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Comparison of block size distribution in rockfalls

Profile image of Olga MavrouliOlga Mavrouli
https://doi.org/10.1007/S10346-015-0600-7
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Abstract

Rock masses detached as rockfalls usually disintegrate upon impact on the ground surface. The knowledge of the rockfall block size distribution (RBSD) generated in the rockfall deposit is useful for the analysis of the trajectories of the rock blocks, runout distances, impact energies and for the quantitative assessment of the rockfall hazard. Obtaining the RBSD of a large rockfall deposit may become a challenge due to the high number of blocks to be measured. In this paper, we present a methodology developed for mid-size fragmental rockfalls (10 3 up to 10 5 m 3) and its application to the Cadí massif, Eastern Pyrenees. The methodology consists of counting and measuring block fragments in selected sampling plots within homogeneous zones in the young debris cover generated by the rockfall along with all the large scattered rock blocks. The size distribution of blocks obtained in the sampling plots is extrapolated to the whole young debris cover and summed to the inventoried large scattered blocks to derive the RBSD of the whole rockfall event. The obtained distributions from the fragments can be well fitted by a power law distribution, indicating the scale invariant character of the fragmentation process (Hartmann (Icarus 2(2):201-203, 1969); Turcotte (J Geophys Res 91(NO B2):1921-1926, 1986). The total volume of the rockfall fragments has been checked against the volume at the rockfall source. The latter has been calculated comparing 3D digital surface models before and after the rockfall event.

