Abstract

The internal blast loading condition in a tunnel constructed in three-layered shale rock has been incorporated using a coupled-eulerian-lagrangian (CEL) approach in this paper. In this research, the three weathered stages of shale were studied, namely minimally, medium, and highly weathered shale in three layers. As we got closer to the earth's surface from the deep beneath, the weathering of the shale rock accelerates. The overburden depth has been changed to integrate several parametric scenarios in an elastoplastic finite element model with dimensions of 60m x 60m x 60m. The presence of 100kg of trinitrotoluene (TNT) as an explosive is expected A 100kg of trinitrotoluene (TNT) explosive is assumed to be suspended in the air at the middle of the tunnel entrance at an equal distance from all sides. To recreate genuine in-situ conditions, the TNT sphere and air inside the rock tunnel were modeled using the CEL approach. Mohr-Coulomb, Concrete Damage Plasticity, and Johnson-Cook constitutive material models were used to mimic the elastoplastic behavior of various materials, including rock, concrete, and steel bars. To make a reinforced concrete liner, a cage of steel bars has been inserted in the concrete liner by interaction constraints. The tunnel was first buried in the upper layer of shale, with a 5m overburden depth. The tunnel's position has also been altered for overburden depths of 15m, 25m, and 35m. Overburden depth and crown displacement are inversely proportional, according to the results obtained in the form of acceleration, velocity, and displacement for rock. Furthermore, the reinforced concrete liner used in this simulation study exhibits no damage in terms of compression, although a small tensile failure is visible in all scenarios.