Environmental and Engineering Geological Problems in Permafrost Regions in the Context of a Warming Climate: The Landslides Induced by the Released Inclusion Water of the Frozen Soil in the side of the Heifangtai Loess Platform, Gansu Province, China

Abstract

The Heifangtai loess platform is a highland which is the forth terrace of the Yellow River. The top of the platform is a cultivated irrigation farmland for setting up the migrants from Yanguoxia, Bapanxia and Liujiaxia reservoir submerged areas. The irrigation water are pumped up from the Yellow River aside the east side of the platform. It has induced a large number of landslides and collapses around the side of the platform since the irrigation system built up in 1967. Investigation suggests that the groundwater level at the centre of the platform has risen up to 20 m in the past decades and the annual rising rate is about 0.27 m. Because most of the landslides occurred in spring, release of the inclusion grounder by frozen soil may deteriorate the slope stability. Observation shows that frozen soil in a winter can cause the groundwater level to rise more than 3 m and extends backward to a range of more than 30 m. As the water released in spring, both high static pore water pressure and steep water gradient are the significant agents for the slope failure. The countermeasures for the slope failure mitigation are the reasonable irrigation method, such as dropping or sprinkling irrigation, to control the irrigation water quantity. In addition, the present grounder water should be drained by vertical or horizontal drilling holes to draw down the water level.