Singapore (18 December 2011) – Ed. Züblin AG, Singapore Branch announced the successful completion of a record-breaking single drive tunnel using pipe jacking method in the Asia- Pacific region.

Züblin was awarded the SGD 23.6 million Submarine Gas Transmission Pipeline Project by Power Gas Ltd., Singapore in January 2011 with contract duration of 24 months. The scope comprised sinking of two deep shafts and an ID2000mm reinforced concrete tunnel over a record length of 1.55km crossing beneath the busy shipping lanes of the West Jurong Channel, including the design, manufacture and supply of precast RC jacking pipes. The tunnel will house a DN700mm high pressure gas transmission pipeline, traversing between the Singapore mainland and Jurong Island.

Temporary jacking and receiving shafts were constructed with circular 1m thick diaphragm walls of ID14m and ID7.5m respectively. Tunnelling operations commenced in August 2011.

Due to the highly variable geological conditions, a Dual Mode TBM was deployed to operate in both Earth Pressure Balance and Slurry modes, thereby providing greater flexibility, safety and efficiency during tunnelling.

Züblin designed and produced all jacking pipes used on the project at its own Quality accredited pipe factory in Thailand. The tunnel design provided for 9 Intermediate Jacking Stations to assist with the pipe jacking process over the 1.55km drive.

An effective Lubrication system was in place to overcome the high skin friction, and this further eliminated the need to use all 9 Intermediate Jacking stations during the drive.

A major challenge for this project was the tunnel alignment control survey. Accuracy in terrestrial survey was achieved through an innovative vertical bob plumb-down system. Precision in the TBM guidance was guaranteed through a Universal Navigation System (UNS). The north-seeking Gyro-compass system controlled and monitored the horizontal alignment, and a Hydrostatic Water Level system monitored the tunnel elevation.

Constant checks and monitoring saw the tunnel vertical alignment at 28mm and the horizontal alignment at 153mm at breakthrough, well within the acceptable tolerances for a long single drive tunnel.