Laboratory experiments on periglacial mass movement and segregated ice

本研究的目的是明确分离冰对融冰期质量运动的重要性。实验室实验采用小尺寸（80 X 40 X 20 cm）和大尺寸（180 X 90 X 60 cm）保温罐进行，其中对易受霜冻影响的火山灰土进行压实。坡度分别为5度、10度、12度、18度。土壤经历了1次和3次冻融循环。利用线性电压位移互感器（lvdt）监测目标在地面上的位置。采用冻管对冻锋和融锋进行监测。由于冻胀是由土壤中分离冰的形成引起的，因此通过冻胀率和融固结率来估计土壤中分离冰的分布。采用钻孔法对冻土进行取样，得到冻土中的冰含量。瓦片柱的变形表示位移剖面。每个周期地表最大冻胀量为6 ~ 18 cm，地表最大下坡量为1 ~ 11 cm。冻融固结率高、下坡位移大的土层与含冰量高的土层相吻合。lvdt的监测结果表明，大部分下坡土移都发生在融化固结发生的时候。将针冰蠕变、霜蠕变和胶凝波动三种不同的土体运动分为lvdt目标的运动。

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.