Rockfall Simulation Research Articles

Evaluating the Impact of DEM Spatial Resolution on 3D Rockfall Simulation in GIS Environment

Evaluating the Impact of DEM Spatial Resolution on 3D Rockfall Simulation in GIS Environment

Rockfall susceptibility analysis of the “San Michele Arcangelo” historic trail (Central Italy) based on virtual outcrops and multiple propagation models

The “San Michele Arcangelo” historic trail (Aurunci Regional Park, central Italy), located along the southern slope of Mt. Altino, which is highly prone to rockfalls, is hiked every year by thousands of faithful on pilgrimage who are exposed to such kinds of instabilities. To contribute to a better understanding of the condition and evolution of such phenomena, providing a susceptibility scenario able to support the adoption of mitigation measures, a specific analysis was completed based on field and literature data. Three-dimensional virtual outcrop models were obtained through both photogrammetric and iPad Pro LiDAR surveys to derive geomechanical features of outcropping rocks and estimate potential detaching block volume. Possible mechanisms of detachment were then analyzed using the Markland test method. Susceptibility to rockfall propagation and block deposition was analyzed using GIS processing and rockfall propagation simulations based on deterministic/stochastic models. Such models consist of a combination of a deterministic algorithm able to simulate the physics of rockfall movement during propagation and a stochastic treatment of input parameters based on random sampling within defined interval. Two different rockfall simulations were compared in this study using the Rockyfor3D™ (ecorisQ Association) software and the newly developed RocFall3© (RocScience) code. The use of iPad Pro LiDAR survey provides accurate and high-resolution point clouds, with high speed of acquisition and real-time processing of data. Discontinuity sets identified from 3D models have represented the input for kinematic analyses of slopes, allowing to identify potential failure mechanisms among wedge and planar sliding or toppling. Rockfall simulations indicate the potential for rock blocks propagation and deposition over the whole study area. Comparing the results of rockfall simulations with the geomorphological map of the area it is evident the control exerted by the hydrographic network on rockfall propagation as demonstrated by the presence of screes and slope deposits along the main channels. Understanding the potential susceptibility to both propagation and deposition of rock blocks along the trail provides useful indication for the assessment of appropriate mitigation measures to realize for the safer touristic fruition of the site.

Evaluating failure regime of an active landslide using instability and rockfall simulation, NW Himalaya

Evaluating failure regime of an active landslide using instability and rockfall simulation, NW Himalaya

Rockfall simulation via spherical harmonic based discrete element method

The trajectory of falling rock is significantly affected by its shape. In order to capture the falling rock shape, spherical harmonic function expansion method is used. The reasonable order of spherical harmonic function expansion items is determined according to the error analysis. Spherical harmonic based discrete element method is utilized to simulate the rockfall process of cylindrical and irregular shape rocks. The influences of the rock and terrain shapes on the rockfall trajectory are analyzed. The results show that the shape of falling rock can be described precisely by spherical harmonic function expansion method, and only a little data should be stored. The predicted trajectory of cylindrical rockfall is close to the experimental result. Spherical and block falling rocks usually show more regular horizontal displacement, lateral offset and jump height during the motion process. Those motion quantities for long strip and flaky falling rocks are more sensitive to their initial rotations. Terrain has a strong influence on rockfall trajectory, falling rocks are prone to move along or rest at mountain valleys.

Evaluation of rockfall hazard based on UAV technology and 3D Rockfall Simulations

