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DSD-NL 2019 Anura3D ontwikkelingen - Analyse grote deformaties in de geotechniek - Martinelli

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Presentatie door Mario Martinelli, Deltares, op de Geo Klantendag 2019, tijdens de Deltares Software Dagen - Editie 2019. Donderdag, 20 juni 2019, Delft.

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DSD-NL 2019 Anura3D ontwikkelingen - Analyse grote deformaties in de geotechniek - Martinelli

  1. 1. G e o K l a n t e n d a g 2 0 1 9 , 2 0 j u n i 2 0 1 9 Anura3D ontwikkelingen: Analyse grote deformaties in de geotechniek Mario Martinelli
  2. 2. GeoKlantendag2019,20juni2019 2 Outline • Large deformation analysis - MPM • Cutting process in layered soils • Monopile installation This Photo by Unknown Author is licensed under CC BY-NC-ND
  3. 3. GeoKlantendag2019,20juni2019 3 Outline • Large deformation analysis - MPM • Cutting process in layered soils • Monopile installation This Photo by Unknown Author is licensed under CC BY-NC-ND
  4. 4. Basic FEM approaches GeoKlantendag2019,20juni2019 4 • elements become inaccurate / unstable if distorted too much • → remeshing needed A deformed mesh at true scale
  5. 5. The Material Point Method GeoKlantendag2019,20juni2019 5LAGRANGIAN EULERIAN (A) initial configuration (B) calculation step (C) after resetting the mesh in each step :
  6. 6. The Material Point Method GeoKlantendag2019,20juni2019 6 initial position of material points final position of material points material points move through mesh total displacements [m]total displacements [m] collapsing soil column: total displacements in [m]
  7. 7. GeoKlantendag2019,20juni2019 7 Large deformation problems dikes, dams, landslides installation, impact flowslides, erosion, liquefaction
  8. 8. GeoKlantendag2019,20juni2019 8 Outline • Large deformation analysis - MPM • Cutting process in layered soils • Monopile installation This Photo by Unknown Author is licensed under CC BY-NC-ND
  9. 9. GeoKlantendag2019,20juni2019 9 Cutting forces in layered soils Figure 1.1 Example of “Dry” chain cutter
  10. 10. GeoKlantendag2019,20juni2019 10 Cutting forces in layered soils underpressureincrease effective stresses Water inflow shear Volume increase due to dilation
  11. 11. GeoKlantendag2019,20juni2019 11 Cutting forces in layered soils • Problem Trench depth’s of the order 6 meter. Hard clays & variability in composition of soils in trenching for cables and pipelines. • Objective cutting forces unknown in inhomogeneous soils consisting of clays and sand. • Approach ✓ laboratory cutting tests on layered clay and sand ✓ Numerical modelling
  12. 12. GeoKlantendag2019,20juni2019 12 Cutting forces in layered soils What if: sand clayclayClay obstructs drainage path: greater sand cutting force expected • Problem Trench depth’s of the order 6 meter. Hard clays & variability in composition of soils in trenching for cables and pipelines. • Objective cutting forces unknown in inhomogeneous soils consisting of clays and sand. • Approach ✓ laboratory cutting tests on layered clay and sand ✓ Numerical modelling
  13. 13. GeoKlantendag2019,20juni2019 13 Cutting forces in layered soils • Cutting blade moving • through layer soils rotated for test and model Linear vertical cut Linear horizontal cut Chain cutter
  14. 14. GeoKlantendag2019,20juni2019 14 Cutting forces in layered soils
  15. 15. GeoKlantendag2019,20juni2019 15 Cutting forces in layered soils Width of the blade is 0.25 m and the instrumented central part is 0.15 m wide
  16. 16. GeoKlantendag2019,20juni2019 16 Cutting forces in layered soils CLAY CLAYSAND • Significant variation in sand reaction forces • Smoother pattern in clay
