The Land Transport Authority (LTA) in Singapore is the first to use a “ground breaking” ground-freezing technology for the construction of the Thomson-East Coast Line of their mass transit system in Marina Bay. LTA is using this ground-freezing method to stabilize the earth before excavating tunnels by creating a stretch of ice walls. The ground at the construction site is made of old alluvium clay, which is hard to stabilise with traditional cement grouting. So the construction companies carried out multiple site checks and soil investigations that led them to conclude that ground-freezing would be the most effective method for this soil type.
LTA installed a series of freeze pipes into the ground around the site and circulated a saline solution chilled to -22°F through the pipes to freeze the surrounding soil. This gradually formed individual columns of ice that eventually grew in size until they connect with the columns around them to form a solid wall of ice. LTA began this process back in March and within 2 months they had created two ice walls almost 6 feet in diameter 130 feet below the surface of the earth. The ice walls will remain in effect for about 3 months until LTA finishes constructing this tunnel of the Thomson-East Coast Line, at which point, the freeze pipes will be deactivated and the ground will thaw. http://bit.ly/2uK1SD5