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| Experimental study on the effect of cyclic freezing-thawing on mechanical properties of silty clay under different cooling temperatures |
| HU Tianfei1，LIU Jiankun1，2，FANG Jianhong2，CHANG Dan1，LIU Dawei1 |
| (1. School of Civil Engineering，Beijing Jiaotong University，Beijing 100044，China；2. Transportation Industry Laboratory of Highway Construction and Maintenance Technology in Permafrost Regions-Qinghai Research Observation Base，Qinghai Transportation Research Institute，Xining，Qinghai 810008，China) |
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Abstract In order to study the influence of cooling temperature on the properties of soil subjected to the cyclic freezing-thawing，a set of freezing-thawing tests under the different cooling temperatures and numbers of freezing-thawing cycles were carried out on samples of silty clay from Qinghai—Tibet Plateau. The triaxial shear tests were subsequently conducted on the samples after freezing-thawing under the different confining pressures. The volume increment and the moisture migration inside the samples were measured after one freezing-thawing cycle. Results show that the expansion and contraction exist simultaneously in the freezing process and both increase with the decrease of cooling temperature. The different ratios between the freezing expansion and the freezing contraction are one of the main reasons for different effects of cyclic freezing-thawing. The freezing expansion reach the maximum state earlier than the freezing contraction，so the volume increment increases initially and then decreases as the decrease of cooling temperature. The failure strengths of samples after freezing-thawing are reduced on the whole and vary the same as the dry density does，i.e.，they decrease initially and then increase with the decrease of cooling temperature. The unfrozen moisture content and the amount of moisture migrated both decrease with the decrease of cooling temperature. Hence the range of failure strength changing due to cyclic freezing-thawing becomes smaller when the cooling temperature is lower. The variation of cohesion and internal friction angle versus the cooling temperatures and the numbers of freezing-thawing cycles were fitted with the Logistic model.
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2017, Vol. 36 
