Complex construction projects often require creative engineering solutions. A good example is the 15-cell “Caterpillar”-shaped cofferdam at Tuen Mun-Chek Lap Kok Link (TM-CLKL) project, which was awarded the HKIE Innovation Award 2020 (Category II – An Innovative Application of Engineering Theories) by the Hong Kong Institution of Engineers.

In the original plan, the project team was required to build a conventional straight diaphragm wall system at the newly reclaimed Boundary Crossing Facility Artificial Island. However, such design in a difficult geology posed a high risk in terms of constructability, programming and budget. With the support of the Highway Departments, AECOM and Atkins China, our project team thought out of the box and formulated the world’s first caterpillar-shaped cofferdam.

With a length of 500m and a depth of 43m, the gigantic “Caterpillar” consists of 15 truncated circular cells that are formed by a perimeter diaphragm wall in arch shape. The unique structure resists the lateral pressure, transferring the pressure to the heavy duty “Y-Panels”. Compared to the conventional diaphragm wall, the caterpillar system involved less steel reinforcement, thus providing unobstructed construction space while requiring less ground treatment. From an environmental point of view, this innovative cofferdam eliminated over 21,000 tons of steel and 80,000m3 of ground treatment, significantly reducing material carbon footprint, plant consumption and groundwater pollution. The design is also more effective in terms of saving time and construction costs.

The TM-CLKL – Northern Connection Sub-sea Tunnel Section project is expected to receive the project substantial completion certificate from the Client this week. The sub-sea tunnel is expected to open to the public at the end of this year. It will connect Tuen Mun Area 40 and the Hong Kong-Zhuhai-Macao Bridge Hong Kong Boundary Crossing Facilities, strengthening the cross-boundary network between Hong Kong, Macao, Shenzhen and Zhuhai by connecting the Northwest New Territories, Hong Kong-Zhuhai-Macao Bridge, Hong Kong International Airport and North Lantau.