地震灾区河道来沙特性突变与河床响应机理研究

In recent years, frequent earthquakes occurred in China, e.g., On May 12, 2008 Wenchuan Ms 8.0 earthquake in the northern section of Longmen mountain, Ms 7.1 earthquake on April 14, 2010 in Yushu County of Qinghai province, the Lushan Ms 7.0 earthquake on April 20, 2013 in the southern segment of Longmen and on August 3, 2014 Ludian Ms 6.5 earthquake in Zhaotong City of Yunnan province. Strong earthquake caused great damage to the surface of the earth, a series of secondary disasters triggered by the earthquake is very serious, causing direct losses to the local people's life and property seriously. . A quake-hit surface deposit a lot of loose materials and secondary disasters such as landslide and debris flow in the late earthquake form continued into the river, often creating local region of open channel to excess supply, thus inducing the river width narrow, blocked off and sedimentation and riverbed scour incised process. These structural damages for open channel have broken the law of original water and sediment motion and its equilibrium state, therefore, the water and sediment response process will enter a new adjustment cycle after the occurrence of earthquake. The new changes of fluvial process pose a serious threat for repairing the earthquake-stricken area rivers and water and sediment disaster prevention. . The topic of this project focus on sediment excess supply caused by typical outstanding problems faced with disaster on the Sichuan Longmen Mountain Fault Zone in Wenchuan earthquake disaster area. On the basis of river dynamics and fluvial geomorphology theory, through the field test, series of flume experiments and typical affected reach physical scale model experiment, excess of river sediment recharge mutation characteristics induced by earthquake, river channel clogging caused by the change of river bed evolution characteristics and rapid response process will be analyzed and discussed. Furthermore, these experiments and analysis will also reveal fluvial response disaster causing mechanism because of excess supply of sediment by the earthquake. The research results can provide the theoretical basis and technical support for the earthquake stricken area in the late master the system of river sediment movement, riverbed evolution law of water and sediment disaster prevention.

地震极重灾区地表破坏严重，大量松散物堆积体在地震后期以滑坡、泥石流等次生灾害形式持续汇入河道，频繁造成河道局部区域来沙超量补给，由此诱发河宽缩窄、堵断及河床淤积、下切等结构性破坏，从而打破了原有河道的水沙运动规律及平衡状态，致使河床水沙响应过程进入一个新的调整演变周期，给地震灾区河流修复与水沙灾害防治带来了严重威胁。本课题针对四川龙门山断裂带汶川地震重灾区典型河段泥沙超量补给致灾面临的突出问题，以河流动力学、河流地貌学理论为基础，通过野外测试、室内水槽试验及典型受灾河段物理比尺模型试验为手段，深入探讨地震诱发的河道泥沙超量补给突变特性，分析河道淤堵变化引起的淤滩体演变特征及河床急剧响应过程，进而揭示震后河道泥沙超量补给诱发的河床响应致灾机理。其研究成果可为系统掌握地震灾区后期河流水沙运动、河床演变规律及水沙灾害防治提供理论依据与技术支助。

地震重灾区地表破碎严重，河道局部区域来沙超量补给，诱发河宽缩窄、堵断及河床淤积、下切等结构性破坏，给地震灾区河流修复与水沙灾害防治带来了严重威胁。本项目以汶川地震灾区岷江支流白沙河、龙溪河等典型灾害河段为研究对象，通过野外考察和原型观测，揭示了灾区漂石河床的近底水流结构、推移质输沙率及河床冲淤变形规律；以系列室内水槽试验和比尺模型试验，发现了山区河流来沙变化下，在变比降河段、宽窄相间河段、交汇区河段常出现较大的淤积变形，并引发水位陡涨致灾；基于CFD和DEM相结合的数值模拟方法，能较好的揭示来沙变化条件下的河床响应过程。总体来讲，项目系统研究了地震灾区典型河道来沙量突变特性、来沙变化条件下的河床冲淤变形规律，以及河床响应突变条件下的致灾机理。该成果对指导汶川地震灾区防灾减灾具有较好的技术支持，针对四川汶川2019年“8.20”山洪灾害治理问题，四川省水利厅特邀请负责人作为专家组成员参加“8.20”山洪灾害现场调研以及“山洪灾害高易发区防御工作座谈会”。项目研究期间共发表学术论文19篇（其中SCI收录论文8篇；EI收录论文7篇；核心期刊论文2篇；会议论文2篇），培养硕博士研究生毕业10名，获国家发明专利授权4项，项目成员参加及邀请境外人员开展国内外学术交流16次。