Study on the strength and deformation property of frozen silty sand with NaCl under tri-axial compression condition

In order to explore the mechanical behavior of frozen silty sand with NaCl, silty sand was taken as objective and reconstructed with a NaCl content of 1.0% (close to natural content). Tri-axial compressive experiment was carried out under − 3 °C, − 5 °C and − 7 °C with confining pressure range of 0.3-6 MPa. The experimental results showed that both temperature and confining pressure had influence on the deformation behavior of frozen silty sand with NaCl. With decrease of temperature, the brittleness of frozen silty sand with NaCl increased while failure strain decreased. Confining pressure restricted the brittleness of soil. Under softening circumstance, failure strain increased with increasing confining pressure. When confining pressure exceeded 2 MPa, the stress-strain curves under each temperature behaved strain-hardening. The strength of frozen silty sand with NaCl increased linearly both with decreasing temperature and with increasing confining pressure. Within the experimental confining pressure range, the strength law could be described by Mohr-Coulomb criterion. The decrease of temperature strengthened the cementation of ice in soil, resulting in linear increase of cohesion with temperature, while it had little impact on internal frictional angle. In addition, the variation laws of initial tangent modulus E0 and secant modulus at 0.5 times of strength E0.5 were investigated, and it was found that E0 had a better dada stability than E0.5 under the influence of temperature and confining pressure.