DSD-NL 2017 Probabilistic analysis macro stability - Brinkman
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Presentatie door Rob Brinkman (Deltares) op de Geo Klantendag, tijdens de Deltares Software Dagen- Editie 2017. Donderdag 15 juni 2017, Delft.
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DSD-NL 2017 Probabilistic analysis macro stability - Brinkman
- 1. Probabilistic analysis macro stability Rob Brinkman, Deltares 21 juni 2017
- 2. 21 juni 2017 Probabilistic analysis macro stability 1. Probabilistic toolkit 2. Macro stability case 3. Sensitivity analysis 4. Semi probabilistic analysis 5. Full probabilistic analysis
- 3. What is the probabilistic toolkit • Application for domain experts, who want to apply probabilistics on their model. • Applicable to each model. Long running calculations can be applied. • The domain expert doesn’t have to be an expert in probabilistics. • Enables the user to determine the sensitivity, probability of failure and band width of a model, given the uncertainties in the input parameters • Gives insight in the performed calculations 21 juni 2017
- 4. 21 juni 2017 Probabilistic toolkit Apply probabilistic techniques on any model Main Tasks Run model Use design values Optimization Sensitivity analysis Single variation Probability of failure Numerical Integration Monte Carlo FORM Band width Monte Carlo FOSM Models Scripts (Python, C#) Executables Batch files Libraries (dll) Combinations Applications Geotechnical failure (slope stability, design optimization, sheet piles, settlement) Asset management Coastal morphology Training probabilistic
- 5. Probabilistic toolkit Workflow 21 juni 2017 Prepare input file Existing application Define distributions Sensitivity analysis Failure probability Bandwidth Inspect calculations Attach input and application Run model
- 6. Macro stability case 21 juni 2017 Realistic but non existing case
- 7. Case description Four regions: below dike and outside dike above phreatic level and below phreatic level Below phreatic level weak soils behave undrained, above they behave drained Soil parameters to determine shear stress Drained: (C, φ) same below dike and outside dike Undrained: (S, m) different below dike and outside dike 21 juni 2017
- 8. Water levels Phreatic level based calculated by flow models Other levels calculated with phreatic level as input 21 juni 2017
- 9. Traffic load Traffic load Lower traffic load when water level is higher WL < 2.6 : 15 kPa 2.6 < WL < 3.29: 12 kPa 3.29 < WL: 5 kPa 21 juni 2017
- 10. Get acquainted with macro stability case • Perform variations on the input data • Perform sensitivity analysis on the input data • By using the Probabilistic Toolkit 21 juni 2017
- 11. DEMO PROBABILISTIC TOOLKIT SENSITIVITY 21 juni 2017
- 12. Probabilistic analysis based on same data Uncertainty in soil parameters Uncertainty in water level Uncertainty in load parameters Norm: Over all allowed probability of failure (1/10000 years) Reduction because taking measures decreases long term average (1/3000 years) 21 juni 2017
- 13. Semi probabilistic analysis • Use design values • Design value = Quantile (stochastic variable) / material factor • Quantile = 0.05 for strength parameters • Material factor = 1 • Use the water level at 1/3000 years • Quantile = 1 – 1/3000, which equals 3.20 m NAP • Required safety factor • Model factors increase the required safety factor • Schade (1.1), Uplift Van (1.06), Schematization (1.1) • Leads to required safety factor of 1.28 21 juni 2017
- 14. Semi probabilistic background 21 juni 2017 Kanning et al. (2015)
- 15. DEMO PROBABILISTIC TOOLKIT SEMI PROBABILISTIC 21 juni 2017
- 16. Full probabilstic analysis Use the water level at 1/3000 years = 3.20 m NAP Equals probability of 3.3E-4 Length effect, cross section representable for 20 km: 1 / (1 + L/lcorr) Other mechanisms, macro stability takes 0.04 Leads to prob of failure of approx. 1E-06 Corresponds with reliability index of 4.78 21 juni 2017
- 17. Probabilistic technique Theoretical approach: Numerical integration over all stochastic variables Each variable varies over its complete range Each combination is calculated Takes lots of calculation time Alternatives Monte Carlo Importance sampling FORM 21 juni 2017
- 18. DEMO PROBABILISTIC TOOLKIT PROBABILITY OF FAILURE 21 juni 2017