Tokyo Electric Power Co. (TEPCO) has been constructing the Sabigawa pumped storage power plant with an output of 900 MW since 1986. In order to develop a more efficient system for measuring the expansion of a loosened zone caused by the excavation of a cavern for the underground power plant (29m wide. 51m high, and 165m long), TEPCO tested various kinds of new in-situ measuring methods, such as a method measuring rock stress changes around the cavern, and a method measuring acoustic emission propagated through the rocks, in addition to an interval strain measuring method using the conventional multi-channel extensometer. The measured results proved some new measuring methods to be effective for practical use.


Depuis 1986, la societe Tokyo Electric Power Co. (TEPCO) construit la centrale electrique d'accumulation par pompage de Sabigawa d'une capacite de 900 MW. En vue de developper un système de mesure plus efficace de l'expansion dans la zone desagregee causee par l'excavation de la cavite pour une centrale electrique souterraine (largeur: 29m. hauteur: 51m, longueur: 165m), TEPCO a effectue des essais portant sur diverses nouvelles methodes de mesure sur le terrain, comme par exemple une methode de mesure les modifications des contraintes internes de la roche autour de la cavite, une methode mesurant l'emission acoustique propagee à travers la ruche, en plus d'une methode de mesure des contraintes par intervalle utilisant l'extensomètre (jauge de contrainte) conventionnel à canaux multiples.


Die Firma "Tokyo Electric Power Co." (TEPCO) baut seit 1986 das pumpenspeicherungs-Kraftwerk Sabigawa mit einer Leistung von 900 MW. Zur Entwicklung eines leistungsfahigeren Systems zur messung der durch die Ausschachtung eines unterirdischen Hohlraums far das unterirdische Kraftwerk (29m breit, 51m hoch und 165m lang) verursachten Erweiterung einer aufgelockerten Zone, hat TEPCO verschiedene Arten von neuen in-situ Meβverfahren getestet, wie einem Verfahren zum Messen von Veranderungen der Spannung im Felsen ringsum den unterirdischen Hohlraum, einem verfahren zum Messen der durch den Felsen propagierten akustischen Emission, zusatzlich zu einem Verfahren zum Messen der Spannung in Abstanden unter Verwendung des herkömmlichen Mehrkanal-Dehungsmessers. Die Meβergebnisse haben gezeigt, daβ einige neue Meβverfarhen fuer pratische Anwendung leistungsfahig sind.


The underground power plant is located at A depth of about 200m from the ground surface and designed to house three sets of 300- MW hydraulic turbine generators and three sets of 335-MVA transformers in the same cavern having a large cross-sectional area of about 1,500m2. Bench-cut excavation was successively carried out from bench No.1 to bench No.14 (each bench has a bench height of 2.5m) from the top arch section to the bottom of the cavern. The geology in and around the cavern is heterogeneous and discontinuous, and consists mainly of various kinds of rhyolites containing fracture zones and planes, in addition to well developed joints. At the time of starting the excavation, the geological condition in and around the cavern to be excavated was investigated in detail and, a large number of various measuring instruments were set around the cavern. The measured results with the instruments were processed and analyzed in real time by means of an EWS (engineering work station) installed at the site office. In addition, in order to make the design more efficient and improve the safety, a so-called observational method system was developed and introduced for predicting the rock behavior in and around the cavern at the next stage of bench-cut excavation on the basis of the processed and analyzed results of the measurements. Since it was considered to be important to establish a standard of judgment for confirming the stability of the cavern.

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