Engineering properties on salt rock as subgrade filler in dry salt lake: Water retention characteristics and water migration patterns

Abstract

As a special road material, salt rock has high strength and stability in arid areas, and has broad application prospects in highway engineering construction in dry salt lake areas. To investigate the water retention characteristics of salt rock and its water migration patterns under the covering effect, and to ensure the long-term durability of salt rock subgrade, this study presents a comprehensive analysis of the effect of initial dry density on the water retention characteristics of fine-grained salt rock fillers. The soil–water characteristic curve model of salt rock was recommended. The capillary water migration patterns of salt rock were proved. The water migration patterns of salt rock under freeze–thaw cycles were clarified. The hydrothermal state of salt rock subgrade under the influence of pavement overburden was evaluated based on the field monitoring. The results indicated that the water retention capacity of fine-grained salt rock filler increases with the decrease of initial dry density during the high suction stage. The Fredlund & Xing model is recommended to address the soil–water characteristic curve of fine-grained salt rock. The capillary action of salt rock filler decreases with increasing compaction. The temperature gradient from the upper boundary to the bottom of the soil column under the effect of freeze–thaw cycles is significant. After five freeze–thaw cycles, the water in the soil column continued to migrate upwards under the covering effect and temperature gradient. The relative humidity and temperature of the salt rock subgrade both show a sinusoidal cyclical variation. When the temperature range of salt rock subgrade is −6°C–30 °C, the relative humidity of subgrade is significantly correlated with temperature. This study can provide theoretical support for the disaster prevention and control of salt rock subgrade covering effect in the Lop Nor area.