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Stability Analysis of Taloun Exploratory Tunnel with Application of Back Analysis Technique and Considering Interaction Between Three Parallels Taloun Tunnels by Three Dimensional Modeling

Rostami, Ali | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42488 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Sedghiani, Mohammad Hossein
  7. Abstract:
  8. The main purpose of this research is to investigate geotechnical parameters of surrounding rock mass of Taloun tunnels (Tehran-Shomal freeway, Iran), with application of back analysis technique and consideration of monitoring data, in order to analyzing stability of tunnel at particular monitoring station 10 (NPI10). First, the geo mechanical parameters were investigated by sensitivity analysis preceded back analysis due to determine significant geotechnical parameters of rock mass contributed to tunnel excavation with respect of displacement and stress level. Following this section sensitivity analysis of different parameters were conducted. In this section it has been found that, the most influential parameters are stress ratio, friction angle and elastic modulus of surrounding rock mass respectively; therefore, according to the mentioned results, direct back analysis has been implemented with offering nonlinear equation of geotechnical parameters of rock mass in order to predict displacements of wall of tunnel. Furthermore, with application of convergence monitoring data and convergence-confinement method, the plastic zones around the tunnel would lead to discern appropriate design for support system of exploratory tunnel. In continue, With attribution of obtained optimum geotechnical parameters to the main tunnels, three dimensional numerical model of three parallel tunnels has been conducted with FLAC3D software, and in this section interaction of main tunnels excavation with exploratory tunnel, according to the steps of excavation , distance between main and middle tunnel, unsupported distance in main tunnel, has been considered. It should be mentioned that, excavation of the three adjacent tunnels will lead to change in stress distribution around the exploratory tunnel, stress through rock bolt and shotcrete and displacements of walls of exploratory tunnel. It has been shown that, excavation of main tunnels lead to increase in normal compressive stress of shotcrete on walls of mid (exploratory tunnel) tunnel and decrease on shotcrete of crown of mid tunnel. The tension stress in the rock bolts of the middle tunnel increases since approaching the face of the main tunnels to the monitoring location in the mid tunnel. The results show that, if distance between the main and the middle tunnel is more than two times of summation of the radius of the main and the middle tunnel, then the adverse effect of adjacent tunnels would be diminished. The significant factors in proximity tunneling which could cause adverse effect on tunnels are tunnels separation, tunnels dimension and rock mass strength
  9. Keywords:
  10. Regression Analysis ; Taloun Exploratory Tunnel ; Three Dimensional Numerical Modeling ; Parallel Taloun Tunnels Interaction

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