Rockfall fragmentation simulations of real scale tests

2020 ◽  
Author(s):  
Gerard Matas ◽  
Nieves Lantada ◽  
Jordi Corominas ◽  
Josep Antoni Gili ◽  
Roger Ruiz-Carulla ◽  
...  
Keyword(s):  
Size Distribution ◽  
Block Size ◽  
Energy Conditions ◽  
Fragmentation Model ◽  
Model Parameters ◽  
Size Distributions ◽  
Lumped Mass ◽  
Fractal Fragmentation ◽  
The Impact ◽  
Real Scale

<p>Consideration of fragmentation during rockfalls is relevant for the assessment of hazard since it affects the number of generated blocks, their trajectories and impact energies, which also depends on the topography. Recently many scholars have paid attention to these phenomena since there are still many uncertainties around fragmentation regarding how mass and energy are distributed after fragmentation and how trajectory dispersion affects risk analysis. We developed a specific fragmentation model (Rockfall Fractal Fragmentation Model), as well as a 3D trajectory simulator called RockGIS with the fragmentation module implemented. In this contribution, we present the calibration of our rockfall trajectory simulator, based on real scale fragmentation tests performed on a quarry.</p><p>The RockGIS model considers a lumped mass approach and accounts block fragmentation upon impact with the terrain. Some improvements have been made on the simulator code regarding the consideration of rotation inside the kinematics of the model and restitution factors. The block size distributions obtained from natural rockfall events inventoried, as well as from the real scale fragmentation tests in a quarry, shows a fractal behaviour. On this way, the fractal fragmentation model implemented in the RockGIS simulator is able to reproduce the observed block size distributions.</p><p>To calibrate the model we used data gathered from a real scale rockfall test performed in a quarry. We calibrate the relations between the impact energy conditions and the fragmentation model parameters to generate the measured fragments size distribution. The initial volume of the tested blocks were measured manually using a tape and the release positions of the blocks were obtained with terrestrial photogrammetry. Both, the volume and spatial distribution of the fragments after each release were measured on the orthophotos obtained from UAV flights. Three calibration criteria were considered: runout distribution, volume distribution and cumulative volume as a function of the runout. Finally, the degree of fragmentation can be adjusted in the simulations allowing the comparison between different possible hazard scenarios (null, moderate, or severe fragmentation).</p><p>Finally, the results of the calibration shows that the RockGIS is able to reproduce the fragmentation behaviour in terms of block size distribution after breakage, as well as the spatial propagation, being a new tool with capabilities to assess the hazard related with fragmental rockfalls and the consequently risk associated.</p><p><span>The RockGIS tool and the fragmentation model based on the data collected from recent rockfall events have been developed within the RockRisk (2014-2016, BIA2013-42582-P) and RockModels (2016-2019, BIA2016-75668-P, AEI/FEDER, UE) projects. Both projects were funded by the Spanish Ministerio de Economía y Competitividad.</span></p>

scholarly journals Controls on the grain size distribution of landslides in Taiwan: the influence of drop height, scar depth and bedrock strength

2021 ◽  
Vol 9 (4) ◽  
pp. 995-1011
Author(s):  
Odin Marc ◽  
Jens M. Turowski ◽  
Patrick Meunier
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Block Size ◽  
Fragmentation Model ◽  
Size Distributions ◽  
Drop Height ◽  
Size Segregation ◽  
Grain Size Distributions ◽  
Strong Segregation

