Ground Freezing and Sampling of Pleistocene Sand near Charleston, South Carolina

Abstract

The procedures used to freeze and sample a Pleistocene sand deposit near Charleston, South Carolina to preserve and study the effects of diagenesis are presented in this paper. Based on the results of geotechnical tests and a feasibility ground freezing study, a freezing system with a central freeze pipe was installed to target a column of clean sand 1 m in radius and 2.3 m in length. Liquid nitrogen was continuously supplied to the freeze pipe fabricated to freeze the sand between depths of 1.8 and 3.8 m below the ground surface for 270 h. Frozen sand cores taken from five locations 0.65 to 0.7 m away from the central freeze pipe indicate the ground was frozen between depths of 1.8 and 3.8 m at all but one location. Ground temperature measurements, growth of the frozen zone, and the amount of liquid nitrogen consumed are presented and compared with predicted values. Recorded temperatures indicate that the freezing was influenced by the direction of groundwater flow, the flow rate of liquid nitrogen, and the location of the liquid nitrogen inlet pipe within the central freeze pipe.