Abstract
Abstract. This paper presents a discrete-element-based elastoplastic-adhesive model which is adapted and tested for producing hillslope debris flows. The numerical model produces three phases of particle contacts: elastic, plastic and adhesive. A parametric study was conducted investigating the effect of model parameters and inclination angle on flow height, velocity and pressure, in order to define the most sensitive parameters to calibrate. The model capabilities of simulating different types of cohesive granular flows were tested with different ranges of flow velocities and heights. The basic model parameters, the microscopic basal friction (ϕb) and ratio between stiffness parameters k1/k2, were calibrated using field experiments of hillslope debris flows impacting a pressure-measuring sensor. Simulations of 50 m3 of material were carried out on a channelized surface that is 41 m long and 8 m wide. The calibration process was based on measurements of flow height, flow velocity and the pressure applied to a sensor. Results of the numerical model matched those of the field data in terms of pressure and flow velocity well while less agreement was observed for flow height. Those discrepancies in results were due in part to the deposition of material in the field test, which is not reproducible in the model. Results of best-fit model parameters against selected experimental tests suggested that a link might exist between the model parameters ϕb and k1/k2 and the initial conditions of the tested granular material (bulk density and water and fine contents). The good performance of the model against the full-scale field experiments encourages further investigation by conducting lab-scale experiments with detailed variation in water and fine content to better understand their link to the model's parameters.
Highlights
Worldwide, the growing demand for land to build on has led to the urbanization of mountainous areas
Hillslope debris flows are one type of mass movement where shallow landslides transform into an unconfined flow following heavy rainfalls or earthquakes
The strong oscillations of discrete element method (DEM) signals are usually linked to many factors including the number of particles, the area that is being impacted, the frequency of recording data, the mean particle www.nat-hazards-earth-syst-sci.net/19/2339/2019/
Summary
The growing demand for land to build on has led to the urbanization of mountainous areas. In Switzerland, shallow landslides and hillslope debris flows (Fig. 1) are responsible for high infrastructure damage, blockage of important highways, evacuations and deaths yearly (Andres and Badoux, 2018). These processes could increase the damage caused by floods by clogging channels and rivers at bridges and passages. Hillslope debris flows are one type of mass movement where shallow landslides transform into an unconfined (unchannelized) flow following heavy rainfalls or earthquakes. They are sometimes referred to as debris avalanches, but unlike the ones described by Hungr et al (2014), they rarely entrain sediments along their way (Hürlimann et al, 2015). Their overall assessment comprises (i) the mechanics of Published by Copernicus Publications on behalf of the European Geosciences Union
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