Caraguatatuba 2,000 MW pumped storage powerplant to be constructed in the next years near the city of São Paulo (Brazil), required a complete FEPI rock mechanics analysis, the aims, methodology, and results of which are the subject of this paper. The correlation among the structural analysis and the geologic survey resolved many conceptual, constructive and operational aspects of the design.
Das Caraguatatuba 2000 MW Pumpspeicherkraftwerk, das in den nachsten Jahren in der Nahe von São Paulo (Brasilien) gebaut werden soll, erforderte eine vollstandige FEIA- Berechnung, deren Ziele, Vorgehensweise and Ergebnisse Gegenstand dieses Beitrags sind. Die Abhangigkeit zwischen statischer Berechnung and geologischen Untersuchungen machte eine grofße Anzahl von Entwurfskriterien hinsichtlich Planung, Konstruktion and Ausfuehrung notwendig.
Caraguatatuba, une centrale electrique de pompage de 2000 MW, qui devra être construite durant les prochaines annees aux environs de São Paulo (Bresil) exige un calcul complet par la methode des elements finis, dont les buts, la marche à suivre et les resultats font l''objet de cet expose. La dependance entre le calcul statique et les investigations geologiques rend, en ce qui concerne la planification, le dimensionnement et l''execution, un grand nombre de critères de conception necessaire.
The High ParaÍba do Sul river course at medium levels between 1,000 and 700 m over the sea, contained by Serra do Mar and Serra da Mantiqueira, in Southeast Brazil Atlantic shore, at distances ranging from 15 to 60 km from the Atlantic Ocean, enabled the formation of one of the highest industrial concentrations in the country along its valley, connecting the two major South American cities: Rio de Janeiro and São Paulo (see Figure 1). In order to meet the electric power production requirements of this region, a number of works were implemented which enabled the partial diversion of watercourses and its water resources to locations technically more convenient for hydroelectric use. It is very well known that the industrial activities are characterized by the continuous power consumption unbalance (the so-called demand peak) and, therefore, the installed power generating plants were the ones more economically suitable to this situation: high-head hydroelectric power plants located close to the power centers and easily supermotorizable to consume the available reasonably small flows. The development of the region in the last decades was based on this scheme. However, studies performed have shown that large peak power demands of approximately 10,000 MW, not covered by the installations presently included in the planning for power supply to the Rio-São Paulo area, shall occur in the year 2000. Therefore, new hydroelectric possibilities shall be found, however taking into account the compatibilization of increasing power requirements with other essential factors: the maximum conservation of the water resources for ecological preservation and, consequently, for preservation of the living conditions in the region. Among these possibilities, one is feasible even in a short-term basis, i.e. the use of the plateau water for power generation taking advantage of the high hydraulic head attained by the mountains and the sea. In addition to this, after total or partially stored in suitable reservoirs on the coastal area, these waters, when pumped back to the plateau, make possible the total reconstitution of the valley''s water resources, they are the so-called Pumped Storage Plants, one of the latest innovations in the hydroelectric field. Installed in underground cavern and equipped with high-power compact generator sets, the Caraguatatuba powerplant will produce at least 1,000 MW in its first phase. When pumped, it can reach 2,000 MW of installed power. It will be embedded in the rock mass of the Serra do Mar foot, near the place called Caraguatatuba with accesses to the roads which cross the area. The water flow required for its initial operation with discharges to the ocean is estimated as 30 cubic meters per second. This will make possible peak power generation during the 1985 - 1995 decade without imparing the other activities of the Upper ParaÍba Valley. In the initial stage, these water will be discharged through a short tailrace up to Santo Antônio River and from there on to the Atlantic Ocean. The pumped storage operation anticipates the water storage in a lower reservoir built in the coastal plains, most likely in the Juqueriquerê river headwaters where different dam alternatives were preliminary designed for this purpose.
To complete the rock engineering studies relative to the construction feasibility of the Caraguatatuba Pumped Storage underground works, the definition of the stress and strain fields that affect the rock mass after the execution of the different excavation stages were computerized. In the light of the results obtained, an attempt was made to determine the necessity and the dimensioning of the temporary supports, as well as the stability of the top and walls of the caverns. In a study of this nature, it is imperative to correctly represent the basic factors which affect the mechanical behavior of the rock.