Settlement of Precast Culverts Under High Fills

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Settlement of Precast Culverts Under High Fills

• The Influence of Construction Sequence and
  Structural Effects of Longitudinal Strains

Doug Jenkins - Interactive Design Services Chris
Lawson - Reinforced Earth Pty. Ltd.
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Acknowledgements

• Joint venture partners for the project
• Roche, Thiess and Linfox.
• Project design engineers
• SMEC Australia

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Introduction

• Morwell River Diversion
• Expansion of Morwell open cut mine
• Embankment up to 45 metres high over four coal
  conveyors
• Foundations approx. 80 metres of brown coal
• Anticipated settlements of the order of 1.5 metres

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Topics

• The project
• Construction
• The design
• Analysis
• Provisions for settlement
• 3D Analysis
• Results
• Comparison with site measurements
• Structural effects

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Overview

• Three dimensional effects
• Effect of construction sequence / direction
• Modelling effects
• Materials properties
• Structural effects of settlement
• Vertical
• Longitudinal spreading
• Conclusions

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Morwell River Diversion
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Foundation Properties
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Original Analysis
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Conveyor vertical profiles
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Construction of Conveyors 210-410
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Original Analysis Results Conveyor 410
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Original Analysis Results Conveyor 310
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Original Analysis Results Conveyor 210
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Original Analysis Results Conveyor 110
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Measured conveyor settlement over time
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Simplified 2D Mesh Conveyor 410
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Settlement predictions for original and
simplified mesh
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Constructing 3D Model
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3D Model
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3D Analysis Results Conveyor 410
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3D Analysis Results Conveyor 310
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3D Analysis Results Conveyor 210
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3D Analysis Results Conveyor 110
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Conveyor 210 Settlement with adjusted stiffness
parameters
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Conveyor 410 Horizontal movements from 2D and 3D
analyses
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Conveyor 210 Horizontal movement
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Conveyor 210 Joint Opening/Closing
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Summary

• Simplified mesh gave good agreement with the
  original 2D analyses.
• 3D analysis replicated the main features of the
  measured settlements - significant influence on
  the settlements.
• Higher settlements at the western end not
  replicated in the analysis poorly compacted fill
• Some discrepancies found for the southern and
  northern tunnels (410 and 110) boundary effects
• Large horizontal soil movements (tunnel 210).
• Joint opening/closing consistent with original
  analysis.

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Conclusions

• 3D effects were shown to have a significant
  effect on foundation settlements.
• Horizontal soil strains need to be considered in
  the design and detailing of concrete structures
  under high fills.
• 3D analysis should be considered for projects
  where settlements are expected to be large.
• Extend 3D models sufficiently far in all
  directions to avoid edge effects.