A sleeve grouting fullness detection method and system based on acoustic emission

Abstract

The application relates to a sleeve grouting fullness detection method and system based on acoustic emission, which comprises the following steps: collecting acoustic emission signals of n grouting sleeves with known fullness under the same working condition through an acoustic emission sensor; then performing N-layer wavelet packet decomposition on each acoustic emission signal to obtain two frequency bands; calculating the energy proportion of each frequency band to obtain energy concentrated frequency bands of the n acoustic emission signals; and obtaining a relationship model of the energy proportion and the fullness according to n groups of energy proportions and corresponding known fullnesses in the energy concentrated frequency bands, so as to realize fullness prediction of the sleeve grouting to be detected according to the model. N The method does not need additional excitation equipment, is simple in principle, easy to understand, convenient to operate, low in cost, small in site restriction in the detection process, low in requirement on the environment of equipment, and can be applied to detection operation requirements of most construction sites.

Description

Technical Field

[0001] This invention relates to the field of sleeve grouting fullness detection technology, and more specifically to a method and system for sleeve grouting fullness detection based on acoustic emission. Background Technology

[0002] Currently, the grouting connection technology for rebar sleeves is most widely used in the connection of rebars at component nodes in prefabricated assembled buildings.

[0003] Grouting sleeve connection relies on injecting specialized cement-based high-strength, non-shrink grout to connect with the threaded reinforcing bars. This method offers advantages such as reliable performance, wide applicability, and ease of construction, making it a primary construction technique for prefabricated concrete structures in my country. The connection strength of the reinforcing bar joint depends heavily on the fullness of the grout within the sleeve; insufficient grouting can negatively impact the overall load-bearing capacity and seismic resistance of prefabricated buildings.

[0004] However, there is currently a lack of effective testing methods, and there is insufficient basis for acceptance. The grouting can only be judged based on the smoothness of grout discharge from the grout outlet of the grouting sleeve, which poses a hidden danger to the safety of the structure.

[0005] Although recent research on grouting sleeve fullness has yielded various methods both domestically and internationally, including X-ray methods, industrial CT methods, pre-embedded steel wire pull-out methods, and pre-drilled hole methods, X-rays have limited penetration depth, are costly, and are radioactive and harmful to human health. Furthermore, site clearing is required during construction. Industrial CT methods have limited applicability, require expensive and demanding equipment, are radioactive, and can only be performed under shielded laboratory conditions. Pre-embedded steel wire pull-out methods require pre-embedded high-strength steel wires, which are susceptible to disturbance or damage at the construction site before testing. Additionally, the pre-embedded sensors cannot be removed for reuse, increasing testing costs. While pre-drilled hole methods offer clear, intuitive, and quantitative observation and measurement of grouting locations to calculate grouting fullness, the high cost of three-dimensional endoscopes significantly increases testing costs.

[0006] Therefore, in view of the shortcomings of the above-mentioned detection methods, proposing a reasonable non-destructive testing method to determine the fullness of the sleeve grouting is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of this, the present invention provides a method and system for detecting the fullness of sleeve grouting based on acoustic emission.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] On one hand, this invention discloses a method for detecting the fullness of sleeve grouting based on acoustic emission, comprising the following steps:

[0010] S1. Acquire acoustic emission signals from n grouting sleeves with known fullness under the same working conditions using an acoustic emission sensor;

[0011] S2. Perform N-level wavelet packet decomposition on each of the acoustic emission signals to obtain 2 N One frequency band;

[0012] S3. Calculate the energy proportion of each frequency band to obtain the energy concentration frequency bands of the n acoustic emission signals;

[0013] S4. Based on the energy proportions of n groups in the energy concentration frequency band and the corresponding known saturation, obtain the relationship model between energy proportion and saturation.

