@article{fdi:010049707,
  title = {{P}article velocity fields and depositional processes in laboratory ash flows, with implications for the sedimentation of dense pyroclastic flows},
  author = {{G}irolami, {L}. and {R}oche, {O}livier and {D}ruitt, {T}. {H}. and {C}orpetti, {T}.},
  editor = {},
  language = {{ENG}},
  abstract = {{W}e conducted laboratory experiments on dam-break flows of sub-250-{A} mu m volcanic ash, generated by the release of gas-fluidized and variably non-expanded to expanded (up to 35%) beds, in order to gain insights into the internal kinematics of pyroclastic flows. {T}he flows were typically several cm thick and had frontal speeds of up to similar to 2 m s(-1). {H}igh-speed videos taken through the transparent sidewall of the 3-m-long channel were analyzed with a particle-tracking algorithm, providing a spatial and temporal description of transport and sedimentation. {T}he flows deposited progressively as they traveled down the flume, being consumed by sedimentation until they ran out of volume. {D}eposition commenced 5-20 cm rearward of the flow front and (for a given expansion) proceeded at a rate independent of distance from the lock gate. {D}eposit aggradation velocities were equal to those inferred beneath quasi-static bed collapse tests of the same ash at the same initial expansions, implying that shear rates of up to similar to 300 s(-1) have no measurable effect on aggradation rate. {T}he initially non-expanded (and just fluidized) flow deposited progressively at a rate indicative of an expansion of a few percent, perhaps due to shear-induced {R}eynolds dilation during initial slumping. {T}he fronts of the flows slid across the flume floor on very thin basal shear layers, but once deposition commenced a no-slip condition was established at the depositional interface. {W}ithin the flows, the trajectory of the constituent particles was linear and sub-horizontal. {T}he velocities of the particles increased with height above the depositional interface, reached a maximum, then declined slightly towards the flow surface, perhaps due to air drag. {A}t a given location, the velocity profiles were translated upwards as the deposit aggraded. {T}he results show that even cm-thin, poorly expanded flows of ash deposit progressively, as inferred for many pyroclastic flows. {T}he change from (frontal) slip to (rearward) no-slip conditions at the bases of the laboratory flows are qualitatively consistent with some textural features of pyroclastic flow deposits.},
  keywords = {{P}yroclastic flow ; {F}luidized granular flow ; {L}aboratory experiment ; {V}elocity profile ; {P}rogressive aggradation},
  booktitle = {},
  journal = {{B}ulletin of {V}olcanology},
  volume = {72},
  numero = {6},
  pages = {747--759},
  ISSN = {0258-8900},
  year = {2010},
  DOI = {10.1007/s00445-010-0356-9},
  URL = {https://www.documentation.ird.fr/hor/fdi:010049707},
}