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The influence of freeze-thaw cycles on the granulometric composition of Moscow morainic clay
Authors:Ze Zhang  Vadim V Pendin  WenJie Feng and ZhongQiong Zhang
Institution:1. State Key Laboratory of Frozen Soil Engineering, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Science, Lanzhou, Gansu 730000, China
2. Department of Engineering Geology, Russian State Geological Prospecting University, Moscow, Russian Federation
Abstract:The freeze-thaw cycling process considerably changes the composition, structure, and properties of soils. Since the grain size is the most important factor in determining soil characteristics, our current research primarily aims to investigate dynamic changes of the soil fraction when exposed to freeze-thaw conditions. We observed two series of Moscow morainic clayey specimens (gQIIm): (I) the original series, and (II) the remolded series. We subjected each series of soil specimens to different frequencies of freeze-thaw cycles (3, 6, 20, and 40 cycles), and we used granulometric tests to analyze both series before and after exposure to freeze-thaw conditions. As a result of our experiments, the granulometric compositions tended to be distributed evenly after 40 freeze-thaw processes (i.e., content of fraction for 0.1-0.05 mm was increased after 40 freeze-thaw cycles) because the division of coarse grains and the aggregation of fine grains were synchronized during the freeze-thaw process. The soil grains in both series changed bi-directionally. In the original series, changes of the sand grains were conjugated with the clay grains, and in the remolded series, changes of the sand grains were conjugated with the silt grains, because potential energy difference caused the division and aggregation processes to relate to the counteraction process. The even distribution of soil grain size indicated the state of equilibrium or balance. The granulometric compositions were altered the most during the sixth freeze-thaw cycle, because the coefficient of the intensity variation of the grain fineness (Kvar) had its maximum value at that time.
Keywords:Moscow morainic clay  freeze-thaw cycles  granulometric composition  variability
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