A stethoscope device for tunnel crack repair detection

Abstract

The application discloses a wave signal amplification stethoscope device for tunnel crack repair detection, which comprises a transmitting system and a signal amplification measuring system. The transmitting system is connected with the signal amplification system through a signal transmission line. Different initial waveforms and frequencies of incident waves are obtained by using prefabricated pneumatic bullets with different diameters, and the incident waves can be transmitted to an ultradynamic strain recorder in real time. The device releases impact load to a tunnel crack repair layer, and the impact load is reflected by the bonding surface between the concrete lining layer and the repair material, so that stress wave reflection waves continue to propagate in the medium. When the reflection waves are transmitted to the interface between the repair material layer and the stethoscope, the different wave impedances of the layers can be caused by controlling the interface density and the longitudinal wave velocity of each layer, so that the transmission signal can be amplified by several times. After being amplified through multiple interfaces, the wave signal which is easy to capture and receive is obtained, and the wave signal can be used to evaluate the quality of the tunnel crack repair after being processed.

Description

Technical Field

[0001] This invention relates to the field of engineering construction testing, specifically a signal amplification stethoscope device for detecting tunnel crack repair. Background Technology

[0002] Tunnels are engineering structures buried underground, and can be divided into traffic tunnels, hydraulic tunnels, municipal tunnels, etc. Regardless of the type, if cracks appear in the tunnel walls after construction, it will significantly impact the stable operation of the project. Cracks, especially in the tunnel roof, can cause water leakage, material loss, and in severe cases, even safety accidents.

[0003] Current methods for repairing tunnel cracks generally employ grouting and sealing. The grout enters the crack and, after being chiseled open, shares the stress with the original concrete lining, forming a bond interface. However, the quality of this bond is currently difficult to measure non-destructively in the field. Traditional methods for measuring bond interface strength, such as drilling and pull-out methods, damage the original bond layer, rendering the measurement impossible. With the gradual maturation of wave testing technology, it has become possible to use waves as information carriers and obtain incident and reflected wave signals through non-contact measurement to determine the stiffness of the bond interface within rock or concrete. This holds promise as an indicator for evaluating the repair status of tunnel lining cracks. However, in practical applications, accurately measuring wave signals in the field is challenging, and the strain signals observed in the field after loading are very small, hindering measurement and analysis. Summary of the Invention

[0004] To address the various shortcomings in the detection and analysis of tunnel crack repair mentioned above, this invention provides a signal amplification stethoscope device for tunnel crack repair detection. Its main purpose is to solve the problem of difficulty in measuring wave signals during tunnel crack repair detection. This device amplifies the transmitted wave signal, thereby making test data more accurate and easier to obtain, and also simplifies its operation.

[0005] The technical solution adopted in this invention is: a signal amplification stethoscope device for tunnel crack repair detection, comprising two parts: a transmitting system and a signal amplification measurement system. The transmitting system 4 and the signal amplification system 5 are wiredly connected via a signal transmission line. The purpose is to drive the pneumatic bullet to obtain different initial velocities by setting different compressor powers to release different impact loads. By using prefabricated pneumatic bullets of different diameters, incident waves with different initial waveforms and frequencies are obtained and can be transmitted to the ultra-dynamic strain recorder 18 in real time and at high speed. The signal amplifier stethoscope device first releases an impact load to the tunnel crack repair layer through device 4. This load will cause the stress wave incident wave ε1(t) to be generated within the repair interface. After being reflected by the bonding surface between the concrete lining layer and the repair material, the stress wave reflected wave ε2(t) will be generated and continue to propagate in the medium. When the reflected wave ε2(t) is transmitted to the interface between the repair material layer and the stethoscope interface, by controlling the different interface densities and longitudinal wave velocities of each layer, the wave impedance of the material layer can be different, which can amplify the transmitted signal several times. After multi-layer interface amplification, a wave signal that is easy to capture and receive will be obtained. The strain-time curve of the amplified time-domain reflected wave ε2(t) will be obtained in the ultra-dynamic strain gauge 18. After processing, it can be used to evaluate the quality of tunnel crack repair.

[0006] The launching system of this invention includes a pneumatic bullet 8, an air valve connection channel 9, an air gun safety switch 10, an air gun sight 11, and an air gun trigger 12. The pneumatic spray gun serves as the carrier of the launching system. The pneumatic bullet 8 is loaded into the barrel of the pneumatic spray gun. The air valve connection channel 9, the pneumatic spray gun barrel, and the pneumatic spray gun chamber are interconnected. The air gun safety switch 10 is located inside the pneumatic spray gun chamber to apply the impact force after the pneumatic bullet 8 is ejected. The air gun sight 11 is located outside the pneumatic spray gun chamber for aiming when launching the pneumatic bullet 8. The air gun trigger 12 is the control switch for the pneumatic bullet 8; pressing the air gun trigger 12 initiates the measurement. An air compressor connected to an air valve drives the pneumatic bullet. The initial velocity of the pneumatic bullet 8 can be changed by adjusting the air pressure, thereby obtaining incident waves ε1(t) with different initial wave velocities. By controlling the diameter of the loaded bullet, incident waves ε1(t) with different initial waveforms can be obtained.

