Study of Rock-Lining Interaction for Circular Tunnels Using Finite Element Analysis

Finite element technique is used to model two phases of tunneling process, namely; excavation and rocklining interaction. The excavation phase is responsible for determining the pre-lining rock mass deformations and the reduced in-situ stresses. The interaction phase models the compatibility of the rock-lining system. The deformations and stresses of the rock-lining system and the final rock mass pressure acting on the lining are determined. The finite element results are compared with the results of the Convergence-Confinement method for the case study (Shimizu Tunnel) that was guided by field measurements. One of the main objectives of this study is to investigate the effect of different parameters on the behavior of excavated tunnel before and after lining activation. The analysis followed the same procedure which had been applied in the analysis of the case of Shimizu Tunnel taking into consideration the different values of the tunnel radius and the depth of excavated tunnel through different qualities of rock ranging between poor, moderate and hard rock. The parametric study has been conducted for circular tunnel. The first lining system involved in this study was assumed to be shotcrete of thicknesses of 20, 30, 40 and 50cm, and the second lining system was steel ribs with shotcrete of thicknesses of 20, 30, 40 and 50cm. The results of Finite Element Analysis were presented for different thicknesses.