Influence of bed slope on breaching process of natural dam
JIANG Xiangang1，2，WU Lei1
(1. School of Civil Engineering，Sichuan Agricultural University，Chengdu，Sichuan 610041，China；2. Key Laboratory of Mountain Hazards and Earth Surface Processes，Chinese Academy of Sciences/ Institute of Mountain Hazards and Environment，Chinese Academy of Sciences，Chengdu，Sichuan 610041，China)
Abstract：Natural dams formed by landslides may produce disastrous floods after dam outburst. However，the breaching characteristics of natural dams influenced by bed slopes are still unclear. In this paper，a series of laboratory tests including seven different flume bed slope angles(1°，2°，3°，7°，9°，11°，and 13°)are conducted. The results show that three stages are observed during dam breaching. In stageⅠ，the breach develops slowly. And，flow break point is occurred on downstream slope. In stageⅡ，the breach develops quickly in depth and width due to backward erosion. The shape of the breach is similar to trapezoid during this period. In stage Ⅲ，the flow water and sediment turns to a new balance. There is a non-monotonic relationship between peak discharge and channel bed slope. With increasing of channel bed slope，peak discharge increases firstly and then decreases. The backward erosion is the main driving force to deepen the breach when slope angle is small. However，the development of the breach could be seriously influenced by traction erosion when slope angle is large. When channel bed slope is below 3°，the ratio of breach width to depth increases as the channel bed slope increasing. Otherwise，the ratio of breaching width to depth decreases with the same tendency. The ratio of breach width to depth after dam failure tends to be 1 and then less than 1 with the slope increasing.
蒋先刚1，2，吴 雷1. 不同底床坡度下的堰塞坝溃决过程研究[J]. 岩石力学与工程学报, 2019, 38(S1): 3008-3014.
JIANG Xiangang1，2，WU Lei1. Influence of bed slope on breaching process of natural dam. , 2019, 38(S1): 3008-3014.
[1] TAKAHASHI T，Debris flow：mechanics，prediction and countermeasures[M]. London，UK：Taylor and Francis Group press，2007：143.
[2] COSTA J E，SCHUSTER R L. The formation and failure of natural dams[J]. Geological Society of America Bulletin，1988，100(7)：1 054– 1 068.
[3] HANISCH J. Usoi landslide dam in Tajikistan-the world's highest dam：first stability assessment of the rock slopes at Lake Sarez[C]// Proceedings of the 1st European Conference on Landslides. [S. l.]：[s. n.]，2002：189–197.
[4] ZECH Y，SOARES-FRAZ?O S，SPINEWINE B，et al. Dam-break induced sediment movement：experimental approaches and numerical modelling[J]. Journal of Hydraulic Research，2008，46(2)：176–190.
[5] PICKERT G，WEITBRECHT V，BIEBERSTEIN A. Breaching of overtopped river embankments controlled by apparent cohesion[J]. Journal of Hydraulic Research，2011，49(2)：143–156.
[6] ROZOV A L. Modeling of washout of dams[J]. Journal of Hydraulic Research，2003，41(6)：565–577.
[7] CAO Z，YUE Z，PENDER G. Landslide dam failure and flood hydraulics. Part I：experimental investigation[J]. Natural Hazards，2011，59(2)：1 003–1 019.
[8] CAO Z，YUE Z，PENDER G. Landslide dam failure and flood hydraulics. Part II：coupled mathematical modelling[J]. Natural Hazards，2011，59(2)：1 021–1 045.
[9] DOU S T，WANG D W，YU M H，et al. Numerical modeling of the lateral widening of levee breach by overtopping in a flume with 180° bend[J]. Natural Hazards and Earth System Sciences，2014，14(1)：11–20.
[10] SINGH V P，QUIROGA C A. A dam-breach erosion model：I. Formulation[J]. Water Resources Management，1987，1(3)：177–197.
[11] FREAD D L. Breach：an erosion model for earthen dam failures[R]. Silver Spring MA：National Weather Service，NOAA，1988.
[12] WALDER J S，O?CONNOR J E. Methods for predicting peak discharge of floods caused by failure of natural and constructed earthen dams[J]. Water Resources Research，1997，33(10)：2 337– 2 348.
[13] MACCHIONE F. Model for predicting floods due to earthen dam breaching. I：Formulation and evaluation[J]. Journal of Hydraulic Engineering，2008，134(12)：1 688–1 696.
[14] BELIKOV V V，VASIL?EVA E S，PRUDOVSKII A M. Numerical modeling of a breach wave through the dam at the Krasnodar reservoir[J]. Power Technology and Engineering：formerly Hydrotechnical Construction，2010，44(4)：269–278.
[15] MA H，FU X. Real time prediction approach for floods caused by failure of natural dams due to overtopping[J]. Advances in Water Resources，2012，35：10–19.
[16] FAN X，TANG C X，VAN WESTEN C J，et al. Simulating dam-breach flood scenarios of the Tangjiashan landslide dam induced by the Wenchuan Earthquake[J]. Natural Hazards and Earth System Sciences，2012，12(10)：3 031–3 044.
[17] COLEMAN S E，ANDREWS D P，WEBBY M G. Overtopping Breaching of Noncohesive Homogeneous Embankments[J]. Journal of Hydraulic Engineering，2002，128(9)：829–838.
[18] MORRIS M W，HASSAN M，VASKINN K A，Breach formation：Field test and laboratory experiments[J]. Journal of Hydraulic Research，2007，45(Supp.1)：9–17
[19] LIU N，CHEN Z，ZHANG J X，et al. Draining the Tangjiashan barrier lake[J]. Journal of Hydraulic Engineering，2010，136(11)：914–923.
[20] DO X K，KIM M，NGUYEN H P T，et al. Analysis of landslide dam failure caused by overtopping[J]. Procedia Engineering，2016，154：990–994.
[21] ZHU Y H，VISSER P J，VRIJLING J K，et al. Experimental investigation on breaching of embankments[J]. Science China Technological Sciences，2011，54(1)：148–155.
[22] SCHMOCKER L，HAGER W H. Modelling dike breaching due to overtopping[J]. Journal of Hydraulic Research，2009，47(5)：585–597.
[23] SCHMOCKER L，FRANK P J，HAGER W H. Overtopping dike-breach：effect of grain size distribution[J]. Journal of Hydraulic Research，2014，52(4)：559–564.
[24] CHANG D S，ZHANG L M. Simulation of the erosion process of landslide dams due to overtopping considering variations in soil erodibility along depth[J]. Natural Hazards and Earth System Sciences，2010，10(4)：933–946.
2019, Vol. 38 
