Effect of Temperature on the Strength Characteristics of Unsaturated Silty Clay in Seasonal Frozen Region

The strength characteristics of unsaturated silty clay after the cooling and single freeze-thaw cycle were studied by using Global Digital Systems Ltd. (GDS) triaxial test system after controlling initial matric suction. The results demonstrate that, the initial matrix suction and freezing process can strengthen the shear strength of the soil, which makes the stress-strain curve of the soil show certain strain hardening characteristics at different temperatures. when the temperature is negative (including 0°C), the curve has a flat transition section whose strength does not change with deformation, and the flat transition section becomes shorter as the temperature and confining pressure decrease. The strength of the soil at negative temperature and the speed at which it reaches its peak value are much greater than those of the soil after positive temperature and single freeze-thaw cycle, and the contribution of confining pressure to the strength decreases with the decrease of temperature. The effect of temperature change (15°C to −15°C) on soil strength is mainly reflected in the total cohesion, and the effect of freeze-thaw on the effective internal friction angle is more significant. The strength and deformation characteristics of soil under the freezing process and freeze-thaw cycle are determined by the initial matric suction, the form of connection between soil particles, the migration of unfrozen water, and the degree of water-ice phase transformation.