青藏高原冻结粉质黏土直剪蠕变特性试验研究

针对青海-西藏±500 kV直流联网输电线路工程塔基基础设计问题，在青藏高原五道梁处取地表粉质黏土，制备不同含水率、不同密实度的重塑土样，在-2 ℃条件下进行了直剪蠕变试验。结果表明，冻结粉质黏土剪切蠕变曲线除了在个别较高应力下具有加速蠕变阶段外，大多数蠕变曲线只有非稳定蠕变和稳定蠕变2个阶段，表现为衰减型蠕变。通过长期强度方程计算出冻土长期强度衰减值。冻结粉质黏土长期强度与含水率、密实度密切相关：在含水率较低情况下，冻土长期强度随含水率的增加较为明显，之后随含水率的增加，冻土长期强度逐渐降低；相同含水率情况下，密实度大的冻土长期强度较高。

Experimental study of direct shear creep properties of frozen silty clay on Qinghai-Tibetan Plateau

To better understand the in-situ engineering conditions of frozen ground where the piers of Qinghai-Tibetan ±500kV Direct Current Transmission Line Project will be constructed; the direct shearing creep experiment for frozen silty clay, a kind of soil taken from Wudaoliang on the Qinghai-Tibetan Plateau and remodeled in different moisture contents and densities in laboratory at -2℃, was carried out. The study results show that most creep of the frozen silty clay appears as attenuation creep which has two phases: unsteady creep phase and steady creep phase; only several creeps of frozen silty clay takes on the third phases: accelerated creep phase. The long-term strength of frozen soil could be calculated by the long-term strength equation. The long-term strength of the frozen silty clay closely affected by the moisture content and density of the soil; the frozen soil with higher moisture content has higher long-term strength at low moisture circumstance; but it shows opposite trend at high moisture circumstance; the frozen soil with higher density has higher long-term strength with the same moisture content.