CN1793898A - Non destructive detection mothod used for anchor rod anchored system - Google Patents

Abstract

The invention discloses a non-destructive flaw detection method for a bolt anchorage system, which is characterized in that: the method includes the following steps: (1) a stress wave generator acts on the excited sound wave signal to the top of the bolt; (2) The stress wave sensor acquires the dynamic measurement signal reflected from the bolt anchorage system and transmits it to the signal receiving device; (3) The signal receiving device transmits the signal to the microprocessor for wavelet packet analysis; (4) The processed The signal is analyzed by intelligent signal processing. According to the actual engineering situation of the bolt anchorage system, the present invention flexibly uses stress waves to replace the commonly used ultrasonic detection, effectively overcomes the technical problems in ultrasonic detection such as short propagation distance, fast attenuation speed, and difficulty in receiving signals. The depth (typically 1.5 meters for ultrasound) extends to more than 20 meters. It can be widely used in non-destructive testing and intelligent diagnosis of anchorage system quality, and has a bright application prospect.

Description

A non-destructive testing method for bolt anchorage system

technical field

The invention relates to a non-destructive testing method for a bolt anchorage system.

Background technique

The traditional detection method of the anchorage state of the bolt mainly relies on the pullout force test of the bolt. Although this method is suitable for some occasions, it has many shortcomings. This method is not only a destructive detection but also a The pullout force of the bolt cannot fully reflect the anchorage state of the bolt. The application of non-destructive testing technology in the safety evaluation of rock and soil anchorage has been developed with the great development of digital electronic technology and computer technology in recent years. After decades of research and application, a variety of methods have been developed, which can be mainly summarized as follows: Electromagnetic wave method and vibration (seismic wave) ~ ultrasonic detection method. The detection range of the electromagnetic wave method is limited and the price is expensive; the propagation distance of the ultrasonic detection method is short, the signal attenuation speed is fast, the signal is difficult to receive, and the detection depth is limited.

Contents of the invention

The object of the present invention is to provide a non-destructive flaw detection method for bolt anchorage system with low cost, wide detection range and convenient operation.

The object of the present invention is achieved like this: a kind of non-destructive testing method for bolt anchorage system, it is characterized in that: this method comprises the following steps:

(1) The stress wave generator acts on the top of the anchor rod with the excited acoustic wave signal;

(2) The stress wave sensor obtains the dynamic measurement signal reflected from the bolt anchorage system and transmits it to the signal receiving device;

(3), the signal receiving device transmits the signal to the microprocessor for wavelet packet analysis;

(4) Perform intelligent signal processing and analysis on the processed signal.

The above-mentioned intelligent signal processing analysis is the analysis of the defect position of the bolt or the quantitative analysis of the anchoring quality of the bolt anchorage system.

The analysis of the above-mentioned bolt defect position includes the following steps:

(1) Carry out three-layer wavelet packet decomposition on the time-domain signal of the measured defect bolt with wavelet, and obtain the low-frequency and high-frequency coefficients of each layer;

(2), carry out threshold de-noising processing to the high-frequency coefficient of signal;

(3) Perform single-branch reconstruction on the high-frequency coefficient part of the signal, and draw the reconstructed waveform diagram;

(4) Identify the positions t ₀ , t _e , and t _i of the incident wave, the reflected wave at the bottom of the club, and the sudden change in the signal;

(5) Calculate the bolt length L=C·(t _e -t ₀ )/2, the anchor rod defect position L _i =C·(t _i -t ₀ )/2, where C is the wave velocity, $C=\sqrt{\mathrm{\ρ}/\mathrm{E.}}=5054m/\mathrm{the\; s}.$

In order to comprehensively evaluate the anchorage state of the bolt anchorage system, the present invention adopts an anchorage quality quantitative analysis method, comprising the following steps:

(1) Calculate the anchoring quality M _s of the actual anchor bolt system:

