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Introduction to trenchless horizontal directional drilling (HDD) technology and its working principle

Nov 04, 2019

I. Brief introduction to HDD technology
Trenchless technology refers to a construction technique for laying, repairing, replacing or detecting underground utilities and pipelines with less excavation or non-excavation. The principle of directional drilling technology is applied in trenchless construction, which greatly reduces the impact of underground pipeline construction on traffic, environment, infrastructure, residential life and work, and becomes an important part of construction and management of modern urban infrastructures.
The trenchless construction began in the United States in 1896, and rose in the developed countries in the 1980s and formed an industry. In China, the trenchless technology was used in Beijing in 1953, started in the 1990s, and develops rapidly this year. At present, it is widely used in the pipeline laying and maintenance of oil and gas, urban water supply and drainage, gas supply, electricity, communication, heat supply, etc.
 


II. Working principle and construction procedures of trenchless horizontal directional drilling
1. Boring of drill bit and pipe
After fixing the machine, according to the set angle, under the action of the power head, the drill bit drives the drill rod to rotate forward, and under the control of the guide instrument, according to the depth and length of the construction requirements, drills through the ground obstacles, and drills out of the ground. In the process of drilling, in order to prevent the drill pipe from being clamped and locked by the soil layer, it is necessary to use the mud pump to erupt the mud via the drill pipe and the drill bit, and at the same time the mud can also solidify the borehole to prevent it from collapsing.


 
2. Backtracking of re-expanding head
After the drill bit drills out of the ground with the drill pipe, remove the drill bit and fasten the re-expanding head to the drill pipe. The power head drags back, and the drill pipe is pulled back with the re-expanding head to expand the borehole size.
 
3. Back-drag of pipeline
When the re-expanding head is being dragged back, after the pipe is fixed to the re-expanding head, the power head drags the drill pipe reversely with the re-expanding head and pipeline until the pipeline is pulled out of the ground, so the pipeline laying is completed.