Figures (16)
Fig. 1 Fragmental rockfall at La Guingueta, Central Pyrenees, Spain. The trajectories of the large scattered blocks diverge after the impact of the rock mass upon the ground surface. A young debris cover, composed of small-size blocks, has been deposited close to the rockfall source
Fig. 1 Fragmental rockfall at La Guingueta, Central Pyrenees, Spain. The trajectories of the large scattered blocks diverge after the impact of the rock mass upon the ground surface. A young debris cover, composed of small-size blocks, has been deposited close to the rockfall source
Fig. 2. Methodology followed to prepare the RBSD. The scheme shows the young debris cover (YDC), the sampling plots (orange squares) for each homogeneous zone A1 to A3 (the symbol X stands for weighted multiplication, see step 2 in the text below) and the large scattered blocks. The plots display the block size distribution where ‘Fr’ is the cumulative relative frequency for each block size bin ‘M’
Fig. 2. Methodology followed to prepare the RBSD. The scheme shows the young debris cover (YDC), the sampling plots (orange squares) for each homogeneous zone A1 to A3 (the symbol X stands for weighted multiplication, see step 2 in the text below) and the large scattered blocks. The plots display the block size distribution where ‘Fr’ is the cumulative relative frequency for each block size bin ‘M’
Fig. 3 Large scattered blocks laying on a previously existing talus deposit. New blocks stand out from the old ones by their most vivid (reddish, yellowish) colours. An almost continuous young debris cover is noticeable at the background. The red dot is the location of the picture in Fig. 4. Vilanova de Banat rockfall at the Cadi massif, Eastern Pyrenees The definition of the homogeneous zones is based on visual field observation and orthophoto interpretation. It is recommend- ed to select more than one sampling plots at each homogeneous zone in order to double check the distribution obtained. The influence of the number of homogenous zones and the selection of the sampling plots is discussed at ‘Results’ section (d). The length of the sampling plots must be at least one order of magni- tude greater than the length of the measured blocks. Consequently, the area of the sampling plots increases with the size of the blocks. Big boulders found in the YDC are considered large scattered blocks when they are more than one order of magnitude bigger than the rest of the blocks. Several constraints must be overcome. In case that rockfall fragments stop over a previously existing talus slope, only the new deposited blocks associated to the recent event are measured. A key issue is thus differentiating young from old rock fragments. When the reconnaissance is made shortly after the occurrence of the event, this should not be a difficulty. New blocks show distinct fresh broken surfaces, including faces with stained coatings and clay fills, and bright colours (Figs. 3 and 4). If the YDC is formed by a thick continuous deposit in which a percentage of blocks are buried and cannot be measured, then the counting becomes uncertain and this becomes a restriction of the proposed approach.
Fig. 3 Large scattered blocks laying on a previously existing talus deposit. New blocks stand out from the old ones by their most vivid (reddish, yellowish) colours. An almost continuous young debris cover is noticeable at the background. The red dot is the location of the picture in Fig. 4. Vilanova de Banat rockfall at the Cadi massif, Eastern Pyrenees The definition of the homogeneous zones is based on visual field observation and orthophoto interpretation. It is recommend- ed to select more than one sampling plots at each homogeneous zone in order to double check the distribution obtained. The influence of the number of homogenous zones and the selection of the sampling plots is discussed at ‘Results’ section (d). The length of the sampling plots must be at least one order of magni- tude greater than the length of the measured blocks. Consequently, the area of the sampling plots increases with the size of the blocks. Big boulders found in the YDC are considered large scattered blocks when they are more than one order of magnitude bigger than the rest of the blocks. Several constraints must be overcome. In case that rockfall fragments stop over a previously existing talus slope, only the new deposited blocks associated to the recent event are measured. A key issue is thus differentiating young from old rock fragments. When the reconnaissance is made shortly after the occurrence of the event, this should not be a difficulty. New blocks show distinct fresh broken surfaces, including faces with stained coatings and clay fills, and bright colours (Figs. 3 and 4). If the YDC is formed by a thick continuous deposit in which a percentage of blocks are buried and cannot be measured, then the counting becomes uncertain and this becomes a restriction of the proposed approach.
