三峡库区滑坡的时空分布特征与成因探讨

三峡库区地质灾害频繁发生,地质历史上大型滑坡广泛发育。近年库区滑坡灾害有逐年增加趋势。这些滑坡形成的堆积体成因复杂,不能单纯从传统的外动力或内动力作用来解释,给库区灾害的防治工程带来了很大困难。三峡库区大型古滑坡主要沿长江干流和支流的深切河谷两岸分布,与河流发育演化史密切相关。15万年以来,长江三峡地区经历了新构造期以来抬升速率最快的一次构造幕,山原期夷平面上升了100m,河流强烈下切,形成高陡岸坡,卸荷效应显著;同时,该时期三峡地区的气候受到青藏高原环境变化的影响,在间冰期可能存在相似的暖湿古气候环境,降水极为丰富。三峡库区的大型古滑坡在新构造快速抬升时期广泛发育,并且与暖湿多雨期相对应,表明库区滑坡的发育演化是新构造运动和气候变化内外动力耦合作用的结果。

ON THE DISTRIBUTION AND MECHANISM OF LANDSLIDES IN THE THREE GORGES RESERVOIR AREA

The Three Gorges area ranging from Yi Chang to Chongqing is located at the upstream of the Yangtze River, where the geological hazards occur at a high frequency, especially the large scale landslides developed at the bank slopes along the river. These landslides are often characterized by their large volume, extensive distribution and great complexity, which often cause serious loss and casualty in the local areas. Therefore, it is very important to understand the formation and evolution history of these major landslides so that their future development can be predicted. The distribution of major landslides in the Three Gorges is mainly controlled by lithology, geological structures and slope geometry etc. The magnitude of landslides is evidently influenced by regional geological structures. The Three Gorges area has experienced a quick tectonic uplift of 100 m since 150 ka B.P with the maximum uplift velocity of 1 mm·a~(-1). The frequency distribution of landslides is accordant with the rate of the crust uplift. The incision to the river valley makes the bank slope unstable and causes landslides occur during the warm and wet climatic periods. It is concluded that the dynamic factors inducing large scale landslides in this area were the coupling process of the quick tectonic uplift and climate changes. Considering the strong rainfall is the dominating triggering factor, it is suggest that the relationship between the landslides and rainfall be studied systematically.