CN112098512A

CN112098512A - Grouting sleeve grouting defect detection method based on acoustic local resonance scattering characteristics

Info

Publication number: CN112098512A
Application number: CN202011038959.6A
Authority: CN
Inventors: 龙士国; 李德辉
Original assignee: Xiangtan University
Current assignee: Xiangtan University
Priority date: 2020-09-28
Filing date: 2020-09-28
Publication date: 2020-12-18
Anticipated expiration: 2040-09-28
Also published as: CN112098512B

Abstract

The invention discloses a grouting sleeve grouting defect detection method based on sound wave local resonance scattering characteristics, which comprises the steps of carrying out sound wave detection outside a to-be-detected part on the same side of a grouting sleeve, carrying out data processing on an obtained original echo signal to obtain an upper pulse envelope diagram, and extracting a sound wave local resonance scattering attenuation characteristic parameter alpha after fitting through a data formula so as to judge whether a void or a cavity exists in the sleeve. Compared with the prior art, the detection method provided by the invention has the advantages that the flow is simple, the labor intensity of workers is effectively reduced, the personnel allocation amount is reduced, the complicated work flow is reduced, the detection is carried out from the angle of energy attenuation in comparison with the traditional detection of the sound velocity and sound time angle of the void, and the accuracy of measurement can be improved.

Description

Grouting sleeve grouting defect detection method based on acoustic local resonance scattering characteristics

Technical Field

The invention belongs to the field of engineering technology detection, and particularly relates to a grouting sleeve grouting defect detection method based on a sound wave local resonance scattering characteristic.

Background

The prefabricated concrete structure building is an industrial building which is built by prefabricating and molding main components in a factory, assembling the main components on a construction site and connecting the components into a whole through a small amount of cast-in-place operation. The steel bar sleeve grouting connection is an important connection method of stressed steel bars in the structure, and a connection joint consists of ribbed steel bars, a sleeve and grouting materials. The connection principle is as follows: the ribbed steel bar is inserted into the sleeve, and the cement-based grouting material without shrinkage or micro expansion is poured into the sleeve to fill the gap between the sleeve and the steel bar, and the hardened grouting material is tightly meshed with the transverse rib of the steel bar and the inner wall groove or the convex rib of the sleeve, so that the external force borne by the two steel bars after connection can be effectively transmitted.

In engineering practice, grouting is completed when grouting slurry is poured into the lower hole and flows out of the upper hole, but actually, due to the fact that field influencing factors are more, the internal condition of the sleeve is more complex, and grouting fullness is difficult to grasp. At present, an effective detection method for detecting the grouting quality of the steel bar connecting sleeve does not exist. Because the grouting quality directly affects the safety of the structure, it is necessary to develop a nondestructive testing technology and an intelligent instrument for the grouting of the steel sleeve, and establish the grouting quality grade and the testing standard of the steel sleeve.

The acoustic wave detection is an effective nondestructive detection method and is widely applied to the detection of internal defects of the structure. The acoustic wave method has the advantages of easy excitation, simple detection process, convenient operation and the like. And sound waves with different frequencies can be selected for detection according to different detection objects. Research shows that much information capable of describing the internal defects of the structure is hidden in echo signals received by a sound wave instrument, and a large number of domestic researchers begin to carry out qualitative and quantitative research on the grouting quality of concrete members. However, the method has not yet researched and accurately detects the internal defects of the structure, and is a problem which needs to be solved urgently in the technical field of engineering structure defect detection.

Disclosure of Invention

In order to solve the technical problems, the invention provides a grouting sleeve grouting defect detection method based on the sound wave local resonance scattering characteristic, which can accurately detect the void position in a grouting sleeve.

A grouting sleeve grouting defect detection method based on sound wave local resonance scattering characteristics comprises the steps of carrying out sound wave detection outside a to-be-detected part on the same side of a compact grouting sleeve and the to-be-detected grouting sleeve, carrying out data processing on an obtained original echo signal to obtain a pulse upper envelope graph, carrying out data fitting through a formula (1), extracting a sound wave local resonance scattering attenuation characteristic parameter alpha through a formula (2), and comparing the characteristic parameters alpha of the compact grouting sleeve and the to-be-detected grouting sleeve, so that whether a void or a cavity exists in the sleeve is judged;

wherein x is a sound time value, x_cTime corresponding to the highest amplitude, y is the amplitude of the sound wave, y₀The initial amplitude of the sound wave when x is 0, e is a natural constant, A is a fitting function of an upper envelope function graph at y₀When the amplitude is 0, alpha is a characteristic parameter of local resonance scattering attenuation of the sound wave, and w is an intermediate parameter for solving alpha, and the parameters are obtained by computer fitting.

