A prestressed concrete hole pressure grouting compactness detection method and system

Abstract

The application provides a prestressed concrete hole grouting compactness detection method and system, and the method comprises the following steps: controlling a vibration source to emit a plurality of vibration excitation signals with vibration values from small to large; receiving a plurality of grating vibration signals corresponding to the plurality of vibration excitation signals, the plurality of grating vibration signals are obtained by a grating array vibration sensing optical cable installed in the prestressed concrete hole, and the grating array vibration sensing optical cable comprises a plurality of measuring points; determining vibration characteristic lines of each measuring point under the plurality of vibration excitation signals based on the grating vibration signals; matching the vibration characteristic lines with a plurality of reference characteristic lines in a standard database, obtaining a target reference characteristic line with the highest matching degree, and taking a reference compactness corresponding to the target reference characteristic line as the grouting compactness of the prestressed concrete hole. The application can realize compactness detection in the prestressed concrete forming process by collecting the grating vibration signals in real time.

Description

Technical Field

[0001] This invention relates to the field of density testing technology, specifically to a method and system for testing the density of grouting in prestressed concrete ducts. Background Technology

[0002] Prestressed concrete, due to its ease of construction and excellent load-bearing capacity, has become an important component of modern infrastructure construction. Grouting of prestressed concrete beam ducts is a crucial operation to ensure its long-term reliability. However, defects in the uniformity and density of the grouting can lead to prestressing unloading and steel corrosion, becoming one of the potential risks to the engineering structure.

[0003] The traditional non-destructive testing (NDT) methods currently in use mainly include electromagnetic radar, ultrasonic testing, radiation, and point-by-point impact rebound wave testing. The biggest problem with these technologies is that they cannot detect the grouting density in real time during the prestressed concrete beam forming process, that is, they cannot provide feedback on the implementation process of the grouting process in the duct.

[0004] Therefore, there is an urgent need to provide a method and system for detecting the grouting density of prestressed concrete ducts, so as to realize real-time detection of grouting density during the prestressed concrete forming process, that is, to realize the detection of grouting density of ducts throughout the entire process, provide feedback for the grouting process in the ducts, and ensure that it meets the requirements of standards and specifications. Summary of the Invention

[0005] In view of this, it is necessary to provide a method and system for detecting the compactness of grouting in prestressed concrete ducts, so as to solve the technical problem that the existing technology cannot detect the compactness of grouting in real time during the prestressed concrete forming process.

[0006] In a first aspect, to solve the above-mentioned technical problems, the present invention provides a method for detecting the compactness of grouting in prestressed concrete ducts, comprising: Control the vibration source to emit multiple vibration excitation signals with vibration values ​​ranging from small to large; The system receives multiple grating vibration signals that correspond one-to-one with the multiple vibration excitation signals under the excitation of the multiple vibration excitation signals. The multiple grating vibration signals are acquired by a grating array vibration sensing optical cable installed in the prestressed concrete duct. The grating array vibration sensing optical cable includes multiple measuring points. Based on the grating vibration signal, determine the vibration characteristic line of each measuring point under the multiple vibration excitation signals; The vibration characteristic line is matched with multiple reference characteristic lines in the standard database to obtain the target reference characteristic line with the highest matching degree, and the reference density corresponding to the target reference characteristic line is used as the grouting density of the prestressed concrete duct.

[0007] In one possible implementation, determining the vibration characteristic line of each measuring point under different vibration excitation signals based on the plurality of grating vibration signals includes: The grating vibration signal is subjected to absolute value taking and low-pass filtering to obtain a low-frequency vibration signal; The peak value of the low-frequency vibration signal is identified based on the peak point identification algorithm; The vibration feature line is obtained by connecting the peak values ​​of the plurality of grating vibration signals along the direction from smallest to largest of the vibration excitation signal.

