Pipe jacking or microtunnelling involves the boring of a tunnel for the proposed sewer/drain, by a tunnelling shield (usually a fully automatic mechanized tunnelling machine) from a launch shaft towards a reception shaft. The shield is jacked forward incrementally by hydraulic jacks at the launch shaft. As the shield advances, jacking pipes are inserted behind the shield one by one and the whole string is jacked forward. When the tunnelling shield reaches the reception shaft, it is removed and the pipeline is complete. Usually, the tunnelling operation is carried out outside the view and the awareness of the public. Nevertheless, the launch shafts and the reception shafts still need to be excavated, and may need to be in operation throughout the tunnelling operation.
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Layout of a Pipejacking / Microtunnelling site |
Central, Western and Wan Chai West (CW3) Sewerage Project
This project involves the laying of 6 km of sewers of diameter 1050mm to 1800mm at a depth of 5 to 18 metres. The works started in 1996 and was completed in early 2000.
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 A tunnelling machine being lowered into a launch shaft |
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Pipe jacking in progress inside a launch shaft -- hydraulic jacks are used to drive the pipe string, i.e. the tunnelling machine and the precast concrete jacking pipes forward |
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Arrival of the tunnelling machine at a reception shaft |
Yuen Long, Tin Shui Wai and Tong Yan San Tsuen Trunk Sewer Project
This project involves the laying of 1300m of trunk sewers of diameter 1000mm and depth 3m to 12m. The works started in 1996 and was completed in 1998.
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Tunnelling machine with hydraulic jacking frame at the back |
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Pipe jacking in progress inside the launch shaft | |