New technical solutions used for concreting tunnels of the Nurek hydroelectric plant

Abstract

The greatest complexity in the concreting of the hydraulic tunnels of the underground Nurek hydroelectric plant complex occurred in the construction of the reinforced concrete linings of three 10-m-diameter headrace tunnels and in the concreting of the trough part of the 10-m-wide, horseshoe-section diversion tunnels.To construct the permanent reinforced concrete linings of these tunnels, use had been made previously of different mechanized formwork systems.In order to increase the rates of concreting of these structures, the writers worked out new technical concreting solutions. For this purpose, the OKSh-lO circular walking formworkwas developed, which consists of the following assemblies and mechanisms ( Fig. 1): a 6 • 6 m in section and 12-m-long portal of welded construction, which has the form of a parallelepiped each of whose faces is a flat latticed truss made from No. 30 l-beams; four telescopic portal supports consisting of welded box-section posts, each of which is moved by a hydraulic Jack along guide grooves welded to the lower part of vertical ribs of the portal; eight decks, the surface of each of which is a part of a cylinder with a 45" arc and 6 m long. Two decks are hinged to each longitudinal portal rib. The free edges of two adjacent decks have locks which are connected in all the eight decks to form a closed cylindrical surface; deck displacement cylinders (two in each deck), 180 nun in internal diameter and with a 1000-~m travel, equipped wlthhydraullc locks, which are hinged to the portal; four two-wheel cars on double-flanged wheels 500 mm in diameter, connected to the portal, forming a 4-m-wlde track with a rigid base of 8 m, each pair of running wheels being kinematically Joined by means of a gear clutch and equipped with stops; a hydrulic pusher for longitudinal displacement of the formwork, which consists of a hydraulic cylinder 180 nun in diameter with a lO00-mm travel, hinged to the portal. At the end of the rod there is a pin catch which interacts with the support plate grooves; a 16.7-m-long support plate, which is more than twice as long as the rigid base, made from No. 50 l-beams.Over the entire length of the plate, in the 4-m track, R-24 rails are placed, and along the center there are grooves with a 900-mm pitch for securing the hydraulic pusher by means of the pin catch. At the front (in the concreting direction) end of the plate there are hinged posts which serve for supporting it on the excavation bottom; two oil stations with control panels: one for paired drive of the deck displacement hydraulic cylinders, and the other for drive of the hydraulic jacks of the telescopic supports and the hydraulic pusher. The oil station includes an oil tank, an NSh-46 hydraulic pump, an electric motor, and an R-75 hydraulic distributor block; a portal equipped with work areas with guardrails, stairways, and passages. In the lower work area, in addition to the oil station there is a switchboard and four welding transformers used for erection of the reinforcement.The formworkmass is 100 tons...