Short Communication: Monitoring rock falls with the Raspberry Shakes

Abstract. We evaluate the performance of the low-cost seismic sensors Raspberry Shake (RS) to identify and monitor rock fall activity in alpine environments. The test area is a slope adjacent to the Great Aletsch glacier in the Swiss Alps, i.e. the Moosfluh deep-seated instability, which is undergoing an acceleration phase since the late summer 2016. A local seismic network composed of three RS seismometers was deployed starting from May 2017, in order to record rock fall activity and its relation with the progressive rock slope degradation potentially leading to a large rock slope failure. Here we present a first assessment of the seismic data acquired from RS sensors after a monitoring period of 1-year. A webcam was installed on the opposite side of the active slope, acquiring images every 10 minutes to validate the occurrence and identify rock falls as well as their location and approximate size. Despite seismic data were collected mainly to identify rock fall phenomena, other event types were recorded during the monitoring period. Thus, this work provides also general insights on the potential use of low cost sensors in environmental seismology investigations.

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Short Communication: Monitoring rockfalls with the Raspberry Shake

Earth Surface Dynamics ◽

10.5194/esurf-6-1219-2018 ◽

2018 ◽

Vol 6 (4) ◽

pp. 1219-1227 ◽

Cited By ~ 3

Author(s):

Andrea Manconi ◽

Velio Coviello ◽

Maud Galletti ◽

Reto Seifert

Keyword(s):

Seismic Data ◽

Slope Failure ◽

Rock Slope ◽

Low Cost ◽

General Information ◽

Swiss Alps ◽

Winter Period ◽

Critical Acceleration ◽

Progressive Rock ◽

Alpine Environments

Abstract. We evaluate the performance of the low-cost seismic sensor Raspberry Shake to identify and monitor rockfall activity in alpine environments. The test area is a slope adjacent to the Great Aletsch Glacier in the Swiss Alps, i.e. the Moosfluh deep-seated instability, which has recently undergone a critical acceleration phase. A local seismic network composed of three Raspberry Shake was deployed starting from May 2017 in order to record rockfall activity and its relation with the progressive rock-slope degradation potentially leading to a large rock-slope failure. Here we present a first assessment of the seismic data acquired from our network after a monitoring period of 1 year. We show that our network performed well during the whole duration of the experiment, including the winter period in severe alpine conditions, and that the seismic data acquired allowed us to clearly discriminate between rockfalls and other events. This work also provides general information on the potential use of such low-cost sensors in environmental seismology.

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Does climate change influence the frequency of large rock slope failures?

10.5194/egusphere-egu2020-7361 ◽

2020 ◽

Author(s):

Simon Loew ◽

Nora Buehler ◽

Jordan Aaron

Keyword(s):

Slope Failure ◽

Rock Slope ◽

Negative Temperature ◽

Climatic Conditions ◽

Swiss Alps ◽

Rock Fall ◽

Mean Annual Temperature ◽

European Alps ◽

Depth Range ◽

Slope Failures

A large number of scientific contributions (e.g. BAFU 2017, Speicher 2017, Phillips et al. 2017, Ravanel et al. 2017, Haque et al. 2016) have suggested that many recent rock slope failures in the European Alps have been triggered by climate warming. For example, Huggel et al. 2012 and Fischer et al. 2012 could show that rock fall frequencies above 2000 masl increased significantly since 1990 at regional (Swiss Alps and adjacent areas) and local (Mont Blanc) scale, based on 52 events larger than 1000 m3 (PERMOS data base) covering the period 1900-2010. This increase in frequency could be correlated with a significant departure of mean annual temperature from the 1960&#8211;1990 average, based on a dataset describing conditions in Switzerland. Paranunzio et al. 2016 systematically studied the climatic conditions and anomalies occurring before 41 rock fall events in the Italian Alps with volumes of several hundred to several million m3. They show that positive and negative temperature anomalies triggered the majority of analysed rock fall events in a complex manner, but that melting of permafrost was clearly not the only rock fall trigger.However, there have been no studies which systematically investigate changes in the frequency of rock fall events based on complete inventories covering a large range of rock fall volumes. To fill this gap, we have generated a new database for rapid rock slope failures in the Swiss Alps covering events larger than 100&#8217;000 m3 (B&#252;hler 2019, BSc Thesis ETH 2019). This catalogue covers the period between 1700 and 2019 and includes 86 events with reliably estimated volume, date and location of occurrence, and pre-disposing factors (such as slope orientation, permafrost occurrence and geological setting). Volume-cumulative frequency plots of the events demonstrate completeness of the catalogue for all size classes, and significant changes in the ratios between large and small events through time.An enhanced frequency of the volume class of 105 m3 (100&#8217;000-999&#8217;000 m3) is observed starting from 1940, predominantly occurring in permafrost areas and elevations ranging between 2800 and 3200 masl. This increasing frequency signal with time disappears for increasing volumes beyond a magnitude of about 400&#8217;000 m3 and is clearly absent for very large rock slope failure of millions to tens of millions of m3.The volume dependence of climate sensitivity can be physically explained, as larger volume slope failures tend to have deeper failure surfaces. Typical failure depth for multi-million m3 slope failures in crystalline rocks are up to a few 100 meters, and beyond the depth of Alpine permafrost. Direct impacts of surface temperature changes on permafrost are mainly manifested through a minor thickening of the active layer, typically ranging between 1 and 10 meters, but indirect effects at the depth range of decameters (i.e. the depth of failure surfaces for events of the 105 m3 class) have been assessed and demonstrated in a large number of studies.

