CN201034984Y - Acoustic vibration method cement pavement slab bottom void detector - Google Patents

Abstract

The utility model discloses an acoustic-vibration method cement road panel bottom disengaging detection device, including a drop hammer, a drop hammer lifting device, a directional sound sensor, a fourier converter, a characteristics parameter calculator, and a disengaging discriminator. The directional sound sensor directs to the drop hammer to knock the road and is connected with the fourier converter. The fourier converter is connected with the characteristics parameter calculator, and the characteristics parameter calculator is connected with the disengaging discriminator. The characteristics parameter calculator includes the power spectrum area calculator, a formant frequency calculator, a centroid calculator with the power spectrum area at the X shaft, the centroid calculator and the formant frequency calculator with the power spectrum area at the Y shaft. The utility model has advantages of convenient operation, fast and correct detecting and low price.

Description

Acoustic vibration method cement pavement slab bottom void detector

technical field

The utility model relates to a void detection technology for cement pavement slab bottom, in particular to an acoustic-vibration method cement pavement bottom void detector.

Background technique

Cement pavement voiding is one of the more difficult diseases to treat in cement pavement diseases. Since the voiding occurs at the bottom of the cement concrete slab, there is no obvious sign on the surface of the pavement, which causes some difficulties in the treatment of voiding. Due to the important influence of void damage on pavement performance, domestic and foreign road workers have done a lot of research on void detection and treatment. At present, the void judgment methods of cement concrete pavement can be mainly divided into the following categories:

(1) Appearance discrimination method

Including manual observation of the vibration of the board when the vehicle passes by, the phenomenon of water and mud pumping at the seam in rainy days, etc., and whether there is mud deposit on the edge of the board seam, etc.

(2) Artificial impact method

Hit the edge of the board with iron brazing, and judge whether it is empty according to different sounds. This method requires experienced people to judge, and only the board with obvious emptying can be judged.

(3) Deflection discrimination method

The deflection of two adjacent slabs is measured by Beckman beams, and a comprehensive judgment is made based on the deflection value of the loaded slab and the deflection difference between the loaded slab and the unloaded slab.

(4) Multi-level load regression method

In this method, the falling weight deflectometer (FWD) is used to carry out multi-level load loading, and the deflection regression lines under different loads are drawn to judge the void.

(5) Back analysis method

The deflection value of the pavement is measured by FWD, the modulus of each layer of the pavement structure is back-calculated, and the gap is judged by comparing the theoretical deflection value of the slab edge with the measured deflection value.

Among the above methods, the appearance discrimination method and the manual impact method are simple to operate, have many human factors, poor accuracy, and cannot be quantified; the deflection discrimination method is simple to calculate but the accuracy is not high, and it cannot be accurately quantified. For different structures, it is necessary to correct the void standard, which does not have wide applicability; the results obtained by different inverse calculation programs for the inversion analysis method are not the same; the multi-level load regression method depends on the detection equipment FWD. The detection cost is much higher than other detection methods. In addition, the road sections that need to be paved and reconstructed are mostly road sections that are open to traffic. In order not to affect the traffic, only a section of road with one lane is usually closed when the pavement is added. Due to its large size, FWD is not convenient for detection close to traffic. The board angle on one side is not easy to turn around (expressway access control, two-way split driving). Therefore, there will be a lot of inconvenience in detection and grouting acceptance. Therefore, there is an urgent need for a detection method with the characteristics of convenient operation, flexibility, speed, accuracy and low cost in actual production.

Utility model content

The purpose of the utility model is to overcome the deficiencies of the prior art, and provide an instrument for void detection at the bottom of the cement pavement slab by the acoustic vibration method, which is easy to operate, flexible, fast, accurate and low in cost.

The technical solution for realizing the utility model is shown in Fig. 1: a kind of vibroacoustic method cement road slab bottom void detector, including drop hammer, drop hammer lifting device, directional sound sensor, Fourier transformer, characteristic parameter calculator, The void discriminator, the directional sound sensor points to the position where the falling hammer hits the road surface, the directional sound sensor is connected with the Fourier transformer, the Fourier transform is connected with the characteristic parameter calculator, and the characteristic parameter calculator is connected with the void discriminator, the feature Parameter calculators include Power Spectral Area Calculator, Formant Frequency Calculator, Centroid Calculator of Power Spectral Area in the X-axis direction, Centroid Calculator of Power Spectral Area around the Y-axis, and Formant Amplitude Calculator.

