Application of ground freezing for underground construction in soft ground

Artificial ground freezing was developed more than 100 years ago for the construction of deep shafts in water bearing soil. In Germany shafts have been constructed using ground freezing down to depths of more than 600 meters (2,000 ft). During the past 20 to 30 years ground freezing has been used more frequently for underground construction, tunneling, deep excavations and special applications. For many cases ground freezing is the only solution to create a watertight and load-carrying soil body in water bearing soil. But with ground freezing numerous applications are possible. With ground freezing economical solutions can be realized even under highly demanding conditions using mobile freeze units for brine freezing or using liquid nitrogen. Ground freezing is based on heat withdrawal from the surrounding soil, so that it is only used as temporary measures for ground support and/or water cut-off. It is environmentally friendly as no barriers like e.g. diaphragm walls, chemical or other grouting material remains in the subsurface environment after the application. Ground freezing is a very safe method but it has to be designed in detail. Ground freezing has been used successfully for many different applications. Four projects are presented which were completed during the last years showing different applications and construction methods.