DBJV to design and build Hong Kong’s deepest and longest sub-sea tunnels
Dragages Hong Kong is proud to announce that it has been awarded a HK$18.2 billion contract by the Highways Department of the HKSAR Government for the design and construction of dual two-lane road tunnels linking Tuen Mun with Chek Lap Kok. This is the largest contract sum ever awarded in Hong Kong, a reflection of the project’s scale and complexity. The completed tunnels will be the deepest and longest sub-sea road tunnels in Hong Kong.
“For almost 60 years, Dragages Hong Kong has played a key role in the development of Hong Kong’s world-class infrastructure,” remarked Nicolas Borit, Managing Director of Dragages Hong Kong. “This high-profile new award once again puts the company at the centre of a landmark project that will help drive Hong Kong’s economy for many decades to come. This highly complex and challenging project is a superb fit for our rich technical expertise.”
The main scope of the project is to design and construct two sub-sea tunnels, each approximately 14m in diameter and 4.2km long. The tunnels will run between Tuen Mun in the western New Territories and the Hong Kong-Zhuhai-Macao Bridge Hong Kong Boundary Crossing Facilities at Chek Lap Kok on Lantau Island. To facilitate maintenance works and to fulfil emergency requirements, these two tunnels will be connected by 42 cross passages arranged at 100m intervals.
Construction of the tunnel will move from north to south. In the north, 16.5 hectares of land will be reclaimed for the construction of a ventilation building, a 530m-long cut-and-cover approach tunnel, and launch chambers for the project’s two Tunnel Boring Machines (TBMs). In the south, there will be another ventilation building, a 670m-long cut-and-cover approach tunnel, and TBM retrieval chambers.
Technological firsts and environmental excellence
A key challenge of the project is that the majority of work must be undertaken in a compressed air environment. As a pioneer in TBM operations and a veteran specialist in compressed air works, Dragages-Bouygues will adopt a ‘saturation diving’ technique for all maintenance work on TBM cutter heads. This means that highly experienced saturation divers will stay for four weeks at a time in specially designed habitats and will be required to undergo only one decompression every four weeks rather than one decompression every day. This approach will maximise health and safety, while also enhancing project efficiency.
To further improve safety and efficiency, two cutting-edge pieces of equipment, namely MOBYDIC and SNAKE, will be installed one each TBM. These sophisticated new technologies will enable real-time geological mapping of rock faces, as well as the robotic detection of damaged components in the cutter head, and the elimination of manual inspections under hyperbaric conditions. Both MOBYDIC and SNAKE are sustainable innovations brought to the project by Bouygues Construction.
Operations will also adhere to strict environmental policies regarding marine ecology, water quality, noise impact, and waste management. For instance, a significant portion of the excavated materials from the north reclamation will be recycled, either to be used as backfilling of the launch shaft or to be returned as public fill.
The two ventilation buildings will likewise be designed to attain a BEAM Plus ‘Gold’ rating. To further maximise energy efficiency, wind turbines will be built in both ventilation buildings for the generation of renewable power.
The project is scheduled for completion in 2018.