摘要
大量工程实践和统计数据表明,水库塌岸多发生在自然坡度15°以上的松散堆积层岸坡。一般认为自然坡度10°左右的平缓堆积层岸坡发生水库塌岸的可能性小,但在四川省宝兴河硗碛水电站库区却发生了大规模的平缓型堆积层塌岸,蚂蝗沟5#堆积体即属于此类型。蚂蝗沟5#堆积体由砾质黏土组成,土中小于0.075mm的细粒含量约占60%,蓄水后塌岸模式为缓慢的蠕滑变形。蓄水9年多来,变形范围由前缘的小规模塌岸逐渐向后缘扩展至大范围滑坡,目前变形仍然在持续。本文以该堆积体为例,通过对土体结构、颗粒组成等的勘探试验,并结合水库运行方式和变形监测成果,采用有限元瞬态渗流分析与稳定性分析的耦合分析计算,系统地开展了其塌岸机理研究。研究结果表明:细粒为主的土体结构及其弱透水性,是平缓堆积体在库水位反复升降作用下蠕滑变形的根本原因;平缓细粒土岸坡的稳定性与库水位的升降具有明显的相关性,随库水位的周期性变化岸坡呈现出不同的稳定状态,其蠕滑变形速率也明显不同。
Engineering practice and statistics show that reservoir bank collapse usually occur in loose accumulation when slope is greater than 15 degrees. Reservoir bank collapse is small possibility when bank slope is 10 degrees or so. But it happens in Qiaoqi hydropower station reservoir area on Sichuan Baoxing River. As an factual example, the Mahuang valley 5# accumulation body is composed of gravelly clay. Particle size of less than 0.075mm is accounted for about 60%.The collapse mode of reservoir bank is slow creeping deformation after impoundment. Deformation range gradually expands backward. After more than nine years, deformation continues. This paper takes Mahuang valley 5^# accumulation body as an example. It is on the basis of exploration and test work about soil structure and soil particle composition, reservoir operation mode and deformation monitoring results, and coupling analysis of finite element analysis of transient seepage and stability analysis. It studies the collapse mechanism of gently inclined slope on reservoir bank. The results show that fine-grained soil structure and weak water permeability are the main causes of accumulation of creep deformation in Qiaoqi reservoir area. The gently inclined slope stability and the periodical change of water level have an obvious correlation. With the rise and fall of water level change, the reservoir bank presents different steady states and the creep deformation rate differently.
出处
《工程地质学报》
CSCD
北大核心
2016年第5期752-759,共8页
Journal of Engineering Geology
关键词
水库塌岸
蠕滑
砾质黏土
瞬态渗流分析
变形监测
Reservoir bank collapse, Creep, Gravelly clay, Transient seepage analysis, Deformation monitoring
