Finite element modeling
The finite element software Abaqus/Explicit has been used for the
present analysis of rock tunnel subjected to internal blast loading. The
model dimensions of the tunnel are 30m x 30m of cross-sectional
dimensions and 35m of extruded length [6,26]. The dimensions of the
finite element model are based on boundary convergence study. Initially,
the thickness of tunnel lining has been kept as 0.22m and later, it has
been varied as 0.35m, 0.45m and 0.55m. Four different depth of
overburden has been considered in the present analysis are 5m, 7.5m, 10m
and 12.5m. The tunnel has a diameter of 6m. The element size of the
model has been kept as 0.2m based on the mesh convergence study. The
tunnel lining and rock model has been meshed with an element type of
C3D8R (Eight-node brick element with reduced integration). Moreover, the
Eulerian Model of Trinitrotoluene (TNT) and air has been modelled as
EC3D8R (8-node linear brick, multimaterial, reduced integration with
hourglass control). The boundary conditions at the base of the rock
model have been restrained in all directions as the rock has infinite
depth. The front and rear of the model has been restrained in all
directions and the deformations are allowed in the vertical direction.
The right and left sides of the model were allowed the deformation in
vertical directions and restrained in other. The finite element model
has been shown in Figure 1.