Effect of Internal Blast on Tunnel Lining and Surrounding Soil

Abstract

With the recent increase in terrorist attacks on the structures with strategic importance, detailed research intervention is required to study their behaviour under extreme loadings such as loading resulting from blast. Hence, in this investigation, three different cross sections of the tunnel with two different soil mediums are investigated under the blast loading. Herein, 3-dimensional nonlinear finite element analysis of tunnels is carried out using ABAQUS/Explicit®. Stress–strain response of soil, concrete and reinforcement has been simulated using Mohr–Coulomb plasticity, concrete-damaged plasticity and Johnson–Cook plasticity material models, respectively. In this study, FE analysis is carried out to compare the damage of tunnel and surrounding soil under three different cross sections of tunnel, i.e. arched, circular and rectangular, and two soil conditions, i.e. saturated and unsaturated soil. Further, tunnel is analysed for an explosion of 100-kg TNT explosive placed at the centre of the cross section of tunnel. Response of the tunnels in terms of displacement and stress at critical locations is computed for the comparison of the results. Results indicate that the variation in cross-sectional shape and surrounding soil affects the behaviour of tunnel for the same amount of the explosive. It has been also observed that displacement in tunnel lining and soil surface is of smaller magnitude for saturated soil. Also, lower stress is observed for saturated soil for all other conditions being same.