Use of the event tree to assess the risk reduction obtained from rockfall protection devices

Self Cite

Abstract. The need for protection against rockfall has led to the development of different types of technological solutions that are able to both prevent blocks from detaching from rock walls and to control, intercept or deviate the blocks during movement. Of the many devices that are able to intercept and stop a block, one of the most frequently used is net fence. Many different types of full-scale tests have been carried out, with different test site geometries and procedures to study their behaviour and to certify these devices. This has led to a series of data and information that are not easy to compare. The recent endorsement, by the European Organization for Technical Approvals (EOTA), of a European Technical Approval Guideline (ETAG), which defines how to test and assess the performance of a net fence, is therefore a great innovation that will change both the market and the design procedures of these devices. The most important innovations introduced by this new guideline are here presented and discussed and a net fence design procedure for protection against rockfall is provided.

Section: Introductionmentioning

confidence: 99%

Technical Note: Design of rockfall net fences and the new ETAG 027 European guideline

Peila

Ronco

2009

Self Cite

“…In order to appropriately account for the positive effects of protective measures on rockfall risk and the associated uncertainties, their design should be based on a quantitative risk analysis (Corominas et al, 2005;Straub and Schubert, 2008;Peila and Guardini, 2008). In doing so, the protective effect of the measure can be expressed in monetary terms, thereby allowing its efficiency to be evaluated in a cost-benefit analysis (Agliardi et al, 2009).…”

mentioning

confidence: 99%

Quantifying the effect of forests on frequency and intensity of rockfalls

Moos

Dorren

Stoffel

2017

Abstract. Forests serve as a natural means of protection against small rockfalls. Due to their barrier effect, they reduce the intensity and the propagation probability of falling rocks and thus reduce the occurrence frequency of a rockfall event for a given element at risk. However, despite established knowledge on the protective effect of forests, they are generally neglected in quantitative rockfall risk analyses. Their inclusion in quantitative rockfall risk assessment would, however, be necessary to express their efficiency in monetary terms and to allow comparison of forests with other protective measures, such as nets and dams. The goal of this study is to quantify the effect of forests on the occurrence frequency and intensity of rockfalls. We therefore defined an onset frequency of blocks based on a powerlaw magnitude-frequency distribution and determined their propagation probabilities on a virtual slope based on rockfall simulations. Simulations were run for different forest and non-forest scenarios under varying forest stand and terrain conditions. We analysed rockfall frequencies and intensities at five different distances from the release area. Based on two multivariate statistical prediction models, we investigated which of the terrain and forest characteristics predominantly drive the role of forest in reducing rockfall occurrence frequency and intensity and whether they are able to predict the effect of forest on rockfall risk. The rockfall occurrence frequency below forested slopes is reduced between approximately 10 and 90 % compared to non-forested slope conditions; whereas rockfall intensity is reduced by 10 to 70 %. This reduction increases with increasing slope length and decreases with decreasing tree density, tree diameter and increasing rock volume, as well as in cases of clustered or gappy forest structures. The statistical prediction models reveal that the cumulative basal area of trees, block volume and horizontal forest structure represent key variables for the prediction of the protective effect of forests. In order to validate these results, models have to be tested on real slopes with a wide variation of terrain and forest conditions.

“…The approach proposed by Peila and Guardini (2008) and used by Budetta et al (2015) falls in the same category, although it takes into account the length of the hazard zone and the vehicle length. However, if we multiply their spatial probability by their temporal probability and by the vehicle frequency, we obtain…”

Section: Approaches Neglecting the Events Dimensionmentioning

confidence: 99%

“…(1). It has to be noted that Peila and Guardini (2008) use a binomial distribution to calculate the probability of one or more impacts, using the rockfall frequency as the number of experiments, and the spatial probability as the probability of success. We neglected this transformation here in order to keep the rockfall frequency out of the calculation, but the general idea is the same.…”

Section: Approaches Neglecting the Events Dimensionmentioning

confidence: 99%

Brief communication: On direct impact probability of landslides on vehicles

Nicolet

Jaboyedoff

Cloutier³

et al. 2016

Abstract. When calculating the risk of railway or road users of being killed by a natural hazard, one has to calculate a temporal spatial probability, i.e. the probability of a vehicle being in the path of the falling mass when the mass falls, or the expected number of affected vehicles in case such of an event. To calculate this, different methods are used in the literature, and, most of the time, they consider only the dimensions of the falling mass or the dimensions of the vehicles. Some authors do however consider both dimensions at the same time, and the use of their approach is recommended. Finally, a method considering an impact on the front of the vehicle is discussed.