practical implications for ensuring the quality and safety of bridge engineering projects.

[0088] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A method for detecting the grout density in prestressed ducts of bridges, characterized in that: The method includes: During the grouting process of the prestressed ducts in the concrete beam, the wall-climbing scanner is attached to the outer wall of the concrete beam. The coupling cavity of the wall-climbing scanner always covers the extension line of the prestressed grouting duct to be tested and proceeds in parallel. The multi-channel array ultrasonic excitation device of the wall-climbing scanner emits ultrasonic signals to the prestressed grouting duct to be tested, and simultaneously detects multiple locations; The multi-channel array ultrasonic receiver of the wall-climbing scanner monitors elastic wave signals in real time. If there is an air cavity in the prestressed duct, the first wave will be totally reflected when the ultrasonic wave propagates and encounters the air. It will also generate a second wave reflection after passing through the concrete interface. The amplitude energy and sound velocity of the reflected signal drop rapidly at the detection position, thereby identifying the grouting non-compacted parts. It can immediately detect the grouting non-compacted parts during the grouting process and supplement the grouting.

2. The method for detecting the grout density in prestressed ducts of bridges according to claim 1, characterized in that: The wall-climbing scanner includes a multi-channel array ultrasonic excitation device, a multi-channel array ultrasonic receiving device, a coupling cavity, a gas / liquid negative pressure cavity, a traveling wheel, and a main battery pack. A multi-channel array ultrasonic excitation device is used to transmit ultrasonic signals to the prestressed grouting duct to be tested; A multi-channel array ultrasonic receiver is used to receive elastic wave signals reflected from the prestressed grouting duct under test. The coupling cavity, filled with a coupling agent, provides a conductive medium for ultrasonic wave transmission. The gas / liquid negative pressure chamber is used to attach the wall-climbing scanner to the outer wall of the concrete beam. Travel wheels are used for the wall-climbing scanner to travel on the outer wall of the concrete beam. The main battery pack powers the wall-climbing scanner.

3. The method for detecting the grout density in prestressed ducts of bridges according to claim 2, characterized in that: The multi-channel array ultrasonic receiver is equipped with signal amplification and filtering circuits. After receiving the elastic wave signal, it performs preliminary amplification and filtering on the elastic wave signal.

4. The method for detecting the grout density in prestressed ducts of bridges according to claim 3, characterized in that: The wall-climbing scanner also includes a data processing module and a data transmission and storage module; The data processing module is used to perform analog-to-digital conversion on elastic wave signals, as well as denoising, feature extraction, and comparative analysis. The data transmission and storage module is used to transmit the elastic wave signal to the data processing module and store the converted data.

5. The method for detecting the grout density in prestressed ducts of bridges according to claim 4, characterized in that: Feature extraction is performed through spectral analysis or time-domain analysis, including the extraction of propagation time, amplitude, and frequency. By comparing the characteristics of elastic wave signals at different locations and times, the density distribution of the grouting body can be determined.

6. The method for detecting the grout density in prestressed ducts of bridges according to claim 5, characterized in that: A relationship model between grouting density and elastic wave signal characteristics is pre-established. The elastic wave signal characteristics acquired in real time are input into the relationship model to obtain the grouting density.

7. The method for detecting the grout density in prestressed ducts of bridges according to claim 6, characterized in that: The wall-climbing scanner is also equipped with a multi-functional inspection module, including an additional power supply and a coupling agent storage tank; Additional power units are used to supplement the main power battery pack; The coupling agent reservoir is used to introduce coupling agent into the coupling cavity.

8. The method for detecting the grout density in prestressed ducts of bridges according to claim 7, characterized in that: The wall-climbing scanner also includes a distance encoder for labeling distance data.

9. The method for detecting the grout density in prestressed ducts of bridges according to claim 8, characterized in that: The multi-functional inspection module also includes a marking tool for marking cross-sectional distances on the outer wall of concrete beams.

10. The method for detecting the grout density in prestressed ducts of bridges according to claim 9, characterized in that: The method further includes: For prestressed ducts in concrete beams with large burial depths, a multi-channel array ultrasonic excitation device uses low-frequency ultrasonic waves for detection.

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