Liquefaction behaviors of the saturated loess in Lanzhou City under freezing-thawing conditions
WANG Qian1，2，ZHONG Xiumei1，2，GAO Zhongnan2，MA Haiping2 ，SU Yongqi1，2，LIU Zhaozhao1，3，LIU Fuqiang1，3
(1. Key Laboratory of Loess Earthquake Engineering，China Earthquake Administration and Gansu Province，Lanzhou，Gansu 730000，China；2. Lanzhou Institute of Seismology，China Earthquake Administration，Lanzhou，Gansu 730000，China；
3. Key Laboratory of Mechanics on Disaster and Environment in Western China，Ministry of Education，Lanzhou University，
Lanzhou，Gansu 730000，China)
Abstract：To investigate the effect of freezing-thawing cycles on the liquefaction characteristics of saturated loess，a series of freezing-thawing cycles and dynamic triaxial tests were conducted. The characteristics of dynamic residual strain and the dynamic pore water pressure of the saturated loess before and after freezing-thawing cycles were determined. The influence of the freezing-thawing cycles on the cyclic shear cycles on liquefaction failure was analyzed. The characteristics of mean effective stress versus the deviatoric stress and the hysteretic curve of dynamic stress-dynamic strain before and after freezing-thawing cycles were discussed. Moreover，the characteristics of structure and its influence on loess liquefaction were analyzed based on the particle analysis tests and SEM results before and after freezing-thawing cycles. The results show that the freezing-thawing cycles leads to the decline of the anti-liquefaction performance of the saturated loess. The cyclic shear cycles on liquefaction failure decrease significantly when freezing-thawing cycles is less than 5. The dynamic residual strain increases with the increase of freezing-thawing cycles. The dynamic pore water pressure of the soil under freezing-thawing conditions is significantly higher than that of the loess without freezing-thawing cycles，however，the regularity of the relationship between the exceed pore water pressure and the freezing- thawing cycles is not obvious. With the freezing-thawing cycles increases，the clay content of the loess increases whereas the sand content decreases. The clusters of the soil are significantly decreasing. The soil particles tend to break，and the overhead pores are damaged. The change of soil particles and structure caused by freezing-thawing cycles is the main reason for the changes of the characteristics of soil liquefaction.
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2020, Vol. 39 
