摘要
西南地区峡谷大型堵江时有发生,由堆积体组成的河道岸坡在堰塞坝溃决形成的超大洪水动水冲刷下的破坏机理及演化过程对水电、道路、城镇建设具有重要的现实意义.在前人研究的基础上,从定性角度分析了河道岸坡在过洪工况下的破坏过程,从理论角度推导了顺直河道岸坡、弯道凹岸岸坡在动水冲刷作用下的掏蚀槽发育机制,并使用Geo-studio软件计算了丹巴县干海子滑坡在水位上涨情况下的多级滑动过程.建立了与时间、水流切应力、岸坡抗剪强度、岸坡起动切应力等因素有关的顺直河道岸坡冲刷程度函数;从定性及定量的角度共同解析了河道岸坡在动水冲刷条件下的滑动过程:岸坡近水面部分由表及里被掏蚀→掏蚀后缘土体发生牵引式滑坡→坡脚被冲蚀且坡体形态不断改变→多级牵引式滑坡;干海子滑坡在水位攀高15 m且冲刷时间足够的情况下将发生多级牵引式滑坡.目前稳定的堆积体岸坡在某些极端过水工况下仍存在大规模滑移致灾的可能.研究成果为崩岸问题的理论分析提供了一种新的思路,并对水库等水利建设的下游堆积体岸坡致灾预防提供了一定的理论指导.
Abstract
[Objective]In the southwest region of China,where canyons are deeply incised and water flows are turbulent,disasters frequently occur.The accumulated masses are widely distributed,and understanding the mech-anisms and evolutionary processes of riverbank slopes composed of these masses under dynamic water scour,such as dam collapses and reservoir flood discharge,is of significant practical importance for hydropower,road construc-tion,and urban development.[Methods]Building upon previous research,this study qualitatively analyzes the progressive deterioration of riverbank slopes under flood conditions.The development mechanisms of erosion grooves on both straight and concave riverbank slopes under dynamic water scour are theoretically derived.Furthermore,the multistage sliding process of the Ganhaizi landslide in Danba County,triggered by rising water levels,was simu-lated using Geo-studio software.[Results]A function describing the extent of erosion in straight riverbank slopes over time,considering factors such as water flow shear stress,slope shear strength,and initial shear stress was es-tablished.Both qualitative and quantitative analyses of the sliding process under dynamic water scour conditions show that erosion begins near the water surface and progresses inward,leading to traction landslides at the rear edge of the erosion groove.This is followed by erosion at the slope foot,resulting in continuously changes in slope mor-phology and multistage traction landslides.The Ganhaizi landslide experienced multiple traction stages due to a 15-meter rise in water levels and extended erosion time.Even currently stable bank slopes of accumulated masses re-main vulnerable to large-scale sliding disasters under extreme hydraulic conditions.[Conclusion]This study offers a novel theoretical framework for analyzing riverbank collapse and provides guidance for preventing downstream dis-asters in water conservancy projects,such as reservoirs.
维普
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