摘要
2019年6月20日晚九寨沟普降大到暴雨,导致九寨沟景区内卓追沟、下季节海子沟、则查洼沟等多处发生泥石流。3条泥石流沟分别冲出固体物质2.79×10^(4)m^(3)、3.7×10^(4)m^(3),2.67×10^(4)m^(3),造成多处停淤挡墙及拦砂坝损坏,并淤埋了景区内的部分道路,造成了交通的短时间中断。根据灾后地面调查和遥感解译,初步查明了本次泥石流灾害的成因和致灾过程机制。灾害成因:地震引发的崩塌滑坡产生大量的新增松散固体物源与原有的沟坡堆积物(包括老泥石流堆积物)在强降水的作用下形成泥石流,因此本次泥石流是地震和降雨共同作用的结果。通过泥石流发生前后各流域沟道纵剖面和典型横断面调查分析,发现泥石流致灾过程机制主要包括:(1)泥石流冲刷沟道使老泥石流堆积物参与泥石流运动、同时诱发沟岸失稳崩塌,因而增强泥石流规模和冲击力等动力学参数;(2)沟道卡口和崩滑体滑入沟道后导致泥石流堵塞,在后续泥石流的作用下发生级联溃决,进而增大泥石流峰值流量和冲击力等动力学参数。在两种机制的共同作用下,泥石流规模和冲击力等参数可能超出防治工程规划设计指标,进而导致防治工程损毁并淤埋道路。因此,建议充分考虑地震与强降雨复合作用下九寨沟景区泥石流风险评估、防治工程规划设计的合理性和可靠性等关键问题,以保障景区安全。
A debris flow hazard triggered by rainstorm occurred in Zhuozhui Gully,Xiajijiehaizi Gully and Zechawa Gully,Jiuzhaigou County,where is the epicenter of the Jiuzhaigou Earthquake on June 20,2019.About 2.79×10^(4)m^(3),3.7×10^(4)m^(3)and 2.67×10^(4)m^(3)solid materials rushed out of the three gullies respectively,caused damage to retaining walls and debris dams,buried part of the scenic road,disrupted traffic temporarily,and had no casualty.This paper identified the cause and mechanism of the debris flow disaster preliminarily,according to the field survey and remote sensing interpretation after the disaster.Cause of disaster is as follows.The earthquake-induced landslide produces a large number of new loose solid material sources and the original gully slope debris(including old debris flow debris)under the action of heavy rainfall to form debris flow.So the debris flows are the results of the earthquake and rainfall.Based on the investigation and analysis of longitudinal profile and typical cross section of gully before and after the debris flow,we find that the mechanisms of debris flow disaster mainly include the follows.(1)The debris flow erodes the old debris flow deposits,at the same time induces the landslide along the bank,so as enhances the debris flow scale and impact force and other dynamic parameters;(2)The channel jam and the landslide slide into the channel and lead to debris flow blockage.Cascade outburst occurs under the action of the subsequent debris flow,and then increase the dynamic parameters such as the peak flow rate and impact force of debris flow.Under the action of the two mechanisms,the parameters such as debris flow size and impact force can exceed the planning and design indexes of the prevention and control project,which leads to the destruction of the prevention and control project and the burying of the road.Therefore,it is suggested that the risk assessment of debris flow and the rationality and reliability of prevention and control engineering planning and design in Jiuzhaigou scenic area under the combined action of earthquake and heavy rainfall should be fully considered to ensure the safety of the scenic area.
作者
李宁
唐川
史青云
龚凌枫
亓星
LI Ning;TANG Chuan;SHI Qingyun;GONG Lingfeng;QI Xing(Xihua University,School of Emergency Science,Chengdu 610039,China;State Key Laboratory of Geohazard Prevention and Geoenvironment Protection,Chengdu University of Technology,Chengdu 610059,China;Chengdu Geological Survey Center,China Geological Survey,Chengdu 610081,China;Sichuan University of Science and Engineering,School of Civil Engineering,Zigong 643000,China)
出处
《工程地质学报》
CSCD
北大核心
2022年第3期740-750,共11页
Journal of Engineering Geology
基金
国家重点研发计划(资助号:2017YFC1501004)
国家自然科学基金(资助号:41672299)。
关键词
泥石流
九寨沟
地震
成因
致灾机制
Debris flow
Jiuzhaigou
Earthquake
Formation cause
Disaster-inducing mechanism