scholarly journals Identification of active release planes using ground-based differential InSAR at the Randa rock slope instability, Switzerland

2009 ◽  
Vol 9 (6) ◽  
pp. 2027-2038 ◽  
Author(s):  
V. Gischig ◽  
S. Loew ◽  
A. Kos ◽  
J. R. Moore ◽  
H. Raetzo ◽  
...  
Keyword(s):  
Rock Slope ◽  
Hazard Analysis ◽  
Failure Surface ◽  
Accurate Estimate ◽  
Slope Instability ◽  
Lateral Release ◽  
Rupture Plane ◽  
Local Movement ◽  
Active Release ◽  
Displacement Patterns

Abstract. Five ground-based differential interferometric synthetic aperture radar (GB-DInSAR) surveys were conducted between 2005 and 2007 at the rock slope instability at Randa, Switzerland. Resultant displacement maps revealed, for the first time, the presence of an active basal rupture zone and a lateral release surface daylighting on the exposed 1991 failure scarp. Structures correlated with the boundaries of interferometric displacement domains were confirmed using a helicopter-based LiDAR DTM and oblique aerial photography. Former investigations at the site failed to conclusively detect these active release surfaces essential for kinematic and hazard analysis of the instability, although their existence had been hypothesized. The determination of the basal and lateral release planes also allowed a more accurate estimate of the currently unstable volume of 5.7±1.5 million m3. The displacement patterns reveal that two different kinematic behaviors dominate the instability, i.e. toppling above 2200 m and translational failure below. In the toppling part of the instability the areas with the highest GB-DInSAR displacements correspond to areas of enhanced micro-seismic activity. The observation of only few strongly active discontinuities daylighting on the 1991 failure surface points to a rather uniform movement in the lower portion of the instability, while most of the slip occurs along the basal rupture plane. Comparison of GB-DInSAR displacements with mapped discontinuities revealed correlations between displacement patterns and active structures, although spatial offsets occur as a result of the effective resolution of GB-DInSAR. Similarly, comparisons with measurements from total station surveys generally showed good agreement. Discrepancies arose in several cases due to local movement of blocks, the size of which could not be resolved using GB-DInSAR.

scholarly journals Unraveling Spatial and Temporal Heterogeneities of Very Slow Rock-Slope Deformations with Targeted DInSAR Analyses

2020 ◽  
Vol 12 (8) ◽  
pp. 1329 ◽  
Author(s):  
Chiara Crippa ◽  
Federico Franzosi ◽  
Mattia Zonca ◽  
Andrea Manconi ◽  
Giovanni B. Crosta ◽  
...  
Keyword(s):  
Rock Slope ◽  
Signal To Noise Ratio ◽  
Structural Heterogeneity ◽  
Linear Displacement ◽  
Slope Instability ◽  
Gps Data ◽  
Displacement Signal ◽  
Spatially Distributed ◽  
Multi Temporal ◽  
Displacement Patterns

Spaceborne radar interferometry is a powerful tool to characterize landslides at local and regional scales. However, its application to very slow rock slope deformations in alpine environments (displacement rates < 5 cm/year) remains challenging, mainly due to low signal to noise ratio, atmospheric disturbances, snow cover effects, and complexities resulting from heterogeneous displacement in space and time. Here we combine SqueeSARTM data, targeted multi-temporal baseline DInSAR, GPS data, and detailed field morpho-structural mapping, to unravel the kinematics, internal segmentation, and style of activity of the Mt. Mater deep-seated gravitational slope deformation (DSGSD) in Valle Spluga (Italy). We retrieve slope kinematics by performing 2D decomposition (2D InSAR) of SqueeSARTM products derived from Sentinel-1 data acquired in ascending and descending orbits. To achieve a spatially-distributed characterization of DSGSD displacement patterns and activity, we process Sentinel-1 A/B images (2016-2019) with increasing temporal baselines (ranging from 24-days to 1-year) and generate several multi-temporal interferograms. Unwrapped displacement maps are validated using ground-based GPS data. Interferograms derived with different temporal baselines reveal a strong kinematic and morpho-structural heterogeneity and outline nested rockslides and active sectors, that arise from the background displacement signal of the main DSGSD. Seasonal interferograms, supported by GPS displacement measurements, reveal non-linear displacement trends suggesting a complex response of different slope sectors to rainfall and snowmelt. Our analyses clearly outline a composite slope instability with different nested sectors possibly undergoing different evolutionary trends towards failure. The results herein outline the potential of a targeted use of DInSAR for the detailed investigation of very slow rock slope deformations in different geological and geomorphological settings.

scholarly journals Changes in ground deformation prior to and following a large urban landslide in La Paz, Bolivia revealed by advanced InSAR

