Page - 1530 - in Book of Full Papers - Symposium Hydro Engineering

COMMISSION INTERNATIONALE DES GRANDS BARRAGES ------- VINGT-SIXIÈME CONGRÈS DES GRANDS BARRAGES Autriche, juillet 2018 ------- HYDRAULIC ASSESSMENT OF TUNNELS Balkrishna Shankar CHAVAN, Scientist-D, Central Water and Power Research Station, Pune India 1. INTRODUCTION A river diversion tunnel is used to divert river water during construction of a project. Once construction is over, diversion tunnel is plugged before initiating storage of water consequently tunnel part becomes redundant. No universally accepted standards are available for design of temporary structures like coffer dams and diversion tunnels. Tunnel construction has high costs and usually adopted when other solutions are unfeasible. Length of tunnel is kept minimum as possible. To minimize the project cost, part of diversion tunnel can be reused for depletion of reservoir storage. There are instances where part of river diversion tunnels have been used as depletion tunnel after construction of dam is completed. In India projects such as Yamuna, Doyang, Nagarjunsagar, Salal have successfully used the concept of multipurpose tunnel for diversion of river flow and depletion of reservoir. Hydraulic design associated with such tunnels has to function satisfactorily for high discharge at low head during construction and also high head 1530