①. After the wavelet packet analysis is performed on the dynamic response signal of the pole top obtained from the test, the eigenvector representing the bolt structure system is obtained;

②, using the obtained eigenvector as network input to identify the measured bolt system (bolt-surrounding rock structure system), and obtain the side stiffness factor of each section along the length of the bolt;

③. According to the geometric parameters of the anchor rod, the stiffness coefficient of each segment is converted from the stiffness factor of each segment to calculate the anchoring quality of the actual anchor rod system $m_{\mathrm{the\; s}}=\underset{i=1}{\overset{\mathrm{no}}{\mathrm{\Σ}}}{l}_i{k}_i,$ In the formula, M _s ——the anchorage amount of the actual bolt anchorage structure system; _ki ——the stiffness coefficient of each section on the rod side of the actual anchor bolt anchorage structure system; l _i ——the length of each section of the actual anchor bolt anchorage structure system;

(2) Calculate the corresponding anchorage amount M _w of the complete anchor system:

①. Obtain the distribution of various surrounding rocks along the side of the bolt and the mechanical properties of various surrounding rocks according to the geological survey data;

②, according to the fitting formula $k_{\mathrm{the\; s}}=-0.000972{\mathrm{E.}}_{\mathrm{the\; s}}^2+0.331{\mathrm{E.}}_{\mathrm{the\; s}}+0.582$ Calculate the stiffness coefficient corresponding to various surrounding rocks;

③. According to the distribution of the surrounding rock on the side of the bolt, calculate the anchorage amount corresponding to the complete bolt system $m_w=\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{L}_j{K}_j;$ In the formula, M _w ——corresponds to the anchorage amount of the complete bolt anchorage structure system; K _j ——according to the actual surrounding rock conditions on the rod side, the stiffness coefficient of each section of the bolt rod side; L _j ——according to the actual surrounding rock conditions on the rod side The length of each section on the side of the anchor rod;

(3), M _s and M _w calculated in steps (1) and (2) are divided to obtain the degree of anchorage of the actual bolt structure system: $Q=m_{\mathrm{the\; s}}/m_w=\underset{i=1}{\overset{\mathrm{no}}{\mathrm{\Σ}}}{l}_i{k}_i/\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{L}_j{K}_j.$

(4) Comprehensively evaluate the anchorage quality of the anchorage system according to the calculated anchorage degree Q: when Q=1, the anchorage system is fully anchored; when Q<1, the anchorage system is not completely anchored, that is, there are defects ; When Q=0, the bolt system fails completely.

The present invention is used for the advantage of the non-destructive testing method of bolt anchorage system:

According to the actual engineering situation of the bolt anchorage system, this technology flexibly uses the stress wave to replace the commonly used ultrasonic detection, which effectively overcomes the technical problems of short propagation distance, fast attenuation speed, and difficulty in receiving signals in ultrasonic detection. The detection depth (ultrasonic is generally 1.5 meters) extends to more than 20 meters. Only using the acceleration response of the anchor head measured by the low-strain test as the input data, quantitative analysis conclusions can be obtained, various defects can be identified more accurately, and the diagnosis problem of the nonlinear dynamic process of the anchorage system is technically solved.

This technology effectively solves the problems of bolt defect identification and anchorage quality evaluation, and can be widely used in natural slopes, road slopes, building slopes, foundations, dangerous rock management, landslide management, dangerous rock reinforcement, tunnel engineering, Non-destructive testing and intelligent diagnosis of anchorage system quality in foundation pit support, bridge engineering, mines and other projects have great application prospects.

Description of drawings

Fig. 1 is a functional block diagram of an embodiment of the present invention;

Fig. 2 is the flow chart diagram of the position analysis of anchor rod defects adopted in the embodiment of the present invention;

Fig. 3 is a flow chart of the quantitative analysis of the anchoring quality adopted in the embodiment of the present invention.

