Highly energetic rockfalls: back analysis of the 2015 event from the Mel de la Niva, Switzerland

Abstract

Process-based rockfall simulation models attempt to better emulate rockfall dynamics to different degrees. As no model is perfect, their development is often accompanied and validated by the valuable collection of rockfall databases covering a range of site geometries, rock masses, velocities, and related energies that the models are designed for. Additionally, such rockfall data can serve as a base for assessing the model’s sensitivity to different parameters, evaluating their predictability and helping calibrate the model’s parameters from back calculation and analyses. As the involved rock volumes/masses increase, the complexity of conducting field-test experiments to build up rockfall databases increases to a point where such experiments become impracticable. To the author’s knowledge, none have reconstructed rockfall data in 3D from real events involving block fragments of approximately 500 metric tons. A back analysis of the 2015 Mel de la Niva rockfall event is performed in this paper, contributing to a novel documentation in terms of kinetic energy values, bounce heights, velocities, and 3D lateral deviations of these rare events involving block fragments of approximately 200 m3. Rockfall simulations are then performed on a “per-impact” basis to illustrate how the reconstructed data from the site can be used to validate results from simulation models.

Occurrence conditions of the reverse rotation of rockfall and its influence on the restitution coefficient

“…Rockfall is a geological hazard that frequently occurs in mountainous and canyon regions. It is characterized by its suddenness, strong randomness, and high energy, posing a serious threat to surrounding infrastructure, personnel, and vehicle safety (Guccione et al, 2021;Chen et al, 2023;Noël et al, 2023;Wang et al, 2023). Particularly in areas with developed structural planes on slopes, incidents such as planar sliding, rotational failure, toppling failure, and wedge failure often occur, forming hazardous rock masses (Azarafza et al, 2020;Azarafza et al, 2021;Nanehkaran et al, 2022).…”

Comparing Flow-R, Rockyfor3D and RAMMS to Rockfalls from the Mel de la Niva Mountain: A Benchmarking Exercise

“…The back analysis and trajectory reconstruction of rockfall events, such as those covered in the companion publication Noël et al [1], provide valuable data for the important calibration of rockfall simulations (Jones et al, [2]; Labiouse, [3]; Berger and Dorren, [4]; Berger et al, [5]; Volkwein et al, [6]; Dorren et al, [7]; Valagussa et al, [8]; Bourrier et al, [9]; Noël et al, [10]). Simulations are often performed with various levels of detail with associated calibrations depending on the required level of certainty and safety margins.…”

“…Domaas [39], Descoeudres [40], Volkwein et al [6], Wyllie [41] and Gerber [42] detail how analytical methods can be used to estimate the translational kinetic energies and bounce heights from the positions of a succession of impact marks and/or combined with the incident angle imprint in the ground at the impacts. These positions can also be determined on 3D detailed terrain models from the imprint impact marks, as in Caviezel et al [43] and Noël et al [1]. If video footage from previous rockfall events is available, these values can be reconstructed as well as the rock trajectory segments, as in Noël et al [44] and Noël et al [1], for example.…”

“…These positions can also be determined on 3D detailed terrain models from the imprint impact marks, as in Caviezel et al [43] and Noël et al [1]. If video footage from previous rockfall events is available, these values can be reconstructed as well as the rock trajectory segments, as in Noël et al [44] and Noël et al [1], for example.…”

“…For this exercise, the historical events from Mel de la Niva Mountain, whose 3D trajectories and 2D paths were reconstructed in detail in the companion publication by Noël et al [1], are used as references in this paper. The 200 m 3 blocks, reaching hundreds of megajoules during their fall, greatly exceeded the common rockfall energies of the empirical databases used for the development of most rockfall models (Noël et al [1]). Such a site can thus be challenging for the simulation models tested in this paper.…”