Rockfall risk management using a pre-failure deformation database

Kromer, Ryan; Rowe, Emily; Hutchinson, Jean; Lato, Matthew J.; Abellán, Antonio

doi:10.1007/s10346-017-0921-9

Cited by 28 publications

(22 citation statements)

References 29 publications

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“…No deformation was detected prior to the rockfalls observed at the site. In this magnitude range, deformation prior to rockfall have been rarely observed [25].…”

Section: Rockfall Analysismentioning

confidence: 94%

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Development and Optimization of an Automated Fixed-Location Time Lapse Photogrammetric Rock Slope Monitoring System

et al. 2019

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An automated, fixed-location, time lapse camera system was developed as an alternative to monitoring geological processes with lidar or ground-based interferometric synthetic-aperture radar (GB-InSAR). The camera system was designed to detect fragmental rockfalls and pre-failure deformation at rock slopes. It was implemented at a site along interstate I70 near Idaho Springs, Colorado. The camera system consists of five digital single-lens reflex (DSLR) cameras which collect photographs of the rock slope daily and automatically upload them to a server for processing. Structure from motion (SfM) photogrammetry workflows were optimized to be used without ground control. An automated change detection pipeline registers the point clouds with scale adjustment and filters vegetation. The results show that if a fixed pre-calibration of internal camera parameters is used, an accuracy close to that obtained using ground control points can be achieved. Over the study period between March 19, 2018 and June 24, 2019, a level of detection between 0.02 to 0.03 m was consistently achieved, and over 50 rockfalls between 0.003 to 0.1 m3 were detected at the study site. The design of the system is fit for purpose in terms of its ground resolution size and accuracy and can be adapted to monitor a wide range of geological and geomorphic processes at a variety of time scales.

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“…No deformation was detected prior to the rockfalls observed at the site. In this magnitude range, deformation prior to rockfall have been rarely observed [25].…”

Section: Rockfall Analysismentioning

confidence: 94%

“…Furthermore, the study also investigates whether such a system can be a viable alternative for the study of rockfall pre-failure deformation and magnitude frequency relationships. This generally requires the detection of deformation on the cm range [22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Development and Optimization of an Automated Fixed-Location Time Lapse Photogrammetric Rock Slope Monitoring System

et al. 2019

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“…[Colour figure can be viewed at wileyonlinelibrary.com] concentrations within the slope (Brain et al, 2014). The change in failure style may dictate the degree of discernible pre-failure deformation, with multi-failure events potentially displaying higher degrees of pre-failure deformation than compared to single stage events as the period of time over which total loss of strength occurs is longer (Kromer et al, 2017b;Petley et al, 2005;Williams et al, 2018). As final failure occurs a distinct period of time after the initial damaging loading event (such as an earthquake or storm), this may explain the low observed correlations between environmental variables and failure (Lim et al, 2010;Rosser et al, 2007;Stock et al, 2012), with a 'lag' between initial and final failure.…”

Section: Implications For Shallow Rock Slope Failuresmentioning

confidence: 99%

“…In such a scenario, even though topographic stress is not a control on the rate of weakening, as we have determined from our experimental datasets, it may therefore control the location of rock failure. The time-scales over which such deformation could be observed is also dependent on the exact rock bridge attributes within an incipient failure mass, with the amount of deformation increasing for larger rockfalls (Kromer et al, 2017b), reflecting the breakage of multiple rock bridges (de Vilder et al, 2017). Monitoring observations have revealed that external precipitation triggering events can initiate extended periods of increased and accelerated deformation indicating a critical damage threshold has been reached in the rock, with previous observations showing that in some settings that this can accelerate to final failure within a week (Carlà et al, 2018;Kromer et al, 2017a;Loew et al, 2016).…”

Section: Implications For Shallow Rock Slope Failuresmentioning

confidence: 99%

“…Pre-failure deformation may also record several stages of macro-scale brittle failure related to rock bridge fracture ( Figure 14) (Carlà et al, 2017;Kromer et al, 2015;Royan et al, 2015). The change in failure style may dictate the degree of discernible pre-failure deformation, with multi-failure events potentially displaying higher degrees of pre-failure deformation than compared to single stage events as the period of time over which total loss of strength occurs is longer (Kromer et al, 2017b;Petley et al, 2005;Williams et al, 2018). The time-scales over which such deformation could be observed is also dependent on the exact rock bridge attributes within an incipient failure mass, with the amount of deformation increasing for larger rockfalls (Kromer et al, 2017b), reflecting the breakage of multiple rock bridges (de Vilder et al, 2017).…”

