Designing U-shaped tunnel linings in stratified soils using the hyperstatic reaction method

Abstract

Tunnels are usually constructed in stratified geotechnical environments. However, most tunnel designers prefer to use a simplified model with the assumption of homogeneous soil conditions. This paper presents a numerical method, the hyperstatic reaction method (HRM), to investigate the effect of multi-layered soils on the design U-shaped tunnel linings. The performance of the presented method was investigated by comparing its results with the ones of a finite difference program. Different stratified soil conditions are considered to investigate the U-shaped tunnel lining behaviour: one homogeneous layer, one layer with a linear cohesion with depth, two layers, and three layers considering a variation of the position and of the thickness of the intermediate layer. The results of two different U-shaped tunnels were compared and analysed for these different stratified soils. In the case of a U-shaped tunnel without invert, the effect of the lining constraint conditions is also investigated.