Abstract. The size of grains delivered to rivers by hillslope processes is thought to be a key factor controlling sediment transport, long-term erosion and the information recorded in sedimentary archives. Recently, models have been developed to estimate the grain size distribution produced in soil, but these models may not apply to active orogens where high erosion rates on hillslopes are driven by landsliding. To date, relatively few studies have focused on landslide grain size distributions. Here, we present grain size distributions (GSDs) obtained by grid-by-number sampling on 17 recent landslide deposits in Taiwan, and we compare these GSDs to the geometrical and physical properties of the landslides, such as their width, area, rock type, drop height and estimated scar depth. All slides occurred in slightly metamorphosed sedimentary units, except two, which occurred in younger unmetamorphosed shales, with a rock strength that is expected to be 3–10 times weaker than their metamorphosed counterparts. For 11 landslides, we did not observe substantial spatial variations in the GSD over the deposit. However, four landslides displayed a strong grain size segregation on their deposit, with the overall GSD of the downslope toe sectors being 3–10 times coarser than apex sectors. In three cases, we could also measure the GSD inside incised sectors of the landslides deposits, which presented percentiles that were 3–10 times finer than the surface of the deposit. Both observations could be due to either kinetic sieving or deposit reworking after the landslide failure, but we cannot explain why only some deposits had strong segregation. Averaging this spatial variability, we found the median grain size of the deposits to be strongly negatively correlated with drop height, scar width and depth. However, previous work suggests that regolith particles and bedrock blocks should coarsen with increasing depth, which is the inverse of our observations. Accounting for a model of regolith coarsening with depth, we found that the ratio of the estimated original bedrock block size to the deposit median grain size (D50) of the deposit was proportional to the potential energy of the landslide normalized to its bedrock strength. Thus, the studied landslides agree well with a published, simple fragmentation model, even if that model was calibrated on rock avalanches with larger volume and stronger bedrock than those featured in our dataset. Therefore, this scaling may serve for future modeling of grain size transfer from hillslopes to rivers, with the aim to better understanding landslide sediment evacuation and coupling to river erosional dynamics.

The RockModels Project: Rockfalls Characterization and Modelling

2020 ◽  
Author(s):  
Nieves Lantada ◽  
Jordi Corominas ◽  
Josep A. Gili ◽  
Gerard Matas ◽  
Roger Ruiz-Carulla ◽  
...  
Keyword(s):  
Size Distribution ◽  
Empirical Data ◽  
High Speed ◽  
Block Size ◽  
Open Pit ◽  
Fragmentation Model ◽  
3D Point Clouds ◽  
The Impact ◽  
Block Size Distribution ◽  
Unstable Rock

<p>A rockfall is a rapid mass movement generated by the detachment of a rock volume from the slope that falls, rolls and bounces during its propagation downhill. Rockfalls have great destructive potential due to the high kinetic and impact energies that may reach during the propagation. Rockfalls are frequent instability processes in road cuts, open pit mines and quarries, steep slopes and cliffs. The initial mobilized mass can be either a single massive block or a set of blocks defined by the joints present in the massif. During the propagation, the block or blocks detached may break when impacts against the terrain, producing a distribution of fragments with independent trajectories. Knowledge of the size and trajectory of the blocks resulting from fragmentation is critical for the assessment of the potential damage and the design of protective structures.</p><p>In this contribution, we summarise the main achievements of the RockModels project (BIA2016-75668-P, AEI/FEDER,UE). This project aims at quantifying the risk induced by fragmental rockfalls, by developing quantitative risk assessment methodologies and providing tools to improve its prevention and mitigation. It has three general objectives: i) Explicit identification of unstable rock volumes and stability assessment; ii)Development and validation of a fragmentation model, iii) Rockfall propagation analysis by means of the development of a 3D simulator tool and its calibration.</p><p>The use of geomatic techniques such as terrestrial photogrammetry or from UAV allow the generation of high-resolution 3D models of cliffs and the joint system characterization based on 3D point clouds. The orientation and persistence of joints within the rock mass define the kinematically unstable rock volumes and determine the initial block size distribution.  We inventoried fragmental rockfalls occurred in Spain by obtaining a 3D model, the orthophoto, specific cartographies and detailed volumes measurements to obtain the block size distribution in the deposits of each event. The fragmental rockfalls inventory have been collected in a spatial database using PostGIS and following the INSPIRE directive for natural hazards. This data can be consulted at different scales with a developed Web Map Service (WMS) (https://rockdb.upc.edu/). The inventory is the empirical data used to developed, calibrate and validate the Rockfall Fractal Fragmentation Model proposed, as well as the 3D trajectory simulator RockGIS that incorporates the fragmentation module.</p><p>More empirical data has been obtained by performing 4 real scale fragmentation test in a quarry. The impact of each block and trajectories of the fragments were recorded by several high speed cameras from different points of view. A program has been implemented to measure the kinematics of each tested block using the high-speed videos. The obtained kinematic parameters have been used for the calibration of the RockGIS simulator. An additional essay was carry out at laboratory to study the effect of the comminution among blocks. The distribution of fragments obtained confirms that the blocks undergoing greater confinement generate a greater number of fragments decreasing their maximum volume.</p>

scholarly journals Simulation of Full-Scale Rockfall Tests with a Fragmentation Model

