基于结构性的冻结黄土力学特性试验研究

Experimental study of frozen loess mechanical behaviour based on constitutive property

通过对重塑冻结黄土和人工结构性冻结黄土(通过对重塑黄土添加水泥获取)进行室内三轴剪切试验,研究了围压、含水量、温度、水泥含量等因素对冻结黄土力学行为的影响.结果表明:不同试验条件下,非饱和土试样和饱和土试样的应力-应变关系呈现不同的特点.温度和围压是影响冻土体强度的主要因素,温度越低,其破坏强度越高;非饱和土样强度随围压增大而增大,饱和土体强度受围压影响很小.初始含水量是影响冻土体强度的另一主要因素,对非饱和土样,随着含水量的增加土体强度逐渐增高,达到某一峰值之后随含水量继续增加而减小,饱和土体强度最低.对非饱和土样,水泥含量越高,对应的破坏强度也就越大;但对饱和土样,水泥含量对冻土的应力-应变行为及强度影响不大.最后,提出了与所试验土体强度参数相关的综合性系数M,通过回归分析,得出了其与c和tanφ的关系,并验证了其可靠性.

In this paper, based on triaxial compression tests of remolded frozen loess and artificially structured frozen loess with different amounts of cement, the effects of confining pressure, initial water content, temperature and cement amount on the frozen loess＇ mechanical behavior are studied. It is found that there are differences in stress-strain relationship between unsaturated and saturated frozen loess, depending on experimental conditions. The temperature and confining pressure are the main factors which influence the shearing strengths of frozen soil. The lower the temperature is, the higher the failure strength is. The shearing strength of unsaturated frozen loess increases with confining pressure, but that of saturated frozen loess has dependent on confining pres- sure a little. The initial water content is another main factor affecting the frozen loess strength. As increasing wa- ter content, the frozen loess strength is also increasing. After the water content reaching a peak point, the frozen loess strength would decrease gradually with the water content increasing. The strength of saturated frozen loess will be the lowest. With regard to the unsaturated frozen loess, the shearing strength of the unsaturated frozen loess increases with the amount of cement, but that of saturated frozen loess has a little dependent on cement amount. At last, a comprehensive coefficient M is put forward, which correlates closely with parameters of shear strength. By regression analysis, two exponential function relationships between M and c and between M and tan φ are obtained, respectively, of which the reliability is verified.