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Concrete Institute of Australia Soil-Structure Interaction Seminar Sydney March 2007

Concrete Institute of Australia Soil-Structure Interaction Seminar Sydney March 2007. Design of Buried Arch Tunnels Under High Fills Doug Jenkins Interactive Design Services. Overview:. Influence of high fills on structural actions Design of foundation structures for high vertical loads

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Concrete Institute of Australia Soil-Structure Interaction Seminar Sydney March 2007

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  1. Concrete Institute of Australia Soil-Structure Interaction Seminar Sydney March 2007 Design of Buried Arch Tunnels Under High Fills Doug Jenkins Interactive Design Services

  2. Overview: Influence of high fills on structural actions Design of foundation structures for high vertical loads Longitudinal differential settlement Longitudinal loads Examples Conclusions

  3. Influence of high fills on structural actions • Axial loads • High fill = high axial load • Effect of foundation stiffness on axial load

  4. Influence of high fills on structural actions • Bending moments and shear forces • Effect of foundation stiffness on axial load • Lower bound stiffness may not be conservative

  5. Influence of high fills on structural actions • Bending moments and shear forces • Effect of arch profile on arch actions • Morwell Tunnels - alternative cross sections

  6. Influence of high fills on structural actions • Bending moments

  7. Influence of high fills on structural actions • Shear Forces

  8. Influence of high fills on structural actions • Bending moments and shear forces • Effect of arch profile on arch actions • Oman Southern Expressway; 20 m span under 25m high fill

  9. Influence of high fills on structural actions • Bending moments

  10. Influence of high fills on structural actions • Shear Forces

  11. Influence of high fills on structural actions • Use finite element analysis. • Consider the effect of boundary conditions in the model. • Consider the effect of upper and lower bound stiffness values in the foundation materials • Model the footing structure accurately • Optimise the arch shape for the fill height

  12. Essential Features of Finite Element Model Include foundation layers. Add arch fill in layers, modelling the actual construction sequence. Allow slip at the arch/soil interface. Non-linear Mohr-Coulomb soil model. Include concrete and geometric non-linearity for large structures.

  13. Design of foundation structures for high vertical loads • Morwell Conveyor Tunnels • Alternative foundation treatments

  14. Design of foundation structures for high vertical loads • Detail of finite element mesh • Alternative simplified model

  15. Design of foundation structures for high vertical loads • Design actions in actual raft under maximum load

  16. Design of foundation structures for high vertical loads • Comparison of bending moments in flat and tapered rafts

  17. Design of foundation structures for high vertical loads • Alternative raft models: bending moments

  18. Design of foundation structures for high vertical loads • Alternative raft models: axial forces

  19. Design of foundation structures for high vertical loads • Larger spans

  20. Design of foundation structures for high vertical loads • Larger spans

  21. Longitudinal Differential SettlementLong Section - Morwell Tunnels

  22. Longitudinal Differential Settlement Morwell conveyor tunnels analysis Deep brown coal deposits + uncompacted fill

  23. Vertical Settlement

  24. Horizontal Movements

  25. Longitudinal Differential Settlement

  26. Longitudinal Differential Settlement

  27. Longitudinal Loads Steep fill slopes above the structure Segmental structures on steep slopes Longitudinal spreading of foundations under high fills Longitudinal differential settlement effects on continuous structures

  28. Longitudinal Loads

  29. Longitudinal Loads Use wider precast elements Provide shear connectors between adjacent elements and/or strengthen crown beam Provide movement joints in the crown beam and footings Design for variation in axial load Detail robust crown joints

  30. Examples - Morwell Conveyor Tunnels

  31. Examples - Mt Arthur, Olympic Dam

  32. Examples - Oman S Expressway

  33. Examples - Spain

  34. Conclusions High axial loads, possibly high bending moments and shear forces Consider upper and lower bound foundation stiffness Consider concrete and geometric non-linearity for large structures Design raft foundations for soil-structure interaction Consider longitudinal effects: Differential settlement Foundation spreading Longitudinal loads due to fill slopes and/or inclined structure

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