干湿和冻融共同作用下压实黏性土回弹模量试验研究

以山东济南和黑龙江大庆的两种低塑性黏性土为研究对象，在不同围压、动偏应力、含水率和冻融循环次数条件下，开展两种压实黏性土动三轴试验确定其回弹模量M_R，研究季节性冻土区域干湿、冻融共同作用对天然路基土M_R的影响规律。试验结果表明：试样冻融循环次数越多、含水率高，围压对M_R的贡献越大。动偏应力有两种刚度效应，即动偏应力下因土体逐渐压实产生的刚度增强效应和动偏应力反复剪切造成的土体结构破坏而产生的刚度衰减效应。高塑性土体M_R对含水率变化较为敏感，但敏感性随冻融循环作用显著降低。两种土的M_R在前3次冻融循环中衰减明显，随着冻融循环次数的继续增加，M_R基本保持不变。

Study on Test of Resilience Modulus of Compacted Clay under Combined Action of Wetting-Drying and Freezing-Thawing Cycles

Taking two kinds of low-plastic clay in Jinan of Shandong and Daqing of Heilongjiang as the research object, the dynamic triaxial tests were carried out with two kinds of compacted clay to determine the respective M_R in the condition of different confining pressure, dynamic deviator stress, moisture content, and the number of freezing-thawing cycles. The laws how the complex action of wetting-drying and freezing-thawing cycles affect the resilience modulus (M_R) of natural subgrade soil in seasonal permafrost regions was studied. The test results show that, the more cycles of freezing and thawing with high moisture content, the greater contribution of confining pressure to the M_R. The dynamic deviator stress is of two kinds of stiffness effect, i.e. the stiffness enhancement effect from gradually compacting of soil mass under the action of dynamic deviator stress and the stiffness decay effect from destruction of soil structure under the repeated shearing of dynamic deviator stress. The soil mass of high plasticity has the M_R sensitive to moisture content, but the sensibility may be decreased significantly with the action of freezing-thawing cycles. The M_R of the two kinds of soil decays obviously in the first three cycles of freezing and thawing and, as the number of the cycles keeps increasing, the M_R remains unchanged substantially.