Method for detecting water filling rate of non-metal drain pipe

Abstract

The invention belongs to the technical field of water supply and drainage pipeline detection, and provides a non-metal drainage pipe water filling rate detection method comprising the following steps: obtaining ground penetrating radar data of a non-metal drainage pipeline; preprocessing the radar data to enhance a pipeline signal; pipeline vertex signals in the B-Scan image are detected, and A-Scan signals at the vertex positions are extracted; according to the A-Scan signal, two-way travel time of the top and the bottom of the pipeline is obtained, and the virtual radius of the pipeline is calculated; and calculating the water filling rate of the pipeline according to the virtual pipe diameter calculation result and the real radius of the pipeline. And whether the pipeline type is a full pipeline or a non-full pipeline is judged in a lossless state, and an efficient and reliable detection means is provided for maintenance and management of the underground pipeline.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of drainage pipeline detection, and particularly relates to a non-metallic drainage pipe water filling rate detection method. BACKGROUND

[0002] Drainage pipelines, as an important part of urban drainage systems, are the basic components for ensuring the safety of circulating water and ecological environment. However, there are different degrees of pollutant accumulation in urban drainage systems all over the world. When accumulation occurs, the hydraulic state in the pipe will change from free surface flow to pressurized flow as the flow gradually increases, and the hydraulic bottleneck formed by the accumulation will continuously increase the upstream water level. This blocking effect makes the upstream pipeline of the accumulation section present a high water filling rate due to the backwater effect, while the downstream section has a relatively lower water filling rate due to the recovery of the flow cross section. Since the accumulation has a direct and significant impact on the size of the flow cross section in the pipe, the research on the accumulation problem of drainage pipelines usually uses the water filling rate as an indicator to quantify the degree of accumulation.

[0003] How to determine the liquid filling level of the pipeline under complex conditions such as settlement is a challenge faced in supporting efficient maintenance and management of the pipeline and ensuring the safe and stable operation of urban underground pipe networks. The current pipeline water filling rate detection method mainly uses closed-circuit television or sonar, which has limitations in practical application. Limited by light conditions and pipe environment, closed-circuit television cannot provide clear images in complex pipeline environments, and the water level in the pipeline also needs to be controlled at a low level to keep the camera from being submerged. On the other hand, since sound waves cannot propagate in air, sonar must carry out detection in liquid media, i.e. the pipeline must be full, and the flow state will cause serious interference to the acoustic signal, affecting accuracy. Neither of the two has the potential to realize intelligent detection, making it difficult to carry out real-time monitoring in large-scale pipe networks. Ground penetrating radar (GPR) as a non-destructive detection technology has been widely used in the field of underground pipeline detection in recent years. GPR has the advantages of fast detection speed, wide coverage, and simple operation, and can obtain the electromagnetic properties of underground media by transmitting high-frequency electromagnetic waves and receiving reflected signals, which can obtain the water filling rate and accumulation information of the pipeline without contacting the inside of the pipeline, with higher detection efficiency and wider application range. For metal drainage pipes, common devices such as electromagnetic flow meters and conductivity sensors can be used to measure the water level; however, for non-metallic drainage pipes, the insulating material cannot form a closed current loop, and other methods such as acoustics and optics must be used. GPR detects the water level of metal pipes by relying on reflected signals, but non-metallic pipes are transparent to radar waves, and the detection signal is relatively weak, requiring higher frequency radar and solving the problem of signal attenuation. Currently, there is no research on using GPR to determine the water filling rate of non-metallic pipelines.

[0004] In summary, the prior art has the following problems: there is a lack of robust detection methods for complex pipeline environments; existing water filling rate detection methods cannot accurately measure the water level in non-metallic drainage pipes. Therefore, it is necessary to further explore new non-metallic pipeline water filling rate detection methods to improve the intelligent level of drainage pipeline operation and maintenance to meet the needs of urban infrastructure construction and pipeline maintenance. SUMMARY

[0005] The present application aims to address the detection difficulties of non-metallic drainage pipeline water filling rate, combining deep learning, signal processing and underground surveying technology to propose a new method to improve the existing water filling rate detection process, improve detection accuracy and efficiency, and provide reliable technical support for urban infrastructure construction and management.

