ABSTRACT
Twin motorways tunnels are constructed in Aravalli Mountains of western India, for providing the smooth transport facility for man and material. These tunnels are located on four lane national highways number 76. The twin tunnel road passage connects the Kandla Port on Arabian Sea to shipment dimensional stones from Rajasthan and adjoining states from western part of the sub-continent, ultimately to the north-central India. It is constructed for fast delivery and in future it will be a catalytic development as economic driven activity. Frequently occurring landslide failure on both ends of tunnels, present study has been planned for failure-risk analysis. Tunnel failure-risk analysis carried out by back and probability analysis. The Multiple Back Analysis approach has been used, where different factor of safety (FoS) curves have been derived by numerical analysis. The back analysis shows that for both, tunnel-1 and tunnel-2, the ideal conditions calculated for minimizing failure risk has been achieved by maintaining the cohesion values 148.41 and 168.33 or more than that respectively. Probability analysis also depicting 0.66 to 2.30 factor of safety and the places of less than 1.00 are unsafe. Frequency percentage vs. factor of safety and probability percentage vs. factor of safety plot shows that there is a risk of failure of the tunnels from the cut hill slopes of corners. There are various reasons of triggering of failures in addition to transmitted vibrations from vehicular movement.