Geosciences ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 168 ◽  
Author(s):  
Gerard Matas ◽  
Nieves Lantada ◽  
Jordi Corominas ◽  
Josep Gili ◽  
Roger Ruiz-Carulla ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Spatial Distribution ◽  
Parametric Analysis ◽  
Fractal Model ◽  
Stochastic Program ◽  
Fragmentation Model ◽  
Volume Distribution ◽  
Fractal Fragmentation ◽  
The Impact ◽  
Real Scale

In this paper, we present the upgraded version of RockGIS, a stochastic program for the numerical simulation of rockfalls and their fragmentation, based on a fractal model. The code has been improved to account for a range of fragmentation scenarios, depending on the impact conditions. In the simulation, the parameters of the fractal fragmentation model that define the sizes of the generated fragments were computed at each impact according to the kinematic conditions. The performance of the upgraded code was verified and validated by real-scale rockfall tests performed in a quarry. The tests consisted of the release of 21 limestone blocks. For each release, the size and spatial distribution of the fragments generated by the impacts were measured by hand and from orthophotos taken via drone flights. The trajectories of the blocks and the resulting fragments were simulated with the code and calibrated with both the volume distribution and the runout distances of the fragments. Finally, as all the relevant rockfall parameters involved were affected by strong uncertainty and spatial variability, a parametric analysis was carried out and is discussed.

Pierre3D: a 3D stochastic rockfall simulator based on random ground roughness and hyperbolic restitution factors

2015 ◽  
Vol 52 (9) ◽  
pp. 1360-1373 ◽  
Author(s):  
Valentin S. Gischig ◽  
Oldrich Hungr ◽  
Andrew Mitchell ◽  
Franck Bourrier
Keyword(s):  
Stochastic Process ◽  
Slope Angle ◽  
Test Site ◽  
Fine Tuning ◽  
Model Parameters ◽  
Observation Data ◽  
Lumped Mass ◽  
Forest Road ◽  
Rockfall Hazard ◽  
The Impact

The use of dynamic computational methods has become indispensable for addressing problems related to rockfall hazard. Although a number of models with various degrees of complexity are available, model parameters are rarely calibrated against observations from rockfall experiments. A major difficulty lies in reproducing the apparent randomness of the impact process related to both ground and block irregularities. Calibration of rigorous methods capable of explicitly modeling trajectories and impact physics of irregular blocks is difficult, as parameter spaces become too vast and the quality of model input and observation data are insufficient. The model presented here returns to the simple “lumped-mass” approach and simulates the characteristic randomness of rockfall impact as a stochastic process. Despite similarities to existing approaches, the model presented here incorporates several novel concepts: (i) ground roughness and particle roughness are represented as a random change of slope angle at impact; (ii) lateral deviations of rebound direction from the trajectory plane at impact are similarly accounted for by perturbing the ground orientation laterally, thus inducing scatter of run-out directions; and (iii) a hyperbolic relationship connects restitution factors to impact deformation energy. With these features, the model is capable of realistically accounting for the influence of particle mass on dynamic behaviour. The model only requires four input parameters, rendering it flexible for calibration against observed datasets. In this study, we calibrate the model against observations from the rockfall test site at Vaujany in France. The model is able to reproduce observed distributions of velocity, jump heights, and runout at observation points. In addition, the spatial distribution of the trajectories and landing points has been successfully simulated. Different parameter sets have been used for different ground materials such as an avalanche channel, a forest road, and a talus cone. Further calibration of the new model against a range of field datasets is essential. This study is part of an extensive calibration program that is still in progress at this first presentation of the method, and focuses on fine-tuning the details of the stochastic process implemented both in two-dimensional (2D) and three-dimensional (3D) versions of the model.

