Blast resistant behaviour of tunnels in sedimentary rocks

Abstract

The tunnels are being constructed for the faster movement of goods and services from different locations. Therefore, Underground Urban Space (UUS) has evolved as an integral part of metro cities. Critical structures like tunnels have to be designed resistant to the blast due to possible threats and attacks. In the present paper, the efforts are made to analyse and understand the response of rock tunnel for an internal blast loading. The numerical analysis based on the finite element method has been carried out for a 35 m long rock tunnel in a rock mass of longitudinal cross-section 30 m × 30 m. The elastoplastic behaviour of the sedimentary rocks, that is, Sandstone, Mudstone and Silty Sandstone has been incorporated by using a Mohr-Coulomb constitutive material model. The plastic behaviour of the concrete tunnel lining has been incorporated by using concrete damage plasticity model. Moreover, for the Trinitrotoluene (TNT) Jones-Wilkens-Lee (JWL) material model has been considered. Analysis has been performed through the Coupled-Eulerian-Lagrangian (CEL) approach, which incorporates the advantages of both Eulerian and Lagrangian modelling. The present study focuses on the analysis of the tunnels constructed in three different sedimentary rocks, that is, Sandstone, Silty Sandstone and Mudstone. It has been concluded that Mudstone rock is more susceptible to failure due to internal blast load. However, Sandstone rocks were found to be relatively higher blast resistant, hence, may be considered as safer rocks for the construction when compared to other rocks of the present study.