Progressive failure in deep-seated rockslides due to seasonal fluctuations in pore pressures and rock mass fatigue

Eberhardt, E.; Preisig, Giona; Gischig, Valentin

doi:10.1201/b21520-13

Cited by 9 publications

(8 citation statements)

References 2 publications

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“…Therefore, we predict that our results may underestimate long-term HM fatigue (cf. Eberhardt et al, 2016;Preisig et al, 2016). Additionally, although fracture permeability is dependent on effective stress, aperture, and shear slip (Preisig et al, 2012), the HM slope response in our models is only semi-coupled; that is, water pressures affect joint aperture and reduce effective stresses, but the mechanical response does not affect the hydraulic properties.…”

Section: 1029/2019jf005494mentioning

confidence: 95%

“…Meanwhile, observations in stable alpine valley flanks have highlighted reversible rock slope deformations associated with annual rising and lowering groundwater tables (Hansmann et al, 2012;Loew et al, 2007;Rouyet et al, 2017). Such coupled HM processes may play an important role in driving cyclic fracture propagation over longer time scales (Eberhardt et al, 2016;Preisig et al, 2016), especially in concert with long-term groundwater table fluctuations, for example, associated with changing ice elevation, that alter the affected area over time.…”

Section: Introductionmentioning

confidence: 99%

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Hydromechanical Rock Slope Damage During Late Pleistocene and Holocene Glacial Cycles in an Alpine Valley

et al. 2020

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Subglacial water pressures influence groundwater conditions in proximal alpine valley rock slopes, varying with glacier advance and retreat in parallel with changing ice thickness. Fluctuating groundwater pressures in turn increase or reduce effective joint normal stresses, affecting the yield strength of discontinuities. Here we extend simplified assumptions of glacial debuttressing to investigate how glacier loading cycles together with changing groundwater pressures generate rock slope damage and prepare future slope instabilities. Using hydromechanical coupled numerical models closely based on the Aletsch Glacier valley in Switzerland, we simulate Late Pleistocene and Holocene glacier loading cycles including long‐term and annual groundwater fluctuations. Measurements of transient subglacial water pressures from ice boreholes in the Aletsch Glacier ablation area, as well as continuous monitoring of bedrock deformation from permanent Global Navigation Satellite Systems stations, help verify our model assumptions. While purely mechanical glacier loading cycles create only limited rock slope damage in our models, introducing a fluctuating groundwater table generates substantial new fracturing. Superposed annual groundwater cycles increase predicted damage. The cumulative effects are capable of destabilizing the eastern valley flank of our model in toppling‐mode failure, similar to field observations of active landslide geometry and kinematics. We find that hydromechanical fatigue is most effective acting in combination with long‐term loading and unloading of the slope during glacial cycles. Our results demonstrate that hydromechanical stresses associated with glacial cycles are capable of generating substantial rock slope damage and represent a key preparatory factor for paraglacial slope instabilities.

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Section: 1029/2019jf005494mentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Hydromechanical Rock Slope Damage During Late Pleistocene and Holocene Glacial Cycles in an Alpine Valley

et al. 2020

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“…These seasonal patterns are driven by changes in temperature and water supply (Kenner et al, 2017;Cicoira et al, 2019). Velocity variations of rockslide are typically comparatively smaller and more spread over the year as many external drivers may impact the strength degradation, internal shearing and progressive failure of rock bridges (Eberhardt et al, 2016), although seasonal influence in relation with freeze/thaw cycles has also been evidenced in periglacial environments (Blikra and Christiansen, 2014;Keuschnig et al, 2015). Based on InSAR, the differentiation of gravitational/irreversible and seasonal/reversible components of the movement and the quantification of the seasonal variations of velocity can be performed by analysing time series (Dini et al, 2019;Rouyet et al, 2019;Strozzi et al, 2020).…”

Section: Update Of the Rockslide Inventorymentioning

confidence: 99%

Regional Morpho-Kinematic Inventory of Slope Movements in Northern Norway

et al. 2021

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Mountain slopes in periglacial environments are affected by frost- and gravity-driven processes that shape the landscape. Both rock glaciers and rockslides have been intensively inventoried worldwide. Although most inventories are traditionally based on morphologic criteria, kinematic approaches based on satellite remote sensing have more recently been used to identify moving landforms at the regional scale. In this study, we developed simplified Interferometric Synthetic Aperture Radar (InSAR) products to inventory ground velocity in a region in Northern Norway covering approximately 7,500 km2. We used a multiple temporal baseline InSAR stacking procedure based on 2015–2019 ascending and descending Sentinel-1 images to take advantage of a large set of interferograms and exploit different detection capabilities. First, moving areas are classified according to six velocity brackets, and morphologically associated to six landform types (rock glaciers, rockslides, glaciers/moraines, talus/scree deposits, solifluction/cryoturbation and composite landforms). The kinematic inventory shows that the velocity ranges and spatial distribution of the different types of slope processes vary greatly within the study area. Second, we exploit InSAR to update pre-existing inventories of rock glaciers and rockslides in the region. Landform delineations and divisions are refined, and newly detected landforms (54 rock glaciers and 20 rockslides) are incorporated into the databases. The updated inventories consist of 414 rock glacier units within 340 single- or multi-unit(s) systems and 117 rockslides. A kinematic attribute assigned to each inventoried landform documents the order of magnitude of the creep rate. Finally, we show that topo-climatic variables influence the spatial distribution of the rock glaciers. Their mean elevation increases toward the continental interior with a dominance of relict landforms close to the land-sea margin and an increased occurrence of active landforms further inland. Both rock glaciers and rockslides are mostly located on west-facing slopes and in areas characterised by strongly foliated rocks, which suggests the influence of geological preconditioning factors. The study demonstrates the value of semi-quantitative InSAR products to characterise kinematic information at large scale and exploit the results for periglacial research. It highlights the complementarity of both kinematic and morphologic approaches for inventorying slope processes.

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“…Superimposed on this are seasonal precipitation and groundwater infiltration patterns. Recent investigations utilizing advanced numerical modeling techniques show that transient pore pressures cause localized reductions in effective stresses along fractures promoting slip, which in turn triggers slip of adjacent fractures and/or the rupture of intact rock bridges (Eberhardt et al 2016;Preisig et al 2016). Over time, this repeated pattern gradually weakens the slope.…”

Section: Introductionmentioning

confidence: 99%

Keynote Address: Influence of Transient Pore Pressures on the Progressive Failure of Rock Slopes

Eberhardt

2022

Geological Society of America Abstracts With Programs

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Progressive failure in deep-seated rockslides due to seasonal fluctuations in pore pressures and rock mass fatigue

Cited by 9 publications

References 2 publications

Hydromechanical Rock Slope Damage During Late Pleistocene and Holocene Glacial Cycles in an Alpine Valley

Hydromechanical Rock Slope Damage During Late Pleistocene and Holocene Glacial Cycles in an Alpine Valley

Regional Morpho-Kinematic Inventory of Slope Movements in Northern Norway

Keynote Address: Influence of Transient Pore Pressures on the Progressive Failure of Rock Slopes

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