Shield tunnel grouting layer thickness intelligent detection method based on constraint positioning

Abstract

The invention relates to a shield tunnel grouting layer thickness intelligent detection method based on constraint positioning, and aims to realize real-time, efficient and intelligent detection of shield tunnel grouting quality. The method comprises the following steps: 1, identifying a direct wave based on original data of a ground penetrating radar to obtain accurate arrival time of the direct wave, and preprocessing the original data; 2, calculating a constraint quantity for interface positioning according to the actual condition of the tunnel, namely theoretical propagation time of electromagnetic waves in an air layer, a duct piece layer and a grouting layer; 3, according to the accurate arrival time and the constraint quantity of the direct wave, sequentially estimating the positions of the three interfaces of air-duct piece, duct piece-grouting layer and grouting layer-surrounding rock, namely the approximate arrival time of the reflected wave of the three interfaces; 4, searching accurate arrival time of the reflected waves of the three interfaces in a wavelength range near the approximate arrival time of the reflected waves of the three interfaces, namely accurate positions of the three interfaces; and 5, calculating the thicknesses of the air layer, the duct piece layer and the grouting layer according to the accurate arrival time of the direct wave and the accurate arrival time of the reflected waves of the three interfaces. According to the method, the thicknesses of the air layer, the duct piece layer and the grouting layer can be accurately obtained in real time to serve as a basis for grouting quality evaluation.

Description

Technical Field

[0001] The invention belongs to the technical field of ground penetrating radar detection application, and relates to an intelligent detection method for the thickness of a shield tunnel grouting layer based on constraint positioning, and aims to realize real-time, efficient and intelligent detection of the shield tunnel grouting quality. Background Art

[0002] Geological radar is an effective method to solve the problem of intelligent detection and identification of coal and rock. It transmits high-frequency electromagnetic waves to the top of the tunnel by continuously moving the antenna. When the electromagnetic wave signal encounters a medium interface with electrical differences (such as dielectric constant differences) during propagation, reflection, transmission and refraction occur. The greater the difference in dielectric constants of the media on both sides of the interface, the greater the energy of the reflected electromagnetic wave. After the reflected electromagnetic wave is received by the receiving antenna that moves synchronously with the transmitting antenna, the radar host accurately records the two-way travel time, amplitude and phase and other motion characteristics of the reflected electromagnetic wave, and obtains the cross-sectional scanning radar image of the coal and rock medium. By processing and interpreting the radar image, the purpose of identifying the coal and rock strata is achieved.

[0003] Ground penetrating radar is an important means to achieve grouting quality detection. Air-coupled ground penetrating radar can detect and identify the layer interface at a certain distance from the target body, realizing non-contact detection. However, when performing real-time dynamic detection of grouting layers, the traditional grouting layer identification method requires layer tracking after manually selecting layer identification points, and requires manual intervention in layer tracking, which not only wastes a lot of manpower and material resources, but also has poor real-time feedback, and cannot meet the real-time, intelligent and efficient application requirements of industrialization.

[0004] Therefore, the present invention proposes an intelligent detection method for the thickness of the grouting layer of a shield tunnel based on constraint positioning, which can realize real-time intelligent detection of the grouting quality of the shield tunnel, and finally calculate the air layer thickness, segment thickness and grouting layer thickness as the basis for grouting quality evaluation. Summary of the invention

[0005] The purpose of the present invention is to achieve real-time, efficient and intelligent detection of shield tunnel grouting quality. To this end, the present invention proposes an intelligent detection method for the thickness of the shield tunnel grouting layer based on constraint positioning. In order to achieve the above purpose, the steps taken by the present invention are as follows:

[0006] 1. Direct wave positioning and data preprocessing;

[0007] 2. Calculation of constraint quantity;

[0008] 3. Estimate the interface position;

[0009] 4. Accurate interface positioning;

[0010] 5. Calculation of layer thickness.

[0011] In the above technical solution, in step 1, for any data in the original data, the time when the first strong amplitude wave is received by the receiving antenna is taken as the precise arrival time of the direct wave, which is recorded as t0. The radar data is preprocessed to improve the data signal-to-noise ratio, so that the interfaces of "air-segment", "segment-grouting layer" and "grouting layer-surrounding rock" are clear, which is convenient for locating the interface.

[0012] Step 2: Measure the thickness of the air layer between the antenna and the segment, and investigate the specified thickness of the segment layer and the approximate thickness of the grouting layer in the actual tunnel structure, and use this as the estimated thickness of the three layers. According to the estimated thickness and relative dielectric constant, the theoretical propagation time of electromagnetic waves in the air layer, segment layer and grouting layer is calculated by the following formula, and these three times are used as the constraints for positioning the "air-segment", "segment-grouting layer" and "grouting layer-surrounding rock" interfaces.