  17. 17. GeoKlantendag2019,20juni2019 17 Cutting forces in layered soils
  18. 18. GeoKlantendag2019,20juni2019 18 Cutting forces in layered soils CLAY SAND 8S4C 4S8C 20S32C • Reaction force in clay is lower than the one of the homogeneous layer • Reaction forces of the interlayered sand-clay system tends to be in between the “homogeneous” clay and “homogeneous” sand
  19. 19. GeoKlantendag2019,20juni2019 19 Cutting forces in layered soils SAND CLAY CLAY FIXEDMATERIAL 4 cm sand, 8 cm clay sequence SAND Close-up view h=3cm
  20. 20. GeoKlantendag2019,20juni2019 20 Cutting forces in layered soils Close-up view SAND CLAY CLAY
  21. 21. GeoKlantendag2019,20juni2019 21 Cutting forces in layered soils TX3 TX3 TX3
  22. 22. GeoKlantendag2019,20juni2019 22 Cutting forces in layered soils Sand permeability Initialcondition Max.porosity K = 6.7 10-5m/s K = 1.5 10-4m/s Analysis no. Dr [%] k [m/s] 1 75 6.7 10-5 2 75 1.5 10-4 3 85 6.7 10-5 4 85 1.5 10-4 Bulk density ring
  23. 23. GeoKlantendag2019,20juni2019 23 Cutting forces in layered soils Suction [kPa] v=2m/s Dr=85% - k=1.5 10-4 m/s: Excess pore pressure
  24. 24. GeoKlantendag2019,20juni2019 24 Cutting forces in layered soils t = 0.01s t = 0.02s t = 0.03s t = 0.05s Suction [kPa] Dr=85% - k=1.5 10-4 m/s: Excess pore pressure
  25. 25. GeoKlantendag2019,20juni2019 25 Cutting forces in layered soils Dr=85% - k=1.5 10-4 m/s: void ratio t = 0.01s t = 0.02s t = 0.03s t = 0.05s Void ratio [-] 0.8 1.0 1.10.7
  26. 26. GeoKlantendag2019,20juni2019 26 Cutting forces in layered soils t = 0.01s t = 0.02s k = 1.5 10-4 m/s k = 6.7 10-5 m/s Suction [kPa] Excess pore pressure: effect permeability
  27. 27. GeoKlantendag2019,20juni2019 27 Cutting forces in layered soils t = 0.01s t = 0.02s Dr = 85% Dr = 75% Suction [kPa] Excess pore pressure: effect Dr
  28. 28. GeoKlantendag2019,20juni2019 28 Cutting forces in layered soils v=2m/s v = 2 m/s
  29. 29. GeoKlantendag2019,20juni2019 29 Cutting forces in layered soils t = 0.01s t = 0.02s t = 0.03s t = 0.05s 4 cm 8 cm CLAY SAND CLAY SAND
  30. 30. GeoKlantendag2019,20juni2019 30 Cutting forces in layered soils • Reaction forces for 8S4C and 4S8C are bounded between Homogeneous Clay and Homogeneous Sand. • 8cm are enough to reach the homogeneous conditions
  31. 31. GeoKlantendag2019,20juni2019 31 Cutting forces in layered soils t = 0.01s t = 0.02s t = 0.03s t = 0.05s Void ratio [-] 0.8 1.0 1.10.7
  32. 32. GeoKlantendag2019,20juni2019 32 Cutting forces in layered soils • Reaction forces for 4S2C and 2S4C are again bounded between homogeneous sand and homogeneous clay 2S4C 4S2C v=2m/s
  33. 33. GeoKlantendag2019,20juni2019 33 Cutting forces in layered soils A.M. Talmon, M. Martinelli and H.J. Luger, 2019, Numerical simulation of cutting tests on layered sand and clay, WODCON XXII, Shanghai, April 25-29. NEW Possibilities in calculation for soil excavation!, reducing risks, facilitating cutting deep trenches. -Calculated shear planes in failure are not as clear cut as in observation- based regime sketches and previous semi-analytical modelling. -Similar time-series pattern in lab tests and MPM calculation. -MPM: ~ weighed average of composited soil. Contrary to a bias to clay domination in measurements.
  34. 34. GeoKlantendag2019,20juni2019 34 Outline • Large deformation analysis - MPM • Cutting process in layered soils • Monopile installation This Photo by Unknown Author is licensed under CC BY-NC-ND
  35. 35. Monopiles GeoKlantendag2019,20juni2019 35
  36. 36. Current monpile installation methods GeoKlantendag2019,20juni2019 36 Jacking Impact driving Vibro- driving Fstat Fdyn Fstat (displacement controlled) Fstat Grabe et al.
