Reply to comment by Davies and McSaveney on “The reduction of friction in long runout landslides as an emergent phenomenon”

Johnson, Brandon C.; Campbell, Charles S.; Melosh, H. J.

doi:10.1002/2016jf003993

Cited by 3 publications

(3 citation statements)

References 14 publications

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“…Analogously, the increased fragmentation for the geometry and volume series causes attenuated seismic efficiency (Figure 12), indicating that the inelastic process associated with viscous damping, friction and irreversible deformation during fragmentation consumes a significant amount of impact energy. As a consequence, these results agree well with the hypothesis that fragmentation is an energy-consuming process (Campbell, 1990;Collins & Melosh, 2003;Crosta et al, 2007;Hungr, 2006;Johnson et al, 2016;Locat et al, 2006).…”

Section: Implicationsupporting

confidence: 90%

“…This hypothesis has been accepted (e.g., Bowman et al, 2012;Imre et al, 2010) but also contradicted (e.g., Haug et al, 2016;Hungr, 2006). An important reason for opposing this hypothesis is that dynamic fragmentation is expected to be an energy-consuming process (Campbell, 1990;Collins & Melosh, 2003;Hungr, 2006;Johnson et al, 2016). Based on data from 9 rock avalanche investigations, Locat et al (2006) suggested that fragmentation depends on the potential energy and rock mass strength, and no clear relationships were found between fragmentation and mobility.…”

mentioning

confidence: 99%

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Block‐Grain Phase Transition in Rock Avalanches: Insights From Large‐Scale Experiments

Zhang,

Yin,

et al. 2023

JGR Earth Surface

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Knowledge of the processes and effects of the block‐grain phase transition in a fragmented system is essential for investigating rock avalanches. Several series of experiments are performed with a very large apparatus, using a jointed block, simulated by an assembly of packed breakable subblocks varying in configuration, as an analog for brittle rock. The analog jointed block is released from a hopper, moves on two inclined flumes with different slopes, and finally deposits on a horizontal platform. The block‐grain phase transition occurs, caused by subblock collisions and explosive impacts with the flume bottom. The dynamic behavior, seismic signal, fragment characteristic, and deposit structure of the analog material are determined. Our results demonstrate that fragmentation influences energy dissipation and momentum transfer, as well as subsequent flow and emplacement processes. A nonunified and piecewise relationship between the fragmentation degree and friction coefficients is observed. We ascribe this nonunified relationship to the varying dynamics and runout regimes that different configurations of jointed blocks undergo. The positive or negative feedback on energy generated by fragmentation is closely associated with the energy budget involved in this fragmented system, which depends substantively on the block configuration. Particularly, for flatter or larger jointed blocks, despite increased fragmentation absorbing the available energy for runout, it simultaneously changes the runout regime toward a more energy‐efficient one, thus instigating positive feedback. Our study further highlights the contribution of post‐fragmentation granular flow to the energy system.

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Section: Implicationsupporting

confidence: 90%

mentioning

confidence: 99%

Block‐Grain Phase Transition in Rock Avalanches: Insights From Large‐Scale Experiments

Zhang,

Yin,

et al. 2023

JGR Earth Surface

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“…Recent studies of debris avalanches have indicated the necessity of the normal stress reduction in debris avalanches (Pudasaini & Miller, 2013), which is also supported by experimental (R H Iverson, 1997;R M. Iverson & Vallance, 2001) and numerical (Gueugneau et al, 2017;Iverson et al, 2015;Lucas et al, 2014) studies. Nevertheless, this is currently the source of active debate (Davies & McSaveney, 2016;Iverson, 2016;Johnson et al, 2016aJohnson et al, , 2016bJohnson et al, , 2016c.…”

Section: Discussionmentioning

confidence: 99%

Enhanced Mobility in Concentrated Pyroclastic Density Currents: An Examination of a Self‐Fluidization Mechanism

Bréard

Dufek

Lube

2018

Geophysical Research Letters

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Pyroclastic density currents (PDCs) are a significant volcanic hazard. However, their dominant transport mechanisms remain poorly understood, in part because of the large variability of PDC types and deposits. Here we combine field data with experimental and numerical simulations to illuminate the twofold fate of particles settling from an ash cloud to form the dense PDC basal flow. At solid fractions >1 vol %, heterogeneous drag leads to formation of mesoscale particle clusters that favor rapid particle settling and result in a mobile dense layer with significant bed weight support. Conversely, at lower concentrations the absence of particle clusters typically leads to formation of poorly mobile dense beds that deposit massive layers. Based on this transport dichotomy, we present a numerical dense‐dilute parameter that allows a PDC's dominant transport mechanism to be determined directly from the deposit geometry and grainsize characteristics.

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Analysis of satellite-derived landslide at Central Nepal from 2011 to 2016

Chen

Shakir

2018

Environ Earth Sci

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Reply to comment by Davies and McSaveney on “The reduction of friction in long runout landslides as an emergent phenomenon”

Abstract: Key Points We reply to comment by Davies and McSaveny We argue that we cannot comment on the role of fragmentation Our work has demonstrated a friction reduction mechanis that does not involve fragmentation

Cited by 3 publications

References 14 publications

Block‐Grain Phase Transition in Rock Avalanches: Insights From Large‐Scale Experiments

Block‐Grain Phase Transition in Rock Avalanches: Insights From Large‐Scale Experiments

Enhanced Mobility in Concentrated Pyroclastic Density Currents: An Examination of a Self‐Fluidization Mechanism

Analysis of satellite-derived landslide at Central Nepal from 2011 to 2016

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