[0006] To achieve the above purpose, the present application provides the following technical solutions:

[0007] The present application provides a non-metallic drainage pipe water filling rate detection method, comprising:

[0008] (1) obtaining ground penetrating radar data of buried non-metallic pipeline;

[0009] (2) image preprocessing is performed on the B-Scan image in the ground penetrating radar data;

[0010] (3) detecting the pipe vertex in the B-Scan image after image preprocessing and extracting the A-Scan signal at the vertex;

[0011] (4) obtaining the two-way travel time of the pipe top and bottom according to the A-Scan signal, and calculating the virtual radius of the pipe;

[0012] (5) calculating the water filling rate of the pipe according to the virtual pipe diameter calculation result and combining the real radius of the pipe.

[0013] Further, the image preprocessing operation adopts a nonlinear time gain algorithm;

[0014] wherein the B-Scan image after background removal is The A-Scan is a matrix composed of sampling points, and for the th row of the th A-Scan signal , the gain compensation calculation method of the th sampling point is:

[0015] ;

[0016] ;

[0017] In the formula, G is the gain factor, G is the gain factor, G is the gain factor, G is the gain factor, G is the gain factor, G is the depth scaling factor, used to control the steepness of the gain curve, G is the baseline offset, used to suppress amplification of noise at shallow depths (when G is the baseline offset, used to suppress amplification of noise at shallow depths (when G is the baseline offset, used to suppress amplification of noise at shallow depths (when G is the baseline offset, used to suppress amplification of noise at shallow depths (when

[0018] Further, the pipe vertex detection operation employs a symmetry algorithm, and the symmetry curve of the B-Scan image is expressed as:

[0019] ;

[0020] wherein, G is the gain factor, G is the gain factor, G is the gain factor, G is the gain factor, G is the gain factor, G is the gain factor, G is the gain factor,

[0021] The pipe signal appears as a hyperbolic curve in the B-Scan image, and the minimum position of the mutation of the symmetry curve is the vertex position of the pipe hyperbolic signal.

[0022] Further, the pipe virtual radius is expressed as:

[0023] ;

[0024] ;

[0025] wherein, G is the gain factor, G is the gain factor, G is the gain factor, G is the gain factor, G is the gain factor, G is the gain factor.

[0026] Further, the water filling rate is calculated from the virtual radius and the real radius of the pipe;

[0027] G is the gain factor, represents the real radius of the pipeline, and and respectively represent the electromagnetic wave propagation time of the gas phase and the water phase in the pipeline, and the sum of the two is the reflection wave delay time between the top and the bottom of the pipeline:

[0028] ;

[0029] ;

[0030] ;

[0031] wherein, is the water filling rate of the pipeline, and according to the definition formula of the virtual radius of the pipeline, the water filling rate is represented as:

[0032] .

[0033] The present application has the following beneficial effects:

[0034] (1) The present application uses a nonlinear time gain algorithm to preprocess the radar data of a non-metal pipeline; uses a symmetry algorithm to extract the symmetry curve of the pipeline signal; proposes a virtual radius concept of the pipeline, and uses the virtual radius and the real radius to realize the water filling rate calculation of the pipeline in a lossless state, reduces the interference of the underground environment and external noise, and has high processing efficiency, thereby providing reliable technical support for the operation and maintenance of the urban underground pipe network.

[0035] (2) The present application can be used to judge the water filling type of the underground pipeline as full pipe or non-full pipe, has excellent robustness and generalization ability, and is suitable for practical engineering application. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a flowchart of the calculation method of the present application.

[0037] Figure 2 is a visual flowchart of the calculation method of the present application.