Fig. 4 View of the lower zone of the YDC. Almost continuous debris cover generated by the Vilanova de Banat rockfall, lying on a previously existing talus deposit. Nev blocks stand out from the old ones by their most vivid colours (reddish, yellowish). Distinct fresh fractures and spalling as a consequence of the impacts are also observed
Fig. 4 View of the lower zone of the YDC. Almost continuous debris cover generated by the Vilanova de Banat rockfall, lying on a previously existing talus deposit. Nev blocks stand out from the old ones by their most vivid colours (reddish, yellowish). Distinct fresh fractures and spalling as a consequence of the impacts are also observed
Fig. 5 Rockfall event occurred in November 2011 in Cadi massif, Eastern Pyrenees. a The rockfall source area before the occurrence of the rockfall event. b The same are after the rockfall event, including the source area (dashed red line), the young debris cover (dashed yellow line) formed in the upper zone of the talus and the larg scattered blocks (dashed red ellipses) deposited in the lower zone of the talus
Fig. 5 Rockfall event occurred in November 2011 in Cadi massif, Eastern Pyrenees. a The rockfall source area before the occurrence of the rockfall event. b The same are after the rockfall event, including the source area (dashed red line), the young debris cover (dashed yellow line) formed in the upper zone of the talus and the larg scattered blocks (dashed red ellipses) deposited in the lower zone of the talus
Table 1 Summary of blocks measured, area of the sampling plots, area of the homogeneous sectors and scaling factors
Table 1 Summary of blocks measured, area of the sampling plots, area of the homogeneous sectors and scaling factors
Fig. 6 Orthophoto map showing the location of the six homogeneous sectors of the YDC, sampling plots, the large scattered blocks and the source area
Fig. 6 Orthophoto map showing the location of the six homogeneous sectors of the YDC, sampling plots, the large scattered blocks and the source area
Fig. 7 Cumulative number of blocks measured versus block volume obtaine: directly from the measurements in the sampling plots (SP) and from the large scattered blocks (LSB)
Fig. 7 Cumulative number of blocks measured versus block volume obtaine: directly from the measurements in the sampling plots (SP) and from the large scattered blocks (LSB)
Fig. 8 Block size distributions obtained from the extrapolation of the measurements using the areas ratios, in terms of cumulative number of blocks versus block volume. The obtained RBSD is representative of the whole deposit. The power laws fitted to these distributions are also represented
Fig. 8 Block size distributions obtained from the extrapolation of the measurements using the areas ratios, in terms of cumulative number of blocks versus block volume. The obtained RBSD is representative of the whole deposit. The power laws fitted to these distributions are also represented
Fig. 9 Block size distribution obtained from the 6 sample plots (SP1-6), from the large scattered blocks (LSB), the obtained rockfall block size distribution (RBSD) and the fitted power law by linear regression method The generated RBSDs have similar shapes and are fitted well by power laws (Fig. 11). The obtained exponents range between 1.26 (six sampling plots), 1.25 (four sampling plots) and 1.22 (three sampling plots). The results show that the visual selection of the block size homogeneous zones and The frequency block size distributions in the Cadi case (Fig. 9) cannot be extrapolated for volumes bigger than the biggest blocks found. Therefore, the right end of the total RBSD is determined by the maximum block volume measured, while the extrapolation to
Fig. 9 Block size distribution obtained from the 6 sample plots (SP1-6), from the large scattered blocks (LSB), the obtained rockfall block size distribution (RBSD) and the fitted power law by linear regression method The generated RBSDs have similar shapes and are fitted well by power laws (Fig. 11). The obtained exponents range between 1.26 (six sampling plots), 1.25 (four sampling plots) and 1.22 (three sampling plots). The results show that the visual selection of the block size homogeneous zones and The frequency block size distributions in the Cadi case (Fig. 9) cannot be extrapolated for volumes bigger than the biggest blocks found. Therefore, the right end of the total RBSD is determined by the maximum block volume measured, while the extrapolation to
Table 2 Obtained values of the fitted power laws using linear regression and maximum likelihood methods