Hacıabdullah village, where rockfall events occur frequently, is an important mountainous region located within the boundaries of Niğde province, which is one of the top provinces in Türkiye in terms of rockfall events and is located in the Central Anatolia Region. Despite the frequent occurrence of many rockfall events of varying sizes, no precautions are taken as a result of these events, leading to economic damages. Therefore, Hacıabdullah village, which poses a high danger and risk in terms of slope instability and rockfall potential, has been selected as the study area. The study aims to evaluate rockfall events occurring on steep slopes in Haciabullah village, based on the potential rock blocks that could fall, by modeling them according to their geometries. Within this scope, the potential 17 rock blocks that could fall have been identified in the field and modelled using RAMMS 3D rockfall software according to their geometric characteristics. In addition to the geometric characteristics of the rock blocks, their potential falling areas, velocities, jump heights, and kinetic energies will also be determined, the basis of the rockfall hazard analysis. For the 3D modeling of the study, UAV-DSM (3cm resolution), which represents the high-resolution surface of the topography, has been used as the main dataset. As a result of 3D rockfall modeling, the maximum kinetic energy, maximum velocity, and maximum jump height of the falling blocks reached 3476 kJ, 23.1 m/s, and 14.57 m, respectively. The result of the kinematic analysis showed a higher probability of toppling type in the whole study area. Rocks that do not move very far from the source area are; in other words and may significantly damage the roads. However, rolling blocks, in other words, blocks that can travel long distances from the source area, have the potential to cause great damage to the settlement areas, roads, and trees. According to the hazard map, blocks involve high and moderate levels of risk for settlement units.

INTEGRIRANI PRISTUP KOD ANALIZA RIZIKA OD ODRONA

The paper presents some elements of intergated approach in rockfall risk analyses prepared for zone of Macedonian village Staro selo in Polog area. The wider zone of Polog is characterized with pronounced rockfall, landslide and flood hazards in general terms, where several critical locations exists. The results from rockfall simulation analyses, contemporary and innovative terrain surveying techniques used in detection of hazardous zones with LIDAR and INSAR methods and other data are presented. Analyses confirmed the possibility for detachment of rockfalls, which is observed in reality, and not only in the exact zone of the village. Integrating findings from rockfall simulations with benefit and cost analysis of suggested protection mesaures, some recomendations from the aspect of tolerable level of risks including possible trends suggested in new Eurocode 7 generation are presented. The main findings leads to the conclusion, that interaction and integration of technical, economic and social aspects and involving different perpectives is necesary in process of rockfall risk management.

Shape still matters: rockfall interactions with trees and deadwood in a mountain forest uncover a new facet of rock shape dependency

Abstract. Mountain forests have a substantial protective function in preventing natural hazards, in part due to the presence of dead wood on the forest floor. Rates of deadwood accumulation have increased within the Alps and are predicted to rise further, due to natural disturbances. In particular, higher windthrow event frequencies are expected, primarily due to large-scale even-aged forest stands in many alpine regions combined with climate change. We quantified the rockfall protection effect of mountain forests with and without deadwood, in unprecedented detail, in experiments using two rock shapes with important hazard potential and masses of 200–3200 kg. Based on a multi-camera setup, pre- and post-experimentally retrieved high-resolution lidar data, and rock data measured in situ, we precisely reconstructed 63 trajectories. The principal parameters of interest describing the rockfall kinematics were retrieved for each trajectory. A total of 164 tree impacts and 55 deadwood impacts were observed, and the currently applied energy absorption curves – partially only derived theoretically – could consequently be corroborated or even expanded to a greater absorption performance of certain species than hitherto assumed. Standing trees, in general, and deadwood, in particular, were found to strongly impede the notorious lateral spreading of platy rocks. Platy rocks featured a shorter mean runout distance than their compact counterparts of similar weight, even in the absence of deadwood. These results indicate that the higher hazard potential of platy rocks compared with more compact rocks, previously postulated for open-field terrain, applies less to forested areas. Last, reproducing the experimental setting showcases how complex forest states can be treated within rockfall simulations. Overall, the results of this study highlight the importance of incorporating horizontal forest structures accurately in simulations in order to obtain realistic deposition patterns.

