CN111487315A - Audio frequency nondestructive testing method for tunnel lining thickness and void - Google Patents
Audio frequency nondestructive testing method for tunnel lining thickness and void Download PDFInfo
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- G01N29/04—Analysing solids
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- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
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Abstract
The invention discloses an audio frequency nondestructive testing method for tunnel lining thickness and void, which comprises the following steps: finding out the known thickness H under the same working condition with the test object areabOr a known void calibration area, collecting effective audio signals; the waveform data analysis is carried out on the audio signal through the audio signal spectrum analysis or the continuous oscillation period of the time domain signal so as to reflect the main frequency value f of the signalbOr sustained oscillation characteristic T of the propagating signaldAs a judgment standard characteristic value; calculating the main frequency f of the test areacOr signal duration oscillation period TcCorresponding characteristic value fbOr TdCarrying out comparison; and imaging all the measuring points, and visually presenting the distribution condition of the quality problem of the whole testing area. The quality problems of void, insufficient thickness, internal defects and the like of the tunnel lining can be efficiently and quickly identified, the accuracy is high, and the application range is wide.
Description
Technical Field
The invention relates to the technical field of railway tunnel detection, in particular to an audio frequency nondestructive detection method for tunnel lining thickness and void.
Background
In the construction of road traffic, a series of diseases are generated due to the existence of irresistible factors in the construction process, such as quality problems of void, lining defect, insufficient lining thickness and the like, uncertain potential safety hazards are buried for the later operation of the tunnel, in order to ensure the quality of tunnel construction and the safety of operation, the importance of tunnel disease detection is obvious, the enhancement of tunnel disease detection can provide guidance for construction, improve the construction process to a certain extent, enhance construction quality management, and simultaneously discover and treat potential safety hazards in the operation and maintenance process in time, the method belongs to the field of nondestructive detection, has no damage to the structure, high detection efficiency, accurate and easily-interpreted result, small influence by traffic environment of an external structural steel bar boundary, the method can comprehensively realize the detection and evaluation of the tunnel lining quality and provide technical support for tunnel construction and operation maintenance.
Electromagnetic wave and impact elastic wave detection are common means for detecting defects, an electromagnetic wave radar judges whether the void exists or not by testing a reflection signal on a void surface, but electromagnetic radar waves are greatly influenced by steel bars, water and the like, the steel bars in a tunnel lining are densely distributed, the moisture content of most regions is high, and the detection can hardly be effectively carried out. The impact elastic wave detection instrument has the advantages of wide frequency band, no electromagnetic impedance, strong signal energy and the like, makes up the defect that an electromagnetic radar is greatly influenced by steel bars, water and the like, and has strong applicability.
Disclosure of Invention
In order to solve the technical problem of low tunnel lining detection efficiency, the invention provides a non-contact audio frequency nondestructive detection method for tunnel lining thickness, defects and void. The quality problems of void, insufficient thickness, internal defects and the like of the tunnel lining can be efficiently and quickly identified, the accuracy is high, and the application range is wide.
In order to realize the purpose of the invention, the invention adopts the technical scheme that:
an audio frequency nondestructive testing method for the thickness and the void of a tunnel lining comprises the following steps:
A. finding out the known thickness H under the same working condition with the test object areabOr a calibration area known to be empty,arranging a certain number of measuring points in a calibration area, knocking by using an excitation hammer or an automatic excitation device, and collecting effective audio signals;
the effective audio signal is smooth and noiseless (smooth and burr-free), and has damping attenuation characteristics as a whole.
B. The waveform data analysis is carried out on the audio signal through the audio signal frequency spectrum analysis or the time domain signal continuous oscillation period, the tunnel lining quality is analyzed through the main frequency change or the duration change of the signal, and the main frequency value f of the reflected signal is obtainedbOr sustained oscillation characteristic T of the propagating signaldAs a judgment standard characteristic value;
C. arranging measuring points in a test area according to test requirements, carrying out coordinate positioning and recording on the measuring points, knocking by using an excitation hammer or an automatic excitation device, collecting effective audio signals, processing and analyzing waveform data by using an audio analysis system, and calculating a main frequency value f of the test areacOr signal duration oscillation period Tc；
D. The obtained main frequency value fcOr signal duration oscillation period TcCharacteristic value f corresponding to step BbOr TdAnd C, comparing, determining coordinates according to the step C, imaging all measuring points, and visually presenting the distribution condition of the quality problem of the whole test area.