[0038] Figure 3 is a result schematic diagram of image preprocessing of the radar data in the embodiment.

[0039] Figure 4 is a typical sample diagram of the symmetry curve in the embodiment.

[0040] Figure 5 is a schematic diagram of the electromagnetic wave propagation time in the gas phase and the water phase in the embodiment.

[0041] Figure 6 is the water filling rate calculation result of the field pipeline test in the embodiment.

[0042] Figure 7is the calculation result of the water filling rate in the forward simulation test in the embodiment. DETAILED DESCRIPTION

[0043] The specific embodiments of the present application are described in detail below with reference to the accompanying drawings. It should be noted that the embodiments are only specific illustrations of the present application and should not be regarded as limiting the present application. The purpose of the embodiments is to enable those skilled in the art to better understand and reproduce the technical solutions of the present application. The protection scope of the present application should still be defined by the scope defined in the claims.

[0044] S101, obtaining ground penetrating radar data of a buried non-metal pipeline by using a ground penetrating radar and simulation software;

[0045] Specifically, in the field pipeline test, the ground penetrating radar is used to collect data of the buried pipeline, the pipeline is covered with original soil, the soil dielectric constant fluctuates with the precipitation, and full-pipe and non-full-pipe conditions are manufactured by calculating the volume of the pipeline section. In the simulation software, an underground pipeline model is established, which is consistent with the rest of the parameters except the water filling rate and the pipeline specification, and two test groups of full-pipe group and half-full-pipe group with representative water filling rates are set.

[0046] S102, performing image preprocessing on the B-Scan image in the ground penetrating radar data;

[0047] The image preprocessing operation adopts a nonlinear time gain algorithm;

[0048] wherein the B-Scan image after background removal is The A-Scan with sampling points form a matrix, for the th row of the th A-Scan signal , the gain compensation calculation method of the th sampling point is as follows:

[0049] ;

[0050] ;

[0051] In the formula, is the signal after gain, is is a gain coefficient, is a gain growth base number, when the gain increases exponentially with depth, is a depth scaling factor, used to control the steepness of the gain curve, is a baseline offset, used to suppress the amplification of noise in the shallow layer (when is small); To limit the gain and avoid deep (when larger) noise overshoot.

[0052] S103, detecting the pipe vertex in the B-Scan image after image preprocessing, and extracting the A-Scan signal at the vertex;

[0053] The pipe vertex detection operation adopts a symmetry algorithm, and the symmetry curve of the B-Scan image is expressed as:

[0054] ;

[0055] In the formula, B is the horizontal and vertical coordinate value of the B-Scan image, is the pixel value at the corresponding coordinate, and the first column is taken as the symmetry axis, and the symmetry degree of the distance on the left and right sides is is the image width, is the image height, is the maximum column width for calculating the symmetry degree; The pipe signal is in the form of a hyperbola in the B-Scan image, and the minimum position of the mutation of the symmetry curve is the vertex position of the pipe hyperbolic signal.

[0056] S104, obtaining the two-way travel time of the pipe top and bottom according to the A-Scan signal, and calculating the virtual radius of the pipe;

[0057] The virtual radius of the pipe is expressed as:

[0058] ;

[0059] ;

[0060] ;

[0061] In the formula, is the virtual radius of the pipe, and are the two-way travel time of the reflection signals of the pipe top and bottom, respectively, is the propagation speed of electromagnetic waves in water, is the speed of light in vacuum, is the relative dielectric constant of water.

[0062] S105, calculating the water filling rate of the pipe according to the virtual pipe diameter calculation result and combining the real radius of the pipe.

[0063] The water filling rate is calculated from the virtual radius and the real radius of the pipe;

[0064] is the real radius of the pipe, and the water filling rate is​​ and respectively represent the electromagnetic wave propagation time of the gas phase and the water phase in the pipeline, and the sum of the two is the reflection wave delay between the top and the bottom of the pipeline:

[0065] ;

[0066] ;

[0067] ;

[0068] wherein, is the water filling rate of the pipeline, and according to the definition formula of the virtual radius of the pipeline, the water filling rate is represented as:

[0069] .

