Surface microtextures of slipping zone soil of some landslides in the Three Gorges Reservoir District and their significance

The mineral assemblage and content and surface microtextures of slipping zo ne soil of several landslides in the Three Gorges Reservoir District have b een analyzed using the scanning electron microscope (SEM) and X-ray diffrac tometer (XRD). All the mineral assemblages are similar in these landslides. The main minerals are montmorillonite, illite, kaolinite, chlorite, quartz and feldspar. There are two kinds of surface microtexture in the slipping zone soil, i.e., linear scratches and arcuate scratches. Based on analyses of the changes of the microtextures, one can obtain information about the n umber, directions and stages of landslide movements. The authors have also studied the mechanism of landslide formation, evaluated the stability of la ndslides and revival possibility of ancient landslides and forecasted the a ctivity of similar landslides in different districts. The surface microtext ure features of stable landslides and mobile landslides are summarized and it is concluded that the existence of filamentous bacteria may result in or increase movements of landslides.