In order to reduce the noise of the drop hammer after hitting the road surface, the drop hammer has been specially designed. As shown in Figure 4, the drop hammer includes a rod body 103 and a hammer body 109; the rod body 103 has a protruding eaves 102, The lower end of the rod body 103 is double-convex, and the lower end has a conical concave; the hammer body 109 is formed by combining a trapezoidal cone and a hemispherical body, and the combined part has convex eaves, and there are more than 3 through holes in the convex eaves. Hole 108, the angle of the conical part of described rod body 103 and hammer body 109 is consistent, and rod body 103 has the corresponding through hole 105 with the through hole 108 of hammer body, and described rod body 103 and hammer body 109 are connected by bolt 104 are fixed together, and there is a plastic gasket 106 corresponding to the through hole 107 in the middle.

In order to reduce the noise when the falling weight falls, as shown in FIG. 4 , there is a plastic cladding 101 from the protruding eaves 102 on the rod body of the dropping weight to the upper end of the rod body.

In order to further reduce the noise when the falling weight falls, as shown in FIG. 4 , there is also a plastic cladding 101 at the lower end of the rod from the protruding eaves 102 on the rod of the falling weight about 10 cm down.

As shown in Figure 6, the drop weight lifting device includes a screw 3, a motor 6 that drives the screw to rotate forward and reverse, a guide rail 7 parallel to the screw, and a hammer grabbing mechanism 5; Grabbing hammer mechanism 5 cooperates with screw mandrel 3, and the rotation of screw mandrel 3 drives grabbing hammer mechanism 5 to move up and down along guide rail 7; Described grabbing hammer mechanism 5 includes a jaw 20, an electromagnet 21 and a positioning ring 19, The rod body 103 of the drop hammer 1 passes through the jaw 20 and the positioning ring 19 .

In order to reduce the noise when the falling hammer falls, as shown in Figure 7, more than three thin ropes 22 are fixed on the positioning ring 19, and the thin ropes 22 prevent the rod body 103 of the falling hammer 1 from touching the positioning ring 19 to emit noise. noise.

In order to further reduce the noise of the system, the jaws 20 can be covered with a plastic coating.

The acoustic vibration method for detecting voids at the bottom of cement pavement slabs comprises the following steps:

(1) The falling hammer hits the cement pavement, and the cement board makes a sound;

(2) The directional sound sensor obtains the sound signal sent by the cement board and transmits it to the PC, and the PC performs follow-up processing;

(3) The sound signal is converted into a frequency domain signal through Fourier transform;

(4) Calculate the power spectrum area according to the frequency domain signal, the calculation formula is

$\mathrm{<span\; class="notranslate">\; AREA</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; ;</span>$

Where: Pi is the power spectrum amplitude corresponding to each frequency,

K is the number of samples collected;

(5) Calculate the formant frequency according to the frequency domain signal, the calculation formula is

Fres=F(Pi.max);

Where: Fi is the frequency corresponding to each power spectrum amplitude;

(6) Calculate the centroid of the power spectrum area in the X-axis direction according to the frequency domain signal, the calculation formula is

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; ;</span>$

(7) Calculate the centroid of the power spectrum area in the Y-axis direction according to the frequency domain signal, the calculation formula is

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; Y</span>}}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; ;</span>$

(8) Calculate the formant amplitude according to the frequency domain signal, the calculation formula is

Amp=A(Pi.max);

(9) According to the calculation results of steps (4) to (8), the discrimination is carried out according to the following discriminant function:

Y＝Y ₀ +Y ₁ ×AREA+Y ₂ ×Fres+Y ₃ ×C _X +Y ₄ ×C _Y +Y ₅ ×Amp;

If the calculated Y<0, the cement board is in a dense state, on the contrary, if Y>0 is in a void state, and if Y=0, the cement board is in a weakly supported state;

In the above formula, Y ₀ , Y ₁ , Y ₂ , Y ₃ , Y ₄ , and Y ₅ are specific data obtained after curve fitting according to test data.

