中文摘要：

以陕西杨凌地区黄土为研究对象,进行了不同含水率、不同干密度的黄土在不同冻融循环次数作用下的直剪试验,探索出进行黄土反复冻融循环试验的方法和控制标准,探讨了封闭系统下黄土在反复冻融循环作用下的抗剪强度劣化特性规律。试验结果表明：黄土在反复冻融循环作用下,表面破坏比较严重;随着冻融次数的增加,黄土的黏聚力先减小后增大,最低值发生在10次冻融循环之内;内摩擦角基本不变;反复冻融循环作用在3~5次对黄土强度有较大的影响,会导致黄土强度的劣化现象发生,但长期冻融作用则会主要体现在对黄土表面的变形破坏等其他方面。

英文摘要：

By taking the loess of Yangling area in Shaanxi province as the research object,a direct shear test is conducted with different water contents,dry densities and times of freezing-thawing cycles.The tests are to explore the way and the criterion of long-term freezing-thawing cycles.Then the characteristic of loess deterioration with long-term freezing-thawing cycles is studied in a closed system.The test result show that：（1）in the condition of long-term freezing-thawing cycles,the surface of loess is destroyed greatly;（2）the cohesion of loess decreases firstly and increases later according to the suggestion.The freezing-thawing cycles and the minimum value are normally appeared in ten freezing-thawing cycles.The internal friction angle of loess keeps invariable basically.The strength of loess is affected greatly in three-five freezing-thawing cycles,which can lead to strength deterioration of loess.But with the time going,the influence of freezing-thawing cycles is reflected on the transmutation of loess surface.