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Concrete Institute of Australia Soil-Structure Interaction Seminar Sydney March 2007 PowerPoint Presentation
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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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Presentation Transcript
slide1

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
Overview:

Influence of high fills on structural actions

Design of foundation structures for high vertical loads

Longitudinal differential settlement

Longitudinal loads

Examples

Conclusions

influence of high fills on structural actions
Influence of high fills on structural actions
  • Axial loads
    • High fill = high axial load
    • Effect of foundation stiffness on axial load
influence of high fills on structural actions4
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
influence of high fills on structural actions5
Influence of high fills on structural actions
  • Bending moments and shear forces
    • Effect of arch profile on arch actions
    • Morwell Tunnels - alternative cross sections
influence of high fills on structural actions8
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
influence of high fills on structural actions11
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
essential features of finite element model
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.

slide13

Design of foundation structures for high vertical loads

  • Morwell Conveyor Tunnels
  • Alternative foundation treatments
slide14

Design of foundation structures for high vertical loads

  • Detail of finite element mesh
  • Alternative simplified model
slide15

Design of foundation structures for high vertical loads

  • Design actions in actual raft under maximum load
slide16

Design of foundation structures for high vertical loads

  • Comparison of bending moments in flat and tapered rafts
slide17

Design of foundation structures for high vertical loads

  • Alternative raft models: bending moments
slide18

Design of foundation structures for high vertical loads

  • Alternative raft models: axial forces
longitudinal differential settlement
Longitudinal Differential Settlement

Morwell conveyor tunnels analysis

Deep brown coal deposits + uncompacted fill

longitudinal loads
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

longitudinal loads31
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

conclusions
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