纵向增强体土石坝新坝型及其安全运行性能分析

New Type of Dam for Longitudinal Reinforced Rockfill Dam and Its Operation Safety Analysis

在总结大量水库大坝加固实践的基础上提出一种新坝型—纵向增强体土石坝,即以常规土石坝为依托,在其内部"插入"集防渗与受力为一体的刚性结构体(纵向增强体)。增强体既起到防渗体系作用,又起到结构体作用,力求克服传统土石坝(如均质坝、土质心斜墙坝等)在漫顶、渗漏、裂缝等原发性病险,以及滑坡、变形、白蚁等次生性灾害,特别针对传统土石坝存在的洪水漫顶溃坝、损毁、失效等灾难提出了尽可能的解决方案。从理论上简要分析了纵向增强体土石坝相对于常规土石坝抵御洪水漫顶破坏的安全程度,初步阐述这一新坝型安全运行的机理,分析洪水漫顶造成下游堆石料被冲刷流失,形成坝体冲坑等水力学过程,冲坑的逐步形成将恶化增强体的受力条件,最终导致增强体上游侧受力而下游侧临空的受力状态,从而影响到整个坝体是否溃决。计算表明,增强体作为刚性结构体延缓了坝体的溃决,并为工程抢险和下游群众转移争取到足够的时间。纵向增强体土石坝在工程建设投资与工期、施工工艺与材料选取方面均有一定优势,对今后建坝或对已建成土石坝的除险加固有着十分重要的意义和广阔的应用前景。

After a long time operation,a conventional earth rockfill dam(e.g.homogeneous dam or core wall dam)may suffer from a lot of dam diseases such as dam-break,overtopping,landslides and leakage.On the basis of a large number of practices of rebuilding and strengthening the medium and small-sized dams,a new type of dam,a longitudinal reinforced rockfill dam,is proposed.This new type of dam has triple functions of seepage control,stress resistance and deformation resistance.It also has significant advantages in both construction material selection and construction technology when compared to a conventional earth rockfill dam.Based on the theoretical research and successful practice of the new dam construction technology by placing rigid structures(also called longitudinal reinforcements)in conventional rockfill dams,the factors of safety against overtopping compared with that of the unreinforced rockfill dams was briefly analyzed in this paper.The hydraulic process of the overtopping is presented,during which the downstream material is washed away and forming a scour hole in the dam.The progressive development of the scour hole will change the stress distribution of the reinforced body.Eventually the reinforced body will reach a state in which it is subjected to the pressure from the upstream when the toe zone is empty.The advantage of this new dam is that it changes the conventional overtopping failure mode to the progressive scour hole development mode,therefore delays the dam breaking,and provides time for repair and evacuation.The longitudinal reinforced rockfill dam has important and broad applications in the construction of new dams or strengthening of existing rockfill dams.