Finite Element Analysis of Static Loading on Urban Tunnels

Tunnels are proven to be the most important mode of transportation, these days. Due to rapid development of underground space in big cities, it is important to study and analyze huge stresses that are coming to the u/g tunnels due to different loading conditions. Mostly, urban tunnels are highly susceptible to deformation even with the small change in stress distribution of surrounding rock mass. Due to moving traffic and construction and demolition of new and existing structure, u/g structures are always subjected to huge stresses which need to be distributed uniformly for the safety of lining and lives of people. In this paper, finite element method is used to study the behavior of lined and unlined tunnels under the weight of overlying strata or litho-static pressure. In the analysis, vertical stresses on tunnel and lining are being applied in terms of unconfined compressive strength of rocks and geo-material (sm1) for better understanding. Authors have also simulated the effect of weathering on the deformation and stresses of different rock masses. The finite element software ABAQUS is used for simulation work. Mohr–Coulomb plasticity model is used for the different rocks. 3D finite element model is considered of size 0.3 × 0.3 × 0.35 m for 0.05 m overburden. UCS of different weathered basalt and a geo-material prepared in the laboratory applied as a load for both lined and unlined tunnel element. The results conclude that with the increase in the weathering indices of surrounding rock mass, massive deformation was encountered even with very less magnitude of applied vertical and horizontal stress.