【摘要】 体积超过1×107m3的大型滑坡是三峡库区主要地质灾害,其发育机理包括形成机理和诱发机理两方面。通过大量现场调查和观测,运用地貌学方法,揭示了三峡库区大型滑坡在地质历史时期的3种形成机理即危岩链式崩落、泥石流堆积和地震,所占比例分别约为70%、10%和20%;发现存在于斜坡表面的大量危岩链式崩落堆积物是形成大型滑坡的基本条件,滑坡类型主要属于堆积层滑坡,而地震作用主要形成基岩滑坡。通过大量室内土工试验和模型试验,揭示了滑坡目前的3种诱发机理即降雨软化滑坡土体、坡顶加载和坡脚切割或工程弃渣堆积等人类工程活动、库水位变化和滑坡体周期性浸泡等;其中前两类诱发机理主要出现在175 m水位以上大量城镇、交通干线及移民等工程建设区段,后一类诱发机理出现在库水位变动带内;位于库水位变动带的大型滑坡,滑坡土体被库水周期性浸泡,强度非线性衰减,同时,库水位降落期间在滑坡体内产生较大的渗透力,两者耦合作用,加速了库岸滑坡的变形与破坏过程。以上研究成果基本概括了三峡库区大型滑坡的主要发育机理。更多还原

【Abstract】 Giant landslides over 1×107 m3 for a single landslide volume are dominant geological disasters in the area of the Three Gorges reservoir,whose developing mechanism include two aspects,i.e.,forming mechanism and triggering mechanism.Based on investigations in real-time field,forming mechanism of giant landslides in the area are revealed by using Geomorphology and are classified into chain avalanching of perilous rock,debris flow deposits,and earthquake,appearing about 70%,10% and 20% respectively.Meanwhile,lots of loose deposits sitting on slopes are initial conditions to form landslides,and almost all landslides are composed of loose deposits;while that by earthquake belongs to rock landslides.According to many geotechnical observations and physical simulations in laboratory,three triggering mechanisms of landslides are promulgated obviously,i.e,(1) softening landslide earth by precipitation;(2) unreasonable mankind actions,such as loading on top and cutting at foot of slope and engineering refuse dump,etc.;(3) variation between 145 m a.s.l.and 175 m a.s.l.of water level of the reservoir,and alternatively soaking of earth at the variation region.In the three mechanisms,the first and the second extensively appear in engineering construction sits,such as urban,roads and highways,villages of immigrants above 175 m a.s.l.,while the third plays a role frequently in landslides locating in the variation region.Giant landslides locating in the variation region are soaked by water of the reservoir totally or partially,so strength of earth is composed of the landslide attenuate by a big margin.Additionally,greater seepage forces exist in these landslides during descending of water level of the reservoir,and coupling both of the aspects speed up forming and rupture processes of landslides sitting on the slope.All results above reveal initially developing mechanisms of giant landslides in the area.更多还原