Excavation sub-grade Ground surface Grout or transfer materials Stressing unit Sheeting Tendon 10-20 0 Bond free zone Assumed surface of sliding wedge Tieback installed at 10 to 20° down from horizontal
Tied-back concrete wall constructed underground for excavation support
Ground freezing is a technique that has been used extensively for groundwater control and excavation support in the underground construction industry for over 100 years.
The process involves the circulation of a refrigerated coolant through a series of subsurface pipes to convert soil water to ice, creating a strong watertight material. The material is so strong, in fact, that it is routinely used as the only method of groundwater control and soil support for the construction of shafts hundreds of feet into water-bearing soils.
Most ground freezing systems are quite similar in principal. The single most important co mponent of a ground freezing system is the subsurface refrigeration system , consisting of a series of refrigeration pipes installed with various drilling techniques. Depending upon the application, the coolant can be brought to temperatures well below -150 degrees celcius Ground freezing can be achieved by using either a large portable refrigeration plant or liquid nitrogen . After the initial freezing has been completed and the frozen barrier is in place, the required refrigeration capacity is significantly reduced to maintain the frozen barrier.