Modeling Ellipsoidal Block Impacts by an Advanced Rheological Model

In this paper, an advanced rheological model for impacts of ellipsoidal blocks on deformable ground surfaces, introducing the effects of block eccentricity and orientation at impact, is presented. This allows us to assess impact penetration and force, restitution coefficients, and block trajectories. A parametric analysis was carried out by considering different block aspect ratios, impact angles and initial block orientations at impact. The results are presented in terms of restitution coefficients, penetration and force time histories, maximum penetration depth, maximum force and rotational/total kinetic ratios. Impacts along the major block axis, versus those along minor axis, are characterized by larger penetrations (ranging from 3.3 to 50%), shorter impact durations (ca 50%) and very slightly larger vertical forces (ranging from 0.3 to 60%) according to the model parameter used. In contrast, the impact angle is shown to strongly affect maximum penetration and force values, and markedly increase rotation at impact. Analogously, normal restitution coefficient is severely dependent on impact angle, with a variation of more than two orders of magnitude. A mathematical expression for computing the energetic restitution coefficient from the normal and tangential apparent restitution coefficients and the ratio between the rotation and total kinetic energy is proposed. This overcomes the drawback of classical restitution coefficients greater than one when a change in block rotation occurs allowing us to bracket the coefficient of restitutions values to support and improve classical rock fall simulations also highlighting their intrinsic limitations. Finally, the effects of block geometry and initial angular velocity on rockfall simulations were analyzed by implementing the approach in the HyStone simulation code. The simulated frequencies of the maximum height during each ballistic trajectory follow an exponential distribution, whereas those for normal and tangential apparent restitution coefficients follow normal distributions.

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

Rockfall simulations are often performed at various levels of detail depending on the required safety margins of rockfall-hazard-related assessments. As a pseudo benchmark, the simulation results from different models can be put side-by-side and compared with reconstructed rockfall trajectories, and mapped deposited block fragments from real events. This allows for assessing the objectivity, predictability, and sensitivity of the models. For this exercise, mapped data of past events from the Mel de la Niva site are used in this paper for a qualitative comparison with simulation results obtained from early calibration stages of the Flow-R 2.0.9, Rockyfor3D 5.2.15 and RAMMS::ROCKFALL 1.6.70 software. The large block fragments, reaching hundreds of megajoules during their fall, greatly exceed the rockfall energies of the empirical databases used for the development of most rockfall models. The comparison for this challenging site shows that the models could be improved and that combining the use of software programs with different behaviors could be a workaround in the interim. The findings also highlight the inconvenient importance of calibrating the simulations on a per-site basis from onsite observations. To complement this process, a back calculation tool is briefly described and provided. This work also emphasizes the need to better understand rockfall dynamics to help improve rebound models.

Accounting for the effect of forest and fragmentation in probabilistic rockfall hazard

Abstract. The presence of trees along the slope and block fragmentation at impact strongly affect rockfall dynamics and hazard as a consequence. However, these phenomena are rarely simulated explicitly in rockfall studies. We performed rockfall simulations by using the 3D rockfall simulator Hy-Stone, modeling both the presence of trees and fragmentation through specific algorithms implemented in the code. By comparing these simulations with a more classical approach that attempts to account implicitly for such phenomena in the model parameters and by using a new probabilistic rockfall hazard analysis (PRHA) method, we were able to quantify the impact of these phenomena on the design of countermeasures and on hazard. We demonstrated that hazard changes significantly when accounting explicitly for these phenomena and that a classical implicit approach usually overestimates both the hazard level and the 95th percentile of kinetic energy, leading to an oversizing of mitigation measures.

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

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.

Using an Inventory of Unstable Slopes to Prioritize Probabilistic Rockfall Modeling and Acid-Base Accounting in Great Smoky Mountains National Park