Step D of the present invention, if fc＞fbJudging that the interior of the structure has no defect and the consolidation grouting quality is good; if fc＜fbJudging that the thickness of the lining is insufficient or the inside of the lining has defects; if fc＝fbAnd the fluctuation is 5 percent up and down, the lining thickness is judged to be normal but the problem of void exists; if Tc＜TdJudging that the interior of the structure has no defect and the consolidation grouting quality is good; if Tc＞TdJudging that the thickness of the lining is insufficient or the inside of the lining has defects; if Tc＝TdAnd the fluctuation is 5 percent up and down, the lining thickness is judged to be normal but the problem of void exists.
The imaging means that a comparison result of corresponding measuring points is displayed through comparison colors in a coordinate system, and transition colors are used for displaying between two adjacent measuring points with different comparison results.
The invention passes through the known thickness HbCalculating the wave velocity value v of the concrete in the calibration areabThe formula is vb＝2Hbfb(ii) a According to wave velocity vbCalculating the concrete thickness H of the test areacThe formula is Hc＝vb/2fc。
As the aggregate proportion adopted in the same tunnel lining construction is basically stable, the wave velocity change of each measuring point is small, the test result cannot be substantially influenced, the wave velocity obtained by calibration can be regarded as a fixed value, and the optimal wave velocity value can be adopted by carrying out multi-point calibration and carrying out statistical processing. By wave velocity vbThe concrete thickness H of the test area can be calculatedcThe concrete quality of the test area can be further accurately evaluated by the specific numerical value.
The spectrum calculation adopts a maximum entropy method or a signal continuous oscillation period, and is suitable for carrying out spectrum analysis on audio signals.
In the step C, aiming at a test area with the thickness within 80cm, the hammer head of the vibration hammer is a stainless steel spherical hammer head with the diameter of 17-40 mm, and the vibration exciting voltage value is 4V. The main frequency of the structure is matched in a mode of changing the excitation frequency, the diameter of the excitation hammer can be changed under the general condition, a test area with the thickness within 80cm is subjected to excitation on a spherical body with the diameter of 17mm-40mm, which is preferable in a tunnel, and the amplitude stability of a vibration signal is limited by 4V.
The invention adopts the directional microphone to collect the audio signals, and the directional microphone should keep a distance of 5-10mm from the test surface during collection to ensure the signal quality.
Preferably, soundproof cotton is wrapped outside the directional microphone, the directional microphone is connected with the high-speed dynamic acquisition instrument, and the soundproof cotton is tightly attached to the surface of the test object.
The soundproof cotton is tightly attached to the surface of the test object, so that the sound generated by knocking can be effectively reduced or blocked, the directional microphone can pertinently collect effective sound field information on the surface of the structure, and the accuracy of the test result is improved.
Further preferably, the high-speed dynamic acquisition instrument adopts direct current signals as carriers to transmit signals, the mode can effectively improve the anti-interference capability of the signals, the high-speed dynamic acquisition instrument can effectively work in environments such as wind interference and static electricity, and the applicable environment is expanded while the signal quality is ensured.
The effective audio signal is subjected to wave filtering processing in the preposed band-pass filter, then the signal is subjected to filtering processing in the range of 1-12kHz, and noise signals of other frequency bands are filtered out, so that effective signal extraction and analysis can be conveniently carried out in the dominant frequency band.
The judgment standard characteristic value of the step B is the main frequency value of each measuring point in the calibration area or the average value of the signal continuous oscillation period, can be corrected with the standard deviation, and has high accuracy when being typically used for comparison and analysis.
