Effect of the umbrella arch technique modelled as a homogenized area above a cross passage

Abstract

The stability of tunnel cross passages excavated in soft soil has always been a major challenge. In recent years, new techniques based on the installation of pre-reinforcements before tunnel excavation have been developed to control excavation-induced deformation and surface settlements. In this paper, a finite element numerical simulation was conducted to study the reduction effect of an umbrella vault element modelled as a homogenized area on the deformations induced after the excavation of a cross passage. The results of this study show that the ground deformations can be controlled efficiently by using this type of pre-reinforcement. However, the findings showed that there is no effect of the umbrella arch length on the reduction of the ground deformations. This paper represents a very good demonstration of 3D modelling of tunnel junctions using pre-support techniques; it is the most advanced/appropriate research tool for studying the behaviour of cross passages and is useful as a paradigm for other researchers and practitioners.