Abstract An important first step in the geotechnical asset management of Great Smoky Mountains National Park (GRSM) is the creation of an unstable slope inventory along major transportation corridors. Slope-stability problems are frequent in GRSM, often initiated in highly weathered and fractured metasedimentary rocks. In this study, an unstable slope inventory was created using the Unstable Slope Management Program for Federal Land Management Agencies protocols. Hazards and risks were evaluated for 285 unstable slopes along 243.67 km of roadway. Kernel density estimation was used to identify unstable slope hotspots and establish 14 sites for site-specific investigations to evaluate potential impacts of discrete unstable slopes along major roadways. Two-dimensional probabilistic rockfall simulations and acid-base accounting tests were used to predict rockfall pathways and evaluate the acid-producing potential of rocks. Simulations indicated that rock material would likely enter the roadway at all 14 sites. Acid-base accounting test results indicated that slaty rocks of the Anakeesta Formation and graphitic schist of the Wehutty Formation are primary acid-producing rocks in rockfall-prone areas. This research illustrates an approach for prioritizing areas for site-specific investigations towards the goal of improving safety in GRSM, including developing mitigation strategies for rockfall by widening ditches, installing barriers, and encapsulating acidic rockfall material.

Seismically induced rockfall hazard from a physically based model and ground motion scenarios in Italy

The majority of landslide susceptibility and hazard zonations are implemented with statistical methods, especially on large scales: mostly because the data needed for physical simulations are only available in small areas. Physically–based simulations for slope stability are conceptually different from widely used statistical approaches. Both methods have specific advantages, depending on available data, their type and resolution, and the aim of the study. Here, we perform a hazard zonation based on the physical model STONE for the simulation of rockfalls, at 10 m resolution consistently all over Italy, and aggregating results at the slope unit level. The novelties, here, are: (i) the introduction of a seismic trigger for rockfalls, which adds a temporal component to an intrinsically static model and allows to obtain an estimate of seismically induced rockfall hazard, (ii) high–resolution application of the model at national scale, and (iii) implementation of the results in a WebGIS. Peak ground acceleration maps with different return times including seismic amplification represent the earthquake trigger. A data–driven map of possible rockfall sources all over Italy, mapped by experts in sample representative locations, allowed statistical generalization to unsurveyed areas, at national scale. Eventually, application of a simple linear transformation, to map values of peak ground acceleration into activation probability of sources, links “static” rockfall simulations with “dynamic”, time–dependent triggering. Results are maps of rockfall susceptibility with different return times, i.e., a step forward to the full assessment of rockfall hazard. Maps of hazard values and corresponding uncertainties, aggregated at slope unit level and categorized, are readily available for download, and for visualization in the new WebGIS. The new model for seismic triggering of rockfalls can be applied at the local and regional scale, calibrated with specific earthquake events instead of the return time scenarios considered here. On the temporal scale, this approach in principle is suited for application in near–real time.

The Influence of the DSM Spatial Resolution in Rockfall Simulation and Validation with In Situ Data

Remote sensing constitutes an advantageous tool towards the landslide/rockfall susceptibility mapping by incorporating optical satellite or radar data and photogrammetric data in Geographical Information System environment. A plethora of rockfall data can be derived by gigital surface models (DSMs). This article focuses on the effect of the spatial resolution of DSMs in rockfall investigations solely. DSMs with pixel size ranging from 5 cm to 90 m were taken into account for the study of three different rockfall events occurring in Western Greece, namely, at Moira, Myloi and Platiana settlements. Elevation profiles along the rockfall bodies were created from the diverse DSMs in GIS environment. Then, these profiles were implemented into the RocFall software for 2D rockfall simulations. The produced simulations were evaluated against their spatial resolution of DSMs and were confirmed with field observations and measurements. The ultimate scope of this paper is to conclude to the most appropriate DSM for rockfall simulations via RocFall software. It is observed that DSMs with high spatial resolution depicted a detailed and realistic topography, while DSMs with coarse/low resolution flattened the surface roughness. As rockfall simulations are linked to slope profile, this observation has an impact on RocFall outcomes. According to this study the most appropriate DSM, pertaining to this type of research, is the UAV, which produces the more accurate and realistic results. These results were assessed through the use of in situ measurements taken by the real rockfall events.

