Shield Tail Deformations <ul><li>Experience, Mechanics and Lessons </li></ul><ul><li>Coen van der Vliet ARCADIS Netherland...
Contents <ul><li>Problem Introduction </li></ul><ul><li>Research </li></ul><ul><li>Analysis </li></ul><ul><li>Recommendati...
Westerscheldetunnel Facts & Figures <ul><li>6 km twin tube road tunnel </li></ul><ul><li>60 m below water table </li></ul>...
Research
Research <ul><li>Shape measurements after arrival </li></ul><ul><li>Metallurgical research </li></ul><ul><li>Strength asse...
Measurements Roundness after arrival <ul><li>Accurate convergence measurements of shield tail. </li></ul><ul><li>Deformati...
Lab Tests Shape and strength <ul><li>Assessment of geometry, structure and strength </li></ul><ul><li>Visible deformations...
Numerical and analytical calculations <ul><li>In order to… </li></ul><ul><li>… understand  what happened </li></ul><ul><li...
Geotechnical aspects “Swimming Shield” <ul><li>General assumption: shield supported by  soil springs . </li></ul><ul><li>S...
Analysis
3D Load Carrying System <ul><li>First system: circumferential </li></ul><ul><li>Membrane forces: stiff </li></ul><ul><li>L...
Buckling Behaviour Cylinder with Stiffeners <ul><li>Elastic 2 nd  Order Calculation </li></ul><ul><li>Buckling Pressure ~ ...
Grout Lines & Plasticity <ul><li>2D Plastic 2 nd  Order Calculation with Groutlines: Buckling Strength </li></ul><ul><li>E...
3D Load Carrying System  <ul><li>3D Plastic 2 nd  Order Calculation with Grout Lines as Layered Shells </li></ul><ul><li>P...
Analytic Solution 2 nd  Order Behaviour <ul><li>Eigenmode = repetition of torsion bars </li></ul><ul><li>Elastic </li></ul...
Recommendations
Design <ul><li>Maidl et al </li></ul><ul><li>Duddeck-like model valid unless more accurate approach is necessary </li></ul...
Manufacture and Delivery <ul><li>Manufacture </li></ul><ul><li>Assembly tolerances </li></ul><ul><li>Material deficiencies...
Use <ul><li>Monitoring </li></ul><ul><li>Air Gap </li></ul><ul><li>Horizontal and vertical diameter </li></ul><ul><li>Auto...
Conclusions
Shield tail deformations are… <ul><li>Expensive </li></ul><ul><li>Analysed </li></ul><ul><li>Understood </li></ul><ul><li>...
Imagine the result
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Shield Tail Deformations - Experiences, Mechanics and Lessons

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  • Thank you mister chairman. This lecture about Shield Tail Deformations will cover experiences in The Netherlands with shield deformation problems, give a short summary of the structural behaviour of shield tails with respect to deformations and will end up with some lessons for the future. My name is Coen van der Vliet, currently working for ARCADIS in The Netherlands. My co-authors are Professor Bijlaard from Delft University of Technology, and Gerard Kooijman and Marius Naaktgeboren from the Dutch Ministry of Transport. I also have to mention Deltares for their contribution to the geotechnical research. ### This lecture is based on experiences at the Westerscheldetunnel Project, and mainly covers the research in charge of the client. So lets be honest: this lecture will cover mainly the client’s point of view.
  • Shield Tail Deformations - Experiences, Mechanics and Lessons

