Detection method and detection system for internal steel bars of cable duct bank structure

Abstract

The invention discloses a detection method and a detection system for reinforcing steel bars in a cable duct bank structure, and belongs to the field of pipeline detection, the detection method comprises the following steps: determining a working range and selecting an electric power well according to related data and on-site survey of a cable duct bank section to be detected; entering the power well, and threading a cable (4) in the cable duct bank structure (1) by using a threading instrument; connecting the cable (4) with the magnetic probe (3), dragging the magnetic probe (3) by using the cable (4), and enabling the probe (3) head to pass through the cable duct bank structure (1) until the probe (3) head passes through the whole duct bank section to be detected; according to data recorded by the magnetic probe (3), a change curve of the magnetic field intensity and the magnetic gradient in the axis direction of the cable duct bank structure (1) is obtained, and the distribution condition of the steel bars in the cable duct bank structure (1) is obtained through analysis. The method is easy to operate and high in efficiency, the arrangement condition of the reinforcing mesh in the cable duct bank structure can be detected, and the method has great significance in improving the engineering quality and reducing potential safety hazards.

Description

Technical Field

[0001] The present invention relates to the technical field of cable laying, and in particular to a method and a system for detecting steel bars inside a cable pipe structure based on a magnetic gradient method. Background Art

[0002] Cable conduits are important power infrastructure that meet the requirements of cable access channels in substations and the undergrounding of overhead lines. They also protect cables from external environmental influences and have the advantages of good economy and easy maintenance. In recent years, the rapid growth of global energy consumption has led to a sharp increase in electricity demand. In particular, driven by high-energy-consuming industries such as artificial intelligence and big data, urban and industrial electricity consumption has repeatedly set new records, and cable conduits have also developed rapidly.

[0003] However, with the rapid development, the quality of cable ducts varies due to factors such as tight construction period, heavy tasks, and lack of responsibility of construction units. In particular, in the reinforced concrete encapsulated boxes of the straight-line laying section, there is a phenomenon of cutting corners in the use of steel bars, or even directly using plain concrete encapsulation, which quietly buries hidden dangers for the safe operation of the main cable equipment in the duct and even the urban power grid in the later stage, and increases the workload of the later operation and maintenance tasks.

[0004] The cable duct structure is a reinforced concrete box with pipes inside that allow cables to pass through it, thus protecting the cables. Using ducts to lay cables in cities is a common method. The construction quality of the steel bar sub-project inside the cable duct structure has a great impact on its overall strength. However, since the cable duct structure is buried deep underground and the steel bars are wrapped in the concrete box, the current steel bar inspection project inside the cable duct can only be carried out by manual sampling and observation after the steel bar installation project is completed and before the concrete is poured. This detection method is time-sensitive, labor-intensive, and has limited detection results. It is also impossible to conduct a secondary inspection of the steel bars inside the duct structure after the concrete is poured.

[0005] In order to improve the shortcomings of the current method of detecting steel bars inside cable ducts, a new type of steel bar detection method is needed. After the construction of the cable duct structure is completed and the project is transferred, the layout of the steel mesh in the structure can be detected to form a practical cable duct structure steel mesh detection technology. Summary of the invention

[0006] In order to solve the deficiencies in the prior art, the present invention provides a method for detecting steel bars inside a cable tube structure based on a magnetic gradient method. This method can effectively curb the bad behavior of cutting corners by omitting steel bar sub-projects and strengthen the control of construction quality.

[0007] The present invention adopts the following technical solution.

[0008] A first aspect of the present invention discloses a method for detecting steel bars inside a cable duct structure, comprising the following steps:

[0009] Determine the scope of work and select the power well based on relevant information and on-site survey of the cable pipe section to be tested;

[0010] Enter the power well and use the threading instrument to thread the cables in the cable pipe structure;

[0011] Connect the cable and the magnetic probe, use the cable to drag the magnetic probe, and make the magnetic probe pass through the cable pipe structure until it passes through the entire cable pipe section to be tested;

[0012] According to the data recorded by the magnetic probe, the change curves of the magnetic field intensity and magnetic gradient along the axis of the cable pipe structure are obtained, and the distribution of steel bars inside the cable pipe structure is analyzed and obtained.

[0013] Preferably, the cable pipe structure comprises a plurality of cable pipes, and the cable pipes selected for inspection are the pipes at the corners of the pipe array, which can simultaneously measure the distribution of stirrups and longitudinal reinforcements.