[0008] In one possible implementation, the peak point identification algorithm for identifying the peak value of the low-frequency vibration signal includes: The derivative of the low-frequency vibration signal is calculated to obtain the signal derivative values ​​at each of the measurement points. The initial peak value is determined based on the signal derivative value, and the left and right peak values ​​adjacent to the initial peak value are determined with the initial peak value as the center; the direction from left to right is the direction in which the measurement point needs to be increased. The left search range and the right search range are determined based on the initial peak value, the left peak value, and the right peak value, and the left valley value within the left search range and the right valley value within the right search range are determined. The ratios of the initial peak value to the left valley value and the right valley value are determined. When the ratios are both greater than a ratio threshold, the initial peak value is taken as the peak value of the low-frequency vibration signal.

[0009] In one possible implementation, the left search range is the range between the left limit position and the position of the initial peak value, where the left limit position is:

[0010] The right search range is the range between the right extreme position and the position of the initial peak value, and the right extreme position is:

[0011] In the formula, w 1 represents the left extreme position; w 0 is a preset constant; t p This is the initial peak value; t p-1 The left peak value; t p0 For the set of all candidate peaks; w 2 represents the rightmost extreme position; t p+1 This is the right peak value.

[0012] In one possible implementation, before matching the vibration characteristic line with a plurality of reference characteristic lines in a standard database, the method further includes: Determine the minimum feature point in the vibration feature line, and divide the feature line into a first feature line segment and a second feature line segment using the minimum feature point; Linear fitting is performed on the first feature line segment and the second feature line segment respectively to obtain the fitted feature line; The vibration characteristic line is then matched with multiple reference characteristic lines in a standard database, including: The fitted feature line is matched with multiple reference feature lines in the standard database.

[0013] In one possible implementation, the low-pass filtering process is performed using a Savitzkey-Golay filter.

[0014] In one possible implementation, before performing absolute value taking and low-pass filtering on the grating vibration signal to obtain the low-frequency vibration signal, the method further includes: The grating vibration signal is subjected to high-pass filtering based on a high-pass filter.

[0015] In one possible implementation, the method further includes: Based on the grating vibration signal, determine the vibration characteristic lines of different measuring points under the same vibration excitation signal; The vibration characteristic lines of the different measuring points are matched with multiple vibration reference characteristic lines of different measuring points in the standard database to determine the maximum matching value. When the maximum matching value is greater than the preset matching value, the reference density corresponding to the target reference characteristic line is used as the grouting density of the prestressed concrete duct.

[0016] In one possible implementation, determining the vibration characteristic lines of different measurement points under the same vibration excitation signal based on the grating vibration signal includes: Obtain the peak value of the current measuring point and the peak values ​​of adjacent measuring points adjacent to the current measuring point; Based on the preset truncation length, the wave packet range of the measuring point and the wave packet range of the adjacent measuring point are determined with the wave peak of the measuring point and the wave peak of the adjacent measuring point as the center, respectively. When the wave packet range of the measuring point and the wave packet range of the adjacent measuring point overlap in the time scale, the wave peak of the measuring point and the wave peak of the adjacent measuring point are marked as wave peaks under the same vibration excitation signal, and the wave peaks under the same vibration excitation signal are connected to obtain the vibration characteristic lines of the different measuring points. The truncated length is proportional to the mean value of the grating vibration signal.

[0017] Secondly, the present invention also provides a prestressed concrete duct grouting density testing system, comprising: A vibration source is used to generate multiple vibration excitation signals with vibration values ​​ranging from small to large. A grating array vibration sensing optical cable is used to collect multiple grating vibration signals that correspond one-to-one with the multiple vibration excitation signals under the excitation of the multiple vibration excitation signals. A data analysis platform is used to receive the multiple grating vibration signals and determine the vibration characteristic lines of each measuring point under the multiple vibration excitation signals based on the grating vibration signals; match the vibration characteristic lines with multiple reference characteristic lines in a standard database to obtain the target reference characteristic line with the highest matching degree, and use the reference density corresponding to the target reference characteristic line as the grouting density of the prestressed concrete duct.