Table 2 Obtained values of the fitted power laws using linear regression and maximum likelihood methods
Fig. 10 Comparison of the fitted power laws using linear regression or maximum likelihood methods for the frequency block size distribution for each sampling plot da‘ the large scattered blocks and the final RBSD The use of two consecutive 3D models to estimate a vol- ume detached from a cliff has been discussed before (Sturzenegger and Stead 2009; Firpo et al. 2011; Viero et al. 2012). The main limitation of this case is that the topographic model is obtained with aerial photogrammetry (with an accu- racy of about 1 m in X and Y coordinates and 1.5 m in Z for the 90 % of the defined points). Meanwhile, the photogram- metric model of the scar is realised using terrestrial pictures, taken from a direction which is almost perpendicular to the aerial orthophoto. Consequently, the errors of these models To validate the proposed procedure, we used an alternative meth- od to calculate the total detached volume from the cliff for the Cadi rockfall event. The total detached volume obtained with the RBSD was approximately 8000 m*. This corresponds to the min- imum volume because blocks smaller than 0.015 m* were not measured. This value has been checked against the volume ob- tained subtracting two digital surface models (DSM). We used the topographic model at 1:5000 scale, of the Cartographic Institute ot Catalonia, generated by aerial photogrammetry before the rockfall
Fig. 10 Comparison of the fitted power laws using linear regression or maximum likelihood methods for the frequency block size distribution for each sampling plot da‘ the large scattered blocks and the final RBSD The use of two consecutive 3D models to estimate a vol- ume detached from a cliff has been discussed before (Sturzenegger and Stead 2009; Firpo et al. 2011; Viero et al. 2012). The main limitation of this case is that the topographic model is obtained with aerial photogrammetry (with an accu- racy of about 1 m in X and Y coordinates and 1.5 m in Z for the 90 % of the defined points). Meanwhile, the photogram- metric model of the scar is realised using terrestrial pictures, taken from a direction which is almost perpendicular to the aerial orthophoto. Consequently, the errors of these models To validate the proposed procedure, we used an alternative meth- od to calculate the total detached volume from the cliff for the Cadi rockfall event. The total detached volume obtained with the RBSD was approximately 8000 m*. This corresponds to the min- imum volume because blocks smaller than 0.015 m* were not measured. This value has been checked against the volume ob- tained subtracting two digital surface models (DSM). We used the topographic model at 1:5000 scale, of the Cartographic Institute ot Catalonia, generated by aerial photogrammetry before the rockfall
Fig. 11 RBSD obtained using six, four or three sampling plots
Fig. 11 RBSD obtained using six, four or three sampling plots
Fig. 12 3D visualization with the location of the used pictures (blue rectangles) and the ground control points (yellow points)
Fig. 12 3D visualization with the location of the used pictures (blue rectangles) and the ground control points (yellow points)
Fig. 13 a Picture of the scar (the rockfall detachment zone is outlined in red). b Topographic DSM (green mesh), scar DSM coloured by the distances to the topographic DSM
Fig. 13 a Picture of the scar (the rockfall detachment zone is outlined in red). b Topographic DSM (green mesh), scar DSM coloured by the distances to the topographic DSM
Fig. 14 Detached volume reconstruction (orange volume) based on the topographic DSM (top), the scar DSM coloured in brown (back, laterals and bottom parts) and two main joints (frontal face) The estimated volume is approximately 10,000 m*, which is bigger than the volume based on measured rock fall blocks (8000 m*). The 2000 m? of difference between both volumes is possibly ought to the fact that approximately the 20 % of the rock mass can result in dust and blocks smaller than 0.015 m? that were not measured in the field. In fact, by extrapolating the RBSD to a block size of 0.005 m?, a volume of 10,000 m? is obtained. Another
Fig. 14 Detached volume reconstruction (orange volume) based on the topographic DSM (top), the scar DSM coloured in brown (back, laterals and bottom parts) and two main joints (frontal face) The estimated volume is approximately 10,000 m*, which is bigger than the volume based on measured rock fall blocks (8000 m*). The 2000 m? of difference between both volumes is possibly ought to the fact that approximately the 20 % of the rock mass can result in dust and blocks smaller than 0.015 m? that were not measured in the field. In fact, by extrapolating the RBSD to a block size of 0.005 m?, a volume of 10,000 m? is obtained. Another

