18. Effective control of groundwater by the use of ground freezing

Introduction Ground freezing is undoubtedly one of the most effective and consistently reliable methods for excluding groundwater from flowing into deep excavations and providing temporary support during excavation or structural underpinning. The basic principle of ground freezing (first used in South Wales circa 1862) is the use of refrigeration to convert the in situ pore water to ice, which then acts to bond adjacent soil particles. This action imparts additional strength characteristics and impermeability to the soil structure. Impermeability is a factor constant to all soil types. The proportion of strength increase, however, varies depending on soil type, degree of saturation and temperature.