[0018] The beneficial effects of this invention are as follows: The method for detecting the grouting density of prestressed concrete ducts provided by this invention acquires grating vibration signals based on a grating array vibration sensing optical cable installed in the prestressed concrete duct. This allows for real-time, full-process detection of grouting density. Due to its advantages such as being unaffected by light and visual perception and minimal environmental interference, it also improves the accuracy of grouting density detection. Furthermore, by determining the vibration characteristic line characterizing the grating vibration signal, this invention can match the vibration characteristic line with multiple reference characteristic lines in a standard database. The reference density corresponding to the most matching target characteristic reference line is taken as the grouting density. The detection / determination process of grouting density is simple, further improving its detection efficiency. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A schematic flowchart of an embodiment of the method for detecting the grouting density of prestressed concrete ducts provided by the present invention; Figure 2 For the present invention Figure 1 A schematic diagram of an embodiment of S103; Figure 3 For the present invention Figure 2 A schematic diagram of an embodiment of S202; Figure 4 This is a schematic flowchart of an embodiment of the present invention that performs segmented fitting of vibration feature lines before matching; Figure 5This is a schematic diagram of an embodiment of the present invention for performing a goose-array test on the grouting density detection results through vibration characteristic lines at different measuring points; Figure 6 For the present invention Figure 5 A schematic diagram of an embodiment of S501; Figure 7 This is a schematic diagram of an embodiment of the prestressed concrete duct grouting density detection system provided by the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] It should be understood that the schematic drawings are not drawn to scale. The flowcharts used in this invention illustrate operations implemented according to some embodiments of the invention. It should be understood that the operations in the flowcharts may be implemented out of order, and steps without logical contextual relationships may be reversed or performed simultaneously. Furthermore, those skilled in the art, guided by the content of this invention, may add one or more other operations to the flowcharts, or remove one or more operations from the flowcharts. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities may be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0023] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0024] This invention provides a method and system for detecting the compactness of grouting in prestressed concrete ducts, which will be described below.

[0025] Figure 1 This is a schematic flowchart of an embodiment of the method for detecting the grouting density of prestressed concrete ducts provided by the present invention, as shown below. Figure 1 As shown, the methods for testing the grouting density of prestressed concrete ducts include: S101, control the vibration source to emit multiple vibration excitation signals with vibration values ​​ranging from small to large.

[0026] Specifically, the vibration source is a series structure comprising multiple nodes, each of which is used to emit a vibration excitation signal. By controlling the number of nodes emitting vibration excitation signals and the magnitude of the vibration values, it is possible to emit multiple vibration excitation signals with varying vibration values.

[0027] The vibration source is an existing mature structure, and its specific structural details are not specified here.

[0028] S102. Receive multiple grating vibration signals that correspond one-to-one with the multiple vibration excitation signals under multiple vibration excitation signals. The multiple grating vibration signals are acquired by a grating array vibration sensing optical cable installed in the prestressed concrete duct. The grating array vibration sensing optical cable includes multiple measuring points.

[0029] Specifically, each grating vibration signal represents the grating vibration signal corresponding to the vibration excitation signal at a vibration value, and each grating vibration signal is composed of the vibration values ​​at multiple measurement points.

[0030] S103. Determine the vibration characteristic lines of each measuring point under multiple vibration excitation signals based on the grating vibration signal.

[0031] The vibration characteristic line refers to the line that characterizes the vibration characteristic value. In a specific embodiment of the present invention, the vibration characteristic line is the line connecting the peak values ​​of each grating vibration signal. Specifically, it is the line connecting the peak values ​​of the grating vibration signals excited by different vibration excitation signals.

[0032] S104. Match the vibration characteristic line with multiple reference characteristic lines in the standard database to obtain the target reference characteristic line with the highest matching degree, and use the reference density corresponding to the target reference characteristic line as the grouting density of the prestressed concrete duct.

[0033] In some embodiments of the present invention, the matching degree between the vibration characteristic line and multiple reference characteristic lines can be calculated using any one of various matching degree calculation methods such as Euclidean distance, cosine similarity, Pearson correlation coefficient, and Manhattan distance.

[0034] The reference feature lines and reference density in the standard database can be constructed based on historical data or expert knowledge.