[0007] The signal amplification and measurement system of this invention comprises three stethoscope interfaces. Following the signal amplification sequence, stethoscope interface 16 is the first stethoscope interface, stethoscope interface 15 is the second amplification interface, and stethoscope interface 14 is the third amplification interface. The wave signal is amplified three times as it passes through these three stethoscope interfaces. The three stethoscope interfaces are 3D printed from the same material. The first stethoscope interface 16 is printed from a solid material, while the second and third stethoscope interfaces 15 and 14 are printed from non-solid materials. Furthermore, the second and third stethoscope interfaces 15 and 14 have different perforation ratios; the second stethoscope interface 15 has a smaller perforation ratio, while the third stethoscope interface 16 has a larger perforation ratio. Although the three stethoscope interfaces are made of the same material, their different perforation ratios result in different apparent densities, wave velocities, and therefore different wave impedances (z). The wave impedance (z) is related to both apparent density and longitudinal wave velocity, with a higher apparent density resulting in a higher longitudinal wave velocity. By controlling the wave impedance of the first stethoscope interface 16 to be less than that of the repair layer material, the wave impedance ratio is made less than 1, and the wave signal will be amplified when it passes through. The wave impedance of the second stethoscope interface 15 is less than that of the first stethoscope interface 16; the wave impedance of the third stethoscope interface 14 is less than that of the second stethoscope interface 15, and the wave signal will also undergo two more amplifications, for a total of three signal amplifications. The three stethoscope interfaces are connected in series by the stethoscope spindle 13. Each interface is fitted with a strain gauge 17, and a hyperdynamic strain gauge 18 is connected to the strain gauge 17. The hyperdynamic strain gauge 18 captures the time-domain reflected wave signal ε2(t)2 after signal amplification. This signal can be used to evaluate the quality of tunnel crack repair. This signal is the signal obtained by amplifying the reflected wave signal ε2(t) through the stethoscope. The reflected wave signal ε2(t) is the signal obtained by reflecting the incident wave signal ε1(t) through the bonding surface between the concrete lining layer and the repair material.

[0008] The wave impedance z of the material:

[0009] Z = ρ × v

[0010] The wave impedance ratio n of the two materials:

[0011] n = z1 / z2

[0012] The transmittance M at the interface between the two materials:

[0013]

[0014] The elastic modulus of the material can be derived from the density ρ and the material wave velocity V:

[0015] E = ρv 2

[0016] The magnitude of the wave signal after transmission through the interface is related to the interface wave impedance ratio, and the stress after transmission is obtained as follows:

[0017] σ2=M×σ1

[0018] According to the constitutive equation of the material:

[0019]

[0020] The strain after interfacial transmission amplification is derived as follows:

[0021]

[0022] In the formula, ρ is the density of the material; v is the longitudinal wave velocity of the material; n is the wave drag ratio at the interface between the two materials; M is the transmission coefficient at the interface between the two materials; σ1 is the stress before amplification; σ2 is the stress after amplification; ε1 is the strain before amplification; and ε2 is the strain after amplification.

[0023] definition H is the signal amplification factor, which determines the amplification factor of the wave signal when it passes through the interface. The density of the material is controlled by 3D printing. For the same material, the greater the porosity, the lower the density, and the longitudinal wave velocity is also relatively reduced.

[0024] Compared with existing technologies, it is difficult to accurately measure the wave signal on-site during tunnel crack repair detection. The strain signal observed on-site after loading is very small, which is not conducive to measurement and analysis. This invention proposes a simple amplified stethoscope for tunnel crack repair detection, comprising a transmitting system and a signal amplification and measurement system. The transmitting system generates an impact load-induced stress wave, and the simple signal amplification and measurement system amplifies the reflected wave signal after reflection, obtaining a time-domain reflected wave signal to evaluate the quality of tunnel crack repair. Compared with existing technologies, this invention has the following gain effects:

[0025] 1) Traditional drilling and pull-out methods for measuring the strength of the bond interface can damage the original bond layer, making it impossible to continue working after the measurement. This invention applies the wave method to the testing technology, using waves as the information carrier. By using the incident and reflected wave signals obtained through non-contact measurement, the stiffness of the bond interface inside the rock or concrete can be obtained to evaluate the quality of tunnel crack repair. Work can continue after the measurement.

