The dimension of the underground power station in Shimogo pumped storage hydro plant project is 171 m in length, 45.5 m in height and 22 m in Width. The rock surrounding this cavern is consisted mainly of diorite, and partly of the formation of sandstone and shale lying underneath the diorite deposit. This paper is mainly undertaken to introduce a rational design procedure of the rock reinforcement which was successfully accepted for the present case. The paper also describes a mechanism of rock movement and its relation to the stability of the cavern. A detail observation of the rock movement gives an interesting fact that the movement induced by the stress relief due to the excavation consists both of elastic and plastic one, and that these two components can be separated phenomenologically from the obtained deformation curve.


Die Ausmaße der unterirdischen Kammer in dem Shimogo Pumpspeicher-Wasserkraft-Projekt sind 171 Meter Lange, 45,5 Meter Höhe und 22 Meter Breite. Das Gestein, welches diesen Hohlraum umlagert, besteht hauptsachlich aus Dlorit, sowie teilweise aus Sandsteinformationen und Schiefer welche unter dem Dioritlager liegen. Dieser Bericht solI in der Hauptsache einen rationalen Vorgang zur Ausfuehrung von Gesteinsverstarkung vorstellen, welcher in dem vorliegenden Fall erfolgreich angewendet wurde. Dieser Bericht befaßt sich ebenfalls mit dem Mechanismus der Gesteinsbewegung im Zusammenhang mit der Stabilitat der Aushöhlung. Eine detaillierte Beobachtung der Gesteinsbewegung ergibt die interessante Tatsache, daß die Bewegung, hervorgerufen durch den Spannungsnachlaß infolge des Aushöhlens, elastischer wie auch plastischer Art ist. Es zeigt sich ferner, daß diese beiden Komponente phanomenalisch von der gewonnenen Deformationskurve getrennt werden können.


Les dimensions de la centrale electrique souterraine du projet de centrale hydro-electrique à accumulation par pompes de Shimogo sont les Suivantes: 171 m de long, 45,5 m de haut et 22 m de large. La roche qui entoure l''abri se compose principalement de diorite, et partiellement d''une formation de gres et de schiste situee sous la couche de diorite. Ce document vise principalement à presenter une procedure,d''etude rationnelle de renforcement de la roche qui a ete un succes en la situation presente. Ce document s''efforce egalement de decrire Ie mecanisme du mouvement de la roche et sa relation avec la stabilite de l''abri. Une observation detaillee du mouvement de la roche revele des faits interessants, à savoir que Ie mouvement occasionne par la reduction de la contrainte due à l''excavation est à la fois elastique et de qualite plastique, et que ces deux composantes peuvent etre separees phenomenologiquement à partir de la courbe de deformation obtenue.


In excavating a large cavern, a great attention must be paid on its stability during and after the construction period. In general, rock reinforcement of large cavern is conducted by means of reinforced shotcrete and anchoring with use of pre-stressing steel wire and/or rock bolt. However, design procedure concerning the reinforcement has not definitely established yet. This paper is undertaken to introduce a rational design procedure of rock reinforcement by means of pre-stressing steel wire, which was successfully accepted in a construction of the underground power station of the hydropower plant at Shimogo, Japan. To accomplish this procedure, characteristics of joint sets existing in rock were geologically investigated in detail, and they were· taken into account in the stress and deformation analysis by means of finite element method.

The paper also deals with a mechanism concerning about rock movement measured during the excavation period, and shows its correlation to the stability of the cavern. A detailed observation of the rock movement gives an interesting fact that the movement induced by the stress relief due to the excavation consists both of elastic and plastic one. It was also found out that concerning the plastic movement, a rate of movement is closely related to amount of pre-stressing force applied to the steel wire. This quantitative evaluation will be an important design criterion on the reinforcement by the steel wire when assessing a stability of large cavern.


A pumped storage hydro plant project is being promoted at Shimogo, Fukushima Prefecture, located at about 200 km north of Tokyo, Japan. A total length of waterway in between upper and lower reservoirs is approximately 3.5 km. The obtained effective head is about 400 m at maximum. The electric power to be expected is 1,000 MW. The construction of the project has begun in April, 1978, and the start of electric generation will be scheduled for July, 1984. Four generating units with a power of 250 MW each and two transformers should be installed in the power station. As shown in the longitudinal section and the cross section of generator room, Figs. 1 and 2, respectively, the dimension of the station is 171 m in length, 45.5 m in height and 22 m in width. The total volume of the space is about 130,000 cubic meter.

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