Ground Freezing Techniques ~ this method is suitable for all types
of saturated soils and rock and for soils with a moisture content in
excess of 8% of the voids. The basic principle is to insert into the
ground a series of freezing tubes to form an ice wall thus creating
an impermeable barrier. The treatment takes time to develop and
the initial costs are high, therefore it is only suitable for large
contracts of reasonable duration. The freezing tubes can be
installed vertically for conventional excavations and horizontally
for tunnelling works. The usual circulating brines employed are
magnesium chloride and calcium chloride with a temperature of 15 °
to 25 °C which would take 10 to 17 days to form an ice wall 1„000
thick. Liquid nitrogen could be used as the freezing medium to
reduce the initial freezing period if the extra cost can be justified.Ground Water Control---Medium Term Exclusion