[0035] Compared with existing technologies, the grouting density detection method for prestressed concrete ducts provided in this invention acquires grating vibration signals based on a grating array vibration sensing optical cable installed in the prestressed concrete duct. This method enables real-time, full-process detection of grouting density. Due to its advantages such as being unaffected by light and visual perception and minimal environmental interference, it also improves the detection accuracy of grouting density. Furthermore, by determining the vibration characteristic line characterizing the grating vibration signal, this invention can match the vibration characteristic line with multiple reference characteristic lines in a standard database. The reference density corresponding to the most matching target characteristic reference line is taken as the grouting density. The detection / determination process of grouting density is simple, further improving its detection efficiency.

[0036] In some embodiments of the present invention, such as Figure 2 As shown, step S103 includes: S201. The absolute value of the grating vibration signal is taken and low-pass filtered to obtain a low-frequency vibration signal.

[0037] In this embodiment of the invention, before performing low-pass filtering on the grating vibration signal, absolute value taking is performed first, which can convert the oscillation signal into a unipolar signal, making it easier to extract low-frequency components later.

[0038] In a specific embodiment of the present invention, low-pass filtering is performed based on a Savitzkey-Golay filter. The Savitzkey-Golay filter is based on least-squares fitting of local polynomials, which can remove noise while preserving the signal trend, and it can better preserve signal characteristics.

[0039] The Savitzkey-Golay filter has a filter window size of 41 data points and an order of 2-5.

[0040] Specifically, the formula for the Savitzkey-Golay filter is described as follows:

[0041] In the formula, and These represent the original value and the filtered value of the k-th sampling point, respectively. w For semi-smooth window width, h This is the smoothing coefficient.

[0042] To further avoid the impact of high frequency on the detection results, in some embodiments of the present invention, before step S201, the following is also included: The grating vibration signal is subjected to high-pass filtering based on a high-pass filter.

[0043] Specifically, the cutoff frequency of the high-pass filter is 150Hz.

[0044] S202. Identify the peak value of low-frequency vibration signal based on peak point identification algorithm.

[0045] The peak value is the maximum vibration value in the low-frequency vibration signal.

[0046] S203. Connect the peak values ​​of multiple grating vibration signals along the direction from smallest to largest vibration excitation signal to obtain vibration characteristic lines.

[0047] In this embodiment of the invention, by connecting the peak values ​​of the vibration signals of each grating along the direction of increasing vibration excitation signals as vibration characteristic lines, the vibration characteristic lines can comprehensively reflect the grouting density in the channel, improve the characteristic characterization ability of the vibration characteristic lines, and thus improve the accuracy of the grouting density determined based on the vibration characteristic lines.

[0048] In specific embodiments of the present invention, such as Figure 3 As shown, step S202 includes: S301. Differentiate the low-frequency vibration signal to obtain the signal derivative values ​​at each measuring point.

[0049] S302. Determine the initial peak value based on the signal derivative value, and determine the left and right peak values ​​adjacent to the initial peak value as the center; the direction from left to right is the direction that needs to be added to the measuring point.

[0050] Specifically, multiple candidate peak values ​​can be determined using the signal derivative value, as shown in the following formula:

[0051] In the formula, t p0 The set of all candidate peaks is the set of points that satisfy the above equation; The derivative value of the signal; The low-frequency vibration signal at a certain measuring point; It is a minimum value.

[0052] In other words, the point where the derivative is zero and the surrounding vibration value is less than the vibration value at the point where the derivative is zero is the candidate peak value.

[0053] S303. Determine the left search range and the right search range based on the initial peak value, the left peak value, and the right peak value, and determine the left valley value within the left search range and the right valley value within the right search range.

[0054] Specifically, the left search range is the range between the left limit position and the initial peak position, where the left limit position is:

[0055] The right search range is the area between the right limit position and the initial peak position. The right limit position is:

[0056] In the formula, w 1 represents the left extreme position; w 0 is a preset constant; t p This is the initial peak value; t p-1 The left peak value; t p0 For the set of all candidate peaks; w 2 represents the rightmost extreme position; t p+1 This is the right peak value.

[0057] Among them, the valley value is the minimum vibration value within the range.

