沟道松散堆积体冲刷启动机理与泥石流-拦挡坝相互作用研究  

Scour initiation mechanism of gully loose deposits and the interaction between debris flow and dam

作　　者：张座雄 刘兴荣[1] 王喜红 王磊 时岩 ZHANG Zuoxiong;LIU Xingrong;WANG Xihong;WANG Lei;SHI Yan(Institute of Geological Hazards Prevention,Gansu Academy of Sciences,Lanzhou 730000,Gansu,China;School of Energy and Power Engineering,Lanzhou University of Technology,Lanzhou 730050,Gansu,China;College of Water Conservancy and Hydropower Engineering,Gansu Agricultural University,Lanzhou 730070,Gansu,China)

机构地区：[1]甘肃省科学院地质自然灾害防治研究所,甘肃兰州730000 [2]兰州理工大学能源与动力工程学院,甘肃兰州730050 [3]甘肃农业大学水利水电工程学院,甘肃兰州730070

出　　处：《地震工程学报》2023年第5期1106-1115,1155,共11页China Earthquake Engineering Journal

基　　金：国家自然科学基金(42067066);甘肃省2021年度重点人才项目(2021RCXM066);甘肃科学院应用研究与开发项目(2021JK-07);甘肃省科学院重点科技研发项目(2023ZDYF-03)。

摘　　要：汶川地震后我国西部山区大量崩滑体堵塞泥石流沟道,形成堰塞坝,暴雨条件下极易溃决形成溃决洪水,剧烈冲刷侵蚀下游松散堆积体,形成或加剧泥石流灾害规模,对下游拦挡工程的破坏性极强。通过室内水槽试验,监测堆积体内和拦挡坝后相关土水、动力参数响应规律,分析松散堆积体冲刷侵蚀启动力学机制及其与拦挡坝相互作用机理,并推导出考虑孔隙水压力的泥石流冲击力计算公式。结果表明:(1)冲刷启动过程中堆积体以溯源侵蚀、侧蚀为主,体积含水率和孔隙水压力先增后减,基质吸力呈波动减小。(2)在泥石流冲击拦挡坝过程中,坝后出现两次冲击峰值,第一次拦挡坝泄水通畅,振动加速度为1.29 m/s^(2);第二次排水受阻,振动加速度为1.22 m/s^(2),同时泥位达到峰值95 mm。(3)泥石流对拦挡坝的整体冲击力由动、静两部分组成,静冲击力与坝后孔隙水压力呈正比,而动冲击力与流速的平方呈正比。研究成果可为震后泥石流沟道松散堆积体冲刷启动机理研究与防治工程优化提供理论与技术支持。After the Wenchuan earthquake,a large number of landslide dams were formed in debris flow channels in the mountainous areas of western China,which were prone to collapse and form outburst floods under heavy rainfall events.The intense erosion and scouring of downstream loose deposits by floods could exacerbate or trigger debris flow disasters and cause severe damage to downstream engineering structures.In this study,indoor flume experiments were performed to explore the responses of soil-water parameters and dynamic parameters in the deposits and behind the dam,which were utilized for the analysis of the initiation mechanism of erosion and scouring of loose deposits and the interaction mechanism between the deposits and the dam.A formula to compute the impact force of debris flow based on pore water pressure was derived.The findings revealed that(1)during the scour initiation process,lateral erosion and retreated erosion are the main modes of the deposits,with volumetric water content and pore water pressure increasing first and then decreasing and matric suction fluctuating and decreasing.(2)During the impact process of debris flow on the dam,two impact peaks appear behind the dam;moreover,the first peak results in unimpeded water discharge and an acceleration of 1.29 m/s^(2),the second peak results in blocked drainage and an acceleration of 1.22 m/s^(2),and the peak debris level reaches 95 mm.(3)The overall impact force of debris flow on the dam is composed of both dynamic and static parts;the static impact force is proportional to the pore water pressure behind the dam,and the dynamic impact force is proportional to the square of the flow velocity.This work offers theoretical and technical support to understand the scour initiation mechanism of gully loose deposits and the prevention of debris flow disasters after earthquakes.

关 键 词：溃决洪水 松散堆积体 启动机理 泥石流拦挡坝 冲击力 

分 类 号：P642.23[天文地球—工程地质学]