  37. 37. Requirements numerical analysis of installation process • Large deformations • Dynamic and cyclic loading under high frequencies • Saturated sand (coupled-analysis) • Generation and dissipation of excess pore water pressures • Liquefaction along shaft for vibrated pile • Sand is complex material with stiffness, strength, dilation depending on density and stress • Interaction between monopile and soil (SSI) • Realistic computation times! GeoKlantendag2019,20juni2019 37
  38. 38. 2D-Axisymmetry MPM • Number of elements and material points can significantly be reduced compared to 3D simulations • In 2D axisymmetric, each particle represents one radian of a ring rotated around the axis of symmetry • The rest of formulation of 2D axisymmetric MPM is similar to the 2D axisymmetric formulation of FEM GeoKlantendag2019,20juni2019 38 Galavi, V., Tehrani, F.S., Martinelli, M., Elkadi, A.S. & Luger, D. (2018). Axisymmetric formulation of the material point method for geotechnical engineering applications. 9th European Conference on Numerical Methods in Geotechnical Engineering (NUMGE18)
  39. 39. Small scale monotonic/cyclic installation GeoKlantendag2019,20juni2019 39 Stoevelaaret al. (2011) Baskarp sand is used Acceleration = 80 g Dimensions of the centrifuge set-up
  40. 40. Small scale monotonic/cyclic installation GeoKlantendag2019,20juni2019 40 Pile Soil ~ 9000 linear triangle elements
  41. 41. Small scale monotonic/cyclic installation GeoKlantendag2019,20juni2019 41 ~ 48000 material points
  42. 42. Small scale monotonic/cyclic installation GeoKlantendag2019,20juni2019 42 Dr = 38%
  43. 43. Small scale monotonic/cyclic installation GeoKlantendag2019,20juni2019 43 Dr = 66%
  44. 44. Small scale impact-driven installation GeoKlantendag2019,20juni2019 44 • Dry sand • Three different relative densities, namely 40%, 60% and 90% (up to 3% error) • Mass of hammer: 3 kg • Fall height: 1 m • Diameter of tank: 2 m; height: 1.6 m
  45. 45. Small scale impact-driven installation GeoKlantendag2019,20juni2019 45
  46. 46. Small scale impact-driven installation GeoKlantendag2019,20juni2019 46
  47. 47. Full scale impact-driven installation • 7.8 m diameter monopile, 0.07 m wall-thickness • Driven in the North Sea • Total length of ~77 m, ~34 m in the sea bed. • Water depth ~40 m Data provided by Boskalis • Soil layers: • CPT values, relative density • Type of hammer • Geometry of pile • Blow counts at different depths GeoKlantendag2019,20juni2019 47
  48. 48. Full scale impact-driven installation • Soil: Double Hardening model • Pile: Rigid • 2-phase formulation • (dynamic consolidation) • Pile embedded initially at 4.7m GeoKlantendag2019,20juni2019 48 MovingmeshCompressingmesh 3.885 m
  49. 49. Full scale impact-driven installation GeoKlantendag2019,20juni2019 49 Vertical effective stress during Hammering Deviatoric strain during Hammering
  50. 50. 0 50 100 150 200 5 6 7 8 9 10 11 12 Blow Depth(m) Full scale impact-driven installation GeoKlantendag2019,20juni2019 50 0 50 100 150 200 250 4 5 6 7 8 9 10 11 BlowDepth ------ 𝜓 = 4 ------ 𝜓 = 1 ------ 𝜓 = 0.5 Field Data o ------ Permeability =1e-3 m/s ------ Permeability =1e-4 m/s Field Data o 0 50 100 150 200 5 6 7 8 9 10 11 12 Blow Depth(m)
  51. 51. Full scale impact-driven installation GeoKlantendag2019,20juni2019 51 Change in density in cross-section after 2 m penetration Horizontal effective stresses after lateral loading
  52. 52. Summary • The material point method has been further developed, optimized, and successfully applied in simulating the process of monopile installation for impact driving (field-scale monopile) and low frequency vibratory driving (centrifuge scale) • The solution is capable of coping with dynamic cyclic, coupled, large-deformation, soil-water- structure interaction problems GeoKlantendag2019,20juni2019 52 V Galavi, FS Tehrani, M Martinelli, AS Elkadi, D Luger. Axisymmetric formulation of the material point method for geotechnical engineering applications. Numerical Methods in Geotechnical Engineering IX, 427-434 Galavi V., Martinelli M., Ghasemi P., Elkadi A., Rene Thijssen R. - Numerical simulation of an impact driven offshore monopile. Geotechnique 2019 (in preparation)
  53. 53. GeoKlantendag2019,20juni2019 53 Deltares Tetra Building – Delft ©Ahmed Elkadi

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