Underground Pipeline Detection: Advantages and Applications of Electromagnetic Methods

　　In urban planning and construction, the distribution and location of underground pipelines are crucial. Whether it is water supply and drainage, electricity, communication or gas, these pipelines are an important part of city operation. However, since these pipelines are buried deep underground, how to accurately detect their location and distribution becomes a difficult problem. Fortunately, electromagnetic detection technology provides us with a solution.

　　Electromagnetic detection of underground pipelines works on the basis of the law of electromagnetic induction. When a pipeline is subjected to a current signal of a specific frequency, an alternating electromagnetic field is generated around it. This electromagnetic field can be detected and localized by a receiver.

　　For this process to be realized, the detectorist needs to have specialized detection techniques and the right tool - a pipeline detector. This instrument consists of a transmitter and a receiver, which together form a transmitter-receiver system.

　　The transmitter consists of a transmitting coil and a set of electronic circuits, whose function is to add a signal current of a certain frequency to the pipeline. This current can be applied to the pipe line by inductive, direct or clamping means. Of these, the inductive method is the most commonly used because it is easy to operate and has less impact on the surrounding environment.

　　Depending on the angle between the transmitting coil and the ground, the transmitting method can be categorized into horizontal and vertical transmitting. In horizontal launching, the transmitter is upright and the surface of the transmitting coil is perpendicular to the ground. When the transmitting coil is located directly above the pipeline, it has the strongest coupling with the underground pipeline and can produce great values. In vertical launch, the transmitter is lying down, the launch coil surface and the ground is horizontal, when the launch coil is located directly above the pipeline, it is not coupled with the underground pipeline, i.e., no excitation. However, when the transmitting coil is located at a distance h (depth of burial) from the pipeline directly above it, it couples well with the underground pipeline, and a pole appears.

　　The receiver, on the other hand, consists of a receiving coil and a corresponding set of electronic circuits as well as a signal indicator. Its function is to detect above the pipeline a current signal of a specific frequency - an electromagnetic anomaly - applied to the pipeline by the transmitter. According to the different structures, the receiver can be divided into single-coil structure, double-coil structure and multi-coil combination structure.

　　Single-coil structures can be further divided into single horizontal coils and single vertical coils. In single horizontal coil, the receiver is placed horizontally and the receiving coil surface is parallel to the ground, which is suitable for detecting horizontal or inclined pipelines. In single vertical coil, the receiver is placed vertically and the receiving coil surface is perpendicular to the ground, which is suitable for detecting vertical pipelines or pipelines with shallow burial depth.

　　Dual-coil structures and multi-coil combinations can further increase the sensitivity and positioning accuracy of the receiver. They can realize three-dimensional positioning and depth measurement of underground pipelines through specific coil configuration and signal processing.

　　Electromagnetic method of detecting underground pipelines is a complex and precise technology. It requires professional techniques and suitable tools for the probers to realize accurate and efficient detection. With the continuous development of science and technology, we have reason to believe that this technology will play an increasingly important role in future urban planning and construction.