The invention has the beneficial effects that:
1. the method adopts the acoustic frequency signal generated by mechanical striking to identify the concrete thickness and the void position of the tunnel lining, is less influenced by external factors, such as concrete reinforcement rate, water content and the like, is more accurate and effective than electromagnetic radar and impact elastic wave detection, and has higher detection efficiency due to non-contact detection. The method can accurately and quickly identify the void position, and the accuracy is as high as more than 95%.
2. The traditional spectrogram imaging method analyzes whether a tunnel region has void in 10-30 minutes or more after multiple data synthesis processing. According to the invention, through frequency spectrum characteristic value comparison and by adopting an imaging technology, plane imaging can be carried out rapidly or thickness three-dimensional imaging can be added, the concrete thickness, the void position and the void area of the tunnel can be identified more intuitively, the comprehensive detection imaging of the tunnel region can be completed within 30 seconds to 1 minute, and the operation rate is higher.
3. Taking the wave velocity obtained by calibration as a constant value, and passing the wave velocity vbThe concrete thickness H of the test area can be calculatedcThe concrete thickness distribution of the test area can be further accurately evaluated by the specific numerical value.
4. The directional microphone is wrapped by soundproof cotton, the directional microphone is subjected to wave filtering treatment in the preposed band-pass filter, and then signals are subjected to filtering treatment in the range of 1-12kHz, so that noise signals are effectively filtered, the anti-interference capability is high, the frequency response range is good, the system noise is reduced, the filtering function is better, the problem of noise collected by traditional knocking is solved, the collected original signals are closer to the actual situation, and the sampling precision is higher.
Drawings
Fig. 1 is a waveform diagram of a signal duration oscillation period.
Fig. 2 is a schematic diagram of a bandpass filter employed in the present invention.
Fig. 3 is a frequency spectrum diagram of the empty calibration area of example 11, the ordinate is frequency value in Khz, and the abscissa is the coordinate of the position corresponding to a single datum in m.
FIG. 4 is a spectrum diagram of the calibration area without void in example 11, with frequency values in Khz along the ordinate, and coordinates of the corresponding positions of the single measured point data in m along the abscissa.
FIG. 5 is a spectrum diagram of the region of the line 3 of example 11.
Fig. 6 is a plane image of the signal spectrum values measured by 5 measuring lines of example 11 compared with the calibration values, where the x-coordinate is the width direction and the y-coordinate is the length direction.
FIG. 7 is a three-dimensional spatial view of the void distribution throughout the test area of example 11, with the x-coordinate being the width direction, the z-coordinate being the survey line direction, and the y-coordinate being the depth direction.
FIG. 8 is a waveform diagram of single station data of the empty calibration area of example 12.
FIG. 9 is a waveform diagram of single station data of the calibration area without voids of example 12.
FIG. 10 is a waveform diagram of the area of the line 3 in example 12.
FIG. 11 is a plan view of an image of the 5 lines of example 12 with the duration of the signal compared to a calibration value, the x-coordinate being the width direction and the y-coordinate being the length direction.
FIG. 12 is a three-dimensional spatial view of the void distribution throughout the test area of example 12, with the x-coordinate being the width direction, the z-coordinate being the survey line direction, and the y-coordinate being the depth direction.
Detailed Description
In order to more clearly and specifically illustrate the technical solution of the present invention, the present invention is further described by the following embodiments. The following examples are intended to illustrate the practice of the present invention and are not intended to limit the scope of the invention.
Example 1
An audio frequency nondestructive testing method for the thickness and the void of a tunnel lining comprises the following steps:
A. finding out the known thickness H under the same working condition with the test object areabOr a certain number of measuring points are arranged in a known empty calibration area, and a vibration exciting hammer or an automatic vibration exciting device is used for knocking to collect effective audio signals;
B. waveform data analysis is carried out on the audio signal through frequency spectrum analysis, tunnel lining quality is analyzed through signal dominant frequency change, and the dominant frequency value f of the reflected signalbAs a judgment standard characteristic value;
C. arranging measuring points in a test area according to test requirements, carrying out coordinate positioning and recording on the measuring points, knocking by using an excitation hammer or an automatic excitation device, collecting effective audio signals, processing and analyzing waveform data by using an audio analysis system, and calculating a main frequency value f of the test areac；
D. The obtained main frequency value and the corresponding characteristic value f in the step B are comparedbAnd C, comparing, determining coordinates according to the step C, imaging all measuring points, and visually presenting the distribution condition of the quality problem of the whole test area.
