<p>A debris avalanche that intrudes into a river channel can cause river blockage, forming a landslide dam that may breach, threatening the safety of human lives and infrastructure. However, studies on the evolution process of river blockage caused by debris avalanche are still in the early stages, with limited focus on the effect of particle size. This gap in knowledge hinders the accurate early identification of landside dam formation. Through 27 flume experiments, we investigated the effect of particle size on river blockage duration, deposit height, and river blockage mode under various combinations of landslide discharge and river water flow rate. Three river blockage modes were presented based on the dimensionless particle size <i>D</i>, which is defined by the ratio of particle diameter and river width. We then proposed a new dimensionless River Blockage Criterion (nRBC) that incorporates particle size effect for predicting landslide dam formation using logistic regression. Our findings reveal a significant linear increase between debris avalanche volume and both river blockage duration and deposit height. For a given debris avalanche volume, larger particle sizes result in longer river blockage durations and greater deposit heights. The erosion rate shows an exponential decay with increasing debris avalanche volume. For a given debris avalanche volume, larger particle sizes lead to a lower erosion rate. Particle size also controls the river blockage mode. When <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$D \le 0.02$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>D</mi> <mo>≤</mo> <mn>0.02</mn> </mrow> </math></EquationSource> </InlineEquation>, the mode is complete river blockage. For <InlineEquation ID="IEq2"> <EquationSource Format="TEX">$0.03 < D \le 0.05$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>0.03</mn> <mo><</mo> <mi>D</mi> <mo>≤</mo> <mn>0.05</mn> </mrow> </math></EquationSource> </InlineEquation>, the mode shifts to complete river blockage with small pore permeable channels, and for <InlineEquation ID="IEq3"> <EquationSource Format="TEX">$D> 0.08$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>D</mi> <mo>></mo> <mn>0.08</mn> </mrow> </math></EquationSource> </InlineEquation>, it becomes partial river blockage with large pore permeable channels. The nRBC predicts landslide dam formation with 82% absolute accuracy in the experiments. Application to three real-world field cases further validates the criterion, as its prediction matches the observed blockage. This study provides valuable insights for the early identification, prevention, and mitigation of river blockage disasters, contributing to enhanced geological hazard assessment and risk management.</p>

Effect of particle size on debris avalanche-induced river blockage by laboratory-scale experiments

期刊论文
发表日期：

2025年10月3日

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Hao Wu,
Defeng Zheng,
Fang Zhang,
Tingkai Nian

摘要

A debris avalanche that intrudes into a river channel can cause river blockage, forming a landslide dam that may breach, threatening the safety of human lives and infrastructure. However, studies on the evolution process of river blockage caused by debris avalanche are still in the early stages, with limited focus on the effect of particle size. This gap in knowledge hinders the accurate early identification of landside dam formation. Through 27 flume experiments, we investigated the effect of particle size on river blockage duration, deposit height, and river blockage mode under various combinations of landslide discharge and river water flow rate. Three river blockage modes were presented based on the dimensionless particle size D, which is defined by the ratio of particle diameter and river width. We then proposed a new dimensionless River Blockage Criterion (nRBC) that incorporates particle size effect for predicting landslide dam formation using logistic regression. Our findings reveal a significant linear increase between debris avalanche volume and both river blockage duration and deposit height. For a given debris avalanche volume, larger particle sizes result in longer river blockage durations and greater deposit heights. The erosion rate shows an exponential decay with increasing debris avalanche volume. For a given debris avalanche volume, larger particle sizes lead to a lower erosion rate. Particle size also controls the river blockage mode. When $D \le 0.02$ $D \leq 0.02$ , the mode is complete river blockage. For $0.03 < D \le 0.05$ $0.03 < D \leq 0.05$ , the mode shifts to complete river blockage with small pore permeable channels, and for $D> 0.08$ $D > 0.08$ , it becomes partial river blockage with large pore permeable channels. The nRBC predicts landslide dam formation with 82% absolute accuracy in the experiments. Application to three real-world field cases further validates the criterion, as its prediction matches the observed blockage. This study provides valuable insights for the early identification, prevention, and mitigation of river blockage disasters, contributing to enhanced geological hazard assessment and risk management.