含水率和温度影响下的高原土体力学特性试验研究

利用自主研制的土体冻融循环剪切试验仪，开展了温度和含水率影响下的青藏高原土体力学特性正交试验，从压缩特性、冻结和冻胀、剪切特性3个方面对土体进行分析。结果表明:土样压缩过程的法向位移随含水率的增大而增加，压缩量与法向应力关系可用双曲线模型进行描述。不同含水率的土体从0 ℃降至?12 ℃过程中均产生了土体冻结现象，含水率12%的土体发生冻胀时的温度集中在?3~?2 ℃范围内。温度越低，土体的应力软化特性越明显，且峰值剪切应力和残余剪切应力越大，土体在最佳含水率附近时峰值剪切应力最大。?12 ℃土体的法向位移变化规律在不同试验条件下均表现出剪胀特性，而12 ℃和0 ℃土体随着含水率的增加由胀缩特性并逐渐变化至完全以剪缩特性为主。内摩擦角随含水率和温度的增大而减小，黏聚力随温度的升高而减小，在最佳含水率附近最大。

Experimental study on effects of water content and temperature on mechanical properties of plateau soil

The orthogonal test of mechanical properties of plateau soil is carried out via a self-developed soil freeze-thaw cyclic shear equipment. The compression characteristics, freezing and frost heaving, and shear characteristics of soil affected by temperature and water content are studied. The results show that the normal displacement of soil samples during compression increases with the water content, and the relationship between compression value and normal stress can be described by hyperbolic model. The soil with different water content is frozen when the temperature drops from 0 ℃ to ?12 ℃. The temperature of frost heaving of soil with 12% water content ranges from ?3 ℃ to ?2 ℃. The stress softening characteristics of soil become more and more obvious with the decrease of temperature, and the peak shear stress and residual shear stress are also the largest under negative temperature. The peak shear stress of soil near the optimum water content is the largest. The variation law of normal displacement of soil at ?12 ℃ shows shear expansion characteristics under different test conditions, while the soil at 12 ℃ and 0 ℃ shows both dilatancy and shrinkage characteristics at low water content, and only shrinkage characteristics at high water content. The internal friction angle decreases with the content and temperature, and the cohesion decreases with the temperature, and reaches the maximum near the optimum water content.