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Magnitude and frequency of rock falls and rock slides along the main transportation corridors of southwestern British Columbia

Canadian Geotechnical Journal ◽

10.1139/t98-106 ◽

1999 ◽

Vol 36 (2) ◽

pp. 224-238 ◽

Cited By ~ 229

Author(s):

O Hungr ◽

S G Evans ◽

J Hazzard

Keyword(s):

British Columbia ◽

Rock Slope ◽

Sampling Procedure ◽

Rock Fall ◽

Rock Falls ◽

Geological Conditions ◽

Transportation Corridors ◽

Risk Magnitude ◽

Frequency Relationship ◽

Rock Slides

The two main transportation corridors of southwestern British Columbia are subject to a range of rock slope movements (rock falls, rock slides, and rock avalanches) that pose significant risks to road and rail traffic travelling through the region. Volumes of these landslides range from less than 1 m3 to over 4.0 × 107 m3. A database of rock falls and slides was compiled for rail and highway routes in each transportation corridor using maintenance records spanning four decades. The records number approximately 3500, of which about one half includes information on volume. Magnitude - cumulative frequency (MCF) relationships were derived for each corridor. A scaled sampling procedure was used in part to reduce the effects of censoring. Both corridors yield MCF curves with significant linear segments on log-log plots at magnitudes greater than 1 m3. The form of both railway and road plots for each corridor shows similarity over several orders of magnitude. The slope of the linear segments of the curves depends on geological conditions in the corridors. Temporal histograms of the data show a trend towards reduction of rock fall frequency as a result of rock slope stabilization measures, implemented during the 1980s and 1990s. A risk analysis methodology using the slope of the magnitude-frequency relationship is outlined. The major part of the risk to life in the case examined results from rock falls in the intermediate-magnitude range (1-10 m3).Key words: rock fall, rock slide, landslide hazard, risk, magnitude-frequency, British Columbia.

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Rock slope failure in a recently deglaciated permafrost rock wall at Piz Kesch (Eastern Swiss Alps), February 2014

Earth Surface Processes and Landforms ◽

10.1002/esp.3992 ◽

2016 ◽

Vol 42 (3) ◽

pp. 426-438 ◽

Cited By ~ 22

Author(s):

Marcia Phillips ◽

Andrea Wolter ◽

Rachel Lüthi ◽

Florian Amann ◽

Robert Kenner ◽

...

Keyword(s):

Slope Failure ◽

Rock Slope ◽

Swiss Alps ◽

Rock Wall ◽

Permafrost Rock

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PRELIMINARY RESULTS REGARDING THE ROCK FALLS OF DECEMBER 17, 2009 AT TEMPI, GREECE

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.11286 ◽

2017 ◽

Vol 43 (3) ◽

pp. 1122 ◽

Cited By ~ 1

Author(s):

B. Christaras ◽

G. Papathanassiou ◽

K. Vouvalidis ◽

S. Pavlides

Keyword(s):

Slope Failure ◽

Field Survey ◽

Water Pressure ◽

Heavy Rain ◽

Rock Fall ◽

Rock Falls ◽

Rocky Slope ◽

The Road ◽

Large Size ◽

National Road

On December 17, 2009, a large size rock fall generated at the area of Tempi, Central Greece causing one casualty. In particular, a large block was detached from a high of 70 meters and started to roll downslope and gradually became a rock slide. About 120 tones of rock material moved downward to the road resulting to the close of the national road. Few days after the slope failure, a field survey organized by the Department of Geology, AUTH took place in order to evaluate the rock fall hazard in the area and to define the triggering causal factors. As an outcome, we concluded that the heavily broken rock mass and the heavy rain-falls, of the previous days, contribute significantly to the generation of the slope failure. The rocky slope was limited stable and the high joint water pressure caused the failure of the slope.

