Rockfall Occurrence and Fragmentation

Corominas, Jordi; Mavrouli, Olga; Ruiz-Carulla, Roger

doi:10.1007/978-3-319-59469-9_4

Cited by 38 publications

(22 citation statements)

References 125 publications

(174 reference statements)

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“…This behavior is observed here, with a threefold reduction in

\overset{V_{R}}{true}

for T int = 1 hr, as compared to T int = 30 days. Conversely, while our monitoring should not alter the assessment of the largest or worst‐case event (Corominas et al, ), an increase in f (V R ) and a reduction in

\overset{V_{R}}{true}

at the point of release is significant for rockfall remediation (Corominas et al, ), for models that predict the ease with which rockfall debris can be remobilized or weathered based on clast volume or surface area (Messenzehl et al, ), and for interpretations of rockfall magnitude‐frequency from deposit granulometry (Crosta et al, ; Ruiz‐Carulla et al, ).…”

Section: Discussionmentioning

confidence: 99%

The Importance of Monitoring Interval for Rockfall Magnitude‐Frequency Estimation

et al. 2019

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Rockfalls commonly exhibit power law volume‐frequency distributions, where fewer large events are observed relative to more numerous small events. Within most inventories, the smallest rockfalls are the most difficult to detect and so may not be adequately represented. A primary challenge occurs when neighboring events within a single monitoring interval are recorded as one, producing ambiguity in event location, timing, volume, and frequency. Identifying measurement intervals that minimize these uncertainties is therefore essential. To address this, we use an hourly data set comprising 8,987 3‐D point clouds of a cliff that experiences frequent rockfalls. Multiple rockfall inventories are derived from this data set using change detections for the same 10‐month period, but over different monitoring intervals. The power law describing the probability distribution of rockfall volumes is highly sensitive to monitoring interval. The exponent, β, is stable for intervals >12 hr but increases nonlinearly over progressively short timescales. This change is manifested as an increase in observed rockfall numbers, from 1.4 × 103 (30 day intervals) to 1.4 × 104 (1 hr intervals), and a threefold reduction in mean rockfall volume. When the monitoring interval exceeds 4 hr, the geometry of detected rockfalls becomes increasingly similar to that of blocks defined by rock mass structure. This behavior change reveals a time‐dependent component to rockfall occurrence, where smaller rockfalls (identifiable from more frequent monitoring) are more sensitive to progressive deformation of the rock mass. Acquiring complete inventories and attributing discrete controls over rockfall occurrence may therefore only be achievable with high‐frequency monitoring, dependent upon local lithology.

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“…This behavior is observed here, with a threefold reduction in

\overset{V_{R}}{true}

\overset{V_{R}}{true}

Section: Discussionmentioning

confidence: 99%

The Importance of Monitoring Interval for Rockfall Magnitude‐Frequency Estimation

et al. 2019

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“…CC BY 4.0 License. various volumes and classifications of rock slope failure relevant to the transition between these two styles of motion is presented by Corominas et al (2017) and suggests that volume thresholds and terminology for these types of events is not yet consistent in the literature.…”

Section: Event Fragmentationmentioning

confidence: 99%

“…At the same time, the decision to model the events as a rapid disaggregation of jointed rock was not arbitrary. This style of fragmentation is akin to the disaggregation-without-breakage rockfall mechanism described by Ruiz-Carulla et al (2017), in which the rockfall body separates along discontinuities present in the source rock mass, with no breakage of individual, discontinuity-bounded blocks. This appears to be the dominant 5 behaviour in the railway rock slope video shown in Figure 10.…”

Section: Fragmentation Timingmentioning

confidence: 99%

Simulation of Fragmental Rockfalls Detected Using Terrestrial Laser Scans from Rock Slopes in South-Central British Columbia, Canada

Sala¹,

Hutchinson²,

Harrap³

2019

Preprint

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Abstract. Rockfall presents an ongoing challenge to the safe operation of transportation infrastructure, creating hazardous conditions which can result in damage to roads and railways, as well as loss of life. Rockfall risk assessment frameworks often involve the determination of rockfall runout in an attempt to understand the likelihood that rockfall debris will reach an element at risk. Rockfall modelling programs which simulate the trajectory of rockfall material are one method commonly used to assess potential runout. This study aims to demonstrate the effectiveness of a rockfall simulation prototype which uses the Unity3D game engine. The technique is capable of simulating rockfall events comprised of many mobile fragments, a common limitation of available rockfall modelling programs. Five fragmental rockfalls were simulated using the technique, with slope and rockfall geometries constructed from high-resolution terrestrial laser scans. Simulated change detection was produced for each of the events and compared to the actual change detection results for each rockfall as a basis for testing model performance. In each case the simulated change detection results aligned well with the actual observed change in terms of location and magnitude. An example of how the technique could be used to support the design of rockfall catchment ditches is shown. Suggestions are made for future development of the simulation technique with a focus on better informing simulated rockfall fragment size and the timing of fragmentation.

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“…We define EERs as those events in which the following three criteria are all met: High specific energy (or equivalently great fall height) .The falling mass should travel along a ballistic trajectory for a height sufficient to disintegrate explosively at contact with the ground, producing some larger blocks and residual particles ranging from a few centimeters to micrometers.It is reasonable to expect that the degree of fragmentation increases progressively as a function of the fall height (Corominas et al, ; Crosta et al, ; Frattini et al, ). However, it is not possible to define unambiguously a threshold limit to an explosive fragmentation.…”

Section: Definition and Identification Of Eersmentioning

confidence: 99%

“…It is reasonable to expect that the degree of fragmentation increases progressively as a function of the fall height (Corominas et al, ; Crosta et al, ; Frattini et al, ). However, it is not possible to define unambiguously a threshold limit to an explosive fragmentation.…”

Section: Definition and Identification Of Eersmentioning

confidence: 99%

Extremely Energetic Rockfalls

2018

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Extremely energetic rockfalls (EERs) are defined here as rockfalls for which a combination of both large volume and free fall height of hundreds of meters results in energy larger than about 80 GJ released in a short time. Examples include several events worldwide. In contrast to low energy rockfalls where block disintegration is limited, in EERs the impact after free fall causes immediate release of energy much like an explosion. The resulting air blast can snap trees hundreds of meters ahead of the fall area. Pulverized rock at high speed can abrade vegetation in a process of sandblasting, and particles suspended by the blast and the subsequent debris cloud may travel farther than the impact zone, blanketing vast areas. Using published accounts and new data, we introduce physically based models formulated on analogies with explosions and explosive fragmentation to describe EERs. Results indicate that a portion of the initial potential energy of the block is spent in rock disintegration at impact (typically 0.2%–18%), while other sources of energy loss (air drag, seismic, sound, and ground deformation) are negligible; consequently, more than 80% of the potential energy is converted to kinetic energy of the fragmented block (ballistic projection, shock wave, sand blast, and dust cloud). We also propose simple estimates for the flow of the dust cloud associated with an EER and its long settling time. The areal extent of the affected zone is estimated from the energy balance and an empirical power law relationship.

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Rockfall Occurrence and Fragmentation

Cited by 38 publications

References 125 publications

The Importance of Monitoring Interval for Rockfall Magnitude‐Frequency Estimation

The Importance of Monitoring Interval for Rockfall Magnitude‐Frequency Estimation

Simulation of Fragmental Rockfalls Detected Using Terrestrial Laser Scans from Rock Slopes in South-Central British Columbia, Canada

Extremely Energetic Rockfalls

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