堰塞坝背水面坡度对溃决过程影响机理大尺度试验  

Large-scale Experiment on Impact of Downstream Slope on Breaching Mechanisms of Landslide Dams

作　　者：黄卫 齐子杰 段文刚[2] 汪利先 李利[2] 於思瀚 HUANG Wei;QI Zijie;DUAN Wengang;WANG Lixian;LI Li;YU Sihan(Hunan Provincial Key Lab.of Key Technol.on Hydropower Development,Changsha 410014,China;Changjiang River Scientific Research Inst.,Changjiang Water Resources Commission of the Ministry of Water Resources,Wuhan 430010,China;School of Naval Architecture,Ocean and Energy Power Eng.,Wuhan Univ.of Technol.,Wuhan 430070,China)

机构地区：[1]水能资源利用关键技术湖南省省重点实验室,湖南长沙410014 [2]水利部长江水利委员会长江科学院,湖北武汉430010 [3]武汉理工大学船海与能源动力工程学院,湖北武汉430070

出　　处：《工程科学与技术》2022年第3期14-24,共11页Advanced Engineering Sciences

基　　金：国家重点研发计划项目(2018YFC1508601);国家自然科学基金项目(51979007,51809209);中央级公益性科研院所基本科研业务费项目(CKSF2019477+SL);水能资源利用关键技术湖南省省重点实验室开放基金项目(PKLHD201705)。

摘　　要：堰塞坝溃决物理概化试验是当前研究堰塞坝溃决机理较为可行的方法,但在现有堰塞坝溃决试验中,由于试验坝体尺寸较小,试验上游库容不足,导致试验的溃决过程与实际堰塞坝溃决存在较大差异。为尽量克服库容不足带来的影响,采用最大库容为380 m^(3)的大尺度堰塞坝溃决试验系统,以无黏性、宽级配砂砾料堰塞坝为对象,开展多组室内大尺度溃决试验,揭示堰塞坝溃决机理,并通过设置不同背水面坝坡研究坡度对溃决过程的影响。通过试验发现:堰塞坝溃决过程可以分为沿程冲刷、溯源冲刷、快速发展和溃口稳定4个阶段;在溃决过程中发现,陡坎侵蚀和溃口两侧土体失稳坍塌是溃口快速发展的主要机理;不同背水面坡度下的沿程冲刷阶段的冲蚀特征基本相似,而溯源冲刷阶段及快速发展阶段溃决过程差异显著,较大的背水面坡度使溯源冲刷阶段跌坎水流更容易得到发展,进而影响溃口处的垂向冲深及侧向发展,导致快速发展阶段更易形成垂向落差较大的陡坎洪水冲蚀;从溃决历时来看,坡度的增加使溃口发展更快,峰值流量出现时间更早,进而导致溃决历时缩短,坝顶溃口宽度及峰值流量也随着坡度的增加而增加。试验较好地重现了天然堰塞坝下游河道两岸的淤积现象。此外,根据堰塞坝溃决过程中的水流特点、泥沙运动及溃决完成后下游河道的地貌,本文初步分析了淤积区的形成机理。Laboratory experiments are one of useful approaches for investigating landslide dam breaching.However,due to the small size of the dam and limited storage volume of the landslide lake,the dam breaching process in the existing experiments differ much from that of the natural landslide dam.A large-scale landslide dam breaching experiment system was built with the lake volume up to 380 m^(3).Series of large-scale tests were conducted to investigate influence of the downstream surface slope of the landslide dam comprising of non-cohesive wide-graded sand-gravel material.It was found that the breaching process of landslide dam can be divided into four stages:longitudinal erosion,back-ward erosion,rapid development and nearly stabilization stage.The erosion characteristics in different stages were quite different.During the breaching process,it is found that head-cut and the collapse of soil on both sides of the breach are the main mechanisms of the rapid breach development.The erosion characteristics are quite similar in the longitudinal erosion stage for cases with different downstream surface slope,while it differs much at both the back-ward erosion and rapid development stages.Larger downstream surface slope means easier for forming water fall at the breach,which further leads rapid vertical and lateral development.This is the reason for the formation of bed-fall of the breach.The breaching duration varies greatly under different downstream surface slope conditions:With a higher downstream surface slope of the landslide dam,the breach duration was shorter,head-cut erosion formed easier,the breach developed faster and the peak of outburst flood appeared earlier and with a larger value.Moreover,the post-flood bed morphology at the downstream channel and formation mechanism of the deposition area on both sides of the down-stream channel were primarily analyzed.

关 键 词：堰塞坝 室内大尺度试验 溃决过程 背水面坡度 淤积机理 

分 类 号：TV65[水利工程—水利水电工程]