季节冻土区黄土抗剪强度变化特征及其影响因素

Variation characteristics and influencing factors of loess shear strength in seasonal frozen soil region

摘要:

黄土作为一种特殊的土质,其力学特性极易受水热效应的影响。为研究温度、压实度、含水率等因素对季节冻土区黄土抗剪强度的影响,以中国西部典型的兰州黄土为研究对象,通过低温三轴试验,探讨温度、压实度、含水率的变化对冻结兰州黄土抗剪强度的影响。结果表明:冻结兰州黄土的黏聚力及内摩擦角随着温度的降低呈升高趋势,其中,黏聚力受温度的影响较大,而内摩擦角受温度的影响相对较小；冻结兰州黄土的黏聚力及内摩擦角随着土体压实度的增加而增大；对于含水率,由于土体中冰晶以及未冻水会使土骨架自身强度以及土颗粒与冰之间的胶结力发生变化,以土体最优含水率为分界点,分界点两边的冻结兰州黄土抗剪强度呈相反的变化趋势。由此可知温度、压实度及含水率会对冻结兰州黄土的抗剪强度产生较大的影响,在有黄土覆盖层的季节冻土区工程建设中应充分考虑。

Abstract:

Loess is a kind of special soil, whose mechanical characteristics are easily affected by hydro-thermal effect. In this study, a typical type of loess (Lanzhou loess) in western China was selected as the research object to investigate the effects of temperature, degree of compaction, and water content on the shear strength of seasonal frozen loess through low temperature triaxial test. Results showed that the cohesion and internal friction angle of the frozen Lanzhou loess increased with the decrease in temperature. The cohesion was greatly affected by temperature, while the internal friction angle was relatively less affected by temperature. In addition, the cohesion and internal friction angle of the frozen Lanzhou loess increased with the increase in the degree of soil compaction. In terms of water content, ice crystal and unfrozen water in the soil changed the strength of soil skeleton and the bonding force between soil particles and ice. Taking the optimal water content of the soil as the boundary point, the shear strength of the frozen Lanzhou loess on both sides of the boundary point showed opposite changing trends. It can be concluded that temperature, compaction degree, and water content have great influence on the shear strength of the frozen loess in Lanzhou, which should be fully considered in the engineering construction of the seasonal frozen soil region covered by loess.