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A temperature- and stress-controlled failure criterion for ice-filled permafrost rock joints

The Cryosphere ◽

10.5194/tc-12-3333-2018 ◽

2018 ◽

Vol 12 (10) ◽

pp. 3333-3353 ◽

Cited By ~ 6

Author(s):

Philipp Mamot ◽

Samuel Weber ◽

Tanja Schröder ◽

Michael Krautblatter

Keyword(s):

Normal Stress ◽

Failure Criterion ◽

Slope Failure ◽

Rock Slope ◽

Shear Resistance ◽

Stress Conditions ◽

Rock Joints ◽

Normal Stresses ◽

Permafrost Rock ◽

Limestone Sample

Abstract. Instability and failure of high mountain rock slopes have significantly increased since the 1990s coincident with climatic warming and are expected to rise further. Most of the observed failures in permafrost-affected rock walls are likely triggered by the mechanical destabilisation of warming bedrock permafrost including ice-filled joints. The failure of ice-filled rock joints has only been observed in a small number of experiments, often using concrete as a rock analogue. Here, we present a systematic study of the brittle shear failure of ice and rock–ice interfaces, simulating the accelerating phase of rock slope failure. For this, we performed 141 shearing experiments with rock–ice–rock “sandwich”' samples at constant strain rates (10−3 s−1) provoking ice fracturing, under normal stress conditions ranging from 100 to 800 kPa, representing 4–30 m of rock overburden, and at temperatures from −10 to −0.5 ∘C, typical for recent observed rock slope failures in alpine permafrost. To create close to natural but reproducible conditions, limestone sample surfaces were ground to international rock mechanical standard roughness. Acoustic emission (AE) was successfully applied to describe the fracturing behaviour, anticipating rock–ice failure as all failures are predated by an AE hit increase with peaks immediately prior to failure. We demonstrate that both the warming and unloading (i.e. reduced overburden) of ice-filled rock joints lead to a significant drop in shear resistance. With a temperature increase from −10 to −0.5 ∘C, the shear stress at failure reduces by 64 %–78 % for normal stresses of 100–400 kPa. At a given temperature, the shear resistance of rock–ice interfaces decreases with decreasing normal stress. This can lead to a self-enforced rock slope failure propagation: as soon as a first slab has detached, further slabs become unstable through progressive thermal propagation and possibly even faster by unloading. Here, we introduce a new Mohr–Coulomb failure criterion for ice-filled rock joints that is valid for joint surfaces, which we assume similar for all rock types, and which applies to temperatures from −8 to −0.5 ∘C and normal stresses from 100 to 400 kPa. It contains temperature-dependent friction and cohesion, which decrease by 12 % ∘C−1 and 10 % ∘C−1 respectively due to warming and it applies to temperature and stress conditions of more than 90 % of the recently documented accelerating failure phases in permafrost rock walls.

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Dynamics of the Askja caldera July 2014 landslide, Iceland, from seismic signal analysis: precursor, motion and aftermath

10.5194/esurf-2017-68 ◽

2017 ◽

Cited By ~ 1

Author(s):

Anne Schöpa ◽

Wei-An Chao ◽

Bradley Lipovsky ◽

Niels Hovius ◽

Robert S. White ◽

...

Keyword(s):