Preferably, the method provided by the invention comprises the following steps:

step a) establishing a computer or physical model, and determining material and sound wave parameters;

step b) determining a data fitting formula, namely formula (1) and formula (2), according to the material and the acoustic wave parameters in the step a;

step c) applying stress waves outside the model to be tested in the step a and receiving original echo signals;

step d) fitting an upper envelope function of the original echo signal obtained in the step c, and fitting an upper envelope function graph to obtain a characteristic parameter alpha of the local resonance scattering attenuation of the sound wave;

and e) comparing the obtained characteristic parameters alpha of the local resonance scattering attenuation of the sound wave, and determining whether the model to be tested is empty.

More preferably, the method specifically comprises:

step 1) applying stress waves to a position to be detected of a compact grouting sleeve by using a rare earth giant magnetostrictive transducer;

step 2) obtaining a sound wave time domain diagram according to the original echo signals received by the sensor on the same side of the compact grouting sleeve;

step 3) fitting an upper envelope function according to the sound wave time domain diagram obtained in the step 2 and the formula (1), and extracting an upper envelope function diagram of the pulse;

step 4) fitting the pulse upper envelope function graph obtained in the step 3 according to the formula (1), and extracting the full width at half maximum of the pulse upper envelope function graph as a characteristic parameter alpha of the local resonance scattering attenuation of the sound wave according to the formula (2);

and 5) repeating the step 1 to the step 4 at the position to be detected of the grouting sleeve to be detected, comparing the obtained compact grouting sleeve with the characteristic parameter alpha of the grouting sleeve to be detected, and judging whether a cavity exists in the position to be detected of the grouting sleeve to be detected.

Compared with the prior art, the method for detecting the grouting cavity of the grouting sleeve based on the acoustic local resonance scattering attenuation characteristic is to perform acoustic detection on the grouting sleeve; carrying out data processing on the received sound wave signals; extracting a characteristic parameter based on the local resonance scattering attenuation characteristic of the sound wave from the pulse echo signal; the parameter is defined as a local resonance scattering attenuation coefficient alpha, the rare earth giant magnetostrictive transducer is used for exciting an optimal fixed frequency sound wave, and the alpha value of the part to be detected is compared with the alpha value of the defect-free part, so that whether a grouting cavity exists in the grouting sleeve or not is judged.

The detection method provided by the invention has simple flow, effectively reduces the labor intensity of workers, reduces the personnel allocation amount, reduces the complicated working flow, is different from the traditional detection of the sound velocity and sound time angle of the void, detects from the angle of energy attenuation, and can improve the accuracy of measurement, and has the advantages that:

(1) the method can judge whether the cavity exists or not by measuring the local resonance scattering attenuation coefficient, overcomes the problem that whether the cavity exists in the sleeve is difficult to quantitatively judge in the prior art, and provides a basis for monitoring the grouting quality of the grouting sleeve;

(2) aiming at the particularity of the sleeve structure of the grouting steel bar, the rare earth giant magnetostrictive transducer is adopted to excite sound waves, so that the generation of the optimal fixed frequency sound waves suitable for the sleeve structure of the component is ensured, and the grouting steel bar sleeve is controlled by an instrument computer and has the advantages of high repeatability and high reliability;

(3) the invention adopts the method for measuring the local resonance scattering attenuation coefficient, can effectively eliminate the external interference such as artificial error or uneven contact surface in the detection process from the angle of energy, has accurate detection result and reduces the accident occurrence probability.

Drawings

FIG. 1 is a schematic diagram of the geometric significance of a fitting function of formula 1;

FIG. 2 is a finite element model diagram of a grouting sleeve with a cavity according to example 1 of the present invention;

FIG. 3 is a finite element model diagram of a grouting sleeve without a cavity according to example 1 of the present invention;

FIG. 4 is a comparison graph of local resonance scattering attenuation characteristic parameters alpha obtained by finite element model simulation of full grouting and non-grouting in embodiment 1 provided by the present invention;

FIG. 5 is a geometric model diagram of a grouting sleeve test piece according to example 2 of the present invention;

FIG. 6 is a drawing of a sample object of a grouting sleeve in example 2 according to the present invention;

FIG. 7 is a comparison graph of local resonance scattering attenuation characteristic parameters alpha obtained by actual measurement of fully grouted and grouted sleeves in example 2 provided by the present invention;

FIG. 8 is a pulse echo diagram of 20kHz, 30kHz, … kHz and 100kHz excitation frequency full grouting obtained by finite element modeling of a grouting sleeve in example 1 provided by the invention;

FIG. 9 is a graph showing the impulse echoes of 20kHz, 30kHz, … kHz and 100kHz excitation frequency of an unslotted grouting sleeve obtained by finite element modeling simulation in example 1 provided by the invention;

fig. 10 is a schematic diagram of a pulse echo actually measured by a grouting sleeve in example 2 according to the present invention;

fig. 11 is a graph of the upper envelope function of fig. 10.

