| Title |
Evaluation of Freezing Rate of Marine Clay by Artificial Ground Freezing Method with Liquid Nitrogen |
| Authors |
최현준(Choi, Hyun-Jun) ; 이동섭(Lee, Dongseop) ; 이효범(Lee, Hyobum) ; 최항석(Choi, Hangseok) |
| DOI |
https://doi.org/10.12652/Ksce.2018.38.4.0555 |
| Keywords |
인공동결공법;액화질소;동결속도;해성점토;동결벽체 Artificial ground freezing method;Liquid nitrogen;Freezing rate;Marine clay;Frozen wall |
| Abstract |
Nowadays, the artificial ground freezing (AGF) method has been used in many geotechnical engineering applications such as temporary excavation support, underpinning, and groundwater cutoff. The AGF method conducts the freezing process by employing a refrigerant circulating through a set of embedded freezing pipes to form frozen walls serving as an excavation support and cutoff wall. Two refrigerants of brine with the freezing temperature of $-20{\sim}-40^{\circ}C$ and liquid nitrogen with the freezing (evaporating) temperature of $-196^{\circ}C$ are commonly being used in geotechnical applications. 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 constructed at a depth of 3.2 m in the ground. The temperature of discharged liquid nitrogen was maintained through the automatic valve, and the temperature change induced by 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 $2.12m^3$. In addition, the frozen-wall formation test used about 18 tons of liquid nitrogen for 4.1 days to form a frozen wall with the volume of about $7.04m^3$. The radial freezing rate decreased with increasing the radius of frozen body because the frozen area at a certain depth is proportional to the square of the radius. The radial freezing rate was formulated as a simple equation. |