天然饱水-失水对三峡库岸边坡土体的影响研究

三峡水库运行后水位周期性涨落，导致边坡土体在天然条件下长期处于被库水饱和-失水-再饱和的交替过程。分析2005－2009年库区水位变化，以及边坡土体在库水涨落被饱水-失水的次数与时间长度，分时段采集三峡库区库岸石榴树包滑坡堆积土样，分析其化学和矿物成分，观察土体微观结构，探索天然饱水-失水过程中水-岩相互作用对库岸边坡土体的影响和力学效应作用规律。研究结果表明，天然饱水-失水过程对库岸不同高程土体的化学组成和物理结构影响显著，其中172 m高程比168 m高程处受饱水-失水过程的影响较大。饱水-失水作用后，土体中SiO2、Al2O3、Na2O成分的含量上升，CaO、烧失量含量下降，土体的结构由致密的斑块状结构逐渐变成散乱的絮凝状结构，对库岸土体的力学效应产生了巨大的影响。

Effect of natural water-saturation and water-loss on bank-slope soil in Three Gorges reservoir

The effects of water-saturation (WS) and water-loss (WL) on bank-slope became obvious over a period of time as reservoir water level fluctuated cyclically when the Three Gorges reservoir became operational in 2003. According to the natural processes of WS and WL during 2005-2009, purple soil samples were collected from the Shiliushubao landslide of Three Gorges to determine chemical and mineral compositions by full quantitative analysis of soil samples and mineral composition analysis of soil samples, and to observe microstructure of samples by soil samples electron microscopy. The impact of water-rock interaction on bank-slope soil and its mechanical law were analyzed during the processes of WS and WL. The study results show that the effects of WS and WL processes on the chemical and mineral compositions of soils from different elevations of the slope are different; soil from higher elevation (172 m) of landslide is impacted more heavily. After the WS and WL processes, the contents of SO2, Al2O3 and Na2O in soil increase while CaO and loss on ignition (LOI) in soil decrease. With the variations of chemical compositions contents, the microstructure of soil changes from dense plaque structure to random flocculation structure; and it is a huge impact on the mechanical effects of bank-slope.