There are great differences in the type, material and distribution of pipelines in underground pipeline detection, so it is necessary to use specific methods to detect them in the process of exploration work in order to better complete the target work. With the continuous development of related technologies, detection technology and equipment are constantly improving, which is very helpful for accurate positioning of pipelines and elimination of various interferences during the detection process.
oneThe principle of underground pipeline detection technology
The purpose of underground pipeline detection is to determine the location, direction, and buried depth of the pipeline. There are physical property differences between underground pipelines and surrounding soils, and the principles of various underground pipeline detection technologies are ultimately based on this physical property difference for detection and positioning. Different physical property differences determine different detection methods.
When an electric current passes through a buried pipe, an alternating magnetic field is generated around it. Using a receiver on the ground, the position, depth and current value of the buried pipe can be measured.
II. II. IIApplication of underground pipeline detection technology
(1) Direct method of underground pipeline detection technology
One end of the transmitter is connected to the outgoing ** of the pipeline, and the other end is connected to the ground line of the vertical pipeline direction, and the transmitter applies a specific frequency alternating current to the pipeline through the connection, and the current flows along the pipeline in the direction of its extension, and returns to the ground wire through the earth to form a loop. At the same time, an alternating electromagnetic field of the same frequency is formed around the pipeline, and then the ground above the pipeline is scanned and received by a receiver to locate and determine the depth of the pipeline.
The direct method is one of the main methods used in underground pipeline detection, which has the advantages of strong transmitter signal output, good anti-interference performance, and accurate pipeline positioning, which is very suitable for the detection of complex on-site pipelines and more metal objects nearby.
When the direct method is selected, the connection point must be well grounded, the insulating layer of the metal should be scraped clean, and the grounding electrode should be laid in the direction of the vertical pipeline as far as possible, and the distance should be greater than 10 times the buried depth, so as to minimize the grounding resistance. The direct method is strictly forbidden to be used on flammable and explosive pipelines.
(2) Electromagnetic induction method for underground pipeline detection technology
The transmitter is placed above the target pipeline, and the transmitter coil emits an alternating electromagnetic field of a specific frequency (called the primary field), and the alternating electromagnetic field will couple an alternating current of the same frequency on the pipeline, and the current flows along the pipeline to its extension direction, and at the same time, an alternating electromagnetic field of the same frequency (called the secondary field) is formed around the pipeline, and then the receiver is used to scan and receive the secondary field above the pipeline, and the pipeline is positioned and deepened.
According to the specific requirements of the induction method, the accuracy and completeness of the location determination of the underground pipeline can be improved, the practical application level and operation efficiency of the underground pipeline detection technology can be improved to a certain extent, and the integrity of the operation process can be optimized.
(3) Clamp method of underground pipeline detection technology
The transmitter signal is applied to the clamp, which is then applied to the metal pipe or cable to be measured. The clamp is equivalent to the primary coil, and the loop formed by the pipeline and the ground is equivalent to the secondary coil. When the alternating current output from the transmitter flows in the primary winding, and the toroidal magnetic field passes through the pipeline loop, an induced secondary current is generated in the pipeline. In the detection of dense pipeline areas, the clamp method is an effective method with little cross-influence.
It should be noted that the current structure generated in this case needs to determine the actual location of the underground pipeline by means of magnetic field measurement, especially the labeling and analysis of its geographical location, and carry out effective underground pipeline detection, which can maintain the overall level and application value of the detection technology on the basis of improving the detection accuracy.
(4) Geological radar method for underground pipeline detection technology
In underground pipeline detection technology, the geological radar method is also known as the ground penetrating radar method. It is a non-destructive geophysical method for detecting subsurface geological structures based on the differences in electrical conductivity, magnetic conductivity, and dielectric constant of different substances. When the electromagnetic wave propagates to the ground, it encounters different degrees of attenuation and reflection when it encounters medium with different conductive properties such as metal, plastic, soil, etc., and carries out data processing and image analysis to achieve the purpose of detecting underground pipelines according to the information such as arrival time, amplitude, phase, wavelength and other information of the received reflected waves.
