Study on the Mechanical Characteristics of Salinized Silt Soil with Low Liquid Limit under Freeze-Thaw Cycle

In order to study the effect of freeze-thaw on the strength of low-liquid limit salinized silt, after the freeze-thaw cycle test of salted silt with different initial moisture content, non-consolidating and non-drainage (UU) shear and scanning electron microscopy (SEM) tests were carried out to reveal the deterioration mechanism of the strength of low-liquid limit salinized silt from macro-micro perspectives. The test results show that the change of moisture content does not cause the stress-strain curve morphology of low-liquid limit salinized silt to change when it is not freeze-thawed, and all of them are softening. Under the action of freeze-thaw, the curve shape of the specimen will not change when the moisture content is less than 14%, showing a softening type, and the stress-strain curve shape of the specimen with high moisture content will change to hardening. By analyzing the relationship between freeze-thaw and moisture content and failure intensity, it is found that the failure intensity of low-liquid limit salted silt decays linearly with the increase of moisture content, and the failure intensity decays exponentially with the increase of freeze-thaw cycles, and the attenuation rate and amplitude of the failure intensity are the largest in the first three freeze-thaw processes, and then tend to be stable. With the increase of confining pressure, the stress-strain curve of the specimen will transition from softening type to hardening type. In terms of microstructure, freeze-thaw will change the contact form between soil particles, resulting in the development of pores and fissures, and the variation law of microstructure and deterioration of macroscopic mechanical indicators in the freeze-thaw process are consistent. Combined with the soil damage mechanics, a low-liquid limit salinized silt cohesion damage deterioration model under freeze-thaw action was constructed, and the deterioration degree during the freeze-thaw process conformed to the hyperbolic relationship, and the final deterioration degree A_c had an exponential relationship with the moisture content, and the deterioration rate was B_c linear relationship with the moisture content.