The reason why the pilot hole of the Horizontal Directional Drilling Machine deviates from the original design curve during the drilling process

The key first step in horizontal directional crossing technology is to drill pilot holes. The quality of the pilot hole directly affects whether the pipe is successfully dragged back or not. It is the main factor that determines the success of the project. The main purpose of the pilot hole is to provide a pilot hole that meets the original design requirements. The pre-expanded holes that meet the crossing requirements at all levels should be widened with the curve of the pilot hole as the axis to meet the diameter of the pullback condition. Therefore, whether the overall curve of the guide hole can reach the elastic radius of the entire pipeline directly determines whether the pre-expansion at all levels can reach the elastic radius of the entire pipeline. The successful design of the pilot hole is the basis for the successful pullback of the pre-expanding holes at all levels. It is also one of the important parts of the entire crossing project.

However, in the process of pilot hole drilling and traversing, deviations from the original design curve often occur. Based on years of work experience in Horizontal Directional Drilling Machine technology, the reasons for the original design curve can be summarized as the following five points.

(1) External unavoidable factors. Such as local topography, underground soil moisture and the deviation of the construction crossing curve caused by the stratum.

(2) Interference by an external magnetic field. Such as: high-voltage lines, underground optical cables and stratum conditions will all affect the magnetic azimuth angle when drilling the pilot hole, thus affecting the display data on the computer and causing deviations from the original design curve data.

(3) There is a deviation between the initial position angle of the drilling rig and the crossing centerline of the pipeline design, which causes the deviation to be corrected as soon as the pilot hole is drilled.

(4) Caused by drilling rig operators. During the pilot hole drilling process, due to improper operation, the traversed trajectory deviated from the design curve.

(5) Inaccuracy of measurement. These include inaccuracies in measuring the magnetic azimuth crossing the centerline, inaccuracies in measuring the elevation difference between the entry point and the entry and exit point, and inaccuracies in the length of the drill pipe when entering the computer.