Experimental study on low temperature triaxial shear of sulfate saline silty clay in Hexi area of Gansu

In order to explore the mechanical properties and microstructure changes of frozen saline silty clay in the Hexi region of Gansu Province, triaxial compression tests and scanning electron microscopy (SEM) analysis experiment were conducted to explore the effects of moisture content, confining pressure, and temperature on the stress-strain characteristics and failure modes of frozen soil, as well as the changes in the internal microstructure of the sample. The experimental results show that the strength of frozen sulfate saline soil first increases and then decreases with the increase of moisture content, and the maximum strength corresponds to a moisture content of 15%. The changes in confining pressure and strength have the same trend. The lower the temperature, the greater the strength of the sample. During the entire loading process, the specimens undergo a gradual transition from volume shrinkage to volume expansion. Due to the strain harden behavior of the stress-strain curve throughout the entire loading process, the failure mode of the specimens is plastic failure. The internal microstructure of the sample gradually transitions from point-point contact and edge-point contact before shearing to edge-surface contact and edge-edge contact after shearing, and the pore size inside the sample increases after shearing, with a loose arrangement of the particle skeleton. The above research conclusions can lay a certain theoretical foundation for the engineering design and construction of sulfate saline soil in cold and arid areas.