[0070] Embodiment

[0071] S101, obtaining ground penetrating radar data of a buried non-metal pipeline by using a ground penetrating radar and simulation software;

[0072] Specifically, in the field pipeline test, the ground penetrating radar is used to collect data of the buried pipeline, wherein the soil covering the pipeline is original soil, the soil dielectric constant is between 3-9, and fluctuates depending on the rainfall, the pipeline burial depth ranges from 0.5m to 0.9m, and the full-pipe working condition and the non-full-pipe working condition are manufactured by calculating the volume of the pipe section, and a total of 20 groups of real data are obtained, wherein the full-pipe working condition and the non-full-pipe working condition are each 10 groups. In the simulation software, an underground pipeline model is established, which is consistent with the rest of the parameters except the water filling rate and the pipeline specification, the pipeline burial depth ranges from 0.6m to 1.6m, and two test groups with representative water filling rates, full-pipe group and half-full-pipe group, are set, and a total of 36 groups of forward simulation data are obtained, wherein the full-pipe working condition and the non-full-pipe working condition are each 18 groups.

[0073] S102, performing image preprocessing on the B-Scan image in the ground penetrating radar data, and the B-Scan image after image preprocessing is as shown in Figure 3 ;

[0074] The image preprocessing operation adopts a nonlinear time gain algorithm, and balances the shallow layer noise suppression and the deep layer signal enhancement by dynamically adjusting the gain coefficient;

[0075] wherein, the B-Scan image after background removal is a matrix composed of number of channels A-Scan and number of sampling points, for the th row of the th A-Scan signal , the gain compensation calculation method of the th sampling point therein is:

[0076] ;

[0077] ;

[0078] wherein, is the gain signal, is the is the gain coefficient, is the gain growth base, when the gain increases exponentially with depth, is the depth scaling factor, used to control the steepness of the gain curve, taking 0.01, is the baseline offset, used to suppress the amplification of noise in the shallow layer (when is small), taking 0.5; is the gain upper limit, to avoid overshoot of noise in the deep layer (when is large), taking 25.

[0079] S103, detecting the pipe vertex in the B-Scan image after image preprocessing, and extracting the A-Scan signal at the vertex;

[0080] The pipe vertex detection operation adopts a symmetry algorithm, and the symmetry curve of the B-Scan image is expressed as:

[0081] ;

[0082] wherein, is the horizontal and vertical coordinate value of the B-Scan image, is the pixel value at the corresponding coordinate, taking the first column as the symmetry axis, and calculating the symmetry degree of the distance on the left and right sides, is the image width, is the image height, is the maximum column width for calculating the symmetry degree, taking 1 / 10 of the image width;

[0083] The pipe signal is in the form of a hyperbola in the B-Scan image, and the minimum position of the sudden change of the symmetry curve is the vertex position of the pipe hyperbolic signal, as shown in Figure 4 .

[0084] S104, obtaining the two-way travel time of the pipe top and bottom according to the A-Scan signal, and calculating the virtual radius of the pipe;

[0085] The pipe virtual radius is expressed as:

[0086] ;

[0087] ;

[0088] wherein, is the virtual radius of the pipe, and are the two-way travel times of the reflected signals from the top and bottom of the pipe, respectively, is the propagation velocity of electromagnetic wave in water, is the speed of light in vacuum, taken as 3 x 10 8 m / s, is the relative dielectric constant of water, taken as 80.

[0089] S105, according to the virtual pipe diameter calculation result, combining the real radius of the pipe to calculate the water filling rate of the pipe.