The spectrum calculation adopts a maximum entropy method.
The maximum entropy method is a method for extrapolating the autocorrelation function, and there is no fixed window function in the analysis process. In each extrapolation process, the estimated correlation function contains the most information of the process, namely the unknown autocorrelation function value is determined under the condition that the entropy of the process is required to be maximum, so that the aim of the spectral estimation with the best fidelity and stability is fulfilled. I.e. the power spectrum is estimated using the criterion that the spectral entropy is maximal.
The maximum entropy spectrum has no defects caused by the consistent weakness that the traditional spectrum is subjected to data windowing, and is a continuous spectrum, so that theoretically, the spectrum is smooth, the spectrum peak is steep, the frequency resolution is infinitely high, the problem that the traditional spectrum is a discrete spectrum band to achieve frequency resolution errors does not exist, signal mutation can be caused due to signals such as defects in the actual tunnel detection process, the problem that the ideal triangular signal maximum entropy spectrum effectively solves the problem and the signal resolution precision is improved, and the calculation formula is as follows:
wherein: f: frequency, should be less than or equal to the nyquist frequency;
Pm+1: carry the output power of an m +1 point prediction error filter of order m (equal to the variance when averaging out)
)；
amnAutoregressive coefficients or linear prediction coefficients;
Pm+1amnand is given by the following relation:
example 2
An audio frequency nondestructive testing method for the thickness and the void of a tunnel lining comprises the following steps:
A. finding out the known thickness H under the same working condition with the test object areabOr a certain number of measuring points are arranged in a known empty calibration area, and a vibration exciting hammer or an automatic vibration exciting device is used for knocking to collect effective audio signals;
B. waveform data analysis is carried out on the audio signal through the continuous oscillation period of the time domain signal, and tunnel lining quality is analyzed through signal duration change so as to propagate signal durationSustained oscillation characteristic TdAs a judgment standard characteristic value;
C. arranging measuring points in a test area according to test requirements, positioning and recording coordinates of the measuring points, knocking by using an excitation hammer or an automatic excitation device, collecting effective audio signals, processing and analyzing waveform data by using an audio analysis system, and calculating a signal continuous oscillation period T of the test areac；
D. The obtained signal is continued for the oscillation period TcCharacteristic value T corresponding to step BdAnd C, comparing, determining coordinates according to the step C, imaging all measuring points, and visually presenting the distribution condition of the quality problem of the whole test area.
The signal oscillation period is a phenomenon that the signal duration time changes due to the change of the structural quality, the tunnel quality is evaluated, the signal duration time can be prolonged after the air is removed in general, the change value can be obtained through an original waveform time domain, and the method is simple and visual.
Example 3
This example is based on example 1:
the step D is carried out if fc＞fbJudging that the interior of the structure has no defect and the consolidation grouting quality is good; if fc＜fbJudging that the thickness of the lining is insufficient or the inside of the lining has defects; if fc＝fbAnd the fluctuation is within 5 percent, the lining thickness is judged to be normal, but the problem of void exists.
And B, taking the average value of the main frequency values of all measuring points in the calibration area as the judgment standard characteristic value in the step B, and correcting the average value and the standard deviation.
Example 4
This example is based on example 2:
the step D is carried out if Tc＜TdJudging that the interior of the structure has no defect and the consolidation grouting quality is good; if Tc＞TdJudging that the thickness of the lining is insufficient or the inside of the lining has defects; if Tc＝TdAnd the fluctuation is within 5 percent, the lining thickness is judged to be normal, but the problem of void exists.
And B, taking the average value of the continuous oscillation period of the signals of all measuring points in the calibration area by the judgment standard characteristic value in the step B, and correcting the average value and the standard deviation.
