The influence of constitutive models for sprayed concrete on the design of tunnel junctions

This study presents a comprehensive analysis of numerical modelling techniques applied to the design and assessment of sprayed concrete-lined (SCL) tunnel junctions, focusing on the lining performance. The approach integrates advanced constitutive models to simulate both ground and lining responses, aiming to provide a robust understanding of tunnel behaviour under a realistically simulated construction sequence. Notable features of the modelling approach include nonlinear elastoplastic models for ground strata, depth-varying properties, variable K0 and pore pressure profiles, and step-by-step construction of cross-passages. The constitutive models for the ground have been validated against real site data, employing moderately conservative input parameters to ensure realistic comparisons with monitoring data.

Results from numerical modelling offer insights into the lining movements, strains and loads at tunnel junctions. Notably, the choice of constitutive model for the lining significantly influences predicted behaviour, with nonlinear elastic models generally exhibiting larger but more localised movements and strains compared to linear elastic models. Furthermore, the study suggests potential optimisations in tunnel design, such as the reduction or elimination of reinforcement in thickening layers, based on the enhanced understanding provided by 3D numerical modelling. This underscores the value of this approach when considering environmental factors, such as carbon footprint reduction, in the design process.