SAFETY AND DEFORMATION ASSESSMENT OF UNDERGROUND METRO TUNNEL

Abstract

Geological conditions such as space-time effect, tunnel dimensions, construction methods, tunneling method, and effect of groundwater on soil/rock are some of the factors influencing the movements of the ground. The magnitude of maximum surface settlement and the shape of the surface settlement curve are greatly influenced by these characteristics. This project is focused on the safety and deformation assessment of underground metro tunnels. The work presents a safety and deformation assessment of the underground twin metro tunnel and also evaluates risk measures related to rock-soil mass concerning different stress-strain states. Empirical and numerical both methods are carried out in this analysis. The numerical analysis of the tunnel deformation is carried out using the finite element method, and an empirical equation is used to validate the results. The Hoek–Brown failure criterion and Mohr-Coulomb criteria were used for numerical calculation of stresses and to find out physical parameters such as cohesion value and angle of friction. The rock-soil mass parameter for this calculation was taken from the Mumbai metro rail project. The worst category of the rock mass was considered in the analysis that may likely encounter TBM tunneling to have a conservative approach for evaluating settlements due to excavation of TBM tunnel. The findings showed that the distance between tunnels, tunnel lining, and the most critical component in twin tunnel-induced surface settling was discovered to be the deformation modulus of the geo-materials surrounding the tunnel.