Jindal Power Ltd., Gurgaon, Haryana, India
Online published on 12 January, 2015.
Most of our hydroelectric projects are situated in Himalayas where tunnelling is required as a part of Water Conductor System. It has been observed that a long tunnel in Himalayas ultimately brings the project on critical path. Not only due to tunnelling but there are many other reasons also for delay of projects. Some of the reasons are poor planning of construction equipment or poor mobilization of equipment by contractors, difficult topography of the area, low availability of skilled manpower, interference by external environment, geological surprises because of unapproachable terrain, poor management of ventilation system, poor management of blasts, use of conventional methods of tunnelling & concreting and final lining of tunnel etc. Advance planning, management of construction equipment and ventilation system and a willing contractor to use modern equipment and methodology can certainly help in reducing the uncertainties and time & cost overrun. It is observed that besides other issues, Final concrete lining of tunnel also takes about 1 to 1.5 years from equipment mobilization and final finish and grouting for a 2.5 km long face of tunnel. An attempt has been made by the author to discuss the use of Unlined Pressure Tunnel especially in Himalayan Geology based on experience gained in India and in Norway where Unlined Pressure Tunnels have been built extensively.