Section: Implications For Shallow Rock Slope Failuresmentioning

confidence: 99%

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Controls on the geotechnical response of sedimentary rocks to weathering

Vilder

Brain

Rosser

2019

Earth Surf Processes Landf

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Weathering reduces the strength of rocks and so is a key control on the stability of rock slopes. Recent research suggests that the geotechnical response of rocks to weathering varies with ambient stress conditions resulting from overburden loading and/or stress concentrations driven by near‐surface topography. In addition, the stress history experienced by the rock can influence the degree to which current weathering processes cause rock breakdown. To address the combined effect of these potential controls, we conducted a set of weathering experiments on two sedimentary lithologies in laboratory and field conditions. We firstly defined the baseline geotechnical behaviour of each lithology, characterising surface hardness and stress–strain behaviour in unconfined compression. Weathering significantly reduced intact rock strength, but this was not evident in measurements of surface hardness. The ambient compressive stress applied to samples throughout the experiments did not cause any observable differences in the geotechnical behaviour of the samples. We created a stress history effect in sub‐sets of samples by generating a population of microcracks that could be exploited by weathering processes. We also geometrically modified groups of samples to cause near‐surface stress concentrations that may allow greater weathering efficacy. However, even these pronounced sample modifications resulted in insignificant changes in geotechnical behaviour when compared to unmodified samples. The observed reduction in rock strength changed the nature of failure of the samples, which developed post‐peak strength and underwent multiple stages of brittle failure. Although weakened, these samples could sustain greater stress and strain following exceedance of peak strength. On this basis, the multi‐stage failure style exhibited by weaker weathered rock may permit smaller‐magnitude, higher‐frequency events to trigger fracture through intact rock bridges as well as influencing the characteristics of pre‐failure deformation. These findings are consistent with patterns of behaviour observed in field monitoring results. © 2019 John Wiley & Sons, Ltd.

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Global warming impacts on rockfall frequency and magnitude due to changing frost distribution and frost cracking effectiveness

Birien,

Gauthier,

Meloche

2024

Earth Surf Processes Landf

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The distribution of freezing and thawing within rock masses is time varying (day to day or season to season) and controls the effectiveness of the frost cracking processes from the surface until various depths. These processes are major contributors to the development of rock instabilities. By altering the thermal regime of rockwalls, global warming could have a major impact on rockfall dynamic by the end of the 21st century. This study seeks to improve our understanding of the influence of this warming on (i) the distribution of freezing and thawing within rock masses, (ii) the effectiveness of frost cracking and (iii) the frequency and magnitude of rockfalls. Thermistor sensors inserted in a 5.5‐m horizontal borehole and a weather station were installed on a vertical rockwall located in the northern Gaspé Peninsula (Canada). This instrumentation was used to calculate the surface energy balance of the rockwall and to measure and model its thermal regime at depth over a period of 28 months. Combining locally recorded historical air temperature data with simulated future data (scenarios RCP4.5 and RCP8.5) made it possible to extend the rockwall thermal regime model over the period 1950–2100. The effectiveness of frost cracking over this 150‐year period has been quantified using a thermomechanical model. Depending on the scenario, warming of 3.3°C to 6.2°C is expected on the northern Gaspé Peninsula by the end of the 21st century. This rapid warming is likely to decrease the maximum depth reaches by the seasonal frost by 1–2 m and shorten its duration by 1–3 months. The frequency of freeze–thaw cycles could increase twelvefold in January. Frost cracking effectiveness should intensify around 70 cm in depth and disappear beyond that (RCP4.5) or diminish starting at 10 cm in depth (RCP8.5). In areas subject to seasonal freeze–thaw cycles, decimetric rockfall frequency could grow considerably in winter but be significantly reduced in fall and spring. Furthermore, frost cracking would cease contributing to the development of larger magnitude instabilities.

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Rockfall risk management using a pre-failure deformation database

Cited by 28 publications

References 29 publications

Development and Optimization of an Automated Fixed-Location Time Lapse Photogrammetric Rock Slope Monitoring System

Development and Optimization of an Automated Fixed-Location Time Lapse Photogrammetric Rock Slope Monitoring System

Controls on the geotechnical response of sedimentary rocks to weathering

Global warming impacts on rockfall frequency and magnitude due to changing frost distribution and frost cracking effectiveness

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