四川安县肖家桥堰塞湖稳定性初步评估

 四川省安县肖家桥堰塞湖是“5·12”汶川地震形成的高危堰塞湖之一，堰塞体高65～75 m，体积约250万m3，堰塞湖最大库容约2 000万m3。将三维激光扫描技术应用于堰塞湖地形测量中，迅速而准确获得堰塞坝的地形信息，为堰塞湖除险设计及稳定性评估提供重要依据。在现场利用三维激光雷达技术地形测绘和初步地质勘察的基础上，经过新旧地形图对比，指出有利于堰塞体稳定的结构性因素；通过经验与反演方法确定堰塞体的物理力学指标，经渗流计算与稳定分析，排除堰塞体坝坡失稳及管涌潜蚀两种溃决模式发生的可能性，指出肖家桥堰塞湖溃决模式可能以漫顶冲刷为主。

PRELIMINARY EVALUATION OF STABILITY OF XIAOJIAQIAO DAMMED LAKE IN ANXIAN COUNTY,SICHUAN PROVINCE

The Xiaojiaqiao danmed lake in Anxian County,Sichuan Province was considered as one of the most dangerous lakes induced by "5·12" earthquake. The height of damming object was 65～75 m with a volume of 2.5 million m~3,and its maximum reservior capacity was about 20 million m~3. The new technology LiDAR had been used in the topographic measurement which had provided precise and prompt topographic information for the dammed lake disaster mitigation design and its stability evaluation. Based on the LiDAR and preliminary geological investigation,the structural factor,which was beneficial for the landslide dam stability,was pointed out by comparison of old and new topographic maps of the landslide lake before and after the earthquake. The physico-mechanical index of damming object had been selected by experience and back analysis. According to the seepage computation and stability analysis,the two failure modes which were slide and seepage had been excluded,while the overtopping and scouring on top of the landslide dam may become governing factor leading to a dam breach for dammed lake.