scholarly journals Controls on the grain size distribution of landslides in Taiwan: the influence of drop height, scar depth and bedrock strength

2021 ◽  
Author(s):  
Odin Marc ◽  
Jens M. Turowski ◽  
Patrick Meunier
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Block Size ◽  
Fragmentation Model ◽  
Drop Height ◽  
Size Segregation ◽  
Key Factor ◽  
Grain Size Distributions ◽  
Strong Segregation

Abstract. The size of grains delivered to river by hillslopes processes is thought to be a key factor to better understand sediment transport, long-term erosion as well as sedimentary archives. Recently, models have been developed for the grain size distribution produced in soil, but they may not apply to active orogens where high erosion rates on hillslopes are driven by landsliding. Until now relatively few studies have focused on landslide grain size distributions. Here we present grain size distribution 5 (GSD) obtained by the grid-by-number sampling on 17 recent landslide deposits in Taiwan, and we compare it to the geometrical and physical properties of the landslides, such as their width, area, rock-type, drop height and estimated depth. All slides occurred in slightly metamorphosed sedimentary units, except two, which occurred in younger unmetamorphosed shales, with rock strength expected to be 3 to 10 times weaker from their metamorphosed counterparts. We found that 4 deposits displayed a strong grain-size segregation on their deposit with downslope toe deposits 3 to 10 times coarser than apex 10 deposits. In 3 cases, we could also measure the GSD inside the landslides that presented percentiles 3 to 10 times finer than the surface of the deposit. Both observations could be due to either kinetic sieving or deposit reworking after the landslide failure but we cannot explain why only some deposits had a strong segregation. Averaging this spatial variability we found the median grainsize of the deposits to be strongly negatively correlated to drop height, scar width and depth. However, previous work suggest that regolith particles and bedrock blocks should coarsen with increasing depth, opposite to our observation. 15 Accounting for a model of regolith coarsening with depth, we found that the ratio of the original bedrock block size and the D50 was proportional the potential energy of the landslide normalized to its bedrock strength. Thus the studied landslides agree well with a published, simple fragmentation model, even if that model was calibrated on much larger and much stronger rock avalanches than those featured in our dataset. This scaling may thus serve for future model of grain size transfer from hillslopes to river, trying to better understand landslide sediment evacuation and coupling to river erosional dynamics.

scholarly journals Grain-size distribution unmixing using the R package EMMAgeo

2019 ◽  
Vol 68 (1) ◽  
pp. 29-46 ◽  
Author(s):  
Elisabeth Dietze ◽  
Michael Dietze
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Synthetic Data ◽  
Model Parameters ◽  
Size Distributions ◽  
Sediment Sources ◽  
Data Set ◽  
Depositional Processes ◽  
Grain Size Distributions

Abstract. The analysis of grain-size distributions has a long tradition in Quaternary Science and disciplines studying Earth surface and subsurface deposits. The decomposition of multi-modal grain-size distributions into inherent subpopulations, commonly termed end-member modelling analysis (EMMA), is increasingly recognised as a tool to infer the underlying sediment sources, transport and (post-)depositional processes. Most of the existing deterministic EMMA approaches are only able to deliver one out of many possible solutions, thereby shortcutting uncertainty in model parameters. Here, we provide user-friendly computational protocols that support deterministic as well as robust (i.e. explicitly accounting for incomplete knowledge about input parameters in a probabilistic approach) EMMA, in the free and open software framework of R. In addition, and going beyond previous validation tests, we compare the performance of available grain-size EMMA algorithms using four real-world sediment types, covering a wide range of grain-size distribution shapes (alluvial fan, dune, loess and floodplain deposits). These were randomly mixed in the lab to produce a synthetic data set. Across all algorithms, the original data set was modelled with mean R2 values of 0.868 to 0.995 and mean absolute deviation (MAD) values of 0.06 % vol to 0.34 % vol. The original grain-size distribution shapes were modelled as end-member loadings with mean R2 values of 0.89 to 0.99 and MAD of 0.04 % vol to 0.17 % vol. End-member scores reproduced the original mixing ratios in the synthetic data set with mean R2 values of 0.68 to 0.93 and MAD of 0.1 % vol to 1.6 % vol. Depending on the validation criteria, all models provided reliable estimates of the input data, and each of the models exhibits individual strengths and weaknesses. Only robust EMMA allowed uncertainties of the end-members to be objectively estimated and expert knowledge to be included in the end-member definition. Yet, end-member interpretation should carefully consider the geological and sedimentological meaningfulness in terms of sediment sources, transport and deposition as well as post-depositional alteration of grain sizes. EMMA might also be powerful in other geoscientific contexts where the goal is to unmix sources and processes from compositional data sets.