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References (27)

  1. Agliardi F, Crosta GB (2003) High resolution three-dimensional numerical modelling of rockfalls. Int J Rock Mech Min Sci 40:455-471
  2. Chau KT, Wong RHC, Wub JJ (2002) Coefficient of restitution and rotational motions of rockfall impacts. Int J Rock Mech Min Sci 39:69-77
  3. Clauset A, Shalizi CR, Newman MEJ (2009) Power-law distributions in empirical data. Soc Ind Appl Math (SIAM) Rev 51(4):664-703
  4. Corominas J, Mavrouli O, Santana D, Moya J (2012) Simplified approach for obtaining the block volume distribution of fragmental rockfalls. In Eberhardt E, Froese C, Turner AK, Leroueil S (eds). Landslides and engineered slopes. Taylor and Francis. 2:1159-1164
  5. Crosta G, Frattini P, Fusi F (2007) Fragmentation in the Val Pola rock avalanche, Italian Alps. J Geophys Res 112, F01006
  6. Dussauge C, Grasso J, Helmstetter A (2003) Statistical analysis of rock fall volume distributions: implications for rock fall dynamics. J Geophys Res B 108(B6):2286. doi:10.1029/2001JB000650
  7. Dussauge C, Helmstetter A, Grasso J, Hantz S, Desvarreux P, Jeannin M, Giraud A (2002) Probabilistic approach to rockfall hazard assessment: potential of historical data analysis. Nat Hazards Earth Syst Sci 2:15-26
  8. Dorren LKA (2003) A review of rockfall mechanics and modeling approaches. Prog Phys Geogr 27(1):69-87
  9. Evans S, Hungr O (1993) The assessment of rockfall hazard at the base of talus slopes. Can Geotech J 30:620-636
  10. Firpo G, Salvini R, Francioni M, Ranjith P (2011) Use of digital terrestrial photogrammetry in rocky slope stability analysis by distinct elements numerical methods. Int J Rock Mech Min Sci 48:1045-1054
  11. Giacomini A, Buzzi O, Renard B, Giani GP (2009) Experimental studies on fragmentation of rock falls on impact with rock surfaces. Int J Rock Mech Min Sci 46:708-715
  12. Hantz D, Rossetti J P, Servant F, D'Amato J (2014) Etude de la distribution des blocs dans un éboulement pour l'évaluation de l'aléa. Proceedings of Rock Slope Stability 2014, Marrakesh
  13. Hartmann WK (1969) Terrestrial, lunar and interplanetary rock fragmentation. Icarus 2(2):201-213
  14. Hecht-Nielsen R (1987) Kolmogorov's mapping neural net-work existence theorem. Proceedings of the first IEEE international conference on neural networks. San Diego, pp 11-14
  15. Hungr O, Leroueil S, Picarelli L (2014) The Varnes classification of landslides types, an update. Landslides 11:167-194
  16. Hungr O, Evans SG, Hazzard J (1999) Magnitude and frequency of rock falls and rock slides along the main transportation corridors of southwestern British Columbia. Can Geotech J 36(2):224-238. doi:10.1139/t98-106
  17. Jaboyedoff M, Dudt JP, Labiouse V (2005) An attempt to refine rockfall hazard zoning based on the kinetic energy, frequency and fragmentation degree. Nat Hazards Earth Syst Sci 5:621-632
  18. Okura Y, Kitahara H, Sammori T, Kawanami A (2000) The effects of rockfall volume on runout distance. Eng Geol 58(2):109-124
  19. Perfect E (1997) Fractal models for the fragmentation of rocks and soils: a review. Eng Geol 48:185-198
  20. Pickering G, Bull JM, Sanderson DJ (1995) Sampling power-law distributions. Tectonophysics 248:1-20
  21. Salciarini D, Tamagnini C, Conversini P (2009) Numerical approaches for rockfall analysis: a comparison, Proceedings of the 18th World IMACS/MODSIM Congress, Cairns Schalkoff R (1997) Artificial neural network. McGraw-Hill, New York Sturzenegger M, Stead D (2009) Close-range terrestrial digital photogrammetry and terrestrial scanning for discontinuity characterization on rock cuts. Eng Geol 106:163-182
  22. Turcotte D (1986) Fractals and fragmentation. J Geophys Res 91(NO B2):1921-1926
  23. Viero A, Furlanis S, Squarzoni C, Teza G, Galgaro A, Gianola P (2012) Dynamics and mass balance of the Cima Una rockfall (Eastern Alps, Italy). Landslides 10:393-408
  24. Wang Y, Tonon F (2010) Discrete element modelling of rock fragmentation upon impact in rock fall analysis. Rock Mech Rock Eng 44:23-35
  25. Wu, C (2011) VisualSFM: a visual structure from motion system. URL: http:// homes.cs.washington.edu/~ccwu/vsfm,9
  26. Zhang ZX, Kou SQ, Jiang LG, Lindqvist PA (2000) Effects of loading rate on rock fracture: fracture characteristics and energy partitioning. Int J Rock Mech Min Sci 37:745-762
  27. R. Ruiz-Carulla ()) : J. Corominas : O. Mavrouli Department of Geotechnical Engineering and Geosciences, Universitat Politècnica de Catalunya -BarcelonaTech (UPC), Barcelona, Spain e-mail: roger.ruiz@upc.edu J. Corominas e-mail: jordi.corominas@upc.edu e-mail: olga-christina.mavrouli@upc.edu

