ABSTRACT
Tunneling is a complex three-dimensional problem, especially due to the sequential excavation and primary support installation procedure. The use of three-dimensional numerical methods, that incorporate the construction sequence, derive the best approximation of the anticipated stresses and displacements of the tunnel lining. This approach is time consuming, and it is often avoided in design practice. This study presents the results of axisymmetric numerical simulations that incorporate sequential excavation and support cycles. Those simulations, in combination with plane strain models provide a good approximation of the three-dimensional conditions that prevail at the proximity of the tunnel face. The results of those simulations are compared with other available methods and indicate the influence of the installed support to the rock mass confinement at the support installation position. The importance of axisymmetric simulation for the estimation of tunnel support pressure for deep tunnels is emphasized, particularly in cases where three-dimensional numerical modeling is not practically available.