[0014] S5. Collect the detection acoustic emission signal of the grouting sleeve to be tested, and obtain 2 according to S2. N The system identifies a detection frequency band and calculates the energy percentage of the detection frequency band within the energy concentration band. Based on the relationship model between the energy percentage and the saturation, the saturation of the grouting in the sleeve to be tested is obtained.

[0015] Preferably, in S1, the working condition includes the diameter of the reinforcing bar and the size of the sleeve;

[0016] Preferably, in S1, the acoustic emission sensor is located on the reinforcing bars on both sides of the grouting sleeve and is tightly connected to the surface of the reinforcing bars by vacuum grease;

[0017] Preferably, in S2, the decomposition level N satisfies the following condition:

[0018]

[0019] In the formula, f s f represents the sampling frequency. min Indicates the lowest effective frequency.

[0020] Preferably, in S3, the calculation of the energy percentage of each frequency band is obtained by the following method:

[0021] m data points are collected in each frequency band, and the energy of each frequency band is:

[0022]

[0023] Where j is the frequency band number;

[0024] The total energy of the acoustic emission signal is:

[0025] The energy percentage for each frequency band is:

[0026] On the other hand, the present invention discloses a sleeve grouting fullness detection system, comprising:

[0027] The signal acquisition module is used to acquire the acoustic emission signals of the grouting sleeve;

[0028] The signal processing module is used to perform wavelet packet decomposition on the acoustic emission signal, calculate the energy proportion of each frequency band, and obtain the energy concentration frequency band.

[0029] The model generation and prediction module is used to generate a saturation prediction model based on the energy proportion and corresponding saturation in the energy concentration frequency band, and to predict the saturation of the grouting of the sleeve to be tested based on the saturation prediction model.

[0030] Preferably, the signal acquisition module includes: an acoustic emission sensor and an acoustic emission instrument.

[0031] There are two acoustic emission sensors, located on the reinforcing bars on both sides of the grouting sleeve to be tested, and they are tightly connected to the surface of the reinforcing bars by vacuum grease.

[0032] As can be seen from the above technical solution, compared with the prior art, this invention discloses a method and system for detecting the fullness of sleeve grouting based on acoustic emission. This method does not require additional excitation equipment, its principle is simple and easy to understand, it is convenient to operate, low in cost, the detection process is less constrained by the site, and it has low environmental requirements for the equipment, making it applicable to the detection requirements of most construction sites. Furthermore, by analyzing the changes in energy ratio to reflect the fullness of sleeve grouting, the analysis of acoustic emission characteristic parameters is more in-depth, with smaller errors, thus making the detection results more reliable. Attached Figure Description

[0033] 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0034] Figure 1 The attached figure is a flowchart of the method for detecting the fullness of sleeve grouting based on acoustic emission provided by the present invention;

[0035] Figure 2 The attached figure is a schematic diagram of acoustic emission signal acquisition provided by the present invention;

[0036] Figure 3 The attached figure shows the energy percentage of each frequency band provided by this invention;

[0037] Figure 4 The attached figure is a model diagram showing the relationship between energy ratio and grout fullness provided by the present invention. Detailed Implementation

[0038] 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 some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] This invention discloses a method for detecting the fullness of sleeve grouting based on acoustic emission:

[0040] First, acoustic emission signals are collected from n grouting sleeves with known fullness under the same working conditions using acoustic emission sensors. The same working conditions include the diameter of the reinforcing bar and the size of the sleeve.

[0041] Specifically, in this embodiment of the invention, acoustic emission signals are acquired using a one-to-one transmission and one-to-reception method. Two acoustic emission sensors are used, respectively mounted on the reinforcing bars on both sides of the grouting sleeve. Vacuum grease is used as a coupling agent to ensure a tight connection between the sensor surface and the surface of the reinforcing bar specimen. The acoustic emission instrument is connected to the two acoustic emission sensors via wires, such as... Figure 2 The AEwin software is used to operate the instrument, enabling the AST function of the acoustic transmitter, and data acquisition is performed by connecting the acquisition channel to the signal processing module.

