Characteristics of the impact pressure of debris flows

Hongchao Zheng, Zhenming Shi, Tjalling de Haas, Danyi Shen, Kevin J. Hanley, Bo Li

Research output: Contribution to journalArticlepeer-review

Abstract

Debris flows are common geological hazards in mountainous regions worldwide. Predicting the impact pressure of debris flows is of major importance for hazard mitigation. Here, we experimentally investigate the impact characteristics of debris flows by varying the concentrations of debris grains and slurry. The measured impact pressure signal is decomposed into a stationary mean pressure (SMP) and a fluctuating pressure (FP) through empirical mode decomposition. The SMP of low frequency is caused by the thrusting of bulk flow while the FP of high frequency is induced by the collision of coarse debris grains, revealed by comparing the features of impact pressure spectra of pure slurries and debris flows. The peak SMP and the peak FP first increase and then decrease with the slurry density. The basal frictional resistance is reduced by the nonequilibrium pore-fluid pressure for debris flows with low-density slurry, which can increase the flow velocity and impact pressures. In contrast, the viscous flow of high-density slurry tends to reduce the flow velocity. The peak SMPs are well predicted by the Bernoulli equation and are related to the hydrostatic pressure and Froude number of the incident flow. The peak FPs depend on the kinetic energy and degree of segregation of coarse grains. The maximum degree of segregation occurs at an intermediate value of slurry density due to the transition of flow regime and fluid drag stresses. Our results facilitate predicting the impact pressures of debris flows based on their physical properties.

Original languageEnglish
Article numbere2021JF006488
JournalJournal of Geophysical Research: Earth Surface
Volume127
Issue number3
Early online date10 Mar 2022
DOIs
Publication statusPublished - Mar 2022

Keywords

  • Debris flows
  • impact pressure
  • grain segregation

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