Experimental Investigation into the Number of Phases in Debris Flows

Controversial number of phases in debris-flow masses involves almost all areas of debris-flow research. In this study, we experimentally investigated the number of phases in fully developed debris flows using six sediments with three maximum diameters of up to 30 mm from two representative debris-fl...

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Main Authors: Bin Li, Ze-Min Xu
Format: Article
Language:English
Published: MDPI AG 2025-04-01
Series:Applied Sciences
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Online Access:https://www.mdpi.com/2076-3417/15/8/4282
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author Bin Li
Ze-Min Xu
author_facet Bin Li
Ze-Min Xu
author_sort Bin Li
collection DOAJ
description Controversial number of phases in debris-flow masses involves almost all areas of debris-flow research. In this study, we experimentally investigated the number of phases in fully developed debris flows using six sediments with three maximum diameters of up to 30 mm from two representative debris-flow deposits in China. Fluid escape tests, displacement experiments, relative motion experiments, and rheometrical tests were conducted using 12 slurries prepared with the sediments. The results from four types of experiments show that debris flows are close to one-phase flow and far from two-phase flow. Under both gravity and artificial hydraulic and mechanical forcing, no relative motion of water or fluid composed of water and fine-grained particles and solids occurs in both the experimental flows and static slurries. This suggests that the water and solids in debris flows move together as a single fluid, and are deposited by “freezing”. The rheological behavior of the experimental debris flows is similar to that of Bingham materials. This indicates that debris flows may be approximated as continuous, homogeneous, isotropic fluids. In conclusion, debris flows behave more like monophasic flow, are far from biphasic flow, and should be treated as one- rather than as two-phase flow.
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spelling doaj-art-0443caefeb66471d9ed51939df8d72fe2025-08-20T03:14:17ZengMDPI AGApplied Sciences2076-34172025-04-01158428210.3390/app15084282Experimental Investigation into the Number of Phases in Debris FlowsBin Li0Ze-Min Xu1Faculty of Civil Engineering and Mechanics, Kunming University of Science and Technology, Kunming 650500, ChinaFaculty of Civil Engineering and Mechanics, Kunming University of Science and Technology, Kunming 650500, ChinaControversial number of phases in debris-flow masses involves almost all areas of debris-flow research. In this study, we experimentally investigated the number of phases in fully developed debris flows using six sediments with three maximum diameters of up to 30 mm from two representative debris-flow deposits in China. Fluid escape tests, displacement experiments, relative motion experiments, and rheometrical tests were conducted using 12 slurries prepared with the sediments. The results from four types of experiments show that debris flows are close to one-phase flow and far from two-phase flow. Under both gravity and artificial hydraulic and mechanical forcing, no relative motion of water or fluid composed of water and fine-grained particles and solids occurs in both the experimental flows and static slurries. This suggests that the water and solids in debris flows move together as a single fluid, and are deposited by “freezing”. The rheological behavior of the experimental debris flows is similar to that of Bingham materials. This indicates that debris flows may be approximated as continuous, homogeneous, isotropic fluids. In conclusion, debris flows behave more like monophasic flow, are far from biphasic flow, and should be treated as one- rather than as two-phase flow.https://www.mdpi.com/2076-3417/15/8/4282debris flownumber of phasesrelative motionphase separationexcess water pressurerheology
spellingShingle Bin Li
Ze-Min Xu
Experimental Investigation into the Number of Phases in Debris Flows
Applied Sciences
debris flow
number of phases
relative motion
phase separation
excess water pressure
rheology
title Experimental Investigation into the Number of Phases in Debris Flows
title_full Experimental Investigation into the Number of Phases in Debris Flows
title_fullStr Experimental Investigation into the Number of Phases in Debris Flows
title_full_unstemmed Experimental Investigation into the Number of Phases in Debris Flows
title_short Experimental Investigation into the Number of Phases in Debris Flows
title_sort experimental investigation into the number of phases in debris flows
topic debris flow
number of phases
relative motion
phase separation
excess water pressure
rheology
url https://www.mdpi.com/2076-3417/15/8/4282
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AT zeminxu experimentalinvestigationintothenumberofphasesindebrisflows