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DSD-NL 2015, Geo Klantendag D-Series, 3 Rekenen aan aardbevingen

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DSD-NL 2015, Geo Klantendag D-Series, 3 Rekenen aan aardbevingen

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DSD-NL 2015, Geo Klantendag D-Series, 3 Rekenen aan aardbevingen

  1. 1. Earthquake resistant design of levees and adjacent sheet piling Marcel Visschedijk
  2. 2. Proven earthquakes damage to levees 24-Jun-15 2 Especially if sand in or under the levee liquefies All pictures from: Y. Sasaki et al. / Soils and Foundations 52 (2012) 1016–1032
  3. 3. Damage caused by liquefaction 24-Jun-15 3
  4. 4. Damage caused by liquefaction Kobe, picture from http://geot.civil.metro-u.ac.jp/archives/eq/95kobe/index.html 24-Jun-15 4
  5. 5. 24-Jun-15 5 Proven earthquakes damage to levees Slide from: Presentation of Ikuo Towhata, at the Second International Conference on Performance‐Based design in Earthquake Geotechnical Engineering, Taormina, Italy on May 29, 2012
  6. 6. Proven earthquake damage in the Netherlands 24-Jun-15 6 Roermond, 1992 (magnitude 5.8) All pictures from: beeldbank.rws.nl
  7. 7. Groningen levees Questions for the 2013 study*: • Show the current state of the primary and regional defences • Give an indication of the required improvement, differentiating between the situation without and with earthquakes 24-Jun-15 7 Continued studies in 2014/2015 on most critical stretches: • Eemskanaal: levees and sheet-piling • Eemshaven-Delfzijl *http://www.rijksoverheid.nl/onderwerpen/aardbevingen-in-groningen/documenten-en-publicaties/rapporten/2014/01/17/deltaers-effecten-van-aardbevingen-op-kritische-infrastructuur.html
  8. 8. Important questions for EQ resistant design • Which mechanisms to consider and which (software) models to use • Which loading to apply • (How to reduce liquefaction, or minimize its effect) 24-Jun-15 8 PGA T (Picture from: Y. Sasaki et al.) (Picture from: Y. Sasaki et al.) (Picture from: I. Towhata)
  9. 9. Further content of the presentation • Which mechanisms to consider • Recently applied software models for the Groningen levees 24-Jun-15 9
  10. 10. Mechanims caused by earthquakes • Instability or damage by earthquake force • Crest settlement or damage by liquefaction of sand 24-Jun-15 10
  11. 11. Content of the presentation • Which mechanisms to consider • Recently applied software models for the Groningen levees 24-Jun-15 11
  12. 12. AAD: dedicated software for embankments 24-Jun-15 12 AardbevingsAnalyse Dijken Input: D-Geostability schematizations + cone resistances Output: Fragility curves
  13. 13. AAD v1: Applied Peak Ground Acceleration Along Eemskanaal 00 01 02 03 04 05 06 07 1 10 100 1000 10000 km31.5 Along Eemshaven-Delfzijl PGA [m/s^2] Return period [year] • Probability distribution According to KNMI • Semi-probabilistic determination of design value 24-Jun-15 13 PGA [m/s^2] Return period [year]
  14. 14. AAD v2: Nonlinear Soil Response 24-Jun-15 14
  15. 15. AAD: Applied Liquefaction model 24-Jun-15 EERI MNO-12*: Determines the excess pore pressure ratio 𝑟𝑢= Δ𝑢 𝜎 𝑣.0 ′ in clean sand as a function of field stresses, CPT resistance (𝑞 𝑐) en Peak Ground Acceleration (PGA) Example: Sand layer of 10m, without cover layer: 𝑟𝑢 5m below surface *Idriss, I.M. and Boulanger, R.W., 2008, Soil liquefaction during earthquakes, EERI MNO-12 𝑞c = 12 Mpa 𝑃𝑃𝑃 = 0.1𝑔 Empirical cyclic shear stress ratio resistance 15
  16. 16. AAD: models for the embankment 24-Jun-15 16 Displacement by sliding Settlement by squeezing Settlement by compaction F
  17. 17. Displacement by sliding 24-Jun-15 17 Force = Mass * Acceleration Displacement above yield value by double integration “Newmark Sliding Block” – also mentioned in EC8 Criterion: maximum sliding displacement = 0.15m (Jibson*) For design: inverse application to determine the critical acceleration value where static stability with D-Geostability has to be preserved to keep displacement below criterion. *Jibson, R.W., 2011, Methods for assessing the stability of slopes during earthquakes—A retrospective: Engineering Geology, v. 122, p. 43-50.
