Numerical Study of the Effects of Segmental Joints and Grouting Pressure on the Behavior of Tunnel Segmental Lining

Tunnel Boring Machine (TBM) is used widely to bore long tunnels in hard rocks. If you choose shield TBMs, precast concrete segments should be installed as permanent tunnel lining. This lining is inherently distinct and therefore in analytical and numerical analyses, the continuity assumption is not acceptable for simplifying. The segmental linings show certain behavior under various loads applied by rock, machine and tunneling processes (such as grouting). In this study, the behavior of segmental lining of Sabzkouh water conveyance tunnel has been compared to full (continuous) lining. In this paper, the behavior of tunnel segmental lining by assigning normal and shear stiffness values for longitudinal and circumferential joints of segments is compared with the continuous lining. The effect of the grouting pressure between rock and segments on the behavior of the tunnel segment is analyzed. Under uniform grouting load, the results of numerical modeling executed by finite difference method show maximum internal forces occur in the joints of segments. With increasing grouting pressure, axial force and bending moment in the joints of the segments is reduced. Moreover, the grouting pressure increases displacements in the segmental lining. In practice, this increase sometimes causes cracking or stepping between segments.