[0014] Preferably, for a cable conduit structure to be tested, at least two diagonal cable conduits are selected for testing.

[0015] Preferably, the magnetic probe travels at a uniform speed in the cable conduit less than 0.5 m / s.

[0016] Preferably, the data include magnetic field strength, magnetic gradient and background field strength;

[0017] The analysis process includes:

[0018] When the magnetic field intensity is greater than the background field intensity, the magnetic probe is closer to the longitudinal ribs;

[0019] When the magnetic field intensity is closer to the background field intensity, the magnetic gradient is maintained at 0nT / m, and there are no longitudinal ribs in this range;

[0020] The greater the fluctuation of magnetic field intensity and magnetic gradient, the denser the spacing of stirrups.

[0021] Preferably, the analysis process further comprises:

[0022] When the magnetic field intensity curve suddenly increases and the magnetic gradient curve has a positive peak, the longitudinal ribs appear;

[0023] When the magnetic field intensity curve suddenly decreases and the magnetic gradient curve has a negative peak, the longitudinal ribs disappear;

[0024] When the magnetic field intensity curve and the magnetic gradient curve fluctuate greatly, there is longitudinal reinforcement overlap here.

[0025] Preferably, the large fluctuation appears in the curve, showing as a sub-peak or peak.

[0026] The second aspect of the present invention discloses a cable tube structure internal steel bar detection system, which executes the cable tube structure internal steel bar detection method, including: a moving module and an analyzing module;

[0027] The moving module is used to pull the magnetic probe to move in the pipeline for detection;

[0028] The analysis module is used to analyze the data collected by the mobile module to obtain the detection results.

[0029] Preferably, the mobile module comprises a cable, a threading instrument and a magnetic probe, the two ends of the cable are respectively connected to the threading instrument and the magnetic probe, and the threading instrument drives the cable to pull the magnetic probe to move in the pipeline for detection.

[0030] Preferably, the analysis module comprises a computer, and the computer is electrically connected to a cable in the mobile module.

[0031] Compared with the prior art, the beneficial effects of the present invention include at least:

[0032] The present invention applies the magnetic gradient method to the steel bar detection inside the cable pipe structure, directly uses the cable pipe as a probe hole, and the detection operation does not require drilling or excavation, which is convenient and quick; during the detection, only a threader is needed to thread and pull the cable, and no complex mechanical facilities are used, which is easy to operate and has a simple process; the magnetic probe works inside the pipe structure and is close to the steel bar to be tested during the detection, and the measurement result is reliable and accurate;

[0033] The present invention uses a wire to drag the magnetic probe to move in the cable pipe, and one drag can detect a cable pipe of a measuring section, with fast detection speed and good continuity; the data obtained by the present invention are a one-dimensional magnetic field intensity curve and a magnetic gradient curve along the cable pipe, with a small amount of data and easy analysis;

[0034] The present invention proposes a one-dimensional magnetic gradient analysis method for cable pipes. The analysis process does not require numerical calculations, and the distribution of main reinforcement and stirrups in the pipe structure can be directly analyzed based on the curve characteristics. The analysis process is simple and the results are clear.

[0035] The present invention can effectively solve the problem of detecting the layout of the steel mesh in the cable pipe structure, and is of great significance for improving project quality and reducing safety hazards. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the entire system of the present invention;

[0037] Figure 2 It is a schematic diagram of the location of the power well and the pipe arrangement structure of the present invention;

[0038] Figure 3 This is a magnetic field strength curve in a cable tube measurement;

[0039] Figure 4 for Figure 3 Magnetic gradient curve measured by cable tube;

[0040] Numbers in the figure: 1-cable pipe structure; 2-cable pipe; 3-magnetic probe; 4-cable; 5-power well. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0042] The basic magnetic field of the earth is a magnetic dipole magnetic field located at the center of the earth and obliquely intersecting the earth's rotation axis. The magnetic field is distributed over the entire surface of the earth. For a certain project, its local geomagnetic field can be regarded as uniformly distributed, forming a background field. Various objects in nature will be magnetized by the geomagnetic field, and a new magnetic field will be generated on the basis of the background field. Especially for ferromagnetic materials, due to their high magnetic susceptibility, they will show stronger magnetism and produce magnetic anomalies on the background field. By detecting this magnetic anomaly, the distribution of ferromagnetic objects within a certain range can be inferred.