Rockfall Intensity under Seismic and Aseismic Conditions: The Case of Lefkada Island, Greece

Rockfall analysis is a multiparametric procedure with many uncertainties and the outputs are largely dependent on some critical engineering geological parameters involved in the used simulation model. In this paper, three completely different limestone rock sequences, named Pantokratoras, Vigla, and Paxos limestones along the western coastal slopes of Lefkada island, in Greece, are examined regarding their rockfall susceptibility as expressed by produced kinetic energy, under aseismic and seismic conditions. A rockfall inventory was prepared through detailed field measurements after the extensive rockfalls which were caused by the strong earthquake of November 2015, while engineering geological surveys were systematically conducted on the limestone rock masses. Two case scenarios were adopted for the rockfall simulations: one without the horizontal initial velocity of the detached rock boulder and the other with an estimated value obtained from the peak ground velocity (PGV) of the main seismic shock. Two-dimensional rockfall simulations were performed in selected cross-sections for each rock mass, and spatial distribution maps of the intensity (kinetic energy) were generated. A comparison of the maps has shown a strong maximum variation in the intensity levels among the three rock masses mainly due to the differential size of the detached boulders because of the inherent engineering geological characteristics of the rock masses. The results show that the earthquake ground velocity generally leads to a fluctuating change in the intensity values due to the trajectory shape and increases the rockfall magnitude as the main triggering factor.

Design of falling rock preventive countermeasure based on three-dimensional simulation

To rationally design rockfall countermeasures, detailed rockfall behavior must be predicted using numerical simulations based on the conditions of slopes and rockfalls. In this study, we perform a rockfall simulation using discontinuous deformation analysis. This method is used to analyze the motion between blocks composed of polygons of arbitrary elastic bodies; furthermore, the energy conservation law and the uniqueness/convergence of the solution are guaranteed for the entire analysis target. Additionally, the rockfall shape is reproduced in detail. Both the rockfall shape and a parameter known as the velocity energy ratio, which indicates the decay of energy at the collision time of the rockfall, significantly affect the rockfall behavior. In this study, we model the actual slope shape from data measured via airborne laser and quantitatively evaluate the effect via simulations by changing the rockfall shape and velocity energy ratio. In this paper, we consider how to use the simulation for the design of rockfall countermeasures based on the results such as the change in the amount of jumping due to the difference in slope shape, geology, and rockfall shape.

Modeling deadwood for rockfall mitigation assessments in windthrow areas

Abstract. Studying how deadwood mitigates the rockfall hazard in mountain forests is key to understanding the influence of climate-induced disturbances on the protective capacity of mountain forests. Both experimental quantification and numerical process modeling are needed to address this question. Modeling provides detailed insights into the rock–deadwood interaction and can therefore be used to develop effective forest management strategies. Here, we introduce an automatic deadwood generator (ADG) for assessing the impact of fresh woody storm debris on the protective capacity of a forest stand against rockfall. The creation of various deadwood scenarios allows us to directly quantify the mitigation potential of deadwood. To demonstrate the functionality of the proposed ADG method, we compare deadwood log patterns, deadwood effective height, and mesoscale surface ruggedness observed in field surveys in a natural windthrow area with their simulated counterparts. Specifically, we consider two sites near Lake Klöntal, Switzerland, where a major windthrow event occurred in 2019. We perform rockfall simulations for the time (a) before, (b) directly after, and (c) 10 years after the windthrow event. We further compare the results with (d) a simulation with complete clearing of the thrown wood: in other words, a scenario with no standing forest remaining. We showcase an integration of deadwood into rockfall simulations with realistic deadwood configurations alongside a diameter at breast height (DBH)- and rot-fungi-dependent maximum deadwood breaking energy. Our results confirm the mitigation effect of deadwood, which significantly reduces the jump heights and velocities of 400 kg rocks. Our modeling results suggest that, even a decade after the windthrow event, deadwood has a stronger protective effect against rockfall than that provided by standing trees. We conclude that an ADG can contribute to the decision-making involved in forest and deadwood management after disturbances.

