Major cutter soil mixing work starts in Hong Kong

Intrafor has started an extensive cutter soil mixing (CSM) treatment at the Boundary Crossing Facilities (BCF) – a non-dredged artificial island in close proximity to Hong Kong International Airport.

The CSM work is part of the Tuen Mun-Chek Lap Kok Link Northern Connection scheme. The project, awarded in 2013 to a joint venture of Dragages Hong Kong and Bouygues Travaux Publics, involves the construction of two 5km-long sub-sea tunnels. These structures, located more than 50m below sea level, will provide a connection between Tuen Mun, in the western New Territories, to BCF. The tunnels are being built by tunnel boring machines (TBMs), including the largest in the world – featuring a diameter of 17.6m.

As part of this project, two ventilations shafts and a TBM parking plug will be built at BCF. To allow the safe construction of these structures, which will be made up of diaphragm walls, the ground strength of the reclaimed island is being improved by means of CSM. These works will prevent marine deposits from being squeezed into the trench during the excavation of the diaphragm wall panels and avoid collapse.

Intrafor is now working with Dragages to build up to 36m-deep CSM panels along the perimeter of the proposed diaphragm walls. Subsequently, the CSM technique will be used as part of the construction of a deep watertight plug for the break-out of the two TBMs at the location of the Southern retrieval shaft.