Tail race complex comprises of Draft tube manifold, collection gallery, surge gallery, lower expansion gallery and the Tail race including junctions and transitions. Six number draft tubes of size 5.34 m finished, D-shaped take off from the downstreamwall of Machine hall one from each machine. This discharges into a Standard Horse shoe shape collection gallery of 172.981 m long. The collection gallery inclined at 120°from centre line of 1st draft tube, is having 2no. transitions and is mainly of size 10.15 m dia finished standard horse shoe shaped. After transition at Station 25 m to 15 m the collection gallery forms a part of square junction . This junction is the meeting point of collection gallery, Tail race tunnel, d/s surge gallery and the Adit to Pressure shafts. All the four tunnels at the junction are of size 10.15 m diameter (finished) and of standard horse shoe shaped. The downstream surge gallery 468.269 m long as is clear from its name in addition to its function of dampening of surges at d/s end has also served as an approach to Tail race complex.The Tail race starts from the junction point longitudinally to collection gallery at an invert level of 980.00 m. In the initial reach the tail race tunnel is also 10.15 m diameter standardhorse shoe shape upto 18.00m. After transition of ten meters i.e., from 18 m to 28 m the tunnel changes into circular tunnel of finished diameter 10.15 m, 982 m long and acquires an invert level of 992.0 m finished at exit. The tail race tunnel is having three different reverse invert slopes in different reaches i.e., from Station 0 to 543.39 m as 1:129.01 from Station 543.39 to 809.50 as 1:80.94 and from Station 809.5 onwards as 1:69.The layout plan of Tail race complex is shown in Fig.1.
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