ABSTRACT
The Artificial ground freezing (AGF) method has been used in many geotechnical engineering applications such as temporary excavation support and underpinning, and groundwater cutoff, especially for constructing cross passages of a subsea tunnel through highly-fractured fault zones. The freezing rate is one the most important factors governing the applicability of the AGF method. This paper performed a series of field experiments to evaluate the freezing rate of marine clay in application of the AGF method. The field experiments consisted of the single freezing-pipe test and the frozen-wall formation test by circulating liquid nitrogen, which is a cryogenic refrigerant, into freezing pipes. The temperature of discharged liquid nitrogen was maintained through the automatic valve, and the temperature change induced by the AGF method was measured at the freezing pipes and in the ground with time. According to the experimental results, the single freezing-pipe test consumed about 11.9 tons of liquid nitrogen for 3.5 days to form a cylindrical frozen body with the volume of about 2.12 m3. The frozen-wall formation test consumed about 18 tons of liquid nitrogen for 4.1 days to form a frozen wall with the volume of about 7.04 m3. The radial freezing rate decreased with increasing the radius of frozen body because the frozen area at a given depth is proportional to the square of radius.