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Jordi Corominas

Landslides, 2015

Rock masses detached as rockfalls usually disintegrate upon impact on the ground surface. The knowledge of the Rockfall Block Size Distribution (RBSD) generated in the rockfall deposit is useful for the analysis of the trajectories of the rock blocks, run-out distances, impact energies and for the quantitative assessment of the rockfall hazard. Obtaining the RBSD of a large rockfall deposit may become a challenge due to the high number of blocks to be measured. In this paper, we present a methodology developed for mid-size fragmental rockfalls (10 3 up to 10 5 m 3) and its application to the Cadí massif, Eastern Pyrenees. The methodology consists of counting and measuring block fragments in selected sampling plots within homogeneous zones in the young debris cover generated by the rockfall along with all the large scattered rock blocks. The size distribution of blocks obtained in the sampling plots is extrapolated to the whole young debris cover and summed to the inventoried large scattered blocks to derive the RBSD of the whole rockfall event. The obtained distributions from the fragments can be well fitted by a power law distribution, indicating the scale invariant character of the fragmentation process (Hartmann 1969 ; Turcotte, 1986). The total volume of the rockfall fragments has been checked against the volume at the rockfall source. The latter has been calculated comparing 3D digital surface models before and after the rockfall event.

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Rockfall Occurrence and Fragmentation
Jordi Corominas

Advancing Culture of Living with Landslides, 2017

Rockfalls are very rapid and damaging slope instability processes that affect mountainous regions, coastal cliffs and slope cuts. This contribution focuses on fragmental rockfalls in which the moving particles, particularly the largest ones, propagate following independent paths with little interaction among them. The prediction of the occurrence and frequency of the rockfalls has benefited by the rapid development of the techniques for the detection and the remote acquisition of the rock mass surface features such as the 3D laser scanner and the digital photogrammetry. These techniques are also used to monitor the deformation experienced by the rock mass before failure. The quantitative analysis of the fragmental rockfalls is a useful approach to assess risk and for the design of both stabilization and protection measures. The analysis of rockfalls must consider not only the frequency and magnitude of the potential events but also the fragmentation of the detached rock mass. The latter is a crucial issue as it affects the number, size and the velocity of the individual rock blocks. Several case studies of the application of the remote acquisition techniques for determining the size and frequency of rockfall events and their fragmentation are presented. The extrapolation of the magnitude-frequency relationships is discussed as well as the role of the geological factors for constraining the size of the largest detachable mass from a cliff. Finally, the performance of a fractal fragmentation model for rockfalls is also discussed.

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RockGIS: a GIS-based model for the analysis of fragmentation in rockfalls
Nieves Lantada

Landslides, 2017

is a mass instability event frequently observed in road cuts, open pit mines and quarries, steep slopes and cliffs. After its detachment, the rock mass may disaggregate and break due to the impact with the ground surface, thus producing new rock fragments. The consideration of the fragmentation of the rockfall mass is critical for the calculation of the trajectories of the blocks and the impact energies, for the assessment of the potential damage and the design of protective structures. In this paper, we present RockGIS, a GIS-Based tool that simulates stochastically the fragmentation of the rockfall, based on a lumped mass approach. In RockGIS, the fragmentation is triggered by the disaggregation of the detached rock mass through the pre-existing discontinuities just before the impact with the ground. An energy threshold is defined in order to determine whether the impacting blocks break or not. The distribution of the initial mass between a set of newly generated rock fragments is carried out stochastically following a power law. The trajectories of the new rock fragments are distributed within a cone. The fragmentation model has been calibrated and tested with a 10,000m 3 rockfall that took place in 2011 near Vilanova de Banat, Eastern Pyrenees, Spain.

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Rockfalls: analysis of the block fragmentation through field experiments
Jordi Corominas

Landslides, 2022

Fragmentation is a common feature of rockfall that exerts a strong control on the trajectories of the generated blocks, the impact energies, and the runout. In this paper, we present a set of four real-scale rockfall tests aimed at studying the fragmentation of the rocky blocks, from the global design of the field procedure to the data analysis and the main results. A total of 124 limestone, dacite, or granite blocks ranging between 0.2 and 5 m3 were dropped from different heights (8.5 to 23.6 m) onto four slopes with different shapes (single or double bench) and slope angles (42º to 71º). The characteristics of the blocks, in particular the size, surface texture and joint condition, were measured before the drops. The trajectories of the blocks and both the initial and the impact velocities were tracked and recorded by means of three high-speed video cameras. A total of 200 block-to-ground impacts have been studied. On average, 40% of the blocks broke upon impact on the slope or on...

