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Study of the Elastodynamic Fields due to the Scattering of P-Waves by a Buried Non-Uniformly Coated Tunnel

Massoumi Goudarzi, Amin | 2024

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  1. Type of Document: Ph.D. Dissertation
  2. Language: English
  3. Document No: 56871 (53)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Mohammadi Shodja, Hossein
  7. Abstract:
  8. With the progress of engineering science, the development of underground spaces and buried tunnels has witnessed remarkable expansion. Considering the frequency of hazardous events such as earthquakes and unforeseen consequences arising from underground activities and geology in underground engineering, the determination of the Dynamic Stress Concentration Factor (DSCF) has been widely recognized as a crucial factor in the study and design of tunnels and underground structures. It is also extensively considered in evaluating their damage. The investigation of wave dispersion and determination of the stress concentration factor was first proposed by Sezawa (1927). In this study, the elastodynamic field and the dynamic stress concentration factor due to the scattering of P-waves on a circular tunnel with a circular lining of variable thickness in a completely elastic and isotropic medium were investigated. Circular cross-section tunnels are of particular interest due to their practical advantages in the field of fluid dynamics, structural flexibility, and stability, as well as their compatibility with drilling techniques for various applications. These applications include the transfer of water, fluids, and pressured liquids, as well as tunnels for mechanical and communication facilities, and flood control tunnels in dams and hydroelectric power plants, making circular tunnels a focus in the development and construction of tunnels. To solve this, the use of the Dynamic Equivalent Inclusion Method (DEIM) has been proposed. Earlier, Fu and Mura investigated the dispersion phenomenon in a medium with impurities. Subsequently, their work was revised by Shodja and Delfani, addressing its shortcomings through the concept of eigenbody-force and compatibility equations for special strains. A particular case, Mow and McCabe (1963) in the literature involves a tunnel with a concentric lining exposed to P-waves, expressed through the method of function expansion, and recovered using the proposed recovery method. In this study, for the first time, the influence of the variability of the liner thickness on the static and dynamic stress levels in critical regions along the liner internal surface and along the interface between the liner-matrix, where no slippage occurs at the common boundaries, was investigated through numerical examples. In this research, the maximum value of the DSCF for concrete (soft) and steel (hard) liners is compared with positive and negative values deviating from the center with their corresponding symmetric cases.
  9. Keywords:
  10. Elastodynamic Field ; Variable Thickness ; Buried Lined Tunnels ; Dynamic Equivalent Inclusion Method (DEIM) ; Buried Lined Tunnels ; P-Waves Scattering ; Dynamic Stress Concentration Factor (DSCF)

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