A Novel Framework for Analysis of Tunneling Projects in Lower Himalaya

Abstract

In the Himalayan region, geology of rock mass is highly complex and fragile and hence excavation of large size underground structures in such a material is a very difficult job. Excavation of large size tunnels and caverns becomes safe if the condition of the ground is known a-priori. Knowledge of the ground condition will not only help in proper design of support system but will also help in keeping contingency plans ready before any untoward eventuality. It is therefore necessary to develop a simple framework that will predict the ground condition. In this paper, a unique multiple-graph based framework has been proposed for the preliminary estimation of ground conditions during tunneling through rock masses. This method has been established based on the estimation of three quantities in a logical sequence, viz., rock mass strength, competence factor, and finally the ground condition. A new empirical ground condition classification has also been suggested in this paper for both soft and hard rock masses. The proposed framework is validated by applying it to five tunnel sections from Sawra-Kuddu Hydroelectric Project in Himachal Pradesh, India. The proposed framework is an efficient tool for quick prediction of ground condition in the preliminary stages of design as well as during the excavation of tunnels.