Artificial ground freezing has been used for over a century to form a temporary support and an impermeable barrier for underground openings and other excavations. Nowadays it can be an efficient barrier to prevent pollution spreading in permeable soils. Depending on circumstances chilled brine or liquid nitrogen is circulated through freeze tubes to form ice walls. This requires a good understanding of the thermal, mechanical and hydraulic properties of frozen and thawed soils. Topics: Heat and mass transfer; Mechanical properties; Engineering design; Case histories; Environmental soil freezing; etc.