Damage to shallow tunnels in different geomaterials under static and dynamic loading

In the present study, an attempt is made to understand the behavior and pattern of tunnel damage subjected to the static and dynamic loading conditions, through the simulation of natural as well as artificial stress states such as loads due to overburden, building, earthquake and blast. The analysis is carried out by using FEM based numerical tool i.e. ABAQUS for different geo-materials. The Mohr-Coulomb plasticity model is used for modeling the rock mass and Johnson Cook plasticity model have been used for the simulation of stress strain response of drop hammer. The results of the analysis are studied for stresses, deformation and safety zones in surrounding rock. The displacement of the crown along the axis of tunnel is quantified. It is observed that the strength properties play a crucial role in quantifying the yielded zone in rock mass under both static and impact loading. The effect of weathering is investigated and the deformations for different weathering stages is measured. The crack dimensions reduce as the brittleness of the material increases. Different zones of influence are investigated for all the materials. It is noticed that the zone is significantly crushed in the case of dynamic loading, due to the high velocity of impact and the length of crack is large in the case of static loading as compared to the dynamic loading.