Stress distribution in tunnel openings constructed using the sprayed concrete method in London clay

Numerical models of tunnel openings constructed using the Sprayed Concrete Method (SCM) typically utilise plate elements to reproduce the concrete lining behavior. Plate elements rely upon the plane stress assumption, which can result in overly conservative values of stress as indicated by the recent fibre optic strain monitoring by De Battista et al. (2015). This study presents an alternative approach to modelling of SCM constructed tunnel openings incorporating discrete volume elements for the primary and thickening layers of concrete. A series of three-dimensional finite element analyses have been completed using model parameters informed by tunnel openings constructed for London Crossrail. Comparison is made between results from models incorporating plate and volume elements. Findings confirm reduced maximum stress values around an opening using the volume element method. The results of the modelling approach corroborate baseline statements made by De Battista et al. (2015) based on field fibre optic strain monitoring.