As part of the extension of Hong Kong International Airport, Soletanche Bachy, a subsidiary of VINCI specialising in foundations and soil technologies, has entered a 50-50 joint-venture with its South Korean partner Sambo E&C. Together, they are carrying out soil reinforcement using the Geomix® technique (or Cutter Soil Mixing – CSM) in height-restricted conditions near the airport’s existing north runway. The contract, signed at the end of September 2016 and worth €380 million (HKD3.31 billion), also includes the construction of a temporary 1,500 square metres metal platform on piles around the approach beacons to the north runway, which will remain in service throughout.
By 2030, the number of passengers forecast to use Hong Kong International Airport will reach 102 million per year, compared to 68 million in 2015. To cope with this increase in traffic and provide airlines with capacity to introduce new destinations and more flights, Hong Kong International Airport is building a third runway on 650 hectares extending over the sea.
Work started at the end of 2016 with the initial measurement and test phases, and maritime operations, and will be completed within two-and-a-half years.
Work carried out from barges, in restricted height areas, and on a site in use
The safety and Airport Height Restriction (AHR) constraints imposed forbid the use of equipment taller than five meters, making this site very complex. The work has to be carried out without ever interrupting the airport’s activity. All of the work will be done from the sea using barges equipped with sophisticated monitoring systems, notably to anticipate the impact on construction from risks such as infringement of AHR, waves and typhoons.
A vast Geomix® operation
Geomix® is a patented Soletanche Bachy process which enables the characteristics of the soil in place to be improved using a soil-cement mix. It offers a more economic and safer solution, that has lower environmental impact, notably due to the reduction in natural resources used and spoil produced. Up to eighteen Geomix® soil-cement mixing plants will be installed on site, allowing for low headroom deep cement mixing. It is the biggest Geomix® soil reinforcing operation ever undertaken by Soletanche Bachy.
Solutions that meet strict environmental requirements
To meet the environmental demands of the contracting authority, Hong Kong International Airport, and the prime contractors, Atkins and Mott MacDonald, numerous protection measures have been put in place to limit the risk of pollution. These include permanent monitoring of water quality, triple anti-pollution floating barriers, the establishment of a safety perimeter, and environmental training to monitor and safeguard marine life in the estuary, in particular the Chinese white dolphin, a protected species also known as the pink dolphin.