Characteristics of the liquid and vapor migration of coarse-grained soil in an open-system under constant-temperature freezing

Abstract

Liquid and vapor migration is the key factor in evaluating the frost heaving properties of coarse-grained soil (CGS) in the high-speed railway (HSR) subgrade in cold regions. A fluorescein tracer was applied to investigate the liquid and vapor migration characteristics of CGS during constant-temperature freezing tests. In addition, the effects of the initial water content on the liquid and vapor migration properties were studied in this paper. The results show that the vapor migration is the dominant factor that causes the water redistribution of CGS in the freezing process. The vapor migration exists both in the supply of the external water sources and internally in the CGS. Water mainly migrates upward in the form of vapor under the effect of a water content gradient and a temperature gradient. The amount of liquid and vapor coupling migration in CGS decreases with the increase in initial water content, followed by a lower amount of external water migration, particularly vapor migration, and a lower height of the upward migration of the liquid. Although the vapor migrates across the freezing front and continually moves upward, the degree of vapor migration will gradually decline with a certain impact time domain and zone.