Example 5
This example is based on example 1:
the imaging means that a comparison result of corresponding measuring points is displayed through comparison colors in a coordinate system, and transition colors are used for displaying between two adjacent measuring points with different comparison results.
Example 6
This example is based on example 1:
by knowing the concrete thickness HbCalculating the wave velocity value v of the concrete in the calibration areabThe formula is vb＝2Hbfb(ii) a According to wave velocity vbCalculating the concrete thickness H of the test areacThe formula is Hc＝vb/2fc。
Example 7
This example is based on example 1:
and C, aiming at a test area with the thickness of 40cm, the hammer head of the vibration hammer is a stainless steel spherical hammer head with the diameter of 17mm, and the vibration voltage value is 4V.
Example 8
This example is based on example 1:
and C, aiming at a test area with the thickness of 80cm, the hammer head of the vibration hammer is a stainless steel spherical hammer head with the diameter of 40mm, and the vibration voltage value is 4V.
And adopting a directional microphone to collect audio signals, wherein the directional microphone keeps a distance of 5-10mm from the test surface during collection.
Example 9
This example is based on example 1:
and C, aiming at a test area with the thickness of 60cm, the hammer head of the vibration hammer is a stainless steel spherical hammer head with the diameter of 25mm, and the vibration voltage value is 4V.
And adopting a directional microphone to collect audio signals, wherein the directional microphone keeps a distance of 5-10mm from the test surface during collection.
The directional microphone is wrapped by soundproof cotton, the directional microphone is connected with the high-speed dynamic acquisition instrument, and the soundproof cotton is tightly attached to the surface of the test object.
Example 10
This example is based on example 2:
and adopting a directional microphone to collect audio signals, wherein the directional microphone keeps a distance of 5-10mm from the test surface during collection.
The directional microphone is wrapped by soundproof cotton, the directional microphone is connected with the high-speed dynamic acquisition instrument, and the soundproof cotton is tightly attached to the surface of the test object.
The effective audio signal is subjected to wave filtering processing in a preposed band-pass filter, and then the signal is subjected to filtering processing in the range of 1-12 kHz.
As shown in fig. 2, a high Q band pass filter circuit. The circuit adopts two high-input impedance operational amplifiers SF356, wherein the first stage is used as a common single-stage filter, the Q value is lower, the R3 value is smaller, the signal attenuation is larger, and the amplification factor is small. However, the second stage inverting proportional amplifier has the amplification factor of tens of times, and a certain amount of positive feedback is introduced to the input end of the first stage through R2, so that the Q value of the whole circuit is improved, and the filter has better frequency selection characteristics.
Example 11
The method for detecting the void of a certain tunnel under construction in Guizhou province comprises the following steps:
A. finding out the known thickness H under the same working condition with the test object areabIn the calibration area, measuring lines are arranged in the area with the void, the distance between each measuring point is 30cm, and data sampling is carried out; analyzing the audio signal by maximum entropy spectrum to determine the dominant frequency range, as shown in FIG. 3, the dominant frequency f of the void regionbIs 2.1Khz (the ordinate is frequency value in Khz, and the abscissa is position coordinate corresponding to single data in m) as judgment standard characteristic value fb(ii) a The data of the good region is sampled, as shown in FIG. 4, and the dominant frequency value of the good region is 4.5Khz (the ordinate is frequency value, single)Bit Khz, the abscissa is the coordinate of the corresponding position of single data, and the unit is m) for verification of the detection result and wave velocity vbCalculating; by a known thickness HbCalculating the wave velocity value v of the concrete at the calibration positionb；
B. Arranging 5 measuring lines along the tunnel direction, wherein 1 line is arched, 2 lines are arched, data testing is carried out by arranging measuring points along the measuring lines, the distance between the measuring points is 30cm, 5 measuring points are tested by each measuring line, knocking is carried out at the positions of the measuring points, signals are picked up, and audio signals are subjected to spectrum analysis by a maximum entropy method;
C. converging the spectrogram picked from one measuring line to the same interface, performing spectrum analysis on all waveforms to find out a main frequency value fcJudging whether the measuring point position is empty or not according to the main frequency value; and according to wave velocity vbCalculating the concrete thickness Hc。
The test result shows that: the main frequency values of the measuring lines 1, 2, 4 and 5 are 4.5Khz according to the main frequency value fc＞fbJudging that the interior of the offset part structure has no defect and the consolidation grouting quality is good without void; the main frequency value of the measuring line 3 is 2.1Khz, and the main frequency value fc＝fbThen, the lining thickness is judged to be normal but a void problem exists, see fig. 5, and the calculated concrete thickness is significantly lower than the known thickness of the calibration area. And comparing the main frequency values of the measuring lines 1, 2, 4 and 5 with the void-free area of the calibration area, wherein the main frequency values are consistent with the main frequency values of the void-free area, and the calculated thickness of the concrete is equivalent to the known thickness of the calibration area, thereby proving that the test result is correct.