[0042] Then, the acoustic emission signal waveform at the receiving end is exported, and N-level wavelet packet decomposition is performed on each of the acoustic emission signals to obtain 2 N In one embodiment, wavelet packet decomposition is performed using Matlab programming to decompose the signal into sub-signals across multiple frequency bands.

[0043] The essence of wavelet packet decomposition is to translate and scale wavelet bases to approximate the original signal as closely as possible. Different wavelet bases have different characteristics, and the same signal will produce different approximation effects under different wavelet bases, further leading to significant differences in the analysis results. In one embodiment, the "dbN" series of wavelet bases is selected, which has finitely supported approximately symmetric orthogonal wavelet functions and can basically satisfy the requirements of orthogonality, locality in the time domain, and lossless signal reconstruction.

[0044] On the other hand, the number of decomposition layers also has a significant impact on the wavelet packet decomposition effect. When the number of decomposition layers is small, the computational efficiency will be significantly improved, but the frequencies of acoustic emission signals will overlap, making the frequency features difficult to distinguish. As the number of decomposition layers increases, the computational load will increase significantly. Therefore, in practical applications, it is necessary to select an appropriate number of wavelet packet decomposition layers.

[0045] In this embodiment of the invention, the decomposition level N must satisfy the following conditions:

[0046]

[0047] In the formula, f s f represents the sampling frequency. min Indicates the lowest effective frequency.

[0048] Furthermore, the sum of the energy of the signals in each frequency band and the energy ratio of each frequency band are calculated to obtain the energy concentration frequency bands of the n acoustic emission signals. The present invention selects the frequency bands where the excitation signal energy is concentrated, which can better eliminate the interference of clutter, highlight the difference between the grouting incomplete detection signal and the grouting compaction detection signal, and better judge the degree of grouting fullness of the sleeve.

[0049] Secondly, the specific calculation process is as follows:

[0050] m data points are collected in each frequency band, and the energy of each frequency band is:

[0051]

[0052] Where j is the frequency band number;

[0053] The total energy of the acoustic emission signal is:

[0054] The energy percentage for each frequency band is:

[0055] Then, based on the energy proportions of n groups in the energy concentration frequency band and the corresponding known saturation, a relationship model between energy proportion and saturation is obtained. This relationship model is used to predict the saturation status of the sleeve grouting. The prediction process is as follows:

[0056] The above method is used to test the grouting sleeve under test, obtain the energy ratio of the detection frequency band in the energy concentration frequency band, and predict the saturation of the grouting of the sleeve under test based on the relationship model between energy ratio and saturation.

[0057] On the other hand, the present invention also discloses a detection system for a method of detecting the fullness of sleeve grouting based on acoustic emission, comprising:

[0058] The signal acquisition module is used to acquire the acoustic emission signals of the grouting sleeve;

[0059] The signal processing module is used to perform wavelet packet decomposition on the acoustic emission signal, calculate the energy proportion of each frequency band, and obtain the energy concentration frequency band.

[0060] The model generation and prediction module is used to generate a saturation prediction model based on the energy proportion and corresponding saturation in the energy concentration frequency band, and to predict the saturation of the grouting of the sleeve to be tested based on the saturation prediction model.

[0061] The signal acquisition module includes an acoustic emission sensor and an acoustic emission instrument.

[0062] There are two acoustic emission sensors, located on the reinforcing bars on both sides of the grouting sleeve to be tested, and they are tightly connected to the surface of the reinforcing bars by vacuum grease.

[0063] To clearly illustrate the technical solution of the present invention, examples are given below:

[0064] Three sets of grouting sleeve specimens with different fullness are pre-prepared, namely 100%, 60%, and 50%. An additional specimen with 80% fullness is then prepared as a test specimen for an unknown fullness. The connection diagram is shown below. Figure 2 As shown, sensor 1 is used as the transmitter and sensor 2 as the receiver. The AST function of the acoustic transmitter is enabled to collect data. Then, the waveform data collected by the receiver is imported into Matlab and decomposed into three layers of wavelet packets using the db3 wavelet function.

