Experimental study on frost heave characteristics and micro-mechanism of fine-grained soil in seasonally frozen regions

In this study, a combination of soil column frost heave tests and microscopic tests (scanning electron microscopy and mercury intrusion test) was conducted to explore the frost heave characteristics of subgrade fine-grained fillings in seasonally frozen regions with different initial water contents under different temperature gradients. Particle image velocimetry (PIV) was employed to clarify the trend in the local deformation at different locations in the soil samples. The test results showed that the total deformation of the soil decreased with the increase in the temperature gradient, and the amount of water replenishment also exhibited a similar trend. Deformation measurements from PIV were in good agreement with the displacement meter measurements. The microscopic test results showed that the porosity of the soil evidently increased after the soil was frozen. Furthermore, when the temperature gradient of the samples was the same, the pore volume of the frozen soil was positively correlated with the initial water content and negatively correlated with the temperature gradient. The study results can help reveal the microscopic mechanism behind the macroscopic frost heave process.