Detailed ways

Referring to Fig. 1, a kind of non-destructive testing method for bolt anchorage system is characterized in that: the method comprises the following steps:

(1) The stress wave generator acts on the top of the anchor rod with the excited acoustic wave signal;

(2) The stress wave sensor obtains the dynamic measurement signal reflected from the bolt anchorage system and transmits it to the signal receiving device;

(3), the signal receiving device transmits the signal to the microprocessor for wavelet packet analysis;

(4) Perform intelligent signal processing and analysis on the processed signal.

The above-mentioned intelligent signal processing analysis is the analysis of the defect position of the bolt or the quantitative analysis of the anchoring quality of the bolt anchorage system.

The defects of the bolt system usually lead to changes in the observed signals of the system. If certain measures can be taken to eliminate the noise caused by external factors, the position of the bolt defects can be detected by directly using the wavelet decomposition transform to detect the singular points of the observed signals. The singular point can be determined by using the relationship between the singular point in the wavelet transform and the modulus maximum value of the wavelet transform. The modulus maxima of the wavelet transform appear in places where the signal has a sudden change, and there are more high-frequency components at the sudden change point. So the singularity of the function can be detected from the modulus maxima of the high frequency part of its wavelet transform. If the signal contains a transient signal, there will be a sudden change in the signal energy at the arrival time of the signal and the scale (frequency) segment, which is manifested in the wavelet transform scale spectrogram as a peak at the corresponding time-scale position. Therefore, the detection of the moment of arrival of the transient signal can be realized by detecting the prominent peak moment on the wavelet transform scale-spectrum.

Based on the above analysis, see Figure 2, the steps to identify the anchor rod defect location are as follows:

The analysis of the above-mentioned bolt defect position includes the following steps:

(1) Carry out three-layer wavelet packet decomposition on the time-domain signal of the measured defect bolt with wavelet, and obtain the low-frequency and high-frequency coefficients of each layer;

(2), carry out threshold de-noising processing to the high-frequency coefficient of signal;

(3) Perform single-branch reconstruction on the high-frequency coefficient part of the signal, and draw the reconstructed waveform diagram;

(4) Identify the positions t ₀ , t _e , and t _i of the incident wave, the reflected wave at the bottom of the club, and the sudden change in the signal;

(5) Calculate the bolt length L=C·(t _e -t ₀ )/2, the anchor rod defect position L _i =C·(t _i -t ₀ )/2, where C is the wave velocity, $C=\sqrt{\mathrm{\&rho;}/\mathrm{E.}}=5054m/\mathrm{the\; s}.$

In order to comprehensively evaluate the anchorage state of the bolt anchorage system, referring to Fig. 3, the present invention adopts an anchorage quality quantitative analysis method, comprising the following steps:

(1) Calculate the anchoring quality M _s of the actual anchor bolt system:

①. After the wavelet packet analysis is performed on the dynamic response signal of the pole top obtained from the test, the eigenvector representing the bolt structure system is obtained;

②. Use the obtained eigenvector as network input to identify the measured bolt system (bolt-surrounding rock structure system), and obtain the stiffness factor of each section uniformly distributed along the length of the bolt;

③. According to the geometric parameters of the anchor rod, the stiffness coefficient of each segment is converted from the stiffness factor of each segment to calculate the anchoring quality of the actual anchor rod system $m_{\mathrm{the\; s}}=L\underset{i=1}{\overset{5}{\mathrm{\&Sigma;}}}{k}_i/5;$ In the formula, M _s ——the anchorage amount of the actual bolt anchorage structure system; _ki ——the stiffness coefficient of each section on the rod side of the actual anchor bolt anchorage structure system; l _i ——the length of each section of the actual anchor bolt anchorage structure system;

(2) Calculate the corresponding anchorage amount M _w of the complete anchor system:

①. Obtain the distribution of various surrounding rocks along the side of the bolt and the mechanical properties of various surrounding rocks according to the geological survey data;

