温度对盐渍土抗剪强度和变形特性的影响

为了明确因冻结温度和结晶差异造成的温度对盐渍土抗剪强度和变形特性的影响，以高含盐量和不同盐分类型的盐渍土为研究对象开展试验研究。首先，选用青藏高原察尔汗-格尔木高速公路沿线采集的含盐量为10%~36%的氯盐含量高、硫酸盐含量低的盐渍土土样（HC-1，HC-2）和硫酸盐含量较高而氯盐含量较低的盐渍土土样（CS）3种高含盐量盐渍土作为试验土样，对3种土样进行冻结温度试验，验证其降温至-20℃时，土体不会发生冻结。其次，在5个不同控制温度（-20℃、-10℃、0℃、10℃和20℃）下，分别进行盐渍土直剪试验以得出温度与抗剪强度参数关系函数。最后，分析温度对抗剪强度和弹性模量的影响，同时，利用数值拟合建立考虑温度影响下的盐渍土抗剪强度和切线弹性模量公式。研究结果表明：当温度由20℃降低至-10℃，3种盐渍土的抗剪强度和初始切线弹性模量均增大后趋于峰值，而随温度继续降低至-20℃后，HC-1和HC-2土样指标呈下降趋势，CS土样各参数结果却趋于稳定；不同含盐类型的盐渍土，温度对其破坏比R_f的影响也不同；在温度由20℃降至-20℃的过程中，HC土样的R_f在-10℃出现峰值，且在较低荷载（100 kPa）下，呈现出先增大后减小的特点，在较高荷载（200，300，400 kPa）下呈现出先增大后趋缓的特点；CS土样的R_f在20℃~10℃、10℃~-10℃和-10℃~-20℃降温段呈现出先增大中趋缓后减小的分段式变化特点。

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 R_f is also different. During the temperature reduction from 20℃ to -20℃, R_f of the HC soil peaks at -10℃. Under lower loads (100 kPa), R_f initially increases then decreases. Under higher loads (200, 300, and 400 kPa), R_f initially increases then decreases slowly. The R_f for CS exhibits three segmental changes:R_f 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.