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Template for the full paper of WLF 4 Rockfall occurrence and fragmentation
Jordi Corominas

2017

Rockfalls are very rapid and damaging slope instability processes that affect mountainous regions, coastal cliffs and slope cuts. This contribution focuses on fragmental rockfalls in which the moving particles, particularly the largest ones, propagate following independent paths with little interaction among them. The prediction of the occurrence and frequency of the rockfalls has benefited by the rapid development of the techniques for the detection and the remote acquisition of the rock mass surface features such as the 3D laser scanner and the digital photogrammetry. These techniques are also used to monitor the deformation experienced by the rock mass before failure. The quantitative analysis of the fragmental rockfalls is a useful approach to assess risk and for the design of both stabilization and protection measures. The analysis of rockfalls must consider not only the frequency and magnitude of the potential events but also the fragmentation of the detached rock mass. The la...

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Cited by

Thermal Remote Sensing from UAVs: A Review on Methods in Coastal Cliffs Prone to Landslides
Giacomo Deiana

Remote Sensing

Coastal retreat is a non-recoverable phenomenon that—together with a relevant proneness to landslides—has economic, social and environmental impacts. Quantitative data on geological and geomorphologic features of such areas can help to predict and quantify the phenomena and to propose mitigation measures to reduce their impact. Coastal areas are often inaccessible for sampling and in situ surveys, in particular where steeply sloping cliffs are present. Uses and capability of infrared thermography (IRT) were reviewed, highlighting its suitability in geological and landslides hazard applications. Thanks to the high resolution of the cameras on the market, unmanned aerial vehicle-based IRT allows to acquire large amounts of data from inaccessible steep cliffs. Coupled structure-from-motion photogrammetry and coregistration of data can improve accuracy of IRT data. According to the strengths recognized in the reviewed literature, a three-step methodological approach to produce IRTs was ...

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Simulation of Full-Scale Rockfall Tests with a Fragmentation Model
Nieves Lantada

Geosciences

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...

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Analysis of Fragmentation of Rock Blocks from Real-Scale Tests
Nieves Lantada

Geosciences

Real-scale fragmentation tests provide high quality data in order to study the fragmentation pattern of rock blocks. In the tests carried out, the initial rock mass, in terms of both volume and shape, was reconstructed by means of 3D photogrammetry. The fragments size distribution of the bocks tested was measured by hand using a tape. The drop tests were performed in four different sites, releasing a total of 124 blocks and measuring 2907 fragments. The obtained fragment size distributions may be well fitted using power laws. The survival rate (Sr), which is the proportion of remaining block shows a wide range of values. Observing the fragment distribution, two parameters are needed to characterize the fragmentation: the number of fragments produced and Sr. The intensity of the fragmentation is expressed by the exponent of the fitted power laws. Although the results are highly variable and show a stochastic behavior of the fragmentation, we have identified different patterns that re...

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Quantifying the effect of forests on frequency and intensity of rockfalls
Luuk Dorren

Natural Hazards and Earth System Sciences

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 power-law magnitude–frequency distribution and determined their propagation probabilities on a virtual slope based on rockfall simulations. Simulations were run for different forest and n...

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Rockfall Occurrence and Fragmentation
Jordi Corominas

Advancing Culture of Living with Landslides, 2017

Rockfalls are very rapid and damaging slope instability processes that affect mountainous regions, coastal cliffs and slope cuts. This contribution focuses on fragmental rockfalls in which the moving particles, particularly the largest ones, propagate following independent paths with little interaction among them. The prediction of the occurrence and frequency of the rockfalls has benefited by the rapid development of the techniques for the detection and the remote acquisition of the rock mass surface features such as the 3D laser scanner and the digital photogrammetry. These techniques are also used to monitor the deformation experienced by the rock mass before failure. The quantitative analysis of the fragmental rockfalls is a useful approach to assess risk and for the design of both stabilization and protection measures. The analysis of rockfalls must consider not only the frequency and magnitude of the potential events but also the fragmentation of the detached rock mass. The latter is a crucial issue as it affects the number, size and the velocity of the individual rock blocks. Several case studies of the application of the remote acquisition techniques for determining the size and frequency of rockfall events and their fragmentation are presented. The extrapolation of the magnitude-frequency relationships is discussed as well as the role of the geological factors for constraining the size of the largest detachable mass from a cliff. Finally, the performance of a fractal fragmentation model for rockfalls is also discussed.

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