[0058] S304. Determine the ratio of the initial peak value to the left valley value and the right valley value respectively. When the ratio is greater than the ratio threshold, the initial peak value is taken as the peak value of the low-frequency vibration signal.

[0059] Specifically, the peak value can be expressed as:

[0060] In the formula, The determined peak value; c This is the ratio threshold.

[0061] Instead of directly taking the point with the largest vibration value as the peak value, this embodiment of the invention determines the candidate peak value, then determines the comparison range, and then determines the valley value within the comparison range. The final peak value is determined based on the ratio of the peak value to the valley value. This not only avoids the influence of noise, but also better adapts to the signal characteristics of density, thereby further improving the accuracy of the density detection results.

[0062] To further highlight the line segment characteristics of the vibration feature line and improve its matching accuracy with the reference feature, in some embodiments of the present invention, before step S104, such as... Figure 4 As shown, it also includes: S401. Determine the minimum characteristic point in the vibration characteristic line, and divide the characteristic line into the first characteristic line segment and the second characteristic line segment based on the minimum characteristic point; S402. Perform linear fitting on the first feature line segment and the second feature line segment respectively to obtain the fitted feature line.

[0063] Specifically, linear fitting involves using the least squares method to perform linear fitting on the first and second feature segments.

[0064] Then, in step S104, matching the vibration characteristic line with multiple reference characteristic lines in the standard database specifically involves: The fitted feature lines are matched against multiple reference feature lines in a standard database.

[0065] This invention divides the vibration feature line into a first feature line segment and a second feature line segment based on the smallest feature point of the vibration feature line. This ensures that the turning feature of the vibration feature line is preserved to the greatest extent in the fitting feature line, thus avoiding the problem of losing this feature during the direct fitting process. This further improves the feature representation ability of the fitting feature line, and thus further improves the accuracy of the matching results.

[0066] Since the characteristics of density are not only reflected in the vibration characteristic lines under different vibration excitation signals, but also under the same vibration excitation signal, in order to further improve the accuracy of density detection results, in some embodiments of the present invention, such as... Figure 5 As shown, after step S104, the following steps are also included: S501. Determine the vibration characteristic lines of different measuring points under the same vibration excitation signal based on the grating vibration signal; S502. Match the vibration characteristic lines of different measuring points with multiple vibration reference characteristic lines of different measuring points in the standard database to determine the maximum matching value. When the maximum matching value is greater than the preset matching value, the reference density corresponding to the target reference characteristic line is used as the grouting density of the prestressed concrete duct.

[0067] This invention, based on the premise of detecting grout compaction by vibration characteristic lines under multiple vibration excitation signals, further verifies the detection results by using vibration characteristic lines at different measuring points under a unified vibration excitation signal, thereby ensuring the accuracy of the detection results.

[0068] The detection principle is as follows: if there is a reference feature line in the standard database that matches the vibration feature line, then there will also be feature lines in the standard database that match the feature lines of different measuring points with a degree greater than the preset matching value. Based on this detection principle, the detection results can be verified.

[0069] The matching degree calculation method in step S502 can also be any of the matching degree calculation methods such as Euclidean distance, cosine similarity, Pearson correlation coefficient, Manhattan distance, etc.

[0070] To ensure the accuracy of vibration characteristic lines at different measuring points, in some embodiments of the present invention, such as... Figure 6 As shown, step S501 includes: S601. Obtain the peak value of the current measuring point and the peak value of the adjacent measuring points adjacent to the current measuring point; S602. Based on the preset truncation length, determine the range of the wave packet of the measuring point and the range of the wave packet of the adjacent measuring point, respectively, with the wave peak of the measuring point and the wave peak of the adjacent measuring point as the center. S603. When the wave packet range of the measuring point and the wave packet range of adjacent measuring points overlap in time scale, mark the wave peak of the measuring point and the wave peak of the adjacent measuring point as the wave peak under the same vibration excitation signal, connect the wave peaks under the same vibration excitation signal, and obtain the vibration characteristic lines of different measuring points.