Detailed Description

The present invention will be further specifically described with reference to the drawings and examples.

In practical development, the grouting cavity in the grouting sleeve is detected by various methods for research, and finally, the concept of the local resonance scattering attenuation coefficient alpha is provided in the invention. Resonance refers to the situation where a physical system vibrates at a specific frequency with a larger amplitude than other frequencies; these specific frequencies are referred to as resonant frequencies. At the resonant frequency, very small periodic oscillations can produce very large oscillations because the system stores kinetic energy. When the drag is small, the resonant frequency is approximately equal to the system natural or natural frequency, which is the frequency of free-running oscillations. Acoustic scattering refers to the phenomenon that when a sound wave encounters an obstacle during propagation, part of the sound wave deviates from the original propagation path and spreads around the obstacle. When sound waves are incident on the obstacle, the obstacle is excited by the incident sound to become a secondary sound source, and part of the incident sound energy is converted into scattered sound energy to be radiated to the periphery of the obstacle. The portion of the sound waves that are scattered around the obstruction is called the scattered sound waves.

Stress waves are excited at the same side of the grouting sleeve to be detected, the stress waves are subjected to acoustic scattering in the member, local resonance is generated at the reinforcing steel bar sleeve and the surrounding concrete, and the process is complex. When a cavity exists in the sleeve, the acoustic impedance value at the cavity wall is large, so that stress waves are reflected, refracted and scattered back and forth between the detection surface of the reinforcing steel bar sleeve and the grouting sleeve, local resonance scattering energy generated between the detection surface of the reinforcing steel bar sleeve and the detection surface of the grouting sleeve is large, the attenuation of echo signals received by the detection surface is slow, and the difference between the attenuation and the defect-free part is obvious, so that the local resonance scattering attenuation coefficient is proposed for quantification. The method proposed by the invention is verified in the following theoretical and physical aspects:

example 1 determination of whether to void by mathematical modeling

(1) Establishing a steel bar sleeve grouting structure finite element model, simulating typical steel bar sleeve grouting defects to select a material model, setting the elasticity modulus (E), the density (rho) and the Poisson ratio (v) of related materials according to actual conditions, establishing the steel bar sleeve grouting structure finite element model in COMSOL Multiphysics, and simulating the typical steel bar sleeve grouting defects, wherein the material parameters are shown in a table 1 as shown in figures 2 and 3.

TABLE 1

	E(GPa)	ρ(kg/m)	v
				Concrete and its production method	33	2600	0.2
Steel pipe	200	7850	0.3

(2) In COMSOL Multiphysics, before exciting the sound wave, the energy a of the excitation signal, the frequency of the half sine function, the position of the excitation point, etc. need to be set, fig. 2 and 3 are respectively full-grouting and non-grouting model diagrams, and specifically, the simulation of the sound wave detection process is performed on the to-be-detected surface of the grouting sleeve model by using the above frequency as the excitation frequency. Specifically, in the present embodiment, the inventors used a half-sine function F ═ Asin (2 tt/t)_C)(1＜t＜t_C) As an excitation function, the test is excited at the point A and received at the point B, and 20kHz, 30kHz, 40kHz, 50kHz, 60kHz, 70kHz, 80kHz, 90kHz and 100kHz are respectively taken as excitation frequencies to carry out simulation, so as to obtain a detection signal simulated in the acoustic wave detection process.

(3) Analyzing the collected simulated detection signal, wherein graphs of the simulated detection signal are shown in fig. 8 and fig. 9, fig. 8 and fig. 9 are graphs of original data waveforms obtained through simulation, acquiring an envelope function graph on a pulse through formula 1 by adopting Origin software, and fitting according to formula 2 by adopting the Origin software to obtain a full width at half maximum (namely, FWHM) value (in the invention, the full width at half maximum is defined as a local resonance scattering attenuation coefficient alpha), and the detection result is shown in table 2, and the data comparison result of the table 2 is shown in fig. 4.

