Comparative studies on mechanical behavior of frozen natural saline silty sand and frozen desalted silty sand

• Triaxial test were conducted on frozen saline silty sand before and after desalting.
• Deformation characteristics of frozen silty sand before and after desalting were analyzed.
• Strength of frozen silty sand before and after desalting was analyzed.
• Elastic modulus of frozen silty sand before and after desalting was analyzed.
• Effect mechanism of saline on mechanical behavior of frozen silty sand was discussed.

To compare the mechanical behavior of natural frozen saline silty sand before and after a desalting process, the collected natural frozen saline silty sand with/without desalting is reconstituted to soil samples with water content at 13%. Triaxial compressive tests are carried out under confining pressures ranging from 0.3 to 3 MPa and at temperatures of − 2 °C, − 4 °C, and − 6 °C. In the testing range of confining pressure and temperature, the natural frozen saline silty sand presents plastic failure and strain-hardening, whereas the desalted silty sand with the same water content exhibits brittle failure and obvious strain-softening. Thus, the experimental results show that the presence of salt obviously weakens soil brittleness. The strength of either the natural frozen saline silty sand or the desalted one increases with the increase of confining pressure but with the decrease of temperature. Additionally, the strength of the natural soil is lower than that of the desalted soil in all tests which indicates that the presence of salt can also reduce the strength of the frozen silty sand. The internal friction angle of the frozen natural soil first increases with the decrease of temperature and then maintains nearly at constant; adversely, the internal friction angle of the desalted soil sustains as a constant within the testing temperature range. The cohesive force of both the natural and desalted frozen soil exhibits a linear growth as temperature decreases. Moreover, the cohesive force and the internal friction angle of the desalted soil are always higher than those of the natural soils. Lastly, the influence of temperature and confining pressure on initial tangent modulus (E0) and secant modulus corresponding to half the strength (E0.5) are analyzed. The E0 and E0.5 of the desalted frozen soil increase with the increase of confining pressure but with the decrease of temperature and are higher than the ones of the natural soil. Additionally, for either the natural or the desalted soil, E0 is more sensitive to confining pressure compared with E0.5.