[0071] The truncated length is proportional to the mean value of the grating vibration signal.

[0072] In summary, the prestressed concrete duct grouting density detection method proposed in this embodiment of the invention, through the built-in grating array vibration sensing optical cable, can collect vibration sensing signals inside the prestressed concrete duct in real time, and use digital signal processing methods to distinguish the characteristics of the vibration excitation signal excited by the vibration source, thereby detecting the grouting density in real time. The grouting process inside the duct can be adjusted based on the detection results to meet the requirements of the standard specifications.

[0073] To better implement the prestressed concrete duct grouting density testing method in this embodiment of the invention, based on the prestressed concrete duct grouting density testing method, this embodiment of the invention also provides a prestressed concrete duct grouting density testing system, such as... Figure 7 As shown, the prestressed concrete duct grouting density testing system 700 includes: Vibration source 701 is used to generate multiple vibration excitation signals with vibration values ​​ranging from small to large. The grating array vibration sensing optical cable 702 is used to collect multiple grating vibration signals that correspond one-to-one with multiple vibration excitation signals under multiple vibration excitation signals. The data analysis platform 703 is used to receive multiple grating vibration signals and determine the vibration characteristic lines of each measuring point under multiple vibration excitation signals based on the grating vibration signals; it matches the vibration characteristic lines with multiple reference characteristic lines in the standard database to obtain the target reference characteristic line with the highest matching degree, and uses the reference density corresponding to the target reference characteristic line as the grouting density of the prestressed concrete duct.

[0074] The prestressed concrete duct grouting density testing system 700 provided in the above embodiments can realize the technical solutions described in the above embodiments of the prestressed concrete duct grouting density testing method. The specific implementation principles of each module or unit can be found in the corresponding content in the above embodiments of the prestressed concrete duct grouting density testing method, and will not be repeated here.

[0075] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware (such as a processor, controller, etc.), and the computer program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0076] The above provides a detailed description of the method and system for detecting the grouting density of prestressed concrete ducts provided by the present invention. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for detecting the compactness of grouting in prestressed concrete ducts, characterized in that, include: Control the vibration source to emit multiple vibration excitation signals with vibration values ​​ranging from small to large; The system receives multiple grating vibration signals that correspond one-to-one with the multiple vibration excitation signals under the excitation of the multiple vibration excitation signals. The multiple grating vibration signals are acquired by a grating array vibration sensing optical cable installed in the prestressed concrete duct. The grating array vibration sensing optical cable includes multiple measuring points. Based on the grating vibration signal, determine the vibration characteristic line of each measuring point under the multiple vibration excitation signals; The vibration characteristic line is matched with multiple reference characteristic lines in the standard database to obtain the target reference characteristic line with the highest matching degree, and the reference density corresponding to the target reference characteristic line is used as the grouting density of the prestressed concrete duct. The method further includes: Based on the grating vibration signal, determine the vibration characteristic lines of different measuring points under the same vibration excitation signal; The vibration characteristic lines of the different measuring points are matched with multiple vibration reference characteristic lines of different measuring points in the standard database to determine the maximum matching value. When the maximum matching value is greater than the preset matching value, the reference density corresponding to the target reference characteristic line is used as the grouting density of the prestressed concrete duct.

2. The method for detecting the grouting density of prestressed concrete ducts according to claim 1, characterized in that, The determination of the vibration characteristic lines of each measuring point under different vibration excitation signals based on the multiple grating vibration signals includes: The grating vibration signal is subjected to absolute value taking and low-pass filtering to obtain a low-frequency vibration signal; The peak value of the low-frequency vibration signal is identified based on the peak point identification algorithm; The vibration feature line is obtained by connecting the peak values ​​of the plurality of grating vibration signals along the direction from smallest to largest of the vibration excitation signal.

