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Grain‐energy release governs mobility of debris flow due to solid–liquid mass release

Zhixian Cao, Ji Li Orcid Logo, Alistair Borthwick, Qingquan Liu, Gareth Pender

Earth Surface Processes and Landforms, Volume: 45, Issue: 12, Pages: 2912 - 2926

Swansea University Author: Ji Li Orcid Logo

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DOI (Published version): 10.1002/esp.4939

Abstract

Debris flows often exhibit high mobility, leading to extensive hazards far from their sources. Although it is known that debris flow mobility increases with initial volume, the underlying mechanism remains uncertain. Here, we reconstruct the mobility–volume relation for debris flows using a recent d...

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Published in: Earth Surface Processes and Landforms
ISSN: 0197-9337 1096-9837
Published: Wiley 2020
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URI: https://cronfa.swan.ac.uk/Record/cronfa54587
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spelling 2020-11-05T15:35:26.0921563 v2 54587 2020-09-23 Grain‐energy release governs mobility of debris flow due to solid–liquid mass release 4123c4ddbcd6e77f580974c661461c7c 0000-0003-4328-3197 Ji Li Ji Li true false 2020-09-23 CIVL Debris flows often exhibit high mobility, leading to extensive hazards far from their sources. Although it is known that debris flow mobility increases with initial volume, the underlying mechanism remains uncertain. Here, we reconstruct the mobility–volume relation for debris flows using a recent depth‐averaged two‐phase flow model without evoking a reduced friction coefficient, challenging currently prevailing friction‐reduction hypotheses. Physical experimental debris flows driven by solid–liquid mass release and extended numerical cases at both laboratory and field scales are resolved by the model. For the first time, we probe into the energetics of the debris flows and find that, whilst the energy balance holds and fine and coarse grains play distinct roles in debris flow energetics, the grains as a whole release energy to the liquid due to inter‐phase and inter‐grain size interactions, and this grain‐energy release correlates closely with mobility. Despite uncertainty arising from the model closures, our results provide insight into the fundamental mechanisms operating in debris flows. We propose that debris flow mobility is governed by grain‐energy release, thereby facilitating a bridge between mobility and internal energy transfer. The initial volume of debris flow is inadequate for characterizing debris flow mobility, and a friction‐reduction mechanism is not a prerequisite for the high mobility of debris flows. By contrast, inter‐phase and inter‐grain size interactions play primary roles and should be incorporated explicitly in debris flow models. Our findings are qualitatively encouraging and physically meaningful, providing implications not only for assessing future debris flow hazards and informing mitigation and adaptation strategies, but also for unravelling a spectrum of earth surface processes including heavily sediment‐laden floods, subaqueous debris flows and turbidity currents in rivers, reservoirs, estuaries, and ocean. Journal Article Earth Surface Processes and Landforms 45 12 2912 2926 Wiley 0197-9337 1096-9837 debris flows; solid-liquid mass release; high mobility; mobility–volume relation; energy transfer; grain-energy release 30 9 2020 2020-09-30 10.1002/esp.4939 COLLEGE NANME Civil Engineering COLLEGE CODE CIVL Swansea University 2020-11-05T15:35:26.0921563 2020-09-23T16:07:32.5450835 College of Engineering Engineering Zhixian Cao 1 Ji Li 0000-0003-4328-3197 2 Alistair Borthwick 3 Qingquan Liu 4 Gareth Pender 5 54587__17856__76c85bc0803841839b17194fbd5ad502.pdf Debris flow Energy transfer_AcceptedManuscript.pdf 2020-08-04T21:11:13.3359588 Output 2333061 application/pdf Accepted Manuscript true 2021-06-26T00:00:00.0000000 true eng
title Grain‐energy release governs mobility of debris flow due to solid–liquid mass release
spellingShingle Grain‐energy release governs mobility of debris flow due to solid–liquid mass release
Ji Li
title_short Grain‐energy release governs mobility of debris flow due to solid–liquid mass release
title_full Grain‐energy release governs mobility of debris flow due to solid–liquid mass release
title_fullStr Grain‐energy release governs mobility of debris flow due to solid–liquid mass release
title_full_unstemmed Grain‐energy release governs mobility of debris flow due to solid–liquid mass release
title_sort Grain‐energy release governs mobility of debris flow due to solid–liquid mass release
author_id_str_mv 4123c4ddbcd6e77f580974c661461c7c
author_id_fullname_str_mv 4123c4ddbcd6e77f580974c661461c7c_***_Ji Li
author Ji Li
author2 Zhixian Cao
Ji Li
Alistair Borthwick
Qingquan Liu
Gareth Pender
format Journal article
container_title Earth Surface Processes and Landforms
container_volume 45
container_issue 12
container_start_page 2912
publishDate 2020
institution Swansea University
issn 0197-9337
1096-9837
doi_str_mv 10.1002/esp.4939
publisher Wiley
college_str College of Engineering
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hierarchy_top_id collegeofengineering
hierarchy_top_title College of Engineering
hierarchy_parent_id collegeofengineering
hierarchy_parent_title College of Engineering
department_str Engineering{{{_:::_}}}College of Engineering{{{_:::_}}}Engineering
document_store_str 1
active_str 0
description Debris flows often exhibit high mobility, leading to extensive hazards far from their sources. Although it is known that debris flow mobility increases with initial volume, the underlying mechanism remains uncertain. Here, we reconstruct the mobility–volume relation for debris flows using a recent depth‐averaged two‐phase flow model without evoking a reduced friction coefficient, challenging currently prevailing friction‐reduction hypotheses. Physical experimental debris flows driven by solid–liquid mass release and extended numerical cases at both laboratory and field scales are resolved by the model. For the first time, we probe into the energetics of the debris flows and find that, whilst the energy balance holds and fine and coarse grains play distinct roles in debris flow energetics, the grains as a whole release energy to the liquid due to inter‐phase and inter‐grain size interactions, and this grain‐energy release correlates closely with mobility. Despite uncertainty arising from the model closures, our results provide insight into the fundamental mechanisms operating in debris flows. We propose that debris flow mobility is governed by grain‐energy release, thereby facilitating a bridge between mobility and internal energy transfer. The initial volume of debris flow is inadequate for characterizing debris flow mobility, and a friction‐reduction mechanism is not a prerequisite for the high mobility of debris flows. By contrast, inter‐phase and inter‐grain size interactions play primary roles and should be incorporated explicitly in debris flow models. Our findings are qualitatively encouraging and physically meaningful, providing implications not only for assessing future debris flow hazards and informing mitigation and adaptation strategies, but also for unravelling a spectrum of earth surface processes including heavily sediment‐laden floods, subaqueous debris flows and turbidity currents in rivers, reservoirs, estuaries, and ocean.
published_date 2020-09-30T04:09:16Z
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