The formation and failure of debris flow-dams,background, key factors and model tests: case studies from China |
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| Authors: | Email author" target="_blank">Chao?DangEmail author Peng?Cui Zun-lan?Cheng |
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| Institution: | (1) Key Laboratory of Mountain Hazards and Surface Process, Chinese Academy of Sciences, 610041 Chengdu, China;(2) Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, 610041 Chengdu, China;(3) Graduate University of Chinese Academy of Sciences, 100039 Beijing, China |
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| Abstract: | Temporary dams can be formed by the sudden injection of debris flow into main streams by some favorable geomorphologic and
hydraulic conditions, resulting in extensive inundations upstream and catastrophic floods downstream due to dam breaches and
consequently dramatic changes of channels and valleys. Expeditious means of assessing dam-forming potential are necessary,
particularly in geologically active regions. Complete blockages or dam formations are significantly related to the discharge
ratio and velocity ratio between the tributary and the main stream, the bulk density of the debris flow, confluent angles
and the degree of unevenness of grain sizes. In order to set up a critical index/C for dam formation, 19 groups of flume tests were conducted. The results showed that there were three types of blockage in
the intersections, and dam-forming processes were mainly controlled by the product of the dimensionless momentum ratio and
the degree of unevenness of grain sizes in the debris flow. Complete blockages or dam formations occurred when C > 83.4, whereas semi-blockages were formed or no dams were formed when C < 71.5, which had been judged to be feasible by historical instances of dam formation in China. Dam failures commonly resulted
from overtopping. No piping was observed in the course of dam failure, and the time elapsed between dams can be denoted by
a linear relation with the momentum ratio. |
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| Keywords: | Debris flow Dam-forming Critical index Key factors Model test China |
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