@article{fdi:010057201,
  title = {{D}epositional processes and gas pore pressure in pyroclastic flows : an experimental perspective},
  author = {{R}oche, {O}livier},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he depositional processes and gas pore pressure in pyroclastic flows are investigated through scaled experiments on transient, initially fluidized granular flows. {T}he flow structure consists of a sliding head whose basal velocity decreases backwards from the front velocity ({U} (f)) until onset of deposition occurs, which marks transition to the flow body where the basal deposit grows continuously. {T}he flows propagate in a fluid-inertial regime despite formation of the deposit. {T}heir head generates underpressure proportional to {U} (f) (2) whereas their body generates overpressure whose values suggest that pore pressure diffuses during emplacement. {C}omplementary experiments on defluidizing static columns prove that the concept of pore pressure diffusion is relevant for gas-particle mixtures and allow characterization of the diffusion timescale (t (d)) as a function of the material properties. {I}nitial material expansion increases the diffusion time compared with the nonexpanded state, suggesting that pore pressure is self-generated during compaction. {A}pplication to pyroclastic flows gives minimum diffusion timescales of seconds to tens of minutes, depending principally on the flow height and permeability. {T}his study also helps to reconcile the concepts of en masse and progressive deposition of pyroclastic flow units or discrete pulses. {O}nset of deposition, whose causes deserve further investigation, is the most critical parameter for determining the structure of the deposits. {E}ven if sedimentation is fundamentally continuous, it is proposed that late onset of deposition and rapid aggradation in relatively thin flows can generate deposits that are almost snapshots of the flow structure. {I}n this context, deposition can be considered as occurring en masse, though not strictly instantaneously.},
  keywords = {{P}yroclastic flow ; {D}ensity current ; {P}ore pressure ; {D}eposition ; {E}xperiments ; {D}am-break},
  booktitle = {},
  journal = {{B}ulletin of {V}olcanology},
  volume = {74},
  numero = {8},
  pages = {1807--1820},
  ISSN = {0258-8900},
  year = {2012},
  DOI = {10.1007/s00445-012-0639-4},
  URL = {https://www.documentation.ird.fr/hor/fdi:010057201},
}