Numerical Simulation of Earthworks and Retaining System for an Excavation F. Geiser and S. Commend

1. Numerical Simulation of Earthworks and Retaining System for an Excavation F. Geiser and S. Commend GeoMod ing. conseils SA

2. Introduction • Offices and commercial building • Lausanne region • 120 x 35(max) x 9.3 m Numerical modelling: 3D numerical simulation (Z_Soil) 30’000 continuum elements

3. Geometry: structural elements Slurry wall

4. Hydrogeotechnical conditions 3.5 m 412.7 msm = 0.0 Remblai 9.3 m Glacio-sableux Glacio-argileux mou 8.0 m Fluvio-glaciaire Glacio-argileux Moraine Molasse imperméable Puits de décharge

5. Excavation stages Piles T = 0. Etat initial

6. Piles realisation

7. Slurry wall realisation

8. Excavation stages T = 1. Excavation globale jusqu’à -3.0 m

9. zone A Excavation stages T = 2. Excavation zone A à -7.0 m, puis étayage à -2.5 m

11. Excavation stages T = 3. Excavation du reste à -7.0 m

12. Excavation stages T = 3.2. Excavation zone A jusqu’à -9.3 m (f.f.)

13. Excavation stages T = 3.4. Excavation de la moitié du reste jusqu’à -9.3 m

14. Excavation stages T = 3.6. Sous-radier à -9.3 m sur la moitié de la surface

15. T = 5 Excavation stages T = 4. Excavation du reste à -9.3 m, puis fin du sous-radier T = 5. Application des charges de service du bâtiment

16. uz B A Results: finalhorizontal displacements

17. Results: horizontal displacements evolution

18. Results: final horizontal displacements

19. Results: final vertical displacements

20. Results: forces in the bracing

21. Results: moments in the slurry wall

22. Results: moments in the slurry wall

23. 17.2 m 15 m Water : particular study

24. Water : simplified 3D model 3.5 m 412.7 msm = 0.0 Remblai K = 10-5 m/s épaisseur = 3.5 à 7.5 m 9.3 m Glacio-sableux K = 10-5 m/s épaisseur = 4 m Glacio-argileux mou K = 10-10 m/s épaisseur = 7.6 m 8.0 m Fluvio-glaciaire K = 10-3 m/s épaisseur = 3.7 m Glacio-argileux K = 10-8 m/s épaisseur = 4 m Moraine K = 10-9 m/s épaisseur = 6 m Molasse imperméable Well (modelwith/without) K = 10-3 m/s e= 15 m

25. Tranche 3D avec puits, esp. = 15 m Coupe 2D avec tranchées drainantes A = 15 * 17.2 = 258 m2 Water : simplified 3D model with well

26. Water : simplified 3D model Clay – low permeability e

27. Low permeability High permeability Water : 3D model

28. Water : 3D model

29. Water : 3D model 1625 m3 / jour

30. Water : 3D model Impermeable wall 0.04 m3 / jour

31. Impermeable wall

32. Temperature effect on bracing : 2D modelgeneral considerations for DT = 30 ° Free truss: Dl = aDT L/2 = 5 mm Fixed conditions DF = 1000 kN Imposed displacement DF = 165 kN Dux imposé = - 5 mm Dux = - 4.2 mm

33. T : from 10 °C to 40 °C => DT = 30 °C Temperature effect on bracing : 2D modelimposing DT on bracing (Q4) T = 10 °C = cte

34. Temperature effect on bracing : 2D modelimposing DT on bracing Dux = 0 (imposed) DN=230 kN

35. Conclusions • Currently under construction • Predictions in the range of deformations and forces • Horizontal displacements slightly > measurements • Linked mainly to: • - « conservative » evaluation of f and c • - real water behaviour