scholarly journals Effects of near-source coagulation of biomass burning aerosols on global predictions of aerosol size distributions and implications for aerosol radiative effects

2019 ◽  
Vol 19 (9) ◽  
pp. 6561-6577 ◽  
Author(s):  
Emily Ramnarine ◽  
John K. Kodros ◽  
Anna L. Hodshire ◽  
Chantelle R. Lonsdale ◽  
Matthew J. Alvarado ◽  
...  
Keyword(s):  
Size Distribution ◽  
Biomass Burning ◽  
Indirect Effect ◽  
Size Distributions ◽  
Aerosol Indirect Effect ◽  
Fresh Biomass ◽  
Biomass Burning Aerosol ◽  
Aerosol Radiative Effects ◽  
The Impact ◽  
Aerosol Radiative

Abstract. Biomass burning is a significant global source of aerosol number and mass. In fresh biomass burning plumes, aerosol coagulation reduces aerosol number and increases the median size of aerosol size distributions, impacting aerosol radiative effects. Near-source biomass burning aerosol coagulation occurs at spatial scales much smaller than the grid boxes of global and many regional models. To date, these models have ignored sub-grid coagulation and instantly mixed fresh biomass burning emissions into coarse grid boxes. A previous study found that the rate of particle growth by coagulation within an individual smoke plume can be approximated using the aerosol mass emissions rate, initial size distribution median diameter and modal width, plume mixing depth, and wind speed. In this paper, we use this parameterization of sub-grid coagulation in the GEOS-Chem–TOMAS (TwO-Moment Aerosol Sectional) global aerosol microphysics model to quantify the impacts on global aerosol size distributions, the direct radiative effect, and the cloud-albedo aerosol indirect effect. We find that inclusion of biomass burning sub-grid coagulation reduces the biomass burning impact on the number concentration of particles larger than 80 nm (a proxy for CCN-sized particles) by 37 % globally. This cloud condensation nuclei (CCN) reduction causes our estimated global biomass burning cloud-albedo aerosol indirect effect to decrease from −76 to −43 mW m−2. Further, as sub-grid coagulation moves mass to sizes with more efficient scattering, including it increases our estimated biomass burning all-sky direct effect from −224 to −231 mW m−2, with assumed external mixing of black carbon and from −188 to −197 mW m−2 and with assumed internal mixing of black carbon with core-shell morphology. However, due to differences in fire and meteorological conditions across regions, the impact of sub-grid coagulation is not globally uniform. We also test the sensitivity of the impact of sub-grid coagulation to two different biomass burning emission inventories to various assumptions about the fresh biomass burning aerosol size distribution and to two different timescales of sub-grid coagulation. The impacts of sub-grid coagulation are qualitatively the same regardless of these assumptions.

scholarly journals Effects of Near-Source Coagulation of Biomass Burning Aerosols on Global Predictions of Aerosol Size Distributions and Implications for Aerosol Radiative Effects

2018 ◽  
Author(s):  
Emily Ramnarine ◽  
John K. Kodros ◽  
Anna L. Hodshire ◽  
Chantelle R. Lonsdale ◽  
Matthew J. Alvarado ◽  
...  
Keyword(s):  
Size Distribution ◽  
Biomass Burning ◽  
Indirect Effect ◽  
Size Distributions ◽  
Aerosol Indirect Effect ◽  
Fresh Biomass ◽  
Biomass Burning Aerosol ◽  
Aerosol Radiative Effects ◽  
The Impact ◽  
Aerosol Radiative

