甘肃黑方台坡面冻融特征及冻结滞水效应分析

Analysis on freezing-thawing characteristics and frozen stagnant water effect of Heifangtai slope in Gansu province

灌溉与冻融作用诱发黄土滑坡是西北地区常见的滑坡灾害类型,该类滑坡形成过程不易察觉,危害巨大。以甘肃永靖黑方台滑坡区季节冻土层水热变化和地下水位监测数据为基础,分析灌溉诱发滑坡区土体冻融特征和地下水位的季节变化特征,讨论土体冻结过程与地下水位波动和坡体稳定性的关系。结果表明:1)坡面非饱和区域土体从11月上旬开始冻结,2月初开始融化,而地下水溢出带土体从11月中旬发生第一次冻结,1月末开始融化。2)地下水位从11月份开始上升,2月初达到峰值,坡体滑移带的冻结滞水效应显著。3)相对于未滑移区域和滑带边缘,黑方台滑坡区地下水溢出带植被丰茂、土体含盐量大,冻结持续时间短、冻结深度浅,冻结滞水引起的水分聚集诱发坡体再次失稳。

Loess landslides induced by irrigation and freeze-thaw are common type of landslide disasters in Northwest China.The landslides are not easy to detect and cause great harm.Based on the monitoring data of seasonal frozen soil water and heat changes and groundwater level in the Heifangtai landslide area in Yongjing,Gansu,the characteristics of soil freezing and thawing and the seasonal variation of groundwater level in the landslide area induced by irrigation were analyzed,the relationships between soil freezing process and groundwater level fluctuation and slope stability were discussed.The results show that:1)The soil above the groundwater level froze since early November and began to melt at the end of January,while the soil near the groundwater level froze for the first time since mid-November and began to melt in early February.2)The groundwater level began to rise in November and reached a peak in early February.Effect of the frozen stagnant water in the slope slip zone was still significant.3)Compared with the non-slip area and the edge of the sliding zone,the vegetation at the groundwater seepage outlet of the Heifangtai landslide area is luxuriant and the soil has high salinity,which leads to short freezing duration and shallow freezing depth,and the water accumulation caused by effect of frozen stagnant water is more likely to induce slope instability again.