2018 ◽  
Author(s):  
Nicholas J. Roberts ◽  
Bernhard T. Rabus ◽  
John J. Clague ◽  
Reginald L. Hermanns ◽  
Marco-Antonio Guzmán ◽  
...  
Keyword(s):  
Ground Deformation ◽  
Ground Surface ◽  
Slope Instability ◽  
Small Scale ◽  
Spatial And Temporal Patterns ◽  
La Paz ◽  
Fine Grained ◽  
Measured Displacement ◽  
Optical Satellite Images ◽  
Displacement Patterns

Abstract. We characterize and compare creep preceding and following the 2011 Pampahasi landslide (∼ 40 Mm3 ± 50 %) in the city of La Paz, Bolivia, using spaceborne RADAR interferometry (InSAR) that combines displacement records from both distributed and point scatterers. The failure remobilised deposits of an ancient landslide in weakly cemented, predominantly fine-grained sediments and affected ∼ 1.5 km2 of suburban development. During the 30 months preceding failure, about half of the toe area was creeping at 3–8 cm/a and localized parts of the scarp area showed displacements of up to 14 cm/a. Changes in deformation in the 10 months following the landslide are contrary to the common assumption that stress released during a discrete failure increases stability. During that period, most of the landslide toe and areas near the headscarp accelerated, respectively, to 4–14 and 14 cm/a. The extent of deformation increased to cover most, or probably all, of the 2011 landslide as well as adjacent parts of the slope and plateau above. The InSAR-measured displacement patterns – supplemented by field observations and by optical satellite images – indicate that kinematically complex, steady-state creep along pre-existing sliding surfaces temporarily accelerated in response to heavy rainfall, after which the slope quickly achieved a slightly faster and expanded steadily creeping state. This case study demonstrates that high-quality ground-surface motion fields derived using spaceborne InSAR can help to characterize creep mechanisms, quantify spatial and temporal patterns of slope activity, and identify isolated small-scale instabilities. Characterizing slope instability before, during, and after the 2011 Pampahasi landslide is particularly important for understanding landslide hazard in La Paz, half of which is underlain by similar, large paleolandslides.

scholarly journals Assessment of Slope Instability and Risk Analysis of Road Cut Slopes in Lashotor Pass, Iran

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Mohammad Hossein Taherynia ◽  
Mojtaba Mohammadi ◽  
Rasoul Ajalloeian
Keyword(s):  
Rock Mass ◽  
Risk Analysis ◽  
Rock Slope ◽  
Classification Systems ◽  
Slope Instability ◽  
Rock Slope Stability ◽  
Rock Slopes ◽  
The Stability ◽  
Cut Slopes ◽  
Road Cut Slopes

Assessment of the stability of natural and artificial rock slopes is an important topic in the rock mechanics sciences. One of the most widely used methods for this purpose is the classification of the slope rock mass. In the recent decades, several rock slope classification systems are presented by many researchers. Each one of these rock mass classification systems uses different parameters and rating systems. These differences are due to the diversity of affecting parameters and the degree of influence on the rock slope stability. Another important point in rock slope stability is appraisal hazard and risk analysis. In the risk analysis, the degree of danger of rock slope instability is determined. The Lashotor pass is located in the Shiraz-Isfahan highway in Iran. Field surveys indicate that there are high potentialities of instability in the road cut slopes of the Lashotor pass. In the current paper, the stability of the rock slopes in the Lashotor pass is studied comprehensively with different classification methods. For risk analyses, we estimated dangerous area by use of the RocFall software. Furthermore, the dangers of falling rocks for the vehicles passing the Lashotor pass are estimated according to rockfall hazard rating system.

Limit analysis of submerged slopes subjected to water drawdown

2006 ◽  
Vol 43 (8) ◽  
pp. 802-814 ◽  
Author(s):  
Chardphoom Viratjandr ◽  
Radoslaw L Michalowski
Keyword(s):  
Limit Analysis ◽  
Limit State ◽  
Failure Surface ◽  
Slope Instability ◽  
Earth Dam ◽  
Temporary Increase ◽  
Stability Of Slopes ◽  
Water Drawdown ◽  
Hydraulic Conditions ◽  
Kinematic Approach

A rapid draw of water from a reservoir can cause a temporary increase in the hydraulic gradient that may not be tolerated by the slope of an earth dam. The increased seepage forces may lead to slope instability, causing the collapse of the structure. The kinematic approach of limit analysis is used to examine stability of slopes subjected to a rapid or slow drawdown. Combinations of slope inclination, soil properties, and hydraulic conditions are found for which the slope becomes unstable. The results are presented in the form of charts for convenient practical use, and the safety factors can be obtained from the charts without the need for iteration. For granular slopes, particularly if shallow, subjected to drawdown, a simple translational mechanism with a shallow failure surface is not the most adverse mechanism for all water-draw regimes.Key words: slopes, stability, rapid drawdown, limit state analysis.

