Laboratory experiments on periglacial mass movement and segregated ice

点击翻译按钮获取中文摘要

The aim of this study was to make clear the importance of segregation ice on mass movement during thaw period. Laboratory experiments were conducted using small scale (80 X 40 X 20 cm) and large scale (180 X 90 X 60 cm) insulated tanks in which frost-susceptible volcanic ash soil was compacted. The inclinations of the slopes were 5, 10, 12, 18 degrees. The soil was subjected to one and three freezing and thawing cycles. The position of a target on the ground surface was monitored by linear voltage displacement transformers (LVDTs). The freezing front and thawing front were monitored by frost tubes. The distribution of segregated ice in soil was estimated by frost heave and thaw consolidation rates, because the frost heave is caused by the development of segregated ice in soil. Frozen soils were sampled by drilling, and ice contents in fozen soils were obtained. Deformation of columns of tiles indicated displacement profiles.The maximum frost heaves and downslope movements at the ground surface were ranging from 6 to 18 cm and from 1 to 11 cm in each cycle respectively. Soil layers of high values in frost heave and thaw consolidation rates, where large downslope displacements occurred, coincided with the soil layers of high ice content. The monitoring of LVDTs revealed that most of all the downslope soil movement occurred just when the thaw consolidation occurred. Three different soil movements such as needle ice creep, frost creep and gelifluction are divided by the movement of the target of LVDTs.