Research on the dynamic and deformation characteristics of unsaturated frozen sulfate saline red clay

In negative temperature environments, the moisture and solutes within saline soils may crystallize into ice and salt, respectively, inducing recurrent frost heave and salt expansion phenomena, and occurring differential settlement under temperature fluctuations and dynamic loading. To elucidate the dynamic behavior of frozen subgrade under cyclic loading, a series of dynamic triaxial tests was conducted on unsaturated, sulfate-contaminated frozen red clay, with systematic variation in confining pressure, moisture content, and salinity. Experimental results reveal that a moderate amount of salt can enhance the structural stiffness of the soil-reflected by an 8 % increase in the dynamic elastic modulus (E_d), reduce the area of the hysteresis loop (36.30 %) and effectively mitigates plastic deformation correspondingly. The dynamic modulus exhibited a non-linear “increase-decrease-increase” trend with rising confining pressure. With the increasing of water contents, more water will transform into ice. To comprehensively evaluate the dynamic response, parameters such as dynamic modulus, hysteresis loop area, and strain rate were analyzed by using the entropy weight method combined with the Rank Sum Ratio (RSR) approach, which indicated that confining pressure of 300 kPa, water content of 18 %, and salinity of 1 % were the optimal combination of test conditions based on the RSR value 0.844 and minimum strain rate 0.008 mm/s to yield maximum dynamic modulus (19GPa) and moderate energy dissipation(110 MPa).