However, georadar can be affected by a number of factors that need to be taken into account.
First of all, the dielectric material around the underground pipeline will have a differential effect on the dielectric constant, and only the larger reflection coefficient can obtain a clearer image.
Secondly, the surrounding medium of the pipeline must be uniform, and if the backfill and the original soil structure cannot be effectively managed, there will be an imbalance of dielectric constant and conductivity, which will seriously affect the identification effect of the target pipeline.
Based on this, in the process of pipeline detection, it is necessary to fully understand the relevant parameters of the target pipeline, especially the specifications, materials and specific burial conditions, fundamentally determine the continuity and randomness of interference, effectively analyze the identification effect and waveform characteristics, and fundamentally improve the application effect of underground pipeline detection technology.
(5) The first-wave method of underground pipeline detection technology
The wave method is also known as the shallow exploration method. The basic principle is to use the difference in wave impedance value (density and velocity) of the underground medium, and the larger the difference between the elastic wave velocity and wave impedance on both sides of the interface of different underground media, the better the detection of the **wave method.
Based on the difference in elasticity and density of various underground media, the ** wave is excited by artificial methods on the surface, and when the ** wave propagating underground encounters the interface of different media (such as the interface between the underground metal and non-metal pipelines and the surrounding media), reflection, refraction and transmission will be generated; The propagation speed of the wave in different underground media is different, and the propagation law of the wave generated by the artificial source is studied and analyzed, and the location and buried depth of the underground pipeline can be inferred by processing and interpreting the wave record. According to the different waves, the wave method is divided into direct wave method, refracted wave method, reflected wave method and Rayleigh wave method. When detecting underground pipelines, the Rayleigh wave method is commonly used to locate underground pipelines by using the difference between the surface waves of underground pipelines and the surrounding medium.
(6) High-density resistivity method for underground pipeline detection technology
The detection principle of the high-density resistivity method is the same as that of the conventional resistivity method, which is a geophysical method based on the conductivity difference between the target pipeline and the surrounding medium. When using the high-density resistivity method, dozens of electrodes are laid at one time, and the converter is used to select different electrode arrangement and movement methods to quickly collect field data. According to the different electrode arrangement forms and movement methods, the resistivity method is divided into electric sounding method, electric profile method and high-density resistivity method. The high-density resistivity method actually concentrates the dual characteristics of the electric profile method and the electric sounding method, which can realize the rapid collection of field data, collect a large amount of information, and carry out real-time data processing in the field, which improves the work efficiency.
(7) Magnetic gradient method in the well of underground pipeline detection technology
Underground metal pipelines generally have strong magnetic properties. The magnetic gradient method in the well is to use the magnetic difference between the metal pipeline and the surrounding medium to determine the magnetic anomaly caused by the underground pipeline by measuring the vertical distribution strength of the magnetic field, so as to detect the direction of the underground pipeline, and then quantitatively calculate to obtain the exact location and buried depth of the underground pipeline projection on the surface.
Each method has its own strengths, and all of them have been applied in practice with good results. However, in the face of many types of pipelines, large differences, chaotic distribution, and complex environment, a single method is often unable to accurately detect all pipelines due to its own limitations, and a comprehensive detection scheme should be formulated according to the detection task and the surrounding environment, considering the characteristics of different methods, to ensure the ideal detection effect. With more than 20 years of professional pipeline detection experience, Smart Golden Horse comprehensively uses a variety of technical means such as direct method, induction method, clamp method, geological radar method, etc., to accurately locate the plane position, direction, buried depth, pipe diameter, material, specification and other attribute information of pipelines of different uses and materials, find out the spatial occurrence status and connection relationship of the underground pipe network, manage pipeline data through R&D information system, and digitally empower enterprises to operate normally and safely!