Managing geological complexity in engineering and construction of tunnels

Prior Estimate of uncertainties and risks involved in the construction process is central to decision making in the underground projects. In such Projects, a significant part of uncertainties results from unknown geological conditions. Timely calculation of risks and action required there in is vital in mitigating of geological risks in the underground construction and tunnelling projects. Continuous updating of geological models, readjustment of excavation and support to actual ground conditions, control all geological risks at the site. Adopting appropriate excavation technology, proper sequences, dependable support and auxiliary measures mitigate the geological risks to a great extent.

The present paper discusses advance identification of geological risks on the basis of continuous updating of geological model of the site, design updating and measures applied to reduce the risks in the Twin-Tail-Race-Tunnels of Tehri Pumped Storage Hydro Project in the Indian Himalaya. The Paper also underlines the meticulous construction planning, on the spot resolution of the problem and visualisation of geological risks involved at every stage of design and execution.