[0043] This method is called the magnetic gradient method. It is currently mostly used to detect metal pipelines and pile foundation steel cages. However, the inventors of the present invention realized that from the perspective of detection principle, it is very suitable for detecting steel bars inside cable tube structures. By implementing a certain method, the magnetic gradient method can be used to detect steel bars inside cable tube structures.

[0044] The inventors of the present invention further realized that there are many technical difficulties to be solved in using the magnetic gradient method to detect steel bars inside cable conduit structures. According to previous technical concepts, the implementation of the magnetic gradient method requires the arrangement of multiple sensors in three-dimensional space, at least four magnetic sensors, and five curves need to be drawn, and data processing is relatively cumbersome; moreover, the detection device is installed above the pipeline, which is far away from the buried pipeline. In actual use, it may be greatly affected by magnetic anomalies in the background environment; when detecting long-distance pipelines such as cable conduits, a movable carrier has to be set up, but when it is set on the carrier, when detecting long-distance pipelines such as cable conduits, the detection continuity is significantly limited during the movement of the carrier.

[0045] like Figure 1-2As shown, embodiment 1 of the present invention provides a method for detecting steel bars inside a cable tube structure, and the specific steps are as follows:

[0046] S1. Investigate relevant information in detail, determine the actual working scope based on on-site survey, and then select the power well 5 at both ends of the cable pipe section to be tested;

[0047] S2. Enter the power well 5, use the threading instrument to pull the cable 4 through the appropriate cable tube 2, and pull it from the power well at one end of the cable tube to the power well at the other end of the tube. The cable 4 is used as both the lead wire of the towed magnetic probe 3 and the data line of the magnetic probe 3;

[0048] In a preferred but non-restrictive embodiment of the present invention, in S2, when selecting cable conduits, try to select conduits at the corners of the conduit array for measurement. Due to the need for laying and convenient concrete pouring, power conduits are all rectangular in cross-section. Selecting corner conduits can measure the distribution of stirrups and longitudinal reinforcement at the same time.

[0049] The threading instrument may be a fiberglass threader.

[0050] S3. Connect the cable 4 and the magnetic probe 3, and use the cable 4 to slowly drag the magnetic probe so that the probe 3 moves uniformly in the cable pipe 2. The speed should not exceed 0.5m / s to avoid the magnetic probe hitting the inner wall of the pipe due to too high a speed, until it passes through the entire pipe section to be tested.

[0051] S4. Analyze the data recorded by the magnetic probe 3 to obtain the change curves of the magnetic field intensity (nT) and magnetic gradient (nT / m) along the axial direction of the cable tube 2, and further analyze to obtain the distribution of steel bars inside the cable tube structure 1.

[0052] Specifically, the difference between the magnetic field intensity and the background field intensity reflects the distribution of the longitudinal steel bars in the pipeline. The greater the magnetic field intensity is than the background field intensity, the closer the magnetic probe is to the longitudinal steel bars. The volatility of the magnetic field intensity and the magnetic gradient reflects the density of the stirrups. The greater the volatility of the two, the denser the stirrups.

[0053] Unlike the vertical movement of magnetic probes in metal pipelines and pile foundation steel cage inspections, the background field is the vertical magnetic field component of the geomagnetic field; in this method, the magnetic probe moves parallel to the ground along the pipeline, so the background field is the horizontal magnetic field component of the geomagnetic field. In the same area, the vertical magnetic field component can be considered equal, while the value of the horizontal magnetic field component is affected by the angle between the detection direction and geographic north. Different detection directions will also lead to different values ​​of the background field. Therefore, it is difficult to directly compare the magnetic field intensity and the background field intensity during detection.

[0054] The magnetic gradient curve reflects the difference in magnetic field intensity between two points on the measuring line path in a very short time, and is not affected by the background field value. Therefore, when analyzing the data, the appearance of longitudinal reinforcement can be confirmed by observing the sudden increase of the magnetic field intensity curve and the positive peak of the magnetic gradient curve; the disappearance of longitudinal reinforcement can be confirmed by the sudden decrease of the magnetic field intensity curve and the negative peak of the magnetic gradient curve; the spacing of stirrups can be determined by observing the fluctuation frequency of the magnetic field intensity curve and the magnetic gradient curve; the large fluctuation of the magnetic field intensity curve and the magnetic gradient curve generally indicates that there is a longitudinal reinforcement overlap here.

