HDD pipeline construction through Yangtze River in Chongqing district is the Key point in Chongqing-Qijiang oil product pipeline project with a diameter Ф323.9mm, entrance angle 14°, exit angle 30°, length 1023m and 105m height difference between entrance point and lowest point. The project was located in a very complex geological conditions area, and the formation is combined with mudstone, sandstone and fracture internally with inclination of 45-52°. Because of the 15° inclination on exit side with no construction area at all, the pipeline precast had to be accommodated at the entrance side even the construction area here was just no more than 50m*30m. To solve this problem, the “21 to 1” pipe-jacking method, which is wielding the 21 pipelines one by one during the pull-back procedure instead of pre-wielding them all together before, invented by HY, was successfully utilized in the pull-back stage of this project.
Making the pilot hole was another difficulty. Due to the geomagnetic interference from the cargo ship, the magnetic guidance for the drill bit was hard to be applied. As a result, the magnetic target locating system, developed by HY, well conquered this issue to keep the drill bit on the pre-project planned track during the pilot holes making.