[0026] 2) Directly applying the wave method to testing techniques has many limitations. Currently, in practical applications, the range of wave signals measured in the field is very limited, and the wave signals generated within rock or concrete layers are also very small. This invention uses a simple signal measurement amplifier to increase the wave signal measurement range.

[0027] 3) The amplifier system of this device is detachable, easy to carry, can be assembled on site, has high measurement accuracy, is easy to operate, and is easy to learn. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the signal amplification stethoscope device for detecting tunnel crack repair, which is involved in the present invention.

[0029] Figure 2 This is a schematic diagram of a signal amplification and measurement system.

[0030] Figure 3 This is a schematic diagram of the cross-sections of each auscultation interface.

[0031] Figure 4 This is a schematic diagram of the signal after being amplified by the device.

[0032] In the diagram: 1-Concrete lining or rock layer; 2-Crack repair layer; 3-Bond interface; 4-Launch system; 5-Signal amplification and measurement system; 6-Incident wave ε1(t); 7-Reflected wave ε2(t); 8-Pneumatic bullet; 9-Air valve connection channel; 10-Air gun safety switch; 11-Air gun sight; 12-Air gun trigger; 13-Stethoscope spindle; 14, 15, 16-Three-stage stethoscope interface; 17-Strain gauge; 18-Ultra-dynamic strain gauge. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0034] The specific implementation process is as follows:

[0035] Step a. In this embodiment, repair material 2 is a geopolymer material with a density ρ1 = 3200 kg / m³. 3 The wave velocity v1 = 3900 m / s. The first layer of the stethoscope interface 16 is made of magnesium using 3D printing technology. It is a solid material, and the cross-sectional view of the material is shown below. Figure 3 As shown, its density ρ2 = 1500 kg / m³ 3 The wave velocity v1 = 3000 m / s. Based on the derivation of the amplification factor, the amplification factor H1 = 1.91 can be calculated. The wave signal will be amplified by 1.91 times after passing through this interface. The second stethoscope interface 15 is also made of magnesium material by 3D printing, but it is not a completely solid material. The hollow ratio is 50%, and its density ρ3 = 750 kg / m³. 3 With a wave velocity v1 = 2300 m / s, the amplification factor H2 = 1.72 can be calculated, meaning the wave signal will be amplified by a factor of 1.72 after passing through this interface. The third stethoscope interface 14 is made of lithium via 3D printing, with a hollowness ratio of 60% and a density ρ4 = 200 kg / m³. 3With a wave velocity v1 = 1500 m / s, the amplification factor H3 = 3.05 can be calculated. The wave signal will be amplified by 2.61 times after passing through this interface. After signal amplification through three layers of stethoscope interfaces, the original signal will ultimately be amplified by 8.5 times.

[0036] Step b. An impact load is released onto the tunnel crack repair layer via the launching device 4. This load will cause the incident stress wave ε1(t) to be generated within the repair interface. Through reflection from the bonding surface 3 between the concrete lining layer 1 and the repair material 2, a reflected stress wave ε2(t) will be generated and continue to propagate in the medium. When the reflected wave ε2(t) reaches the junction of the geopolymer repair material layer 2 and the first stethoscope interface 16, by controlling the density of the material printing, the amplified strain can be made 1.91 times the original strain, making it easier to detect. By using 3D material printing, the hollow ratio of each stethoscope interface is different, and the signal can ultimately be amplified to 8.5 times. After signal amplification through the three stethoscope interfaces, the strain-time curve of the time-domain reflected wave ε2(t) will be obtained in the ultra-dynamic strain gauge 18. The strain-time curve of the time-domain incident wave ε1(t) can be obtained from the air pressure and the diameter of the bullet.

[0037] Step c. Process the obtained wave signal to evaluate the quality of tunnel crack repair. Figure 4 This is a magnified waveform diagram of the different auscultation interfaces of this device.

[0038] The core of this invention is a wave signal amplification stethoscope device for tunnel crack repair detection based on stress wave wave theory. It emits stress waves through a transmission system and amplifies the time-domain reflected wave signal through a simple signal amplification and measurement system, resulting in a large wave signal measurement range, high measurement accuracy, and simple operation.