Seismic Data ◽

Signal Analysis ◽

Slope Failure ◽

Stable State ◽

Seismic Signal ◽

Early Warning Systems ◽

High Energy ◽

Stick Slip ◽

Short Period ◽

Large Landslide

Abstract. Using data from a network of 58 seismic stations, we characterise a large landslide that occurred at the southeastern corner of the Askja caldera, Iceland, on 21 July 2014, including its precursory tremor and mass wasting aftermath. Our study is motivated by the need for deeper generic understanding of the processes operating not only at the time of catastrophic slope failure, but also in the preparatory phase and during the transient into the subsequent stable state. In addition, it is prompted by the high hazard potential of the steep caldera lake walls at Askja as tsunami waves created by the landslide reached famous tourist spots 60 m above the lake level. Since direct observations of the event are lacking, the seismic data give valuable details on the dynamics of this landslide episode. The excellent seismic data quality and coverage of the stations of the Askja network made it possible to jointly analyse the long- and short-period signals of the landslide to obtain information about the triggering, initiation, timing, and propagation of the slide. The seismic signal analysis and a landslide force history inversion of the long-period seismic signals showed that the Askja landslide was a single, large event starting at the SE corner of the caldera lake at 23:24:05 UTC and propagating to the NW in the following 2 min. The bulk sliding mass was 7–16 × 1010 kg, equivalent to a collapsed volume of 35–80 × 106 m3, and the centre of mass was displaced horizontally downslope by 1260 ± 250 m during landsliding. The seismic records of stations up to 30 km away from the landslide source area show a tremor signal that started 30 min before the main landslide failure. It is harmonic, with a fundamental frequency of 2.5 Hz and shows time-dependent changes of its frequency content. We attribute the complex tremor signal to accelerating and decelerating stick-slip motion on failure planes at the base and the sides of the landslide body. The accelerating motion culminated in aseismic slip of the landslide visible as a drop in the seismic amplitudes down to the background noise level 2 min before the landslide high-energy signal begins. We propose that the seismic signal of the precursory tremor may be developed as an indicator for landslide early-warning systems. The 8 hours after the main landslide failure are characterised by smaller slope failures originating from the destabilised caldera wall decaying in frequency and magnitude. We introduce the term afterslides for this subsequent, declining slope activity after a large landslide.

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The role of frost cracking in local denudation of steep Alpine rockwalls over millennia (Eiger, Switzerland)

Earth Surface Dynamics ◽

10.5194/esurf-8-637-2020 ◽

2020 ◽

Vol 8 (3) ◽

pp. 637-659

Author(s):

David Mair ◽

Alessandro Lechmann ◽

Romain Delunel ◽

Serdar Yeşilyurt ◽

Dmitry Tikhomirov ◽

...

Keyword(s):

Swiss Alps ◽

Rock Fall ◽

Temperature Changes ◽

Rock Face ◽

Temperature Conditions ◽

Denudation Rates ◽

Reconstructed Temperature ◽

Cryogenic Processes

Abstract. Denudation of steep rockwalls is driven by rock fall processes of various sizes and magnitudes. Rockwalls are sensitive to temperature changes mainly because thermo-cryogenic processes weaken bedrock through fracturing, which can precondition the occurrence of rock fall. However, it is still unclear how the fracturing of rock together with cryogenic processes impacts the denudation processes operating on steep rockwalls. In this study, we link data on long-term rockwall denudation rates at the Eiger (Central Swiss Alps) with the local bedrock fabric and the reconstructed temperature conditions at these sites, which depend on the insolation pattern. We then estimate the probability of bedrock for failure through the employment of a theoretical frost cracking model. The results show that the denudation rates are low in the upper part of the NW rockwall, but they are high both in the lower part of the NW rockwall and on the SE face, despite similar bedrock fabric conditions. The frost cracking model predicts a large difference in cracking intensity from ice segregation where the inferred efficiency is low in the upper part of the NW rockwall but relatively large on the lower section of the NW wall and on the SE rock face of the Eiger. We explain this pattern by the differences in insolation and temperature conditions at these sites. Throughout the last millennium, temperatures in bedrock have been very similar to the present. These data thus suggest the occurrence of large contrasts in microclimate between the NW and SE walls of the Eiger, conditioned by differences in insolation. We use these contrasts to explain the relatively low denudation rates in the upper part of the NW rockwall and the rapid denudation in the SW face and in the lower part of the NW rock face where frost cracking is more efficient.

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ROCK SLOPE SURFACE STABILITY ANALYSIS: A CASE STUDY ON HON LON ISLAND, KIEN HAI DISTRICT, KIEN GIANG PROVINCE, VIETNAM

Journal of Southwest Jiaotong University ◽

10.35741/issn.0258-2724.56.5.29 ◽

2021 ◽

Vol 56 (5) ◽

pp. 340-350

Author(s):

Ngoc Binh Vu ◽

Truong Thanh Phi ◽

Thanh Cong Nguyen ◽

Hong Thinh Phi ◽

Quy Nhan Pham ◽

...

