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Abstract
Numerical modeling of ash plume dispersal is an important tool for forecasting and mitigating potential hazards from volcanic ash erupted during explosive volcanism. Recent tephra dispersal models have been expanded to account for dynamic ash aggregation processes. However, there are very few studies on rates of disaggregation during transport. It follows that current models regard ash aggregation as irrevocable and may therefore overestimate aggregation-enhanced sedimentation. In this experimental study, we use industrial granulation techniques to artificially produce aggregates. We subject these to impact tests and evaluate their resistance to break-up processes. We find a dependence of aggregate stability on primary particle size distribution and solid particle binder concentration. We posit that our findings could be combined with eruption source parameters and implemented in future tephra dispersal models.
Highlights
We find a dependence of aggregate stability on primary particle size distribution and solid particle binder concentration
Overpressure experiments of 400 kPa led to total disintegration of the aggregate, no fragments could be observed in the high-speed video or recovered from the ground after the experiment (Fig. 2c)
This study evaluated the stability of aggregates produced artificially from analogue soda-lime silicate glass beads and natural volcanic ash
Summary
There are very few studies on rates of disaggregation during transport It follows that current models regard ash aggregation as irrevocable and may overestimate aggregation-enhanced sedimentation. In this experimental study, we use industrial granulation techniques to artificially produce aggregates. Analysis of large volcanic aggregates (i.e. mm- to cm-size) from several locations has shown secondary mineral phases like NaCl, MgSO4 or CaSO42, 8, 12, 23–25 that act as binding agents between particles Crack initiation in such solid salt bridges may lead to either internal failure of the solid bridge (cohesive failure) or failure of the contact line between solid bridge and particle (adhesive failure[26]). The probability of disaggregation processes and resultant influence of locally increased ash concentrations on bulk ash plume dispersal remains unexplored and is not explicitly implemented in tephra dispersal models
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