[0065] The energy proportion of each frequency band is obtained through calculation, such as Figure 3 As shown, the energy is mainly concentrated in frequency band 1 (0–62.5 kHz) and frequency band 2 (62.5–125 kHz). Here, we selected frequency band 2 to establish the relationship between the wavelet packet energy ratio and the grout fullness, as shown below. Figure 4 As shown,

[0066] The 80% saturation sleeve, used as the test specimen, was tested. Analysis showed that the energy percentage of the 80% saturation specimen in frequency band 2 was 62.38%. Substituting this into... Figure 4 In the model, the obtained detection value is 72.91%, which is about 7% different from the accurate value. It is very close to the accurate value, indicating that the detection method can meet the requirements of sleeve grouting fullness detection in engineering.

[0067] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0068] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting the fullness of grouting in sleeves based on acoustic emission, characterized in that, Includes the following steps: S1. Acquire acoustic emission signals from n grouting sleeves with known fullness under the same working conditions using an acoustic emission sensor; S2. Perform N-level wavelet packet decomposition on each of the acoustic emission signals to obtain 2 N One frequency band; decomposed into N levels, satisfying the following conditions: In the formula, f s f represents the sampling frequency. min Indicates the lowest effective frequency; S3. Calculate the energy proportion of each frequency band to obtain the energy concentration frequency bands of the n acoustic emission signals; S4. Based on the energy proportions of n groups in the energy concentration frequency band and the corresponding known saturation, obtain the relationship model between energy proportion and saturation. S5. Collect the detection acoustic emission signal of the grouting sleeve to be tested, and obtain 2 according to S2. N The system identifies a detection frequency band and calculates the energy percentage of the detection frequency band within the energy concentration frequency band. Based on the relationship model between the energy percentage and saturation, the saturation of the grouting in the grouting sleeve to be tested is obtained.

2. The method for detecting the fullness of sleeve grouting based on acoustic emission according to claim 1, characterized in that, In S1, the working condition includes the diameter of the reinforcing bar and the size of the sleeve.

3. The method for detecting the fullness of sleeve grouting based on acoustic emission according to claim 1, characterized in that, In S1, the acoustic emission sensor is located on the reinforcing bars on both sides of the grouting sleeve and is tightly connected to the surface of the reinforcing bars by vacuum grease.

4. The method for detecting the fullness of sleeve grouting based on acoustic emission according to claim 1, characterized in that, In S3, the calculation of the energy proportion of each frequency band is obtained through the following method: m data points are collected in each frequency band, and the energy of each frequency band is: Where j is the frequency band number; The total energy of the acoustic emission signal is: The energy percentage for each frequency band is:

5. A detection system for implementing the method for detecting the fullness of sleeve grouting based on acoustic emission as described in any one of claims 1-4, characterized in that, include: The signal acquisition module is used to acquire the acoustic emission signals of the grouting sleeve; The signal processing module is used to perform wavelet packet decomposition on the acoustic emission signal, calculate the energy proportion of each frequency band, and obtain the energy concentration frequency band. The model generation and prediction module is used to generate a saturation prediction model based on the energy proportion and corresponding saturation in the energy concentration frequency band, and to predict the saturation of the grouting of the sleeve to be tested based on the saturation prediction model.

6. The detection system for the method of detecting the fullness of sleeve grouting based on acoustic emission according to claim 5, characterized in that, The signal acquisition module includes: an acoustic emission sensor and an acoustic emission instrument. There are two acoustic emission sensors, located on the reinforcing bars on both sides of the grouting sleeve to be tested, and they are tightly connected to the surface of the reinforcing bars by vacuum grease.

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