The above formula is preferred:

Y=4.59492-0.0021×AREA-13.9658×Fres

+0.05971×C _X −0.00023×C _Y −5.62116×Amp.

Compared with the prior art, the utility model has the following advantages and effects:

(1) The selection of the directional sound sensor weakens the interference of the vehicle noise on the detection signal;

(2) Easy to operate;

(3) Fast and accurate detection;

(4) The cost is low.

Description of drawings

Fig. 1 is the structural block diagram of the detector of the present invention.

Fig. 2 is a schematic diagram of the internal structure of an embodiment of the detector of the present invention.

Fig. 3 is a schematic front view of an embodiment of the detector of the present invention.

Fig. 4 is a structural schematic diagram of the drop hammer.

Fig. 5 is a schematic top view of the drop hammer.

Figure 6 is a schematic diagram of the lifting device.

Fig. 7 is a schematic diagram of the positioning ring string.

As shown in the figure, 1: drop hammer, 2: drop hammer fixing device, 3: screw rod, 4: battery, 5: hammer grabbing mechanism, 6: motor, 7: guide rail, 8: casing, 9: electric control device , 10: Fixing screw, 11: Power inverter, 12: Directional sound sensor, 13: Power switch, 14: Start button, 15: Up limit switch, 16: Down limit switch, 17: Up indicator light, 18: Clamping indicator light, 19: Positioning ring, 20: Gripper jaw, 21: Electromagnet, 22, string, 101: Plastic cladding, 102: Convex eaves, 103: Rod body, 104: Bolt, 105: Tong Hole, 106: plastic gasket, 107: gasket through hole, 108: through hole, 109: hammer body.

Detailed ways

Below in conjunction with accompanying drawing, the utility model is described in detail.

Fig. 1 is the schematic block diagram of the structure of the detector of the present utility model, and the water surface road surface sends out sound after the falling weight hits the ground, and the directional sound sensor obtains the sound signal and is transformed into a frequency domain signal by a Fourier transformer, and the Fourier transform formula is:

<x(τ), g _{t, Ω} (τ)>=<x(τ), g(t-τ)e ^jΩτ dτ>=STFT _x (t, Ω)

In the formula:

Ω=2πf, the unit is rad/s

After Fourier transform, five sound characteristic parameters such as power spectrum area, formant frequency, center of mass of power spectrum area in the X-axis direction, center of mass of power spectrum area around the Y-axis and formant amplitude are extracted from the frequency domain. The void discriminator performs void discrimination according to the discriminant formula.

Fig. 2 is a schematic diagram of the internal structure of an embodiment of the detector of the present invention, Fig. 3 is a schematic diagram of the corresponding front panel, and Fig. 6 is a corresponding more concise schematic diagram. In the picture, 1 is the drop hammer, which is used to hit the ground to make a sound; 2 is the drop hammer fixing device, which prevents the drop hammer from damaging other parts during transportation; 3 is the screw rod; 4 is the battery; 5 is the hammer grasping mechanism, controlled by the electromagnet 21 After the gripper 20 is closed and the drop hammer 1 is lifted to the upper limit position, the start button 14 is manually pressed to power off the electromagnet, the gripper 20 is released, the up indicator light 17 is off, and the drop hammer 1 falls and hits the ground; 6 is the motor; 7 8 is the casing, protecting the internal structure; 9 is the electric control device, controlling the power on and off, and controlling the lifting of the falling hammer; 10 is the fixing screw, preventing the falling hammer from damaging other parts during transportation 11 is a power inverter for the power supply of parts such as motor 6 and electromagnet 21; 12 is a directional sound sensor; 13 is a power switch; 14 is a start button; 15 is an upward limit switch, and the hammer mechanism rises to touch Travel limit switch 15, the motor stops rotating immediately, and the up indicator light 17 is bright; 16 is the down limit switch, and the hammer mechanism descends and touches the down limit switch 16, and the motor stops rotating immediately; 17 is the up indicator light; 18 : Clamp indicator light.

