关键词: 黄土, 冻结锋面, 冻融循环, 试验研究, 比拟法

Abstract: Freezing-thawing cycles result in changes of the structure and thermal physical properties of soil, which affect the process of soil temperature change,leading to the shift of stable position of soil freezing front. In order to study the freezing front movement process under the effect of freezing- thawing cycles,a series of freezing-thawing experiments on Lanzhou Loess under an open system were conducted. It is found that freezing front moves rapidly from top to bottom during the early period of soil freezing,while the speed reduces when the cold end temperature reaches a stable state. When soil temperature field reaches a stable state,the freezing front position tends to be stationary. The freezing front stability depth increases with freezing-thawing cycles. To expound the freezing front movement regularity with time,an analogy curve is adopted by using analogy method, which transforms the freeze-thawing cycles to time. After six freezing-thawing cycles the freezing front position is at the height of 24.4 mm,derived from the fitting curve,while the measured position is at the height of 24.3 mm,with a relative error of 0.4%.

Key words: loess, freezing front, freezing-thawing cycle, experimental study, analogy method