NUMERICAL SIMULATION OF SHALLOW TUNNELS LINED IN STEEL REINFORCED CONCRETE CONSIDERING THE EFFECTS OF CRACKING

Resumo

Tunnel design requires the correct evaluation of both soil strains and lining stresses levels
through an analysis that must contemplate the soil-structure interaction and the excavation process.
When tunnels are installed close to the ground surface, the complexity of the problem increases in
comparison to deep tunnels, since shallow tunnels show an ovalized shape of the deformed cross-section
and a heterogeneous stress field around the excavation, inducing tension stresses to appear and possibly
resulting in the cracking of the concrete lining. In this context, this paper presents a numerical simulation
in finite elements, with the software Ansys, focused on the study of the structural behavior of shallow
tunnels lined in steel reinforced concrete. To perform such analysis, the soil mass was represented by a
plastic model using the Mohr-Coulomb criterion and, regarding the concrete, three different models of
behavior were admitted: an elastic, a viscoelastic and a viscoelastic with cracking consideration.
Moreover, the embedded reinforcement model was adopted to represent the steel reinforcement of the
concrete. The results obtained in the investigation indicate the influence of the cracking consideration
in the tunnel model, which modifies the stresses field of the lining and causes higher values of final
convergence.