Estimation of support required to stabilize a tunnel, especially in the vicinity of the face, is essentially a four-dimensional problem. To analyze the ground condition at the face, it is advisable to use advanced three-dimensional numerical codes. Moreover, it is possible to employ the convergence-confinement method, in a simplified manner to evaluate the ground condition in the face area. This method also enables one to assess the load imposed on a support installed behind the face of a tunnel. In this study, the convergence-confinement method was utilized to evaluate the appropriate support system for Taloun road tunnels. These tunnels which cross various rock types consist of twin-road tunnels with a service tunnel in between measuring about 5 km in length and run through the high elevation portions of the Alborz mountain range, connecting the capital city of Tehran to the north of Iran.

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