Introduction

Underground structures have become an essential part of the metro cities. Construction of the underground structures especially tunnels for the efficient movement of humans and goods has resulted in the investment of a massive amount of money in the underground space. Therefore, underground structures especially rock tunnel has been an active area of research since mid-nineteenth century. Manouchehrian and Cai carried out a finite element study for static and dynamic loading for a circular tunnel. They have used finite element software Abaqus/Explicit and Python scripting for the study. They have shown the importance of using a finite element analysis for case histories are useful for the rockburst phenomenon due to the presence of discontinuities [1]. Mishra et al., [2] carried out the study for tunnels when subjected to static and dynamic loading using finite element software Abaqus/Explicit. The analysis has been carried out for different geomaterials, and it has been concluded that the settlement of the tunnel crown has a direct relationship with the friction angle. Mishra et al., [3]concluded that the effect of load in deformation of tunnel reduces as the distance of loading position increases. They have calculated different zones of deformations for different rock mass for shallow rock tunnels. Bobet carried out the study under static and seismic loading for the effect of pore water pressure on the stability of tunnel support. It has been concluded that the racking deformation and the flexibility of the tunnel are directly related [4].
Furthermore, the underground tunnels have been subjected to dynamic loads such as seismic loads, impact loads, blast loads and other types of loading. Stability of tunnels under blast loading has attracted several researchers in recent decades [5]–[13]. Moreover, Matsagar has carried out the comparative study for composite sandwich panel and non-sandwich panel for blast loading. They have utilised finite element analysis for comparison of different materials and concluded that cenosphere aluminium alloy syntactic foams found to be the superior material for the reduction in the damage caused by the blast load [14][15]. Jaini and Feng have studied the response of reinforced cement concrete (RCC) slab using computational modelling. They have carried out a finite discrete element analysis for the damage analysis of RCC slab. It has been concluded from the study that the use of both positive and negative phase of blast response may give more realistic results [16].
Further, blast study has also been carried out for the response of concrete pavement slab by Luccioni and Luege [17]. They have considered three different explosive charge weights and the stand-off distance of explosive remains constant as 5m. Based on experimental, numerical and limit analysis, they have proposed an equation that relates the diameter of crater and the explosive charge. The behaviour of spherical explosive charge has been discussed by Brode [18]. When a blast event occurs, there has been the presence of vibrations in addition to heating effect of blast. Hence, Berta has carried out the study on the vibrations induced in tunnel by the blast loading [19]. Jingbo et al., [20] had studied the blast wave propagation in the tunnel by using finite element software LS-DYNA. Chen and Zhao have utilized UDEC modeling for the study of blast wave propagation in the jointed rockmass [21]. Choi et al., have used AUTODYN software for the 3D nonlinear dynamic analysis of tunnel subjected to internal blast loading. They have used Coupled-Eulerian-Lagrangian modeling to simulating the blast response[22]. Buonsanti and Leonardi had carried out the study on rail tunnel subjected to internal blast loading using ANSYS code [23]
The present paper deals with the response of a rock tunnel when subjected to internal blast loading using finite element software Abaqus/Explicit [24], [25]. The Mohr-Coulomb constitutive material model has been considered for the Quartzite rock. In the present study, the effect of the weight of explosive charge has been carried out. Also, the response of rock tunnel under varying thickness of tunnel lining has been incorporated. The four different overburden depths are also considered.