Hydromechanical Rock Mass Fatigue in Deep-Seated Landslides Accompanying Seasonal Variations in Pore Pressures

Preisig, Giona; Eberhardt, E.; Smithyman, Megan; Preh, Alexander; Bonzanigo, Luca

doi:10.1007/s00603-016-0912-5

Cited by 62 publications

(44 citation statements)

References 24 publications

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“…At the same time, increasing water pressure results in abrupt increases of rockslide displacement rates. These results suggest that “mature” rockslides become hydromechanically independent from the rest of the slope and increasingly more sensitive to hydrological triggers (Agliardi & Crosta, ; Crosta et al, ; Preisig et al, ).…”

Section: Resultsmentioning

confidence: 96%

“…This is due to the almost complete lack of knowledge of slope hydrology and hydraulic boundary conditions in deglaciating settings (Figure ), including the recharge contribution of melting glaciers, the role of permafrost on the availability and mobility of liquid water in slopes, and the geometry and extent of groundwater below the ice cover (Crosta et al, ; McColl, ). In addition, while the influence of crack damage on the permeability of rocks has been studied in rock mechanics laboratory and underground field experiments (Fortin et al, ; Rutqvist, ; Zoback & Byerlee, ), the mechanisms and timing of development of rock mass permeability between deglaciation and complete rockslide development (Preisig et al, ) are not well known.…”

Section: Numerical Model: Dadyn‐rsmentioning

confidence: 99%

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Damage‐Based Time‐Dependent Modeling of Paraglacial to Postglacial Progressive Failure of Large Rock Slopes

et al. 2018

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Large alpine rock slopes undergo long‐term evolution in paraglacial to postglacial environments. Rock mass weakening and increased permeability associated with the progressive failure of deglaciated slopes promote the development of potentially catastrophic rockslides. We captured the entire life cycle of alpine slopes in one damage‐based, time‐dependent 2‐D model of brittle creep, including deglaciation, damage‐dependent fluid occurrence, and rock mass property upscaling. We applied the model to the Spriana rock slope (Central Alps), affected by long‐term instability after Last Glacial Maximum and representing an active threat. We simulated the evolution of the slope from glaciated conditions to present day and calibrated the model using site investigation data and available temporal constraints. The model tracks the entire progressive failure path of the slope from deglaciation to rockslide development, without a priori assumptions on shear zone geometry and hydraulic conditions. Complete rockslide differentiation occurs through the transition from dilatant damage to a compacting basal shear zone, accounting for observed hydraulic barrier effects and perched aquifer formation. Our model investigates the mechanical role of deglaciation and damage‐controlled fluid distribution in the development of alpine rockslides. The absolute simulated timing of rock slope instability development supports a very long “paraglacial” period of subcritical rock mass damage. After initial damage localization during the Lateglacial, rockslide nucleation initiates soon after the onset of Holocene, whereas full mechanical and hydraulic rockslide differentiation occurs during Mid‐Holocene, supporting a key role of long‐term damage in the reported occurrence of widespread rockslide clusters of these ages.

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Section: Resultsmentioning

confidence: 96%

Section: Numerical Model: Dadyn‐rsmentioning

confidence: 99%

Damage‐Based Time‐Dependent Modeling of Paraglacial to Postglacial Progressive Failure of Large Rock Slopes

et al. 2018

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“…We demonstrated that glacial cycles strongly affect the amount of critically stressed joints within an alpine valley (Figures f and h) and each phase of glacier retreat places adjacent rock slopes into a more critically stressed condition (Figure c). Other environmental processes can act on the critically stressed slopes contributing to additional damage and promoting time‐dependent failure, e.g., chemical weathering within joints [ Jaboyedoff et al , ], stress corrosion at fracture tips [ Faillettaz et al , ], ice segregation [ Wegmann et al , ; Hales and Roering , ; Sanders et al , ; Krautblatter et al , ], changes in joint water pressure [ Hansmann et al , ; Preisig et al , ], thermal stresses [ Wegmann and Gudmundsson , ; Gischig et al , ; Baroni et al , ], or seismic fatigue [ Gischig et al , ]. Each of these processes can contribute to further rock slope damage, especially at times when ice loading conditions increase the criticality of the slope.…”

