Dynamic analysis of twin tunnel subjected to internal blast loading

Abstract

The present study deals with three dimensional nonlinear finite element analyses of underground twin tunnels in soil with reinforced concrete (RC) lining subjected to internal blast loading for blast occurring in one tunnel. The blast load has been simulated using coupled Eulerian-Lagrangian (CEL) analysis tool available in finite element software Abaqus/Explicit. Soil mass and RC lining have been modeled using three dimensional eight node reduced integration Lagrangian elements (C3D8R). Beam elements (B31) have been used to model reinforcement of RC lining. A 50 kg TNT charge weight has been used in the analysis. Eight node reduced integration Eulerian elements (EC3D8R) have been used to model the TNT explosive and the surrounding air. Drucker-Prager plasticity model available in Abaqus has been used to simulate strain rate dependent behavior of soil mass. For simulating strain rate dependent behavior of concrete and steel, concrete damaged plasticity and Johnson-Cook plasticity models, available in Abaqus, have been used, respectively. The explosive (TNT) has been modeled using JWL equation-ofstate. Investigations have been performed for studying the deformation of RC lining and surrounding soil mass. Pressure in the RC lining and surrounding soil mass, caused by explosive induced shock wave have also been studied for both tunnels. It is observed that deformation in tunnel away from blast decreases with increasing soil cover in between two tunnels.