Wherein x is a sound time value, x_cTime corresponding to the highest amplitude, y is the amplitude of the sound wave, y₀The initial amplitude of the sound wave when x is 0, e is a natural constant, A is a fitting function of an upper envelope function graph at y₀When the maximum amplitude is 0, α is a characteristic parameter of local resonance scattering attenuation of the acoustic wave, w is the length of an intersection point in the abscissa direction at a half value of the maximum value of y after fitting according to formula 1, and the length is obtained by computer fitting, wherein w is 1 in the embodiment; wherein α in formula 2 is a full width at half maximum value of the function of formula 1.

TABLE 2

As can be seen from table 2 and fig. 4, the difference between the α value when the grouting sleeve is grouted with a cavity and the α value when no cavity is present is significant, the α value is small when the grouting sleeve is fully grouted, and the α value is large when the grouting sleeve is not grouted.

Example 2 determination of whether or not to void by Material-of-Place experiments

In this embodiment, a TH402 type bellows grouting quality nondestructive detector is used for acoustic detection and analysis.

As shown in fig. 5 and 6, the inventor designs a properly simplified concrete grouting member physical model, and performs a sound wave test on the complete emptying and the complete compaction of the pipeline in the grouting member, and the concrete experimental steps are as follows:

(1) and dividing two groups of 6 measuring points on the surface to be measured of the grouting sleeve model, and respectively locating the full grouting part and the non-grouting part.

(2) Using a half-sine function F ═ Asin (2 π t/t)_C)(1＜t＜t_C) As an excitation function, exciting a stress wave on a to-be-detected surface of a grouting sleeve model through a TH-CCJ rare earth super-magnetic transducer, receiving the stress wave by a TH piezoelectric transducer, and performing data acquisition on the same side of a concrete grouting component model by using a TH402 type corrugated pipe grouting quality nondestructive detector, wherein an obtained original data waveform diagram is shown in FIG. 10;

(3) analyzing the collected detection signal measured value, fitting according to formula 1 to obtain an envelope function graph 11 on the pulse of the graph 10, fitting according to formula 2, extracting a full width at half maximum value, and obtaining local resonance scattering attenuation coefficient alpha data which is shown in a table 3 and a data comparison result of the table 3 which is shown in a table 7.

TABLE 3

Alpha/s of full grouting	Grouted alpha/s
		0.1172	0.2766
0.1041	0.1852
		0.00957	0.2007

As can be seen from table 3 and fig. 7, the difference between the α value when the grouting sleeve has a cavity and the α value when the grouting sleeve does not have a cavity is significant, the α value is small when the grouting sleeve is fully grouted, and the α value is large when the grouting sleeve is not grouted, which is consistent with the conclusion of example 1.

The foregoing is considered as illustrative of the preferred embodiments of the invention and is not to be construed as limiting the invention in any way. Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention should fall within the protection scope of the technical scheme of the present invention, unless the technical spirit of the present invention departs from the content of the technical scheme of the present invention.

Claims

1. A grouting sleeve grouting defect detection method based on sound wave local resonance scattering characteristics is characterized in that sound wave detection is carried out outside a to-be-detected part on the same side of a compact grouting sleeve and a to-be-detected grouting sleeve, an obtained original echo signal is subjected to data processing to obtain a pulse upper envelope graph, data fitting is carried out through a formula (1), a sound wave local resonance scattering attenuation characteristic parameter alpha is extracted through a formula (2), and the characteristic parameter alpha of the compact grouting sleeve and the to-be-detected grouting sleeve are compared, so that whether a void or a cavity exists in the sleeve is judged;

wherein x is a sound time value, x_cTime corresponding to the highest amplitude, y is the amplitude of the sound wave, y₀The initial amplitude of the sound wave when x is 0, e is a natural constant, A is a fitting function of an upper envelope function graph at y₀When the amplitude is 0, alpha is a characteristic parameter of local resonance scattering attenuation of the sound wave, w is an intermediate parameter for solving alpha, and w is 1 in the invention.

2. The grouting sleeve grouting defect detection method based on the acoustic local resonance scattering characteristic as claimed in claim 1, comprising the following steps:

3. The grouting sleeve grouting defect detection method based on the acoustic local resonance scattering characteristic as claimed in claim 1, comprising the following steps:

step 3) fitting an upper envelope function according to the sound wave time domain diagram obtained in the step 3 and the formula (1), and extracting an upper envelope function diagram of the pulse;