[0039] The specific implementation methods described above are a detailed explanation of the purpose, technical solution, and beneficial effects of the present invention, and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A signal amplification stethoscope device for tunnel crack repair detection, characterized by, It comprises two parts: a launching system and a signal amplification and measurement system. The launching system and the signal amplification system are wiredly connected via a signal transmission line. The purpose is to drive the pneumatic bullet to achieve different initial velocities by releasing different impact loads through different compressor powers. By using pre-made pneumatic bullets of different diameters, different initial waveforms and frequencies of incident waves are obtained and transmitted in real-time to the ultra-dynamic strain recorder. The signal amplification and measurement system includes three stethoscope interfaces. Following the signal amplification sequence, the first stethoscope interface is the first amplification surface, the second stethoscope interface is the second amplification surface, and the third... The stethoscope interface is the third amplification interface; the wave signal is amplified three times as it passes through the three layers of the stethoscope interface. The three stethoscope interfaces are 3D printed from the same material, with the first stethoscope interface being a solid material, while the second and third stethoscope interfaces are made of non-solid materials. The second and third stethoscope interfaces have different perforation ratios; the second stethoscope interface has a smaller perforation ratio, while the third stethoscope interface has a larger perforation ratio. Because the three stethoscope interfaces are made of the same material but have different perforation ratios, their apparent density and wave velocity differ, resulting in different wave impedances (z). The wave impedance z is different from the apparent density and the longitudinal wave velocity; the higher the apparent density, the higher the longitudinal wave velocity. By controlling the wave impedance at the first auscultation interface to be less than the wave impedance of the repair layer material, the wave impedance ratio is made less than 1, and the wave signal will be amplified when it passes through. The wave impedance at the second auscultation interface is less than that at the first auscultation interface. The wave impedance at the third auscultation interface is less than that at the second auscultation interface, and the wave signal will also undergo two more amplifications, for a total of three signal amplifications. The device releases an impact load to the tunnel crack repair layer, which will cause the incident wave signal ε1(t) of the stress wave to be generated in the repair interface, and then pass through the concrete lining. The reflection from the bonding surface between the masonry layer and the repair material generates a stress wave signal ε2(t) that continues to propagate in the medium. When the reflected wave signal ε2(t) reaches the interface between the repair material layer and the auscultation interface, the wave impedance of the auscultation interface layer material is different due to the control of the interface density and longitudinal wave velocity of each auscultation interface layer, which amplifies the transmitted reflected wave signal several times. After multi-layer interface amplification, a wave signal that is easy to capture and receive is finally obtained. The strain-time curve of the amplified time-domain reflected wave signal ε2(t)2 is obtained by the ultra-dynamic strain gauge and processed to evaluate the quality of tunnel crack repair.

2. A signal amplifying stethoscope device for tunnel crack repair detection according to claim 1, wherein, The launching system includes a pneumatic bullet, an air valve connection channel, an air gun safety switch, an air gun sight, and an air gun trigger. The pneumatic spray gun serves as the carrier of the launching system, with the pneumatic bullet loaded into its barrel. The air valve connection channel, the pneumatic spray gun barrel, and the pneumatic spray gun chamber are interconnected. The air gun safety switch is located inside the pneumatic spray gun chamber to brake the impact force after the pneumatic bullet is ejected. The air gun sight is located outside the pneumatic spray gun chamber for aiming when launching the pneumatic bullet. The air gun trigger is the control switch for the pneumatic bullet; pressing the trigger starts the measurement. An air compressor connected to the air valve drives the pneumatic bullet. The initial velocity of the pneumatic bullet is changed by the air pressure, thus obtaining incident wave signals ε1(t) with different initial wave velocities. By controlling the diameter of the loaded bullet, incident wave signals ε1(t) with different initial waveforms are obtained.

3. The signal amplification stethoscope device for tunnel crack repair detection according to claim 1, characterized in that, The three-layer stethoscope interface is connected in series by the stethoscope spindle. Each layer has a strain gauge attached to it, and a super-dynamic strain gauge is connected to the strain gauge.

4. The signal amplification stethoscope device for tunnel crack repair detection according to claim 1, characterized in that, The time-domain reflected wave signal ε2(t)2 is the signal obtained by amplifying the reflected wave signal ε2(t) through a stethoscope. The reflected wave signal ε2(t) is the signal obtained by reflecting the incident wave signal ε1(t) through the bonding surface between the concrete lining layer and the repair material. The wave impedance z of the material: ； The wave impedance ratio n of the two materials: ； The transmission coefficient M at the interface between the two materials: ； According to density and material wave velocity Derive the elastic modulus of the material: ； The magnitude of the wave signal after transmission through the interface is related to the interface wave impedance ratio, and the stress after transmission is obtained as follows: ； According to the constitutive equation of the material: ； The strain after interfacial transmission amplification is derived as follows: ； In the formula, -Density of the material; - Longitudinal wave velocity of the material; n - Wave impedance ratio of the interface between the two materials; M - Transmission coefficient of the interface between the two materials. - Stress before amplification; - Magnified stress; - Unamplified strain; -Magnified strain; definition H is the signal amplification factor, which determines the amplification factor of the wave signal when it passes through the interface.

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