[0013]

[0014] Where dt is the theoretical two-way propagation time of an electromagnetic wave in a certain layer of medium, v0 is the propagation speed of an electromagnetic wave in a vacuum, i.e. 30 cm / ns, and d and ε are the estimated thickness and relative dielectric constant of the layer of medium, respectively.

[0015] Step 3 calculates the approximate arrival time of the reflected waves at the "air-segment", "segment-grouting layer" and "grouting layer-surrounding rock" interfaces in turn as the estimated position of the interface.

[0016] According to the arrival time t0 of the direct wave and the constraint dt0 of the “air-segment” interface positioning, the approximate arrival time t1′ of the “air-segment” interface reflection wave is estimated. The calculation formula is as follows:

[0017] t1′=t0+dt0 (2)

[0018] According to the approximate arrival time t1′ of the reflected wave at the “air-segment” interface and the constraint dt1 of the “segment-grouting layer” interface positioning, the approximate arrival time t2′ of the reflected wave at the “segment-grouting layer” interface is estimated. The calculation formula is as follows:

[0019] t2′=t1+dt1 (3)

[0020] According to the approximate arrival time t1′ of the reflected wave at the “segment-grouting layer” interface and the constraint dt2 of the “grouting layer-surrounding rock” interface positioning, the approximate arrival time t3′ of the reflected wave at the “grouting layer-surrounding rock” interface is estimated. The calculation formula is as follows:

[0021] t3′=t2+dt2 (4)

[0022] Step 4: For any data in the radar profile, the precise positions of the "air-segment", "segment-grouting layer" and "grouting layer-surrounding rock" interfaces are obtained by the constrained positioning method, as follows.

[0023] Constrained positioning of the precise interface of the "air-segment": Search for the precise arrival time of the reflected wave at the "air-segment" interface within a wavelength range near the approximate arrival time of the reflected wave at the "air-segment" interface, denoted as t1, which is also the precise position of the "air-segment" interface.

[0024] Constrained positioning of the precise interface of "segment-grouting layer": search for the precise arrival time of the reflected wave at the "segment-grouting layer" interface within a wavelength range near the approximate arrival time of the reflected wave at the "segment-grouting layer" interface, denoted as t2, which is the precise position of the "segment-grouting layer" interface.

[0025] Constrained positioning of the precise interface of "grouting layer - surrounding rock": search for the precise arrival time of the reflected wave at the "grouting layer - surrounding rock" interface within a wavelength range near the approximate arrival time of the reflected wave at the "grouting layer - surrounding rock" interface, denoted as t3, which is the precise position of the "grouting layer - surrounding rock" interface.

[0026] Step 5: Based on the precise arrival time of the direct wave and the reflected waves at the interfaces of “air-segment”, “segment-grouting layer” and “grouting layer-surrounding rock”, the thickness of the air layer, segment layer and grouting layer can be calculated, which are denoted as h0, h1 and h2 respectively. The calculation formula is as follows:

[0027]

[0028]

[0029]

[0030] Where ε0, ε1 and ε2 are the relative dielectric constants of the air layer, segment layer and grouting layer, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the automatic layer recognition flow chart of the present invention

[0032] Figure 2 Schematic diagram of the present invention applied to an actual shield tunnel grouting detection system DETAILED DESCRIPTION

[0033] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments:

[0034] Figure 1Flow chart of the intelligent detection method of the thickness of the grouting layer of a shield tunnel according to an embodiment of the present invention. The method can be applied to the actual detection of the grouting thickness of a shield tunnel through a grouting quality detection system, such as Figure 2 The specific steps include:

[0035] 1. Aim the ground penetrating radar at the surface of the tunnel segment. As the ground penetrating radar moves along the tunnel circumference with the help of the slide rail, the raw data of the ground penetrating radar is collected and transmitted to the main control unit in real time.

[0036] 2. In the main control unit, the direct wave is identified based on the raw data of the ground penetrating radar, the precise arrival time of the direct wave is obtained, and the raw data is preprocessed;

[0037] 3. Calculate the theoretical propagation time of electromagnetic waves in the air layer, segment layer and grouting layer according to the actual situation of the tunnel, which is the constraint used for interface positioning.

[0038] 4. According to the precise arrival time of the direct wave and the constraint amount, the approximate arrival time of the reflected waves at the three interfaces of "air-segment", "segment-grouting layer" and "grouting layer-surrounding rock" is estimated in turn, that is, the estimated positions of the three interfaces;

[0039] 5. Search for the exact time of arrival of the reflected wave from each interface within a wavelength range near the approximate time of arrival of the reflected wave from each interface, that is, the exact position of the interface;

[0040] 6. Based on the precise arrival time of the direct wave and the precise arrival time of the three interface reflection waves, the thickness of the air layer, segment layer and grouting layer is calculated and used as the basis for grouting quality evaluation.