②, according to the fitting formula $k_{\mathrm{the\; s}}=-0.000972{\mathrm{E.}}_{\mathrm{the\; s}}^2+0.331{\mathrm{E.}}_{\mathrm{the\; s}}+0.582$ Calculate the stiffness coefficient corresponding to various surrounding rocks;

③. According to the distribution of the surrounding rock on the side of the bolt, calculate the anchorage amount corresponding to the complete bolt system $m_w=\underset{i=1}{\overset{5}{\mathrm{\&Sigma;}}}{L}_j{K}_j;$ In the formula, M _w ——corresponds to the anchorage amount of the complete bolt anchorage structure system; K _j ——according to the actual surrounding rock conditions on the rod side, the stiffness coefficient of each section of the bolt rod side; L _j ——according to the actual surrounding rock conditions on the rod side The length of each section on the side of the anchor rod;

(3), M _s and M _w calculated in steps (1) and (2) are divided to obtain the degree of anchorage of the actual bolt structure system: $Q=m_{\mathrm{the\; s}}/m_w=L\underset{i=1}{\overset{5}{\mathrm{\&Sigma;}}}{k}_i/5\underset{i=I}{\overset{5}{\mathrm{\&Sigma;}}}{L}_j{K}_j.$

(4) Comprehensively evaluate the anchorage quality of the anchorage system according to the calculated anchorage degree Q: when Q=1, the anchorage system is fully anchored; when Q<1, the anchorage system is not completely anchored, that is, there are defects ; When Q=0, the bolt system fails completely. It can be seen that the degree of anchorage Q well describes the anchorage state of the bolt-surrounding rock structure system.

In the process of calculating the anchoring mass M _s of the actual bolt system, after wavelet packet analysis is performed on the dynamic response signal of the top of the bolt obtained from the test, the eigenvector characterizing the bolt structure system is obtained, and the eigenvector is obtained by the following method:

The bolt is divided into 5 sections along the length, and there are only 14 parameters to be identified, so it is enough to decompose the signal with 3 layers of wavelet packets, and then perform feature extraction on the wavelet components in each frequency band, and the extracted parameters are the range of each frequency band The mean value of the power spectrum that reflects the energy distribution and the variance that reflects the speed of the frequency change, the specific steps are as follows:

①. Use the db6 wavelet to decompose the three-layer wavelet packet on the sampling sequence of the signal, and obtain 8 wavelet packet decomposition coefficient sequences {CAAA ₃ , CDAA ₃ , CADA ₃ , CDDA ₃ , CAAD ₃ , CDAD ₃ , CADD ₃ , CDDD ₃ } ;

②. Reconstruct wavelet packet decomposition coefficients to obtain signal components X ₃₀ , X ₃₁ , X ₃₂ , X ₃₃ , X ₃₄ , X ₃₅ , X ₃₆ , and X ₃₇ in each frequency band;

③. Welch method is used for power spectrum analysis of each signal component;

④. Composition of eigenvectors, the eigenvectors F={E ₁ , E ₂ , E ₃ , E ₄ , E ₅ , E ₆ , E ₇ , E ₈ , S ₁ are composed of the power spectrum mean and variance of 8 signal components , S ₂ , S ₃ , S ₄ , S ₅ , S ₆ , S ₇ , S ₈ }.

Claims (4)

