Numerical simulation of dry granular flows: from rhe reproduction of small-scale experiments to the prediction of rock avalanches

 

Despite of the efforts performed by several researchers, the mechanisms of dry granular flows are not yet completely understood. This lack of knowledge has a negative fall-out on the assessment of the run-out of dry debris flows or rock avalanches, on the proposal of adequate monitoring and early monitoring systems, and on the design of the protection structures.

 

Despite of the efforts performed by several researchers, the mechanisms of dry granular flows are not yet completely understood. This lack of knowledge has a negative fall-out on the assessment of the run-out of dry debris flows or rock avalanches, on the proposal of adequate monitoring and early monitoring systems, and on the design of the protection structures.

In this paper the use of a numerical model based on Distinct Element Method (DEM) is considered. DEM is based on the modelling of the particle-to-particle interaction, and should therefore put in evidence the basic mechanisms of the granular flow. The two-dimensional code PFC 2D [ITASCA, 1996] is used, which models the behaviour of a system composed by an assembly of rigid disks connected by elastic springs. In the first part of the paper, the numerical model is used to reproduce a series of experiments on a small-scale laboratory model of a slope. The DEM parameters (contact stiffness, surface friction of particles, surface friction of the slope and numerical damping) are back analysed to make the model match the experiments. Particular attention is devoted to the calibration of the numerical damping parameter, which is the only one which cannot be clearly related to a specific mechanical property of the particles. Next, by using the calibrated model, the influence ofthe geometry (inclination of the slope) and of the global mass of material flowing down the chute are studied and interpreted in the light ofthe micro—mechanical measurements provided by the numerical code.

In the last part of the paper, the numerical model is applied to the simulation of a real scale rock avalanche that took place in Valtellina (northern Italy) on the 28th of July, 1987. During this event, which is commonly referred to as the “Val Pola" rock avalanche, about 40X105 m2 of rock initially located between 2350 and 1550 metresa.s.l. on the steep side of mount Zartdila, crumbled into the valley (1000 m. a.s.l.) causing the destruction of three villages: Morignone, Antonio Morignone and Aquilone. Unfortunately, the last was not evacuated since it was considered safely located, which provoked 29 casualties.


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AUTORI: Calvetti F., Crosta G., Tatarella M.
RIG ANNO:1999 NUMERO:2
Numero di pagine: 21


Allegato: https://associazionegeotecnica.it/wp-content/uploads/2010/03/RIG_2000_2_21.pdf
Allegato:
Articolo completo: https://associazionegeotecnica.it/wp-content/uploads/2010/03/RIG_2000_2_21.pdf