The Suitability of UAV-Derived DSMs and the Impact of DEM Resolutions on Rockfall Numerical Simulations: A Case Study of the Bouanane Active Scarp, Tétouan, Northern Morocco

Rockfall simulations constitute the first step toward hazard assessments and can guide future rockfall prevention efforts. In this work, we assess the impact of digital elevation model (DEM) resolution on the accuracy of numerical rockfall simulation outputs. For this purpose, we compared the simulation output obtained using 1 m, 2 m and 3 m resolution UAV-derived DEMs, to two other models based on coarser topographic data (a 5 m resolution DEM obtained through interpolating elevation contours and the Shuttle Radar Topographic Mission 30m DEM). To generate the validation data, we conducted field surveys in order to map the real trajectories of three boulders that were detached during a rockfall event that occurred on 1 December 2018. Our findings suggest that the use of low to medium-resolution DEMs translated into large errors in the shape of the simulated trajectories as well as the computed runout distances, which appeared to be exaggerated by such models. The geometry of the runout area and the targets of the potential rockfall events also appeared to be different from those mapped on the field. This hindered the efficiency of any prevention or correction measures. On the other hand, the 1m UAV-derived model produced more accurate results relative to the field data. Therefore, it is accurate enough for rockfall simulations and hazard research applications. Although such remote sensing techniques may require additional expenses, our results suggest that the enhanced accuracy of the models is worth the investment.

Rockfall trajectory reconstruction: a flexible method utilizing video footage and high-resolution terrain models

Abstract. Many examples of rockfall simulation software provide great flexibility to the user at the expense of a hardly achievable parameter unification. With sensitive site-dependent parameters that are hardly generalizable from the literature and case studies, the user must properly calibrate simulations for the desired site by performing back-calculation analyses. Thus, rockfall trajectory reconstruction methods are needed. For that purpose, a computer-assisted videogrammetric 3D trajectory reconstruction method (CAVR) built on earlier approaches is proposed. Rockfall impacts are visually identified and timed from video footage and are manually transposed on detailed high-resolution 3D terrain models that act as the spatial reference. This shift in reference removes the dependency on steady and precisely positioned cameras, ensuring that the CAVR method can be used for reconstructing trajectories from witnessed previous records with nonoptimal video footage. For validation, the method is applied to reconstruct some trajectories from a rockfall experiment performed by the WSL Institute for Snow and Avalanche Research SLF. The results are compared to previous ones from the SLF and share many similarities. Indeed, the translational energies, bounce heights, rotational energies, and impact positions against a flexible barrier compare well with those from the SLF. The comparison shows that the presented cost-effective and flexible CAVR method can reproduce proper 3D rockfall trajectories from experiments or real rockfall events.

Risk Assessment and Mitigation Evaluation for Rockfall Hazards at the Diversion Tunnel Inlet Slope of Jinchuan Hydropower Station by Using Three-dimensional Terrestrial Scanning Technology

Rockfall is a major geological disaster that frequently occurs on rock slopes in alpine and gorge regions and poses a significant threat to life and property in areas exposed to rockfall hazards. In this study, a methodology is presented for comprehensive rockfall hazard analysis, including data acquisition, source identification, numerical simulation, quantitative assessment and mitigation evaluation. A high-precision and high-resolution digital terrain model (DTM) is generated based on the point cloud data obtained by terrestrial laser scanning (TLS) and is utilized for rockfall simulation and automatic identification of structural planes. The model parameters are calibrated by three-dimensional (3D) back analysis, and the rockfall motion is simulated based on a probabilistic model and an energy dissipation model. Rockfall mitigation under passive protection is evaluated according to the rockfall interception ratio (RIR), hazard reduction rate (HRR) and statistics of the rockfall characteristics and hazards within the rockfall threat area. Under the influence of construction excavation, the diversion tunnel inlet slope of Jinchuan Hydropower Station has suffered from a series of rockfall events and potential overall instability, which has become a great threat to the construction personnel, equipment and vehicles below the slope. Thus, the presented methodology is applied to thoroughly study the example case of the rockfall events at the inlet slope of the diversion tunnel of Jinchuan Hydropower Station. The advantages, limitations and notes of each link of the presented methodology are discussed, and the suggestion of strengthening the cracked area with integral active support is proposed.