Section: Implications For Paraglacial Rock Slope Instabilitiesmentioning

confidence: 99%

Beyond debuttressing: Mechanics of paraglacial rock slope damage during repeat glacial cycles

et al. 2017

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Cycles of glaciation impose mechanical stresses on underlying bedrock as glaciers advance, erode, and retreat. Fracture initiation and propagation constitute rock mass damage and act as preparatory factors for slope failures; however, the mechanics of paraglacial rock slope damage remain poorly characterized. Using conceptual numerical models closely based on the Aletsch Glacier region of Switzerland, we explore how in situ stress changes associated with fluctuating ice thickness can drive progressive rock mass failure preparing future slope instabilities. Our simulations reveal that glacial cycles as purely mechanical loading and unloading phenomena produce relatively limited new damage. However, ice fluctuations can increase the criticality of fractures in adjacent slopes, which may in turn increase the efficacy of fatigue processes. Bedrock erosion during glaciation promotes significant new damage during first deglaciation. An already weakened rock slope is more susceptible to damage from glacier loading and unloading and may fail completely. We find that damage kinematics are controlled by discontinuity geometry and the relative position of the glacier; ice advance and retreat both generate damage. We correlate model results with mapped landslides around the Great Aletsch Glacier. Our result that most damage occurs during first deglaciation agrees with the relative age of the majority of identified landslides. The kinematics and dimensions of a slope failure produced in our models are also in good agreement with characteristics of instabilities observed in the field. Our results extend simplified assumptions of glacial debuttressing, demonstrating in detail how cycles of ice loading, erosion, and unloading drive paraglacial rock slope damage.

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“…Other studies reveal the impact of glacier retreat on permafrost penetration in rock walls at high altitudes, which may enhance frost cracking (Wegmann et al, ; Wegmann & Gudmundsson, ), but did not analyze damage caused by thermal strain in fractured rock masses. In a paraglacial environment (Slaymaker, ), where rock slopes are adjusting to the change from glacial to nonglacial conditions (Figure a), several other processes also act in conjunction with glacier advance and retreat, include chemical weathering (Jaboyedoff et al, ), stress corrosion (Faillettaz et al, ), changes in joint water pressure (Hansmann et al, ; Preisig et al, ), or seismic fatigue (Gischig et al, ; McColl et al, ). Each of these processes is affected by the current and past position of the proximal valley glacier, which controls the location and magnitude of local rock slope damage.…”

Section: Introductionmentioning

confidence: 99%

Thermomechanical Stresses Drive Damage of Alpine Valley Rock Walls During Repeat Glacial Cycles

et al. 2018

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Cycles of glaciation alter the temperature field in proximal alpine valley flanks, driving rock slope damage through thermomechanical stresses. Here we extend simplified assumptions of glacial debuttressing to quantitatively examine how paraglacial bedrock temperature changes, acting in concert with changing ice loads during Late Pleistocene and Holocene glacial cycles, create damage in adjacent rock slopes and prepare future slope instabilities. When in contact with temperate glacier ice, valley walls maintain near isothermal ~0 °C surface temperatures and are shielded from daily and annual cycles. With retreat, rock walls are rapidly exposed to strongly varying temperature boundary conditions, a transition we term “paraglacial thermal shock.” Using detailed, conceptual numerical models based on the Aletsch Glacier in Switzerland, we show that including thermomechanical stresses during simulated glacial cycles creates significantly more rock slope damage than predicted for purely mechanical ice loading and unloading. Glacier advances are especially effective in generating damage as rapid cooling drives contraction of the rock mass reducing joint normal stresses. First time exposure to annual temperature cycles during deglaciation induces a shallow damage front that follows the retreating ice margin, generating damage in a complementary process at shorter time scales. Acting on a reduced strength rock mass, modeled thermomechanical cycles enhance the development of a slope instability with similar attributes as observed in our study area. Our results demonstrate that thermomechanical stresses acting in conjunction with changing ice loads are capable of generating considerable rock slope damage with spatial and temporal patterns controlled by glacier extents.

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Hydromechanical Rock Mass Fatigue in Deep-Seated Landslides Accompanying Seasonal Variations in Pore Pressures

Cited by 62 publications

References 24 publications

Damage‐Based Time‐Dependent Modeling of Paraglacial to Postglacial Progressive Failure of Large Rock Slopes

Damage‐Based Time‐Dependent Modeling of Paraglacial to Postglacial Progressive Failure of Large Rock Slopes

Beyond debuttressing: Mechanics of paraglacial rock slope damage during repeat glacial cycles

Thermomechanical Stresses Drive Damage of Alpine Valley Rock Walls During Repeat Glacial Cycles

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