Stability of Arch Tunnel in Different Magnitude of Earthquake with Effect of Weathering in Western Ghats of India

Abstract

Tunnels are the lifeline of modern civilization. With the ongoing scarcity of open ground space, the demand for underground tunnels has increased many folds. Stability of tunnels is influenced by many natural and manmade activities. Earthquake is one of the fiercest natural calamities, and like every other structure, tunnels are prone to be affected by it. Past studies show that tunnels in rocks are more stable than in soils during earthquake, but the studies have ignored the weathering of rock with the passage of time. Weathering of rock has a significant effect on its properties, and hence, the stability of tunnel is affected by it during an earthquake event. The present study aims to analyze the stability of underground rock tunnel affected by weathering phenomenon. An arch tunnel, surrounded by basalt rock material undergone weathering, is subjected to four different earthquake events of the past. The rock is modeled using Mohr–Coulomb criteria in a finite element-based software Abaqus. 2D plane stain modeling has been considered for the present study. The absorbing boundary condition has been applied for the earthquake analysis. The stability of tunnel is analyzed by determining the deformation at different depth of overburden. The results of the paper conclude that as the depth of overburden increases, the range of deformation at different locations reduces, thus showing the effect of lithostatic condition. Also, the deformation increases as the weathering stage of the rock increases for each magnitude of earthquakes. The results also show that as the depth of overburden increases, the weathering has significant effect on the tunnel stability. Finally, it is concluded that the overburden depth does not have much effect on the stability of tunnel under the event of minor earthquakes while the overburden depth proved to be of greater significance in case of major earthquake events.