Loew - pore pressure

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International Conference Vajont2013 - 8 October

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Loew - pore pressure

  1. 1. Engineering Geology Pore Pressure Diffusion in Brittle Translational Rockslides Simon Loew Chair of Engineering Geology, ETH Zuerich, Switzerland Thomas Strauhal alpS – Centre for Climate Change Adaptation Technologies, Innsbruck, Austria • Simon Loew • Chair of Engineering Geology • ETH Zuerich, Switzerland • Contributors • Tokyo University August 31, 2011 & Marc Diederichs Giovanni Barla Photo: Alptransit – Gotthard Basistunnel Vajont Conference 2013 Transient Pore Pressures in Brittle Translational Rockslides Introduction
  2. 2. Engineering Geology Complex Hydrostratigraphy in Brittle Rockslides (Aknes) Eastern Alps Central Alps Western Alps Vajont Conference 2013 Transient Pore Pressures in Brittle Translational Rockslides Introduction
  3. 3. Engineering Geology Multiple Groundwater Tables & Perched Aquifers separated by Sliding Planes Tokyo University August 31, 2011 Vajont Conference 2013 Transient Pore Pressures in Brittle Translational Rockslides Introduction
  4. 4. Engineering Geology Confined or Artesian Pore Pressures below Basal Sliding Plane Tokyo University August 31, 2011 Vajont Conference 2013 Transient Pore Pressures in Brittle Translational Rockslides Introduction
  5. 5. Engineering Geology Generic Translational Rockslide Model Potential Recharge: 300mm/year (=9.5E-9 m/s) Stable Rock Mass Saturated Hydraulic Conductivity [m/s] Rockslide Mass Clayey Shear Zone Alluvial Deposits Base Case Parameter Var. 1 1.5·10-7 1.5·10-8 8.9·10-5 8.9·10-5 1.2·10-9 1.2·10-9 1.0·10-5 1.0·10-5 Parameter Var. 2 1.5·10-8 8.9·10-7 1.2·10-9 1.0·10-5 Parameter Var. 3 4.5·10-8 8.9·10-7 1.2·10-9 1.0·10-5 Vajont Conference 2013 Transient Pore Pressures in Brittle Translational Rockslides Generic Rockslide Model
  6. 6. Engineering Geology Fully Saturated (a) versus Partially Saturated (b) Groundwater Flow Lines and Pressure Fields Tokyo University August 31, 2011 Vajont Conference 2013 Transient Pore Pressures in Brittle Translational Rockslides Generic Rockslide Model
  7. 7. Engineering Geology No low-K Clayey Shear Zone One low-K Clayey Shear Zone Shallow & Limited Extent Rockslide (with/out Shear Zone) Vajont Conference 2013 Transient Pore Pressures in Brittle Translational Rockslides Steady State Pore Pressure Fields
  8. 8. Engineering Geology No low-K Clayey Shear Zone Two low-K Clayey Shear Zones Deep & Slope Extent Rockslide (with/out Shear Zones) Vajont Conference 2013 Transient Pore Pressures in Brittle Translational Rockslides Steady State Pore Pressure Fields
  9. 9. Engineering Geology Reduction of Stable Mass (Variation 1) & Rockslide Mass (Variation 2) Hydraulic Conductivity Tokyo University August 31, 2011 Vajont Conference 2013 Transient Pore Pressures in Brittle Translational Rockslides Steady State Pore Pressure Fields
  10. 10. Engineering Geology Reactions to Seasonal Groundwater Recharge (Transient Pressure Gradients below upper Sliding Zone) Tokyo University August 31, 2011 Vajont Conference 2013 Transient Pore Pressures in Brittle Translational Rockslides Pore Pressure Transients
  11. 11. Engineering Geology Reactions to Seasonal Lake Level Variations (Transient Pressure Gradients below/above upper Clayey Shear Zone) Pressures Above Shear Zone Tokyo University August 31, 2011 Pressures Below Shear Zone Vajont Conference 2013 Transient Pore Pressures in Brittle Translational Rockslides Pore Pressure Transients
  12. 12. Engineering Geology Superposition of Lake Level and Recharge Transients Vajont Conference 2013 Transient Pore Pressures in Brittle Translational Rockslides Pore Pressure Transients
  13. 13. Engineering Geology Dutchman’s Ridge Pore Pressure Transients Vajont Conference 2013 Transient Pore Pressures in Brittle Translational Rockslides Pore Pressure Transients
  14. 14. Engineering Geology Slope Stability with/out Consideration of Shear-StrengthSuction-Relationships (Fredlund 1995) Tokyo University August 31, 2011 Vajont Conference 2013 Transient Pore Pressures in Brittle Translational Rockslides Generic Rockslide Model
  15. 15. Engineering Geology Summary: Quasi-planer (2D) translational rockslides • Translational rockslides in brittle materials often developed complex hydrostratigraphy, composed of multiple water tables, confined pressures or suction below sliding planes • Pore pressure conditions are strongly influenced by ratio of recharge rate to surface layer hydraulic conductivity. Strongly fractured rockslide masses often show thin layers of (perched) groundwater at the interface to less deformed ground. • Unsaturated conditions further decrease hydraulic conductivities, recharge rates and groundwater table elevations • Clayey shear bands with reduced hydraulic conductivity favour the development of large zones with negative pore pressures, and/or strong pressure gardients (pressure compartments) • Pore pressure transients from lake evelation and periodic recharge variations show significant phase shifts when passing through lower permeability layers • Lake elevation transients are measurable up to a few tens of meters above the shore line and then become dominated by groundwater recharge from snow melt • Significant knowledge gaps refer to saturation-suction relationships in fractured rock slopes Vajont Conference 2013 Transient Pore Pressures in Brittle Translational Rockslides Generic Rockslide Model
  16. 16. Engineering Geology Thank you for your attention! Any Question ? Open postdoc/lecturer positions in rockslide processes at ETH: www.engineering-geology.ethz.ch Vajont Conference 2013 Transient Pore Pressures in Brittle Translational Rockslides Generic Rockslide Model

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