First infilling of the underground structures of the Gouvães hydroeletric scheme - Monitoring and observed behaviour

Abstract

The Gouvães pump-storage hydroelectric scheme includes a 7800m-long underground power conduit connecting the Gouvães and the Daivões reservoirs, with a hydraulic head of 657 m and a 49 m-high underground powerhouse located at the depth of 300 m. To monitor the behaviour of the main caverns during the construction stages, a monitoring plan was developed and implemented. For the first infilling of the power conduit, a detailed plan was prepared, and the monitoring plan was upgraded to account for the hydraulic actions and the water flow in the rock mass. This paper describes the main structures of this scheme, presents the main geological and geotechnical information and introduces the main aspects of the monitoring system used for the construction stage of the underground structures. The paper outlines and justifies the proposed sequence and schedule for the first infilling phase, as well as the upgrades made to the monitoring system for this stage. It examines the observed behaviour during infilling, such as flow rates and water pressures, and how these factors influenced adjustments to the original infilling plan. Finally, it reviews the condition of the underground structures at the start of their service life.