库水降落作用下无基坑振冲土石坝的渗流安全分析

无基坑振冲加密施工是一种比较先进的土石坝建筑方法。以海南省三亚市西部的宁远河中下游河段的大隆水利枢纽工程土石坝为研究对象,对其进行准确分区,以饱和-非饱和渗流理论为基础,通过三维有限元数值方法,模拟库水下降作用下的土石坝渗流场,并对各级水位下的孔压、流速及流向进行分析,评价大坝的渗流安全。研究结果表明：采用无基坑振冲加密施工方法后,坝体内填砂砾振冲层形成上游排水通道,在坝前水位骤降工况下,防渗土料内有效流速方向和渗透压力的方向由近水平的指向坝面变为竖直向下指向填砂砾振冲层,而且有效流速明显变大,利于渗透水通过填砂砾振冲层排到下游,有利于上游坝体稳定。

Analysis of Seepage Safety of Dam without Foundation Pit during Reservoir Water Drawdown

Vibroflotation compaction method is one of the advanced construction methods for earth-rock dam.As the main research object in this paper,the earth dam of Dalong water-control project is located in the middle and lower reaches of Ningyuan River,Sanya city,Hainan Province.Based on the unsaturated seepage theory and finite element method,the different partitions of dam are accurately expressed and a three-dimensional model is built to simulate the seepage field of earth-rock dam,The pore pressure and the flow velocity under each water level are analyzed.The seepage safety is evaluated as well.The research results show that the upstream drainage channels are made in the vibroflotation gravel layer of dam by using the construction methods of vibroflotation compaction.Under the condition of reservoir water drawdown,the direction of effective seepage velocity and seepage pressure in impervious soils are obviously reversed from the approximate horizontal to the straight downward,meanwhile,the increasing of effective seepage velocity leads to more water drainage from vibroflotation gravel layer.In a word,the construction methods of vibroflotation compaction are of benefit to the dam safety.