Abstract
Two analytical block models to estimate the maximum velocity reached by granular flows are proposed. The first one models the speed evolution of coarse-grained materials flows (e.g. debris flows, avalanches); it is based on the power balance of a granular mass sliding along planar surface, written by taking into account the volume of the debris mass, an assigned interstitial pressure, the energy dissipation due to (i) grain inelastic collisions (‘granular temperature’ within a basal ‘shear layer ’); (ii) friction along sliding surface; (iii) fragmentation of grains. The second model allows to simulate the speed evolution of fine-grained materials flows (e.g. mudflows, quick clays) by taking into account the dissipation of the excess pore water pressure due to consolidation phenomena. Finally, the comparison between the results obtained through the proposed models and field and laboratory measures is carried out.
Highlights
Very high stresses arise at the contact surface between an impacting fluid and a solid body that constitutes an obstacle to the fluid flow; these stresses act only for a very short time period
Two analytical block models to estimate the maximum velocity reached by granular flows are proposed
The first one models the speed evolution of coarse-grained materials flows; it is based on the power balance of a granular mass sliding along planar surface, written by taking into account the volume of the debris mass, an assigned interstitial pressure, the energy dissipation due to (i) grain inelastic collisions (‘granular temperature’ within a basal ‘shear layer’); (ii) friction along sliding surface; (iii) fragmentation of grains
Summary
Very high stresses arise at the contact surface between an impacting fluid and a solid body that constitutes an obstacle to the fluid flow; these stresses act only for a very short time period. Structures exposed to the impact with a fluid or a fluidized granular mass may be affected by serious damages, mainly due to the shock pressures. Several relationships to estimate the maximum impact force per unit width (F) or pressure (pmax) applied by a debris flow against structures have been proposed [1,2,3,4]: p. All previously described expressions show the dependence of the maximum pressure pmax or force F on the velocity (v) of the granular flow at the impact zone with rigid structures. A granular flow generally reaches the maximum velocity at the end of the ‘first’ slope, where safeguarding measures (e.g. walls, barriers) are usually built. Two analytical (block) models to estimate the maximum velocity reached by coarse and fine grained material flows are developed and proposed
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