三峡库区土质岸坡塌岸发育分布特征与易发性评价

Development Distribution and Susceptibility Evaluation of Soil Bank Slope in the Three Gorges Reservoir Area

土质岸坡塌岸是目前三峡库区最为普遍和日益严重的地质灾害,确定塌岸特征和发育分布规律是库区地质灾害防治的关键工作之一。在三峡水库低水位运行期开展了库首秭归-重庆涪陵区段的全面塌岸调查,确定了库区典型的土质岸坡塌岸段,总结了土质岸坡塌岸的主要影响因素,并以巫山库岸段为例进行了土质岸坡塌岸易发性评价。结果表明:塌岸多发库岸的物质组成以粘性土夹碎块石为主,巴东、巫山、奉节等库岸段的土质岸坡塌岸最为发育;土质岸坡塌岸的内因为地质构造、地层岩性、岸坡及岸线形态,外因为水作用因素,库水位变动和波浪作用是导致土质岸坡坍塌和渐进式侵蚀的最主要原因;调查确定的塌岸影响因素与塌岸情况有显著的相关性,塌岸易发性预测结果与现场调查吻合度较好,研究将为三峡库区地质灾害防治提供必要基础资料和技术支撑。

Soil bank slope collapse is the most common and increasingly serious geological disaster in the Three Gorges Reservoir(TGR) area. Determining the characteristics and development and distribution of bank collapse is one of the key tasks in the prevention and control of geological disasters in the reservoir area. During the lower water level operation period of the TGR, a comprehensive bank collapse survey was carried out in the Zigui-Fuling section of the reservoir. The typical soil bank collapse section of the reservoir were determined, and the main influencing factors of the soil bank collapse were summarized.The bank section of Wushan Reservoir was taken as an example to evaluate the susceptibility of soil bank slope to bank collapse. The results shown that the material composition of the bank collapsed frequently is mainly cohesive soil mixed with broken stones, and the soil slope collapses of the banks of Badong, Wushan, Fengjie and other reservoir banksare the most developed;the internal cause of soil bank slope collapse is geological structure, formation lithology, bank slope and shoreline shape, and the external cause is water action. The variation of reservoir water level and wave action are the main causes of soil bank slope collapse and progressive erosion;the influencing factors of bank collapse determined by the investigation are significantly related to the situation of bank collapse, and theprediction results of bank collapse susceptibility were in good agreement with the field survey. This study will provide necessary basic data and technical support for the prevention and control of geological disasters in the TGR area.