[0041] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. The present invention provides an intelligent detection method for the thickness of the grouting layer of a shield tunnel based on constraint positioning, which mainly solves the problem that the conventional grouting quality detection technology has the limitations of low detection accuracy and poor feedback effectiveness and cannot meet the real-time, intelligent and efficient application requirements of industrialization. It includes the following steps:

1. Direct wave positioning and data preprocessing.

2. Constraint calculation.

3. Estimated interface position.

4. Accurate interface positioning.

5. Layer thickness calculation.

2. According to claim 1, the intelligent detection method for the thickness of the grouting layer of a shield tunnel based on constraint positioning is characterized in that: For any data in the original data, the time when the first strong amplitude wave is received by the receiving antenna is taken as the precise arrival time of the direct wave, recorded as t0. The radar data is preprocessed to improve the data signal-to-noise ratio, making the "air-segment", "segment-grouting layer" and "grouting layer-surrounding rock" interfaces clear and convenient for locating the interfaces.

3. The intelligent detection method for the thickness of the grouting layer of a shield tunnel based on constraint positioning according to claim 1 is characterized in that: According to the estimated thickness and relative dielectric constant, the theoretical propagation time of electromagnetic waves in the air layer, segment layer and grouting layer is calculated by the following formula. These three times are used as the constraints for the positioning of the "air-segment", "segment-grouting layer" and "grouting layer-surrounding rock" interfaces. Where dt is the theoretical two-way propagation time of an electromagnetic wave in a certain layer of medium, v0 is the propagation speed of an electromagnetic wave in a vacuum, i.e. 30 cm / ns, and d and ε are the estimated thickness and relative dielectric constant of the layer of medium, respectively.

4. The intelligent detection method for the thickness of the grouting layer of a shield tunnel based on constraint positioning according to claim 1 is characterized in that: The approximate arrival time of the reflected wave at the "air-segment", "segment-grouting layer" and "grouting layer-surrounding rock" interfaces is calculated in turn as the estimated position of the interface. The approximate arrival time t1′ of the reflected wave at the "air-segment" interface is estimated based on the direct wave arrival time t0 and the constraint dt0 of the "air-segment" interface positioning. The calculation formula is as follows: t1′=t0+dt0 (2) According to the approximate arrival time t1′ of the reflected wave at the "air-segment" interface and the constraint dt1 of the "segment-grouting layer" interface positioning, the approximate arrival time t2′ of the reflected wave at the "segment-grouting layer" interface is estimated. The calculation formula is as follows: t2′=t1+dt1 (3) According to the approximate arrival time t1′ of the reflected wave at the "segment-grouting layer" interface and the constraint dt2 of the "grouting layer-surrounding rock" interface positioning, the approximate arrival time t3′ of the reflected wave at the "grouting layer-surrounding rock" interface is estimated. The calculation formula is as follows: t3′=t2+dt2 (4) 5. The intelligent detection method for the thickness of the grouting layer of a shield tunnel based on constraint positioning according to claim 1 is characterized in that: For any data in the radar profile, the precise positions of the "air-segment", "segment-grouting layer" and "grouting layer-surrounding rock" interfaces are obtained through the constrained positioning method. Constrained positioning of the precise "air-segment" interface: Search for the precise arrival time of the "air-segment" interface reflection wave within a wavelength range near the approximate arrival time of the "air-segment" interface reflection wave, denoted as t1, which is also the precise position of the "air-segment" interface. Constrained positioning of the precise interface of "segment-grouting layer": Search for the precise arrival time of the reflected wave at the "segment-grouting layer" interface within a wavelength range near the approximate arrival time of the reflected wave at the "segment-grouting layer" interface, recorded as t2, which is the precise position of the "segment-grouting layer" interface. Constrained positioning of the precise interface of "grouting layer-surrounding rock": Search for the precise arrival time of the reflected wave at the "grouting layer-surrounding rock" interface within a wavelength range near the approximate arrival time of the reflected wave at the "grouting layer-surrounding rock" interface, recorded as t3, which is the precise position of the "grouting layer-surrounding rock" interface.

6. The intelligent detection method for the thickness of the grouting layer of a shield tunnel based on constraint positioning according to claim 1 is characterized by: According to the precise arrival time of the direct wave and the reflected wave at the "air-segment", "segment-grouting layer" and "grouting layer-surrounding rock" interfaces, the thickness of the air layer, segment layer and grouting layer can be calculated, which are recorded as h0, h1 and h2 respectively. The calculation formula is as follows: Where ε0, ε1 and ε2 are the relative dielectric constants of the air layer, segment layer and grouting layer, respectively.

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