Penta-Ocean – China State Joint Venture
SCA 2020 Contractor in New Works - Merit Award
Practices
As part of the Shatin to Central Link (SCL), the project involves construction of a 1.7 km cross-harbour tunnel mainly using the immersed tube tunnel (IMT) method. Creative construction methods, innovative design and sustainable materials have been adopted, e.g. alternative proposal of extension of IMT section to prevent temporary reclamation; tailor-made gravel spreader, plasma cutting & recycling shot blasting machine; application of BIM and fabrication of IMT units in Shek O casting yard.
The project design extended the IMT sections into the CBTS with the installation of a temporary wave barrier by pipe piles. This change enabled approximately 2.2 hectares of temporary reclamation to be saved, still maintaining the wave barrier function of the breakwater during construction. This brought significant safety, programming and environmental benefits.
To meet the latest seismic design requirement, the IMT foundation used gravel bedding instead of sand filling as used in previous IMT projects in HK. Our project team therefore invented and tailor-made a gravel spreader for spreading gravel by pumping from barges through a tremie pipe and spreading evenly over the dredged trench in Victoria Harbour to create a uniform surface for installation of IMT units.
Towing the tunnel units from Shek O casting yard to Victoria Harbour is one of the most crucial works in the construction process. To ease this, steel bulkheads were installed at both ends of each tunnel segment such that it floated in the water. Tunnel units are then towed by tug boat to the designated location in Victoria Harbour for installation. This is an energy saving and environmentally friendly transportation method.