Keyword(s):

Slope Failure ◽

Rock Slope ◽

Slope Surface ◽

Plane Failure ◽

Surface Stability ◽

Average Percentage ◽

The Road ◽

Wedge Failure ◽

Analytical Results

The research aimed to study 24 rock slope surfaces along the road around Hon Lon Island, Kien Hai district, Kien Giang province, Vietnam. The analytical results have determined slope failure, wedge failure, and toppling, which occurred on almost slope surface and the average percentage of plane failure is the largest. The average percent of plane failure is 19.23%, the wedge failure is 15.35%, and the toppling fault is 6.73%. Besides, the analytical results have also identified the slope surfaces which can be the key blocks: ND-13, 18, 23, 25, 34, 37, 45, 51, 62, 63. The other analytical results show that the existence of key blocks at the rock slope surfaces in the N-S direction, dip to E at the survey locations: ND-13, 23, 63 and dip to W at the survey locations: ND-37, 45; in the NE-SW direction, dip to SE at the survey locations: ND-15, 62 and dip to NW at the survey locations: ND-18, 34; in the NW-SE direction, dip to SW at the survey location ND-51. These results have important significance to support for protecting slope surface safety.

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High alpine rock-wall retreat rates over millennia through thermo-cryogenic pre-conditioned rock fall (Mt. Eiger, Switzerland)

10.5194/egusphere-egu21-5908 ◽

2021 ◽

Author(s):

David Mair ◽

Alessandro Lechmann ◽

Romain Delunel ◽

Serdar Yeşilyurt ◽

Dmitry Tikhomirov ◽

...

Keyword(s):

Swiss Alps ◽

Rock Fall ◽

Rock Wall ◽

Rock Face ◽

Depth Profiles ◽

Weathering Processes ◽

Temperature Conditions ◽

Low Efficiency ◽

Cryogenic Processes

Rock fall processes of various size and magnitude control retreat rates of high alpine rock-walls. For millennial time scales, these retreat rates can be quantified in-situ from concentrations of cosmogenic nuclides along bedrock depth profiles (Mair et al., 2019). We measured cosmogenic 36Cl and 10Be along several such profiles at Mt Eiger in the Central Swiss Alps to study the local rock-wall retreat on this time scale (Mair et al., 2019; 2020). The resulting spatial pattern shows that rock-wall retreat rates are low (0.5 to 0.6 &#177; 0.1 mm/yr) in the higher region of the NW rock-wall, in contrast to both the lower part of the NW rock-wall and the SE face, where rates are high (1.7 &#177; 0.4 to 3.5 &#177; 1.4 mm/yr). We link these retreat rates to differences in local temperature conditions, because the patterns of faults and fractures and the lithology of the bedrock are similar at all sites, and thermo-cryogenic processes are known to weaken the bedrock through fracturing, thereby preconditioning the occurrence of rock fall (e.g., Draebing and Krautblatter, 2019). However, it is still unclear how effective and at which rate individual thermo-cryogenic processes contribute to the preconditioning through fracturing. Therefore, we investigate several processes and estimate the probability of bedrock fracturing through the employment of a theoretical frost-cracking model, which predicts cracking intensity from ice segregation. The model results infer a low efficiency in the higher region of the NW rock-wall, but a relatively high one in the lower section of the NW wall and on the SE rock face of Mt. Eiger. Although the model is rather generic, the results disclose a significant control of temperature conditions on the erosional processes and rates. Furthermore, temperature conditions for the last millennia have been similar to present day conditions, as our reconstructions disclose, therefore the cosmogenic-nuclide-based long-term differences in rock-wall retreat rates predominantly stem from large contrasts in the microclimate between the NW and SE walls of Mt. Eiger. Accordingly, the site-specific differences in microclimate conditions could explain the lower retreat rates in the upper part of the NW rock-wall and the rapid retreat in the SW face and in the lower part of the NW rock face.ReferencesDraebing, D. and Krautblatter, M.: The Efficacy of Frost Weathering Processes in Alpine Rockwalls, Geophys. Res. Lett., 46, 6516&#8211;6524, doi:10.1029/2019GL081981, 2019.Mair, D., Lechmann, A., Yesilyurt, S., Tikhomirov, D., Delunel, R., Vockenhuber, C., Ak&#231;ar, N. and Schlunegger, F.: Fast long-term denudation rate of steep alpine headwalls inferred from cosmogenic 36Cl depth profiles, Sci. Rep., 9, 11023, doi:10.1038/s41598-019-46969-0, 2019.Mair, D., Lechmann, A., Delunel, R., Ye&#351;ilyurt, S., Tikhomirov, D., Vockenhuber, C., Christl, M., Ak&#231;ar, N. and Schlunegger, F.: The role of frost cracking in local denudation of steep Alpine rockwalls over millennia (Eiger, Switzerland), Earth Surf. Dyn., 8, 637&#8211;659, doi:10.5194/esurf-8-637-2020, 2020.

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