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Evaluation of the Methods of Circular Tunnels Lining Design Under Seismic Loads

Motalleb Nezhad, Mohammad | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43746 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Paak, Ali
  7. Abstract:
  8. The use of public transportation in metropolises has developed due to the increase in the population and the need for within-city transportation. Among public transportation service, the use of city subways has attracted more public interest due to its speed, safety, and matching with the environment. Also, one solution for reducing the between-city transit distances,decreasing the accidents and above all, saving the time of the travel is building tunnels and underground lines. Design and construction of underground structures (tunnels),in comparison with surfacestructures, has more complex conditions and considerations that require special studies. One challenging problem fortunnel design-engineersisto design final lining of the tunnel under seismicloads. Nowadays,many of the tunnels are constructedinareas with high seismicpotential, due tothe increasinginterest inthe use of underground spaces. The failure of structures under earthquake shaking can cause signific an teconomiclosse sand human disaster. So the comprehensive studiesinthis field couldbe usefulindesign of thesestructures.Inthis thesisthe mainissueisto evaluate the response of the deep circular-tunnel liningunderseismicloads by using numericalmethod (Finite difference). It has been tried to examine the design of tunnels under Seismic loads by performing numerical analysis by computer program FLAC and comparing the results with those of the existing analytic methods. These numerical analyses, has been performed in two conditions: 1) full slip condition which exists between lining and soil interface, 2) no slip condition that the slippage between lining and soil is not allowed.Numerical analyses show that, assuming elastic behavior for soil, there is strong compatibility with theresults of the analytic methods. Numerical analysis results supposing elastoplastic behavior for soil (Mohr-coulomb),shows that the plastic flow of the soil around the tunnel changes the amounts of forces andbending momentsin the tunnellining. In this situation, reductionor increaseof forces and bending moments dependson the flexibility ratio (F).Numerical analyses also show that the results of full dynamic analyses and quasi-static analyses are the same.

  9. Keywords:
  10. Tunnel Lining ; Seismic Loading ; Numerical Modeling ; FLAC Software ; Dynamic Behavior

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