    1. 1. Shield Tail Deformations <ul><li>Experience, Mechanics and Lessons </li></ul><ul><li>Coen van der Vliet ARCADIS Netherlands </li></ul><ul><li>Frans Bijlaard Delft University of Technology </li></ul><ul><li>Gerard Kooijman Ministry of Transport, Public Works </li></ul><ul><li>Marius Naaktgeboren and Water Management </li></ul>
    2. 2. Contents <ul><li>Problem Introduction </li></ul><ul><li>Research </li></ul><ul><li>Analysis </li></ul><ul><li>Recommendations </li></ul>
    3. 3. Westerscheldetunnel Facts & Figures <ul><li>6 km twin tube road tunnel </li></ul><ul><li>60 m below water table </li></ul><ul><li>2 slurry shields Ø11,3 m </li></ul><ul><li>shield activities: 2000-2001 </li></ul><ul><li>deformation problems </li></ul>
    4. 4. Research
    5. 5. Research <ul><li>Shape measurements after arrival </li></ul><ul><li>Metallurgical research </li></ul><ul><li>Strength assessment </li></ul><ul><li>Numerical simulations </li></ul><ul><li>Geotechnical research </li></ul>
    6. 6. Measurements Roundness after arrival <ul><li>Accurate convergence measurements of shield tail. </li></ul><ul><li>Deformations ~ 20 mm </li></ul><ul><li>Deformation pattern still recognisable </li></ul><ul><li>Elastic + plastic deformations </li></ul>
    7. 7. Lab Tests Shape and strength <ul><li>Assessment of geometry, structure and strength </li></ul><ul><li>Visible deformations </li></ul><ul><li>Strength one grout pipe too low </li></ul>
    8. 8. Numerical and analytical calculations <ul><li>In order to… </li></ul><ul><li>… understand what happened </li></ul><ul><li>… generate a toolbox for design calculations </li></ul>
    9. 9. Geotechnical aspects “Swimming Shield” <ul><li>General assumption: shield supported by soil springs . </li></ul><ul><li>Soil support may get lost due to overcut, conical shape and support pressures (Bezuijen) </li></ul><ul><li>Soil moves inward and relaxes, until… </li></ul><ul><li>… it contacts the shield </li></ul><ul><li>… soil stresses balance support pressures </li></ul><ul><li>Gap depends on </li></ul><ul><ul><li>stiffness </li></ul></ul><ul><ul><li>stress </li></ul></ul><ul><ul><li>overcut </li></ul></ul><ul><ul><li>support pressure </li></ul></ul>
    10. 10. Analysis
    11. 11. 3D Load Carrying System <ul><li>First system: circumferential </li></ul><ul><li>Membrane forces: stiff </li></ul><ul><li>Limited by plastic strength grout pipes </li></ul><ul><li>Second system: load transfer </li></ul><ul><li>Bending: large deformations </li></ul><ul><li>Limited by second order effects </li></ul>
    12. 12. Buckling Behaviour Cylinder with Stiffeners <ul><li>Elastic 2 nd Order Calculation </li></ul><ul><li>Buckling Pressure ~ 20 bar </li></ul><ul><li>Star-shaped Eigenmode </li></ul><ul><li>Plastic 2 nd Order Calculation </li></ul><ul><li>Soil support prevents shell from buckling </li></ul>
    13. 13. Grout Lines & Plasticity <ul><li>2D Plastic 2 nd Order Calculation with Groutlines: Buckling Strength </li></ul><ul><li>Elastic: 19 bar </li></ul><ul><li>Plastic: 16 bar </li></ul><ul><li>Elastic with imperfections: 16 bar </li></ul><ul><li>Plastic with imperfections: 11 bar </li></ul><ul><li>Section Model: Yield Locus </li></ul>
    14. 14. 3D Load Carrying System <ul><li>3D Plastic 2 nd Order Calculation with Grout Lines as Layered Shells </li></ul><ul><li>Plastic buckling strength ~ 10 bar </li></ul><ul><li>Load-carrying system 2 too weak to play important role </li></ul>
    15. 15. Analytic Solution 2 nd Order Behaviour <ul><li>Eigenmode = repetition of torsion bars </li></ul><ul><li>Elastic </li></ul><ul><li>Plastic </li></ul>
    16. 16. Recommendations
    17. 17. Design <ul><li>Maidl et al </li></ul><ul><li>Duddeck-like model valid unless more accurate approach is necessary </li></ul><ul><li>DAUB </li></ul><ul><li>Shield tail deformations: SLS, load factor 1,0 </li></ul><ul><li>Steering loads </li></ul><ul><li>But mind… </li></ul><ul><li>Possibility of gap around tail: no soil support, uniform high (grout) pressures </li></ul><ul><li>Higher load factor for deformations (say 1,2) because of high economic risk </li></ul><ul><li>Incorporate weaker details in overall calculations </li></ul><ul><li>Transparancy in design process </li></ul>
    18. 18. Manufacture and Delivery <ul><li>Manufacture </li></ul><ul><li>Assembly tolerances </li></ul><ul><li>Material deficiencies </li></ul><ul><li>Check! </li></ul><ul><li>Delivery </li></ul><ul><li>Roundness measurements </li></ul>
    19. 19. Use <ul><li>Monitoring </li></ul><ul><li>Air Gap </li></ul><ul><li>Horizontal and vertical diameter </li></ul><ul><li>Automated laser measurements (Thewes, Budach & Edelmann, STUVA 2007) </li></ul><ul><li>Recovery </li></ul><ul><li>Increase overcut </li></ul><ul><li>Reduce support pressures </li></ul><ul><li>Additional support </li></ul><ul><li>Depends on actual situation </li></ul>
    20. 20. Conclusions
    21. 21. Shield tail deformations are… <ul><li>Expensive </li></ul><ul><li>Analysed </li></ul><ul><li>Understood </li></ul><ul><li>Avoidable </li></ul>
    22. 22. Imagine the result

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