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环境温度是土体冻结和融化过程中常见的变量。为明确冷却温度对土体冻融循环效应的影响规律,以青藏高原粉质黏土为对象,进行不同冷却温度和冻融次数的冻融循环试验及三轴剪切试验,并测定试样冻融循环后的水分重分布和体积变化特征。结果表明,冻胀和冻缩在冻结过程中是同时存在的,且均随冷却温度的降低而增大,两者正负变形量比例关系的不同是土体冻融循环效应多变的主要原因之一。随着冷却温度的降低,由于冻胀先于冻缩达到极限状态,体积增加量呈先增大、后减小的规律,转折点对应的是冻胀和冻缩在微小温差条件下变形附加量相对大小关系发生改变的临界温度值。破坏强度随冷却温度的变化与干密度一致,呈先减小、后增大的规律,以劣化为主。未冻水含量和水分迁移量均随冷却温度的降低而减小,因此冷却温度越低,破坏强度随冻融次数的变化范围越小,达到新的稳定状态所需的冻融次数也越少。黏聚力和内摩擦角随冷却温度和冻融次数的变化规律可以采用Logistic模型拟合与预测,以方便工程应用。
Ambient temperature is a common variable in soil freezing and thawing processes. In order to clarify the influence of cooling temperature on the freeze-thaw cycle, the freeze-thaw cycles and triaxial shear tests with different cooling temperatures and freeze-thaw cycles were conducted on silty clay in the Qinghai-Tibet Plateau. Circulation of water redistribution and volume change characteristics. The results show that both frost heave and freeze-thaw exist simultaneously in the freezing process and both increase with decreasing cooling temperature. The difference between the positive and negative deformation rates is the main reason for the variable effect of soil freeze-thaw cycles one. With the decrease of the cooling temperature, the frost heave reached the limit state before the frost-thawing, and the volume increase increased first and then decreased. The inflection point corresponded to the frost heave and the frost heave shrinkage in the condition of slight temperature difference The size of the relationship between the critical temperature changes. The damage intensity changes with the cooling temperature and dry density, was first reduced, then increase the law to deterioration. The unfrozen water content and water migration amount both decrease as the cooling temperature decreases, so the lower the cooling temperature, the smaller the range of the breaking strength changes with the number of freeze-thaw cycles, and the less the number of freeze-thaw cycles required to reach the new steady state . Cohesion and internal friction angle with the cooling temperature and the number of freeze-thaw cycles Logistic model can be used to fit and predict to facilitate engineering applications.