[0055] The large fluctuation appears in the curve as a sub-peak or peak.

[0056] It should be noted that the magnetic gradient curve reflects the difference in magnetic field intensity between two points on the survey line path in an extremely short period of time and is less affected by external continental anomalies and local anomalies. When the analysis results of the magnetic field intensity curve and the magnetic gradient curve are inconsistent, the magnetic gradient curve is more credible.

[0057] The measurement described in the present invention is a one-dimensional measurement. It only needs to set two magnetic sensors along the pipeline axis. In this way, the change of magnetic field intensity at a point in a short period of time can be measured to obtain the magnetic gradient. The magnetic probe 3 actually has two magnetic sensors inside. At present, this one-dimensional method is mainly used for pile foundation steel cage measurement, and has not been used for cable pipe internal structure measurement. The pile foundation is vertical to the ground, while the cable pipe is horizontal. Therefore, the present invention solves the problem that the implementation of the magnetic gradient method in the cable pipe detection requires the arrangement of multiple sensors in three-dimensional space, the drawing of multiple curves, and the data processing is relatively cumbersome.

[0058] In a preferred but non-limiting embodiment of the present invention, for a cable conduit structure to be tested, at least two cable conduits are selected for testing to enhance the credibility of the results.

[0059] When selecting cable tubes, choose the corners of the tube array, which are close to the longitudinal reinforcement and have more stirrups. Furthermore, the two diagonal cable tubes are the most representative;

[0060] There is no time requirement for the detection of the two cable ducts. The measurement results of each curve indicate the internal steel reinforcement around the measured cable duct.

[0061] The number of measuring pipes can be increased during detection in order to cover a larger measurement area and improve measurement reliability, but generally two diagonal pipes are sufficient to cover the entire pipe array.

[0062] Further preferably, during the detection process, there should be no ferromagnetic metal around the magnetic probe that may affect the detection result.

[0063] refer to Figure 3-4, are one-dimensional magnetic field intensity curve and magnetic gradient curve data of a cable tube in an embodiment;

[0064] At about 0-2m from the pipe mouth, the magnetic field strength continues to rise, and the magnetic gradient curve has a positive peak at 2m from the pipe mouth, indicating that the longitudinal reinforcement starts from here; within the range of 2-9m from the pipe mouth, the magnetic field strength curve and the magnetic gradient curve fluctuate gently, indicating that the spacing between the stirrups in this range is large; at 9m from the pipe mouth, the magnetic field strength continues to drop to the initial value, and the magnetic gradient curve has a negative peak, indicating that the longitudinal reinforcement ends here; within 9-14m from the pipe mouth, the magnetic field strength fluctuates around 23000nT. Combined with the starting point of the magnetic field strength curve, it can be inferred that the longitudinal reinforcement along this range is The background field intensity in the pipe arrangement direction is about 23000nT, and the magnetic gradient is maintained at about 0nT / m, indicating that there is no longitudinal reinforcement in this range; 15m away from the pipe mouth, the magnetic field intensity rises again, and the magnetic gradient curve shows a positive peak, indicating that the longitudinal reinforcement reappears from this point; the magnetic field intensity curve and the magnetic gradient curve at 15-23m fluctuate violently, indicating that the spacing between stirrups in this range is relatively dense; 20m away from the pipe mouth, the magnetic field intensity curve shows a positive peak again, and the magnetic gradient curve has a "reflection signal" similar to neck shrinkage and neck expansion, indicating that there may be longitudinal reinforcement overlap here.

[0065] Embodiment 2 of the present invention provides a device for detecting steel bars inside a cable tube structure, comprising: a moving module and an analyzing module;

[0066] The mobile module includes: a cable, a threading instrument and a magnetic probe, the two ends of the cable are respectively connected to the threading instrument and the magnetic probe, the threading instrument drives the cable to pull the magnetic probe to move in the pipeline for detection;

[0067] The analysis module includes a computer, which is connected to the cable in the mobile module and is used to analyze the data transmitted by the cable to obtain the detection result.