3. The method for detecting the grouting density of prestressed concrete ducts according to claim 2, characterized in that, The peak value identification algorithm for the low-frequency vibration signal includes: The derivative of the low-frequency vibration signal is calculated to obtain the signal derivative values ​​at each of the measurement points. The initial peak value is determined based on the signal derivative value, and the left and right peak values ​​adjacent to the initial peak value are determined with the initial peak value as the center; the direction from left to right is the direction in which the measurement point needs to be increased. The left search range and the right search range are determined based on the initial peak value, the left peak value, and the right peak value, and the left valley value within the left search range and the right valley value within the right search range are determined. The ratios of the initial peak value to the left valley value and the right valley value are determined. When the ratios are both greater than a ratio threshold, the initial peak value is taken as the peak value of the low-frequency vibration signal.

4. The method for detecting the grouting density of prestressed concrete ducts according to claim 3, characterized in that, The left search range is the range between the left limit position and the position of the initial peak value, and the left limit position is: The right search range is the range between the right extreme position and the position of the initial peak value, and the right extreme position is: In the formula, w 1 represents the left extreme position; w 0 is a preset constant; t p This is the initial peak value; t p-1 The left peak value; t p0 For the set of all candidate peaks; w 2 represents the rightmost extreme position; t p+1 This is the right peak value.

5. The method for detecting the grouting density of prestressed concrete ducts according to claim 1, characterized in that, Before matching the vibration characteristic line with multiple reference characteristic lines in a standard database, the method further includes: Determine the minimum feature point in the vibration feature line, and divide the feature line into a first feature line segment and a second feature line segment using the minimum feature point; Linear fitting is performed on the first feature line segment and the second feature line segment respectively to obtain the fitted feature line; The vibration characteristic line is then matched with multiple reference characteristic lines in a standard database, including: The fitted feature line is matched with multiple reference feature lines in the standard database.

6. The method for detecting the grouting density of prestressed concrete ducts according to claim 2, characterized in that, The low-pass filtering process is based on the Savitzkey-Golay filter.

7. The method for detecting the grouting density of prestressed concrete ducts according to claim 2, characterized in that, Before performing absolute value taking and low-pass filtering on the grating vibration signal to obtain the low-frequency vibration signal, the method further includes: The grating vibration signal is subjected to high-pass filtering based on a high-pass filter.

8. The method for detecting the grouting density of prestressed concrete ducts according to claim 1, characterized in that, The determination of vibration characteristic lines at different measurement points under the same vibration excitation signal based on the grating vibration signal includes: Obtain the peak value of the current measuring point and the peak values ​​of adjacent measuring points adjacent to the current measuring point; Based on the preset truncation length, the wave packet range of the measuring point and the wave packet range of the adjacent measuring point are determined with the wave peak of the measuring point and the wave peak of the adjacent measuring point as the center, respectively. When the wave packet range of the measuring point and the wave packet range of the adjacent measuring point overlap in the time scale, the wave peak of the measuring point and the wave peak of the adjacent measuring point are marked as wave peaks under the same vibration excitation signal, and the wave peaks under the same vibration excitation signal are connected to obtain the vibration characteristic lines of the different measuring points. The truncated length is proportional to the mean value of the grating vibration signal.

9. A system for detecting the compactness of grouting in prestressed concrete ducts, characterized in that, include: A vibration source is used to generate multiple vibration excitation signals with vibration values ​​ranging from small to large. A grating array vibration sensing optical cable is used to collect multiple grating vibration signals that correspond one-to-one with the multiple vibration excitation signals under the excitation of the multiple vibration excitation signals. A data analysis platform is used to receive the multiple grating vibration signals and determine the vibration characteristic lines of each measuring point under the multiple vibration excitation signals based on the grating vibration signals; match the vibration characteristic lines with multiple reference characteristic lines in the standard database to obtain the target reference characteristic line with the highest matching degree, and use the reference density corresponding to the target reference characteristic line as the grouting density of the prestressed concrete duct. The data analysis platform is also used to determine the vibration characteristic lines of different measuring points under the same vibration excitation signal based on the grating vibration signal; The vibration characteristic lines of the different measuring points are matched with multiple vibration reference characteristic lines of different measuring points in the standard database to determine the maximum matching value. When the maximum matching value is greater than the preset matching value, the reference density corresponding to the target reference characteristic line is used as the grouting density of the prestressed concrete duct.

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