Effect of Temperature on Shear Strength and Deformation Characteristics of Saline Soil

To clarify the effect of freezing temperature and crystallization differences on the shear strength and deformation characteristics of saline soil, three types of saline soil were selected as test specimens from the Qarhan-Germu Expressway. The three specimens had salt contents ranging between 10% and 36%, and were designated high chloride salt content (HC-1), low sulfate salt content (HC-2), and higher sulfate content with lower chloride content (CS). Prior to testing, a freezing temperature test was conducted on the CS specimen, where the temperature was lowered to -20℃. As the CS specimen had the lowest salt content, this test verified that all three selected saline soil specimens (HC-1, HC-2, and CS) would not freeze when the temperature was lowered to -20℃. Direct shear tests were carried out on selected saline specimens at five control temperatures of 20℃, 10℃, 0℃, -10℃, and -20℃ to obtain the relationship between temperature and shear strength. Based on the plotted stress-strain curves, the effect of temperature on shear strength and elastic modulus of elasticity were analyzed, and a numerical model was used to establish the shear strength and tangent elastic modulus model of saline soil under the influence of temperature. The test results indicate that the shear strength and initial tangent elastic modulus of the three types of saline soil increase, and tend to peak as the temperature decreases from 20℃ to -10℃. The HC-1 and HC-2 soil specimens exhibit a downward trend when the temperature continues to decrease to -20℃. The results for the CS soil specimen tend to be stable. For saline soils of different salt types, the effect of temperature on the destruction ratio Rf is also different. During the temperature reduction from 20℃ to -20℃, Rf of the HC soil peaks at -10℃. Under lower loads (100 kPa), Rf initially increases then decreases. Under higher loads (200, 300, and 400 kPa), Rf initially increases then decreases slowly. The Rf for CS exhibits three segmental changes: Rf first increases, then tends to smooth out, and finally decreases in the temperature ranges of 20℃ to 10℃, 10℃ to -10℃, and -10℃ to -20℃, respectively. © 2020, Editorial Department of China Journal of Highway and Transport. All right reserved.