The detection process of the detector is as follows:

Turn on the main power switch 13 to obtain power, press the start button 14, the jaws 20 clamp the drop hammer 1, the clamping indicator light 18 lights up, the motor 6 drives the screw rod 3 to drive the grasping hammer mechanism to rise, and the drop hammer 1 rises to a certain level. The height touches the upper limit limit switch 15 to stop, and the upward in place indicator light 17 is on; after pressing the start button 14, the jaws 20 are released, the clamping indicator light 18 is off, the upward in place indicator light 17 is off, and the drop hammer 1 falls freely, slightly The rear grasping hammer mechanism 5 is driven down by the screw rod 3 to trigger the lower limit switch 15 and then stops, then the jaws 20 clamp the falling hammer 1, the clamping indicator light 18 lights up, and the motor 6 drives the screw rod 3 to drive the hammer grasping mechanism to rise. Falling weight 1 rises to a certain height and touches the upper limit switch 15 to stop, and the up indicator light 17 is on, waiting to manually press the start button 14 to detect next time.

Fig. 4 is a structural schematic diagram of the drop hammer of the embodiment, and Fig. 5 is a corresponding top view schematic diagram. It can be seen from FIG. 5 that the present embodiment is fixed by 6 bolts 104 , but it does not mean that 6 bolts 104 must be used for fixing, and the number of bolts 104 should be more than 3. In order to facilitate transportation, a screw hole can be opened at the upper end of the rod body 103 of the drop hammer 1 to facilitate fixing.

Fig. 7 is a schematic diagram of the positioning ring string. In the figure, the number of strings is 8, but it does not mean that there must be 8 strings. More than 3 strings can ensure that the rod body 103 of the drop hammer 1 does not touch the positioning ring, but it is necessary to ensure that the rod body 103 Certain free swinging space is arranged, can not destroy the free fall of drop hammer 1.

Claims (7)

1. A void detection instrument at the bottom of a vibratory acoustic cement pavement, comprising a drop hammer and a drop hammer lifting device, characterized in that: it also includes a directional sound sensor, a Fourier transformer, a characteristic parameter calculator, a void discriminator, and an orientation The sound sensor points to the position where the falling weight hits the road surface, the directional sound sensor is connected with the Fourier transformer, the Fourier transformer is connected with the characteristic parameter calculator, and the characteristic parameter calculator is connected with the void discriminator, and the characteristic parameter calculator includes the power spectrum Area Calculator, Formant Frequency Calculator, Centroid Calculator of Power Spectral Area in X-axis Direction, Centroid Calculator of Power Spectral Area Around Y-axis, and Formant Amplitude Calculator. 2. The acoustic-vibration method cement pavement bottom void detector according to claim 1 is characterized in that: the drop hammer includes a rod body and a hammer body: there is a protruding eaves on the rod body, and the lower end of the rod body is Double convex, and a conical concave at the lower end; the hammer body is composed of a trapezoidal cone and a hemispherical body. It is consistent with the angle of the conical part of the hammer body. The rod body has a through hole corresponding to the through hole of the hammer body. The rod body and the hammer body are fixed together by bolts, and there is a plastic gasket with a corresponding through hole in the middle. . 3 . The acoustic-vibration method cement pavement bottom void detector according to claim 2 , characterized in that: there is a plastic cladding from the protruding eaves on the rod body of the drop hammer to the upper end of the rod body. 4 . 4 . The vibratory-acoustic method for detecting voids at the bottom of cement pavement slabs according to claim 3 , wherein there is a plastic cladding on the protruding eaves on the rod body of the drop hammer down to the lower end of the rod body. 5. The acoustic-vibration method cement pavement slab bottom void detector according to claim 4 is characterized in that: the drop weight lifting device comprises a screw mandrel, a motor that drives the screw mandrel to rotate forward and reverse, A guide rail parallel to the screw rod, and a hammer grab mechanism; the hammer grab mechanism is matched with the screw rod, and the hammer grab mechanism is driven to move up and down along the guide rail by the rotation of the screw rod; the hammer grab mechanism includes a gripper, an electromagnetic Iron and a positioning ring, the rod body of the drop hammer passes through the jaws and positioning ring. 6. The acoustic-vibration method cement pavement bottom void detector according to claim 5, characterized in that: more than 3 thin ropes are fixed on the positioning ring, and the thin ropes prevent the rod body of the falling hammer from touching to the retaining ring and make noise. 7. The instrument for void detection at the bottom of cement pavement slab by acoustic vibration method according to claim 6, characterized in that: said clamping jaws are covered with plastic.

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