Mechanical behavior and microstructural evolution of frozen soils under the combination of confining pressure and water content

It is essential and important for engineering design and maintenance to systematically investigate the physical–mechanical properties of frozen soils. At present, a series of tests have been carried out on frozen silty clay based on improved testing techniques. The results indicate that brittle and plastic failures occur for frozen silty clay under low and high confining pressures, respectively, and strengthening and weakening effects from the water content and confining pressure on the frozen strength are also observed. With the increase in confining pressure or water content, the compressive strength first increases to a maximum and then begins to decrease, and at the same time, the pressure fracturing of pore ice is gradually aggravated. Under the combination of confining pressure and water content, the microstructure evolution of frozen silty clay includes the soil particles or cementing soil crushed and reclotted, the initial soil skeleton destroyed, the pore ice fractured and melted, and the growth of microcracks, which mainly depends on the amount of water content and axial and radial loads. The tearing of cementing soil or sliding of soil particles causes drum-shaped deformation of the sample.