Numerical study on pre-fabricated composite segment with compressible layer combined at their extrados

Abstract

The development of TBM technology enables continuous tunnel excavation with limited deformation of the ground, so it is also being utilized in challenging conditions. Nevertheless, geo-risk problems, such as squeezing during tunneling in overstressed rock, like deep soft rock, cause excessive stress in the segmental lining. The conventional structural solution based on the resistance principle causes the problem of overdesigning the segmental lining. Therefore, studies have been conducted on various yielding supports to reduce support pressure by allowing some internal displacement of the tunnel wall after excavation. Pre-fabricated composite segments with a compressible layer combined at their extrados can be considered in the shield tunnel, but this design is not well established. In this study, a numerical analysis based on the finite element method was performed to investigate the effect of the compressible layer on the segmental lining and the surrounding ground during the excavation of the shield tunnel in the deep soft rock. A parametric study was conducted with the characteristics of the compressible layer, the physical properties of the rock, and the presence or absence of backfill material as the main factors.