Diversion tunnel of the Irganaiskaya waterworks facility and prospects of its use in the period of erection of the dam to intermediate levels

Abstract

General information on the diversion tunnel and statement of the problem of its use at normal maximum operating level NMOL = 521 m. The Irganaiskaya waterworks facility is being built in Dagestan on the Avarskoe Koisu River. The design engineering solutions for this waterworks facility and the stage of the construction have been considered in [1]. Excess water volumes of this waterworks facility are passed through the right-bank combined diversion and operational tunnel-kind spillway designed for freeflow operation in all stages of flow passage. The diversion tunnel is the first story of the spillway, which serves for passing flows in the initial period of the erection of the waterworks facility and in temporary operation. This structure consists of an intake channel, intake portal, slightly inclined part of the tunnel, and a tail device. The gretaer part of the slightly inclined tunnel and the tail device are to be used later in the period of continuous operation after the erection of the sluiceway entrance and inclined part of the sluice of the upper (second) story. Some data on the structure of the diversion tunnel and of laboratory hydraulic studies performed for its design are presented in [2]. The full length of the diversion tunnel is 965 m, and a two-span gates chamber is constructed in its intake portal (Fig. 1). The sizes of the entrance cross-section of the gates chamber (in front of the slots of the guard gates), which determine the diversion capacity of the tunnel, are h b = 6 4.5 m; the sizes of the main gates are 6.3 3.5 m. The operating gates were actuated by hydraulic actuators mounted at a level of 522.0 m of the upper part of the intake portal of the tunnel. Metallic facing exists in the gates chamber only on the zone adjoining the gate slots. Behind the gates chamber and the bottleneck transition part, the tunnel has a trough shape with a height of 11 m and a width of 8 m; the interface of the trough and of the vertical side walls of the tunnel is rounded. On the upstream region (in front of the connection between the tail reach of the tunnel and the inclined conduit of the operational spillway) the tunnel has a sloped bottom (the slope is 0.006) and on the downstream discharge region the slope is 0.0235. In the greater part of the length the diversion tunnel is made of concrete of class B30, but in the upstream region the Power Technology and Engineering Vol. 39, No. 6, 2005