Signal spectral values f measured by pairs of 5 measuring linescAnd a void-off calibration value fbAnd performing planar imaging on the comparison result, displaying the comparison result of the corresponding measuring point through a comparison color in a coordinate system, displaying the adjacent two measuring points with different comparison results by adopting a transition color (the x coordinate is the width direction, the y coordinate is the length direction), and displaying the difference in color as a measuring line 3 area as shown in fig. 6, wherein the difference in color is obviously empty and is abnormal to other measuring lines. Fig. 7 is a three-dimensional view of the void distribution state of the entire test area (x coordinate is the width direction, z coordinate is the survey line direction, and y coordinate is the depth direction).
Example 12
The method for detecting the void of a certain tunnel under construction in Guizhou province comprises the following steps:
for the detection of the under-construction tunnel void in the sichuan province, the detection method is the same as that in embodiment 11, the audio signal is analyzed through the continuous oscillation period of the time domain signal, and whether the void exists is judged through the signal continuous period. The method is visual and simple, and the void position can be judged from the duration time of the original signal.
Continuous oscillation characteristic T of propagation signals of each measuring point in void calibration areadReferring to fig. 8, the data feature has a long continuous oscillation time, a slow attenuation, and a cut-off standard of 0.2V or more, and an oscillation time of 5ms as a judgment standard characteristic value Td(ii) a The continuous oscillation characteristic of the propagation signal of each measuring point in the non-void calibration area is shown in figure 9, the continuous oscillation time of the data characteristic is short, the voltage with obvious attenuation is 0.2V and is used as the oscillation cut-off standard, the oscillation time is 1.2ms, and the continuous oscillation characteristic is used for verifying the detection result and the wave velocity VbCalculating; and calculating the wave velocity value v of the concrete at the calibration position through the known thickness of the non-void calibration areab。
Knocking and picking up signals at the positions of the measuring points, analyzing audio signals through the continuous oscillation period of time domain signals, converging the oscillogram picked up on one measuring line to the same interface, and calculating the continuous oscillation period T of the signals in the test area by taking the voltage of more than 0.2V as a cut-off standardc(ii) a And according to wave velocity vbCalculating the concrete thickness Hc。
The test result shows that: the oscillation time of the lines 1, 2, 4 and 5 is 1.2ms, according to Tc＜TdJudging that the interior of the part structure has no defect and the consolidation grouting quality is good without void; the oscillation period of the measuring line 3 is 5ms according to Tc＝TdThen, the lining thickness is judged to be normal but the problem of void exists, see fig. 10, and the calculated concrete thickness is significantly lower than the known thickness of the calibration area. And comparing the oscillation periods of the measuring lines 1, 2, 4 and 5 with the non-void area of the calibration area, wherein the oscillation periods are equivalent to the oscillation periods of the non-void area, and the calculated thickness of the concrete is equivalent to the known thickness of the calibration area, thereby proving that the test result is correct.
The oscillation period T of the signal measured by the 5 measuring linescAnd a void-off calibration value TdThe comparison result is subjected to planar imaging (x coordinate is the width direction, y coordinate is the length direction), as shown in fig. 11, the color difference part is the area of the measuring line 3, and there is an obvious void condition, which is abnormal to other measuring lines. Fig. 12 is a three-dimensional view of the void distribution state of the entire test area (x coordinate is the width direction, z coordinate is the survey line direction, and y coordinate is the depth direction).
