Numerical analysis of segmental tunnel linings - Use of the beam- spring and solid-interface methods

The effect of segmental joints is one of main importance for the segmental lining design when tunnels are excavated by a mechanized process. In this paper, segmental tunnel linings are analyzed by two numerical methods, namely the Beam-Spring Method (BSM) and the Solid-Interface Method (SIM). For this purpose, the Tehran Subway Line 6 Tunnel is considered to be the reference case. Comprehensive 2D numerical simulations are performed considering the soil's calibrated plastic hardening model (PH). Also, an advanced 3D numerical model was used to obtain the stress relaxation value. The SIM numerical model is conducted to calculate the average rotational stiffness of the longitudinal joints considering the joints bending moment distribution and joints openings. Then, based on the BSM, a sensitivity analysis was performed to investigate the influence of the ground rigidity, depth to diameter ratios, slippage between the segment and ground, segment thickness, number of segments and pattern of joints. The findings indicate that when the longitudinal joints are flexible, the soil-segment interaction effect is significant. The joint rotational stiffness effect becomes remarkable with increasing the segment thickness, segment number, and tunnel depth. The pattern of longitudinal joints, in addition to the joint stiffness ratio and number of segments, also depends on the placement of longitudinal joints of the key segment in the tunnel crown (similar to patterns B and B').