Physical model tests and numerical simulation for assessing the stability of tunnels

Nowadays, numerical modelling is increasingly used to assess the stability of tunnels and underground caverns. However, an analysis of the mechanical behaviour of existing brick-lined tunnels remains challenging due to the complex material components. In order to study the mechanical behaviour of the masonry in brick-lined tunnels, this paper proposes a series of small scale physical tunnel model tests to represent the true behaviour of a real tunnel under extreme loading. Advanced monitoring techniques of laser scanning and photogrammetry are used to record tunnel deformation and lining defects. This investigation shows how these techniques may substitute or supplement the conventional monitoring procedures. Simultaneously, the corresponding numerical models of these small scale physical models have been developed using FLAC and UDEC software and verified by the experimental results to assess the overall stability of these tunnels. Predictions using numerical models under various conditions have also been carried out to show the mechanical behaviour of a masonry tunnel and to quantify the influence of the surrounding and loading conditions.