Abstract. Biomass burning is a significant global source of aerosol number and mass. In fresh biomass burning plumes, aerosol coagulation reduces aerosol number and increases the median size of aerosol size distributions, impacting aerosol radiative effects. Near-source biomass burning aerosol coagulation occurs at spatial scales much smaller than the grid boxes of global and many regional models. To date, these models ignore sub-grid coagulation and instantly mix fresh biomass burning emissions into coarse grid boxes. A previous study found that the rate of particle growth by coagulation within an individual smoke plume can be approximated using the aerosol mass emissions rate, initial size distribution median diameter and modal width, plume mixing depth, and wind speed. In this paper, we use this parameterization of sub-grid coagulation in the GEOS-Chem-TOMAS global aerosol microphysics model to quantify the impacts on global aerosol size distributions, the direct radiative effect, and the cloud-albedo aerosol indirect effect. We find that inclusion of biomass burning sub-grid coagulation reduces the biomass burning impact on the number concentration of particles larger than 80 nm (a proxy for CCN-sized particles) by 37 % globally. This CCN reduction causes our estimated global biomass burning cloud-albedo aerosol indirect effect to decrease from −76 to −43 mW m−2. Further, as sub-grid coagulation moves mass to sizes with more efficient scattering, including it increases our estimated biomass burning all-sky direct effect from −224 to −231 mW m−2 with assumed external mixing and from −188 to −197 mW m−2 with assumed internal mixing with core-shell morphology. However, due to differences in fire and meteorological conditions across regions, the impact of sub-grid coagulation is not globally uniform. We also test the sensitivity of the impact of sub-grid coagulation to two different biomass burning emission inventories, to various assumptions about the fresh biomass burning aerosol size distribution, and to two different timescales of sub-grid coagulation. The impacts of sub-grid coagulation are qualitatively the same regardless of these assumptions.

FRAGMENTATION OF SOIL INITIATORS: APPLICATION OF THE PORE-SOLID FRACTAL MODEL

Fractals ◽  
2004 ◽  
Vol 12 (04) ◽  
pp. 357-363 ◽  
Author(s):  
H. MILLÁN
Keyword(s):  
Size Distribution ◽  
Fragment Size ◽  
Fractal Model ◽  
Scaling Factor ◽  
Size Distributions ◽  
Fractal Approach ◽  
Fractal Models ◽  
Distribution Probability ◽  
Scaling Parameters ◽  
Fractal Fragmentation

The quantification of fragmentation of natural, polidisperse, porous media using fractal models is well documented in the literature. However, in many cases, fractal exponents (fractal fragmentation dimension) and coefficients (fractal lacunarity) arising from a power law behavior do not make clear differences between different media. In the present work, the pore-solid fractal (PSF) model was used as a new fractal approach for deriving four scaling parameters (fractal dimension of the particle-size distribution, fractal fragmentation dimension of the fragment-size distribution, probability of fragmentation and scaling factor) from soil initiators subjected to different energy density input. The fractal fragmentation dimension for all soil samples was Df=2.42±0.16 without correlating with the energy expended in the fragmentation process. By contrast, probability of fragmentation and scaling factor correlated significantly with the energetic term. The PSF model is useful for estimating a group of scaling parameters more appropriate for the quantification of complex patterns associated to fragment-size distributions.

Size Distributions of Asteroidal Dust: Possible Constraints on Impact Strengths

1996 ◽  
Vol 150 ◽  
pp. 473-476
Author(s):  
Daniel D. Durda ◽  
Stanley F. Dermott
Keyword(s):  
Size Distribution ◽  
Size Distributions ◽  
Scaling Properties ◽  
Equilibrium Size ◽  
Asteroidal Dust ◽  
The Impact ◽  
Impact Experiments ◽  
Asteroid Families

AbstractWe present results of a numerical collisional model which shows that the slope index of the equilibrium size distribution is dependent upon the size-strength scaling properties of the colliding bodies. This implies that individual asteroid families or distinct taxonomic classes within the mainbelt asteroid population may evolve different equilibrium size distributions. Well constrained observations of the size distribution over particular size ranges may allow constraints to be placed on the impact strengths of particles much larger or smaller than are capable of being measured in laboratory impact experiments.

Sign in / Sign up

Export Citation Format

Share Document