1. A non-destructive testing method for bolt anchorage systems, characterized in that: the method comprises the following steps: (1) The stress wave generator acts on the top of the anchor rod with the excited acoustic wave signal; (2) The stress wave sensor obtains the dynamic measurement signal reflected from the bolt anchorage system and transmits it to the signal receiving device; (3), the signal receiving device transmits the signal to the microprocessor for wavelet packet analysis; (4) Perform intelligent signal processing and analysis on the processed signal. 2. The non-destructive testing method for bolt anchorage system according to claim 1, characterized in that: said intelligent signal processing and analysis is the analysis of the defect position of the bolt or the quantitative analysis of the anchorage quality of the bolt anchorage system. 3. The non-destructive testing method for bolt anchorage system according to claim 2, characterized in that: the analysis of the defect position of the bolt comprises the following steps: (1) Carry out three-layer wavelet packet decomposition on the time-domain signal of the measured defect bolt with wavelet, and obtain the low-frequency and high-frequency coefficients of each layer; (2), carry out threshold de-noising processing to the high-frequency coefficient of signal; (3) Perform single-branch reconstruction on the high-frequency coefficient part of the signal, and draw the reconstructed waveform diagram; (4) Identify the positions t ₀ , t _e , and t _i of the incident wave, the reflected wave at the bottom of the club, and the sudden change in the signal; (5) Calculate the bolt length L=C·(t _e -t ₀ )/2, the anchor rod defect position L _i =C·(t _i -t ₀ )/2, where C is the wave velocity, $C=\sqrt{\mathrm{\&rho;}/\mathrm{E.}}=5054m/\mathrm{the\; s}.$ 4. The non-destructive testing method for bolt anchorage system according to claim 2, characterized in that: the quantitative analysis of the anchorage quality of the bolt anchorage system comprises the following steps: (1) Calculate the anchoring quality M _s of the actual anchor bolt system: ①. After the wavelet packet analysis is performed on the dynamic response signal of the pole top obtained from the test, the eigenvector representing the bolt structure system is obtained; ②. Use the obtained eigenvector as network input to identify the measured bolt system, and obtain the rod side stiffness factor along each section of the rod length; ③. According to the geometric parameters of the anchor rod, the stiffness coefficient of each segment is converted from the stiffness factor of each segment to calculate the anchoring quality of the actual anchor rod system $m_{\mathrm{the\; s}}=\underset{i=1}{\overset{\mathrm{no}}{\mathrm{\&Sigma;}}}{l}_i{k}_i,$ In the formula, M _s ——the anchorage amount of the actual bolt anchorage structure system; _ki ——the stiffness coefficient of each section on the rod side of the actual anchor bolt anchorage structure system; l _i ——the length of each section of the actual anchor bolt anchorage structure system; (2) Calculate the corresponding anchorage amount M _w of the complete anchor system: ①. Obtain the distribution of various surrounding rocks along the side of the bolt and the mechanical properties of various surrounding rocks according to the geological survey data; ②, according to the fitting formula $k_{\mathrm{the\; s}}=-0.000972{\mathrm{E.}}_{\mathrm{the\; s}}^2+0.331{\mathrm{E.}}_{\mathrm{the\; s}}+0.582$ Calculate the stiffness coefficient corresponding to various surrounding rocks; ③. According to the distribution of the surrounding rock on the side of the bolt, calculate the anchorage amount corresponding to the complete bolt system $m_w=\underset{j=1}{\overset{m}{\mathrm{\&Sigma;}}}{L}_j{K}_j,$ In the formula, M _w ——corresponds to the anchorage amount of the complete bolt anchorage structure system; K _j ——according to the actual surrounding rock conditions on the rod side, the stiffness coefficient of each section of the bolt rod side; L _j ——according to the actual surrounding rock conditions on the rod side The length of each section on the side of the anchor rod; (3), M _s and M _w calculated in steps (1) and (2) are divided to obtain the degree of anchorage of the actual bolt structure system: $Q=m_{\mathrm{the\; s}}/m_w=\underset{i=1}{\overset{\mathrm{no}}{\mathrm{\&Sigma;}}}{l}_i{k}_i/\underset{j=1}{\overset{m}{\mathrm{\&Sigma;}}}{L}_j{K}_j.$ (4) Comprehensively evaluate the anchoring quality of the anchorage system according to the calculated degree of anchorage Q: when Q=1, the anchorage system is fully anchored; when Q<1, the anchorage system is not fully anchored and there are defects ; When Q=0, the bolt system fails completely.