Thermomechanical forcing of deep rock slope deformation: 2. The Randa rock slope instability

2011 ◽  
Vol 116 (F4) ◽  
Author(s):  
Valentin S. Gischig ◽  
Jeffrey R. Moore ◽  
Keith F. Evans ◽  
Florian Amann ◽  
Simon Loew
Keyword(s):  
Rock Slope ◽  
Slope Deformation ◽  
Slope Instability ◽  
Deep Rock

scholarly journals Stability assessment of degrading permafrost rock slopes based on a coupled thermo-mechanical model

2020 ◽  
Author(s):  
Philipp Mamot ◽  
Samuel Weber ◽  
Saskia Eppinger, ◽  
Michael Krautblatter
Keyword(s):  
Slope Stability ◽  
Rock Slope ◽  
Fracture Network ◽  
Slope Instability ◽  
Rock Slope Stability ◽  
Permafrost Degradation ◽  
Rock Slopes ◽  
High Mountains ◽  
Permafrost Rock ◽  
Wide Range

Abstract. In the last two decades, permafrost degradation has been observed to be a major driver of enhanced rock slope instability and associated hazards in high mountains. While the thermal regime of permafrost degradation in high mountains has already been intensively investigated, the mechanical consequences on rock slope stability have so far not been reproduced in numerical models. Laboratory studies and conceptual models argue that warming and thawing decrease rock and discontinuity strength and promote deformation. This study presents the first general approach for a temperature-dependent numerical stability model that simulates the mechanical response of a warming and thawing permafrost rock slope. The proposed procedure is applied to a rockslide at the permafrost-affected Zugspitze summit crest. Laboratory tests on frozen and unfrozen rock joint and intact rock properties provide material parameters for the discontinuum model developed with the Universal Distinct Element Code (UDEC). Geophysical and geotechnical field surveys deliver information on the permafrost distribution and fracture network. The model demonstrates that warming decreases rock slope stability to a critical level, while thawing initiates failure. A sensitivity analysis of the model with a simplified geometry and warming trajectory below 0 °C shows that progressive warming close to the melting point initiates instability above a critical slope angle of 50–62°, depending on the orientation of the fracture network. The increase in displacements intensifies for warming steps closer to zero degree. The simplified and generalised model can be applied to permafrost rock slopes (i) which warm above −4 °C, (ii), with ice-filled joints, (iii) with fractured limestone or probably most of the rock types relevant for permafrost rock slope failure, (iv) with a wide range of slope angles (30–70°) and orientations of the fracture network (consisting of three joint sets). The presented model is the first one capable of assessing the future destabilisation of degrading permafrost rock slopes.

scholarly journals Multiple rock-slope failures from Mannen in Romsdal Valley, western Norway, revealed from Quaternary geological mapping and 10Be exposure dating

The Holocene ◽  
2018 ◽  
Vol 28 (12) ◽  
pp. 1841-1854 ◽  
Author(s):  
Paula Hilger ◽  
Reginald L Hermanns ◽  
John C Gosse ◽  
Benjamin Jacobs ◽  
Bernd Etzelmüller ◽  
...  
Keyword(s):  
Slope Failure ◽  
Rock Slope ◽  
Significant Risk ◽  
Geological Mapping ◽  
Slope Instability ◽  
Permafrost Degradation ◽  
Geomorphological Mapping ◽  
Exposure Dating ◽  
Western Norway ◽  
Air Temperatures

Oversteepened valley walls in western Norway have high recurrences of Holocene rock-slope failure activity causing significant risk to communities and infrastructure. Deposits from six to nine catastrophic rock-slope failure (CRSF) events are preserved at the base of the Mannen rock-slope instability in the Romsdal Valley, western Norway. The timing of these CRSF events was determined by terrestrial cosmogenic nuclide dating and relative chronology due to mapping Quaternary deposits. The stratigraphical chronology indicates that three of the CRSF events occurred between 12 and 10 ka, during regional deglaciation. Congruent with previous investigations, these events are attributed to the debuttressing effect experienced by steep slopes following deglaciation, during a period of paraglacial relaxation. The remaining three to six CRSF events cluster at 4.9 ± 0.6 ka (based on 10 cosmogenic 10Be samples from boulders). CRSF events during this later period are ascribed to climatic changes at the end of the Holocene thermal optimum, including increased precipitation rates, high air temperatures and the associated degradation of permafrost in rock-slope faces. Geomorphological mapping and sedimentological analyses further permit the contextualisation of these deposits within the overall sequence of post-glacial fjord-valley infilling. In the light of contemporary climate change, the relationship between CRSF frequency, precipitation, air temperature and permafrost degradation may be of interest to others working or operating in comparable settings.

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