Laboratory experiments on periglacial mass movement and segregated ice

这项研究的目的是明确冰层离析对融化期间群体运动的重要性。室内试验采用小型(80×40×20 cm)和大型(180×90×60 cm)隔热罐，压实易冻的火山灰土壤。坡度分别为5度、10度、12度、18度。土壤经历了一次和三次冻融循环。利用线性电压位移传感器(LVDT)监测目标在地面上的位置。冰冻锋面和解冻锋面由霜管监测。由于冻胀是由离冰在土壤中的发展引起的，因此可以用冻胀和融化固结速率来估计离冰在土壤中的分布。通过钻探对冻土进行取样，得到冻土中的冰含量。各周期地表最大冻胀和最大下移幅度分别为6~18 cm和1~11 cm。冻胀和融化固结率高的土层，发生较大的下坡位移，与高含冰量的土层相吻合。LVDTs的监测表明，大多数下坡土壤运动发生在融化固结发生的时候。根据靶标的运动情况，将土体分为针状冰蠕变、霜冻蠕变和冻胀三种不同的运动形式。

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.