(Proceedings of Conference on Large Dams and Hydropower Development, 26–28 May 2004, New Delhi, pp. V/25–32).
Scheduled completion of a hydroelectric project depends to a large extent on timely break through of tunnels and other underground excavations. Despite modern tunnelling equipments and techniques being available, accelerated and assured rate of progress has been a challenge reason for which is often attributed to frequently changing geological media of tunnelling. Remedy may however, be effectively sought by reducing the constructional uncertainties by resorting to required level of construction discipline, commitment to right tunnelling method and continuous geological appraisal. Study of freshly excavated tunnel face enables one to use simple modification in the face blast locally to remedy likely under cut, over break, poor advance etc. This requires to understand the tunnelling not a repetitive rather every face blast a new activity. It has been possible to achieve 90% and more pull per round of tunnelling and cycle time as low as 8 hours in NHPC projects. This paper attempts to discuss the issues involved in high rate of tunnelling by drilling and blasting method (DBM).
Scheduled completion, Hydroelectric project, Break through, Tunnels, Underground excavations, Modern tunneling equipments, Techniques, Constructional uncertainties, Blasting method (DBM)