[0090] The water filling rate is calculated from the virtual radius and the real radius of the pipe;

[0091] The real radius of the pipe is represented by The electromagnetic wave propagation times of the gas and water phases in the pipe are represented by and respectively, and as shown in Figure 5 The sum of the two is the delay of the reflected wave between the top and bottom of the pipe:

[0092] ;

[0093] ;

[0094] ;

[0095] wherein, is the water filling rate of the pipe, according to the definition formula of the virtual radius of the pipe, the water filling rate is represented as:

[0096] .

[0097] The data of the field pipe test is calculated by the method of the present application to calculate the water filling rate, and the results are shown in Figure 6 The data of the forward simulation test is calculated by the method of the present application to calculate the water filling rate, and the results are shown in Figure 7 The water filling rates of all test groups are calculated accurately. Therefore, the present application can accurately detect the water filling rate of the drainage pipe under the non-destructive state, and provide reliable technical support for the construction and management of urban infrastructure.

[0098] While the preferred embodiments of the application have been described, additional variations and modifications can be made to the embodiments by those skilled in the art once they learn of the basic inventive concepts. Therefore, the appended claims are intended to encompass within their scope all possible variations and modifications of the preferred embodiments.

[0099] It is noted that technical features not described in detail in the present application can be implemented by any prior art.

Claims

1. A method for detecting the water filling rate of a non-metallic drainage pipe, characterized in that: include: (1) Obtaining ground penetrating radar data of buried non-metallic pipelines; (2) performing image preprocessing on the B-Scan image in the ground penetrating radar data; (3) Detect the pipeline vertices in the B-Scan image after image preprocessing and extract the A-Scan signals at the vertices; (4) Obtaining the two-way travel time at the top and bottom of the pipeline based on the A-Scan signal and calculating the virtual radius of the pipeline; (5) Calculate the water filling rate of the pipeline based on the calculation results of the virtual pipe diameter and the actual radius of the pipeline.

2. A method for detecting water filling rate of a non-metallic drainage pipe according to claim 1, characterized in that: The image preprocessing operation adopts a nonlinear time gain algorithm; Among them, the B-Scan image after background removal is A-Scan and The matrix composed of sampling points, for the The first A-Scan signal , for which The gain compensation calculation method for each sampling point is: ； ； Where, is the signal after gain, for is the gain coefficient, is the gain growth base, When the gain increases exponentially with depth, is the depth scaling factor, which controls the steepness of the gain curve. is the baseline offset, used to suppress shallow layers (when When the value is small) the noise amplification; To increase the gain, avoid deep (larger) noise overshoot.

3. A method for detecting water filling rate of a non-metallic drainage pipe according to claim 1, characterized in that: The pipeline vertex detection operation adopts a symmetry algorithm, and the symmetry curve of the B-Scan image is expressed as: ； Where, is the horizontal and vertical coordinate value of the B-Scan image, is the pixel value at the corresponding coordinate, The column is the axis of symmetry, and the distance between the left and right sides is calculated as The symmetry of is the image width, is the image height, is the maximum column width for calculating symmetry; The pipeline signal appears as a hyperbola in the B-Scan image, and the minimum value position where the symmetry curve suddenly changes is the vertex position of the pipeline hyperbola signal.

4. A method for detecting water filling rate of a non-metallic drainage pipe according to claim 1, characterized in that: The virtual radius of the pipeline is expressed as: ； ； Where, is the virtual radius of the pipe, and are the two-way travel time of the reflected signal at the top and bottom of the pipeline, is the propagation speed of electromagnetic waves in water, is the speed of light in vacuum, is the relative dielectric constant of water.

5. A method for detecting water filling rate of a non-metallic drainage pipe according to claim 1, characterized in that: The water filling rate is calculated from the virtual radius and the real radius of the pipe; by Indicates the actual radius of the pipe, and They represent the electromagnetic wave propagation time corresponding to the gas phase and water in the pipeline respectively. The sum of the two is the reflection wave delay between the top and bottom of the pipeline: ； ； ； Where, is the water filling rate of the pipeline. According to the definition of the virtual radius of the pipeline, the water filling rate is expressed as: 。

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