  18. 18. Displacement by sliding in case of liquefaction 24-Jun-15 18 Reduced tangent of the angle of friction tan(𝜙) by (partial) liquefaction • 50 % reduction during earthquake: tan 𝜙reduced = 1 − 0.5ru ⋅ tan 𝜙initial • 100 % reduction after earthquake: tan 𝜙reduced = max (0.06, 1 − ru ⋅ tan 𝜙initial) (analogous to draft Dutch National Application Document – NPR 9989)
  19. 19. 24-Jun-15 19 Scaling of measured accelerogram Derivation of (horizontal) design accelerograms 1. EC8: use at least 3 representative ground signals (4 used) 2. Scale measured signals for acceleration and time* with the Peak Ground Acceleration ratio: 𝑃𝑃𝐴design/𝑃𝑃𝐴measured PGA
  20. 20. Crest settlement by squeezing 24-Jun-15 20 h_levee d_top d_liquefied Finite Element results were used to fit an approximate (!) function between crest settlement and ℎlevee ⋅ 𝑑liquefied 𝑑top 2 (inspired by Finn*) * Finn, W. (2000). State-of-the-art of geotechnical earthquake engineering practice. Soil Dynamics and Earthquake Engineering, 20, pp 1-15.
  21. 21. Crest settlement by compaction Accepted empirical function of cyclic Factor of Safety against liquefaction and Relative Density 𝐷𝑟 (based on Ishihara & Yoshimine*) 24-Jun-15 21 * Ishihara, K., & Yoshimine, M. (1992). Evaluation of settlements in sand deposits following liquefaction during earthquakes. Soils and Foundations, Vol. 32, No.1, March 1992, pp 173-188. Factor of safety is cyclic shear ratio (CSR) divided by cyclic resistance ratio (CRR)
  22. 22. Example of resulting Fragility Curves 24-Jun-15 22 FoS Slope Stability versus PGA Crest Settlement versus PGA
  23. 23. Models for Sheet-Piling: before and after EQ Before earthquake: D-Sheetpiling 24-Jun-15 23 After earthquake: D-Sheetpiling with 100 % reduced strength by (partial) liquefaction
  24. 24. Models for Sheet-Piling: during EQ 24-Jun-15 24 Comparison of bending moments between generalized Mononobe-Okabe method (also suited for cohesive soil) and Finite Element Method (FEM) FEM is preferred: Mononobe-Okabe method is too conservative, and not able to find solutions for larger PGA values M-O M-O M-O FEM
  25. 25. • Used to derive an approximate factor between static and dynamic moments and anchor forces (load and site specific) • Liquefaction modeling by manual strength reduction (using 50 % of the final 𝑟𝑢) in combination with (damping) Hardening Soil Small Strain model • In progress: comparison with implicit pore pressure generation by constitutive models such as UBC-Sand or Hypoplasticity. 24-Jun-15 25 Current usage for Groningen levees: Dynamic FEM for sheetpiling during EQ
  26. 26. 24-Jun-15 26 Dynamic FEM for sheetpiling during EQ Derivation of (horizontal) base acceleration 1. EC8: use at least 3 representative ground signals (4 used) 2. Translate measured surface signals to the base at the location of the measurement, using the local soil profile and for example the EERA* software 3. Scale the base signals for acceleration and time with the ratio 𝑃𝑃𝐴design/𝑃𝑃𝐴measured (see Newmark Sliding Block) *A Computer Program for Equivalent linear Earthquake site Response Analyses of Layered Soil Deposits. Bardett et all, 2000 surface base
  27. 27. Finite Element simulation of liquefaction 24-Jun-15 27 • Hypoplasticity model is more generic than UBC-Sand model (initial state, different CSR values), but parameter determination is more difficult • Models are sensitive to variations of dominant parameters (HP: blow count, UBC-Sand: initial void ratio) • Current models can determine the undrained onset of liquefaction, but don’t supply reliable post-liquefaction deformations
  28. 28. Cyclic DSS test simulation on Loose sand 0.08 0.1 0.12 Green: UBCSAND Green: Hypoplastic Excess Pore Pressure Ratio 28 Shear Stress Ratio 24-Jun-15
  29. 29. Expected further application of Finite Elements • Liquefiability of Groningen sand with “single pulse” signals, compared to tectonic signals • Nonlinear response of subsoil plus levee, incl. pore pressure generation • Effectivity of mitigating measures 24-Jun-15 29

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