Bouygues Construction, through two of its subsidiaries, Dragages Hong Kong and Bouygues Travaux Publics, has won a €1.15 billion ($1.5 billion) contract for the construction of a 4.2km undersea road tunnel in Hong Kong.
The scope of the project involves construction of an undersea twin-tube tunnel, each tube with two traffic lanes and 14m in diameter. The tunnel will connect the New Territories, north of Hong Kong, to Lantau Island, where the international airport is located. It will be bored 50m below sea level, which will constitute a record depth for Bouygues Construction.
Bouygues Construction will use two tunnel boring machines (TBMs) for excavating and building the structure. The two tunnel tubes will be connected every 100m by 42 cross passages. The firm will also deploy ground-freezing technology to provide a watertight environment to enable these passages to be bored.
The project will be executed in compliance with strict environmental standards with regard to marine ecology, water quality, noise impact and waste management. The two ventilation buildings powered by wind energy that will be constructed to the north and south of the tunnel have been designed to qualify for BEAM Plus Gold rating.
The Bouygues Construction Research & Development Department has developed two innovations: Mobydic and Snake, which will be used on the project in order to reduce the need for manual operations in hyperbaric conditions.
Mobydic is a system of sensors incorporated into the disc cutters in the heads of the TBMs, will make it possible to permanently monitor the state of wear of the cutters while allowing real-time geological mapping of rock faces. Snake is a remote-controlled exploration arm equipped with a high-pressure jet, will clean the TBM heads and eliminate clogging to enable them to be inspected.
The works are scheduled to take 63 months and the handover is scheduled for the end of 2018. During peak periods, more than 1,000 employees will be working on the project.