Avalanche impact pressure on an instrumented structure

Thibert, Emmanuel; Baroudi, Djebar; Limam, Ali; Berthet-Rambaud, Philippe

doi:10.1016/j.coldregions.2008.01.005

Cited by 50 publications

(60 citation statements)

References 25 publications

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“…De nombreux travaux expérimentaux, conduits récemment sur des sites test [Sovilla et al, 2008 ;Thibert et al, 2008 ;Baroudi et Thibert, 2009 ], ont montré un comportement singulier en matière de pression d'impact des avalanches lentes et épaisses, classe à laquelle appartiennent les avalanches de neige humide qui s'écoulent lentement avec des épaisseurs et des masses volumiques très élevées.…”

Section: Connaissances Récentes Sur La Pression D'impact Et Impliunclassified

Impact du réchauffement climatique sur l'activité avalancheuse et multiplication des avalanches humides dans les Alpes françaises

et al. 2016

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RÉSUMÉ. -Sur l'ensemble des Alpes françaises, le croisement de deux bases de données bien documentées, la chronique d'avalanches EPA et les réanalyses nivo-météorologique, a permis de quantifier la réponse de l'activité avalancheuse aux évolutions récentes du climat hivernal. Même si le signal est affecté d'une variabilité interannuelle importante, il est démontré qu'en moyenne sur les trente dernières années on observe une augmentation des altitudes d'arrêt et une diminution du nombre d'avalanche avec aérosols et du nombre moyen d'avalanches. Sur le massif du Mont-Blanc, l'article présente les résultats obtenus sur l'augmentation, quasi concomitante avec le récent réchauffement, de la proportion des avalanches humides, de même que les corrélations obtenues entre les paramètres de frottement des avalanches et les propriétés de la neige. Par la suite l'article synthétise les nouvelles avancées en matière de pression d'impact des avalanches et souligne les conséquences attendues notamment pour les avalanches humides. Enfin, l'article se conclut par la présentation synthétique des projections au prochain siècle des quantités de précipitations, de la qualité de la neige et des décalages attendus, à la fois en saisons et en altitude, de l'activité avalancheuse.Mots clefs : Avalanches, neige humide, réchauffement climatique, impacts, aléa, risque. Impact of climate warming on avalanche activity in French Alps and increase of proportion of wet snow avalanchesABSTRACT. -The cross-analysis of two well documented databases, EPA snow avalanche chronicles and the reanalysis of snow mantle, allows quantifying the changes in avalanche activity as a response to climate warming. In the French Alps and even if the signal is affected by a significant variability, it is shown that, on average over the past thirty years, the run-out altitudes increased and the frequency and the proportion of powder avalanches decreased. In Chamonix valley a substantial increase of the proportion of wet snow avalanches since the seventies has been shown, concomitant to the local climate warming. The reanalysis of a large number of avalanches that occurred in Chamonix valley between 1958 and 2010 allowed drawing up significant correlations between the basal friction coefficient and the snow properties. On average, the friction coefficient increases with snow temperature. This trend is coherent with the run-out altitude increase observed over the French Alps since 1980. However the friction coefficient drops to small values when snow water content exceeds a certain threshold, hence very wet snow avalanches have large extensions. In addition, because their density and height are high and the velocity low, the pressure they develop is higher than expected notably in the run-out zone. The expected consequences on the avalanche hazard of these proved trends is presented together with the projections concerning amount and quality of snow for the next century as well as expected altitudinal and seasonal shifts in avalanche activity.Key words: Avalanches, we...

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Section: Connaissances Récentes Sur La Pression D'impact Et Impliunclassified

Impact du réchauffement climatique sur l'activité avalancheuse et multiplication des avalanches humides dans les Alpes françaises

et al. 2016

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“…In the above equations, C d denotes the empirical drag coefficient, which is a function of the Froude number (Fr) and two empirical constants, a 5 10?8 and n 5 1?3 (Thibert et al, 2008), r is the density of granular flow, v is the In previous studies (Jiang & Towhata, 2013), only the force normal to the retaining wall surface has been primarily studied, while the influence of the force tangential to the retaining wall has hardly been investigated. This paper thus reports experimental results of granular flow impact studied via measurements of both the normal and tangential forces on a retaining wall.…”

Section: =2mentioning

confidence: 99%

Experimental investigation of dry granular flow impact via both normal and tangential force measurements

Jiang

Zhao

2015

Géotechnique Letters

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The study of granular flow is important for natural hazards such as avalanche and debris flow. In this context, granular flow impact against a retaining wall was investigated through the measurement of both normal and tangential sub-forces. The tangential sub-forces change from positive to negative with respect to the wall in the impact process, which can be classified into two impact states according to the development of the stagnant zone. In the process, interface friction between the granular material and the wall is calculated according to normal and tangential forces and defined as the equivalent interface friction angle, which is observed to vary, and is smaller than the value measured in interface friction tests. The absolute value of the equivalent interface friction angle decreases with slope angle. It was also observed that a reduction in the interface friction angle of the wall has a negligible influence on the impact force calculation, while a reduction in the interface friction angle of the flume base leads to a significant overestimation of the force. These findings should significantly aid the study of granular flow and its applications.

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“…For instance, small-scale experiments were conducted to reproduce the granular behavior of snow and study its interaction with obstacles . Moreover, real-scale experiments have been conducted to measure the pressure magnitudes reached by dense avalanche flows (Thibert et al, 2008) and powder avalanches (Sovilla et al, 2008). …”

Section: Snow Avalanche Loadingmentioning

confidence: 99%

A reliability assessment of physical vulnerability of reinforced concrete walls loaded by snow avalanches

Favier

Bertrand

Eckert³

et al. 2014

Nat. Hazards Earth Syst. Sci.

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Abstract. Snow avalanches are a threat to many kinds of elements (human beings, communication axes, structures, etc.) in mountain regions. For risk evaluation, the vulnerability assessment of civil engineering structures such as buildings and dwellings exposed to avalanches still needs to be improved. This paper presents an approach to determine the fragility curves associated with reinforced concrete (RC) structures loaded by typical avalanche pressures and provides quantitative results for different geometrical configurations. First, several mechanical limit states of the RC wall are defined using classical engineering approaches (Eurocode 2), and the pressure of structure collapse is calculated from the usual yield line theory. Next, the fragility curve is evaluated as a function of avalanche loading using a Monte Carlo approach, and sensitivity studies (Sobol indices) are conducted to estimate the respective weight of the RC wall model inputs. Finally, fragility curves and relevant indicators such a their mean and fragility range are proposed for the different structure boundary conditions analyzed. The influence of the input distributions on the fragility curves is investigated. This shows the wider fragility range and/or the slight shift in the median that has to be considered when a possible slight change in mean/standard deviation/inter-variable correlation and/or the non-Gaussian nature of the input distributions is accounted for.

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Avalanche impact pressure on an instrumented structure

Cited by 50 publications

References 25 publications

Impact du réchauffement climatique sur l'activité avalancheuse et multiplication des avalanches humides dans les Alpes françaises

Impact du réchauffement climatique sur l'activité avalancheuse et multiplication des avalanches humides dans les Alpes françaises

Experimental investigation of dry granular flow impact via both normal and tangential force measurements

A reliability assessment of physical vulnerability of reinforced concrete walls loaded by snow avalanches

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