The above-mentioned embodiments only express the specific embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.
Claims (10)
1. An audio frequency nondestructive testing method for tunnel lining thickness and void is characterized by comprising the following steps:
A. finding out the known thickness H under the same working condition with the test object areabOr a certain number of measuring points are arranged in a known empty calibration area, and a vibration exciting hammer or an automatic vibration exciting device is used for knocking to collect effective audio signals;
B. the waveform data analysis is carried out on the audio signal through the audio signal frequency spectrum analysis or the time domain signal continuous oscillation period, the tunnel lining quality is analyzed through the main frequency change or the duration change of the signal, and the main frequency value f of the reflected signal is obtainedbOr sustained oscillation characteristic T of the propagating signaldAs a judgment standard characteristic value;
C. arranging measuring points in a test area according to test requirements, carrying out coordinate positioning and recording on the measuring points, knocking by using an excitation hammer or an automatic excitation device, collecting effective audio signals, processing and analyzing waveform data by using an audio analysis system, and calculating a main frequency value f of the test areacOr signal duration oscillation period Tc；
D. The obtained main frequency value fcOr signal duration oscillation period TcCharacteristic value f corresponding to step BbOr TdAnd C, comparing, determining coordinates according to the step C, imaging all the measuring points, and visually presenting the distribution condition of the quality problem of the whole test area.
2. The method of claim 1, wherein step D, if f, is a non-destructive acoustic test of tunnel lining thickness and voidc＞fbJudging that the interior of the structure has no defect and the consolidation grouting quality is good; if fc＜fbJudging that the thickness of the lining is insufficient or the inside of the lining has defects; if fc＝fbAnd the fluctuation is 5 percent up and down, the lining thickness is judged to be normal but the problem of void exists; if Tc＜TdJudging that the interior of the structure has no defect and the consolidation grouting quality is good; if Tc＞cdJudging that the thickness of the lining is insufficient or the inside of the lining has defects; if Tc＝TdAnd the fluctuation is within 5 percent, the lining thickness is judged to be normal, but the problem of void exists.
3. The method for audio frequency nondestructive testing of tunnel lining thickness and void as claimed in claim 2 wherein said imaging means displaying the comparison result of the corresponding measuring point by contrast color in the coordinate system, and displaying the transition color between two adjacent measuring points with different comparison results.
4. The method of claim 1, wherein the concrete thickness H is known by an acoustic nondestructive test of tunnel lining thickness and voidbCalculating the wave velocity value v of the concrete in the calibration areabThe formula is vb＝2Hbfb(ii) a According to wave velocity vbCalculating the concrete thickness H of the test areacThe formula is Hc＝vb/2fc。
5. The method of claim 1, wherein the spectrum is calculated by maximum entropy method or signal duration oscillation period method.
6. The acoustic nondestructive testing method for the thickness and the void of the tunnel lining according to claim 1, wherein in the step C, aiming at a testing area with a thickness within 80cm, the hammer head of the vibration hammer is a stainless steel ball-shaped hammer head with a diameter of 17mm-40mm, and the vibration exciting voltage value is 4V.
7. The method of claim 1, wherein the acoustic frequency signal is collected by a directional microphone, and the directional microphone is spaced from the test surface by a distance of 5-10 mm.
8. The method of claim 7, wherein the directional microphone is wrapped with sound insulation cotton, the directional microphone is connected with the high-speed dynamic collection instrument, and the sound insulation cotton is tightly attached to the surface of the test object.
9. The method of claim 7, wherein the effective acoustic signal is filtered in a pre-bandpass filter and then filtered in the range of 1-12 kHz.
10. The audio frequency nondestructive testing method for tunnel lining thickness and void according to claim 1, wherein the judgment standard characteristic value of the step B is a main frequency value of each measuring point in a calibration area or an average value of a signal continuous oscillation period.
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