[0068] Compared with the prior art, the beneficial effects of the present invention include at least:

[0069] The present invention applies the magnetic gradient method to the steel bar detection inside the cable pipe structure, directly uses the cable pipe as a probe hole, and the detection operation does not require drilling or excavation, which is convenient and quick; during the detection, only a threader is needed to thread and pull the cable, and no complex mechanical facilities are used, which is easy to operate and has a simple process; the magnetic probe works inside the pipe structure and is close to the steel bar to be tested during the detection, and the measurement result is reliable and accurate;

[0070] The present invention uses a wire to drag the magnetic probe to move in the cable pipe, and one drag can detect a cable pipe of a measuring section, with fast detection speed and good continuity; the data obtained by the present invention are a one-dimensional magnetic field intensity curve and a magnetic gradient curve along the cable pipe, with a small amount of data and easy analysis;

[0071] The present invention proposes a one-dimensional magnetic gradient analysis method for cable pipes. The analysis process does not require numerical calculations, and the distribution of main reinforcement and stirrups in the pipe structure can be directly analyzed based on the curve characteristics. The analysis process is simple and the results are clear.

[0072] The present invention can effectively solve the problem of detecting the layout of the steel mesh in the cable pipe structure, and is of great significance for improving project quality and reducing safety hazards.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for detecting steel bars inside a cable tube structure, characterized in that: The following steps are involved: Determine the scope of work and select the power well based on relevant information and on-site survey of the cable pipe section to be tested; Entering the power well, and using a threading instrument to thread a cable (4) through the cable conduit structure (1); Connecting the cable (4) and the magnetic probe (3), using the cable (4) to drag the magnetic probe (3), so that the magnetic probe (3) passes through the cable tube structure (1) until it passes through the entire cable tube section to be tested; Based on the data recorded by the magnetic probe (3), the curves of the change of the magnetic field intensity and magnetic gradient along the axial direction of the cable tube structure (1) are obtained, and the distribution of the steel bars inside the cable tube structure (1) is analyzed and obtained.

2. A method for detecting steel bars inside a cable duct structure according to claim 1, characterized in that: The cable pipe arrangement structure (1) comprises a plurality of cable pipes (2), and the cable pipes (2) selected for detection are pipes at the corners of the pipe array, which can simultaneously measure the distribution of stirrups and longitudinal reinforcements.

3. A method for detecting steel bars inside a cable duct structure according to claim 2, characterized in that: For a cable conduit structure (1) to be tested, at least two diagonal cable conduits (2) are selected for testing.

4. A method for detecting steel bars inside a cable duct structure according to claim 1, characterized in that: The magnetic probe (3) travels uniformly in the cable conduit (2) at a speed less than 0.5 m / s.

5. A method for detecting steel bars inside a cable duct structure according to claim 1, characterized in that: The data include magnetic field strength, magnetic gradient and background field strength; The analysis process includes: When the magnetic field intensity is greater than the background field intensity, the magnetic probe (3) is closer to the longitudinal ribs; When the magnetic field intensity is closer to the background field intensity, the magnetic gradient is maintained at 0nT / m, and there are no longitudinal ribs in this range; The greater the fluctuation of magnetic field intensity and magnetic gradient, the denser the spacing of stirrups.

6. A method for detecting steel bars inside a cable duct structure according to claim 5, characterized in that: The analysis process also includes: When the magnetic field intensity curve suddenly increases and the magnetic gradient curve has a positive peak, the longitudinal ribs appear; When the magnetic field intensity curve suddenly decreases and the magnetic gradient curve has a negative peak, the longitudinal ribs disappear; When the magnetic field intensity curve and the magnetic gradient curve fluctuate greatly, there is longitudinal reinforcement overlap here.

7. A method for detecting steel bars inside a cable tube structure according to claim 6, characterized in that: The large fluctuation appears in the curve as a sub-peak or peak.

8. A cable tube structure internal steel bar detection system, which implements a cable tube structure internal steel bar detection method according to any one of claims 1 to 7, characterized in that: include: Mobile module and analysis module; The moving module is used to pull the magnetic probe to move in the pipeline for detection; The analysis module is used to analyze the data collected by the mobile module to obtain the detection results.

9. A cable duct structure internal steel bar detection system according to claim 8, characterized in that: The mobile module includes a cable, a threading instrument and a magnetic probe. The two ends of the cable are respectively connected to the threading instrument and the magnetic probe. The threading instrument drives the cable to pull the magnetic probe to move in the pipeline for detection.

10. A cable duct structure internal steel bar detection system according to claim 8, characterized in that: The analysis module includes a computer, which is electrically connected to the cable in the mobile module.

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