Experimental Study on Shear Strength Characteristics of Silty Sand Under Freezing and Thawing Conditions

This paper combines the construction process and geological conditions of the artificial freezing method on the contact channel of Zhengzhou Metro Line 3, according to the remolded silty soil with the moisture content of 19.5% at room temperature and negative temperature (−1, −5 and −10 °C) to conduct a large-scale direct shear test. This study analyzed the variation of shear properties of silty sand with temperature. Test results show that the shear stress–shear displacement curve of silty soil in the melted state is of the strain hardening type, while under freezing conditions it shows to be a strain softening type. As the cooling temperature decreases, the peak strength and cohesion of the silty soil increase significantly, but the internal friction angle increases relatively small. When the silty soil is in the melted state and frozen at −1 °C, the shearing phenomenon occurs in the initial stage of the test, while only the dilatancy occurs when freezing at −5 and −10 °C; the maximum amount of dilatancy is negatively correlated with vertical pressure and positively correlated with cooling temperature.