The sixth underground pumped powerhouse cavern is under construction now in Korea. For the stability analysis of the five underground powerhouses, finite element method was used. For this analysis, in-situ rock stresses were measured by overcoring method and horizontal to vertical stress ratio was calculated 1.07–1.32 at four sites. Rock mass strength and elasticity were assumed from intact rock properties. The ratio of elasticity of rock mass was 0.16–0.55 of intact rock core elasticity. In general, elasto-plasticity with Mohr-Coulomb failure criterion was applied and the input cohesion and internal friction angle were approximately 0.12–0.22, 0.6–0.87 of intact rock strength parameters, respectively.

Der sechste Untergrund-gepumpt-Powerhouse-Cavern ist jetzt im Bau in Korea. Fuer die vergan-gene Stabilitatsanalyse des fuenf unterirdischen Powerhouses in Gebrauch wurde ein begrenztess Elementsmethode benutzt. Fuer die Analyse wurden In-Situ Felsenspannungen von overcoring Methode gemessen und Horizontale zu senkrechtem Spannungsverhaltnis waren als 1.07–1.32 an vier Stellen kalkuliert. Felsenmassenkraft und Elastizitat wurden von unversehrtem Felsenei-gentuemern angenommen. Das Verhaltnis der Elastizitat von Felsenmasse war 0.16–0.55 von un-versehrter Felsenkernelastizitat. Im allgemeinen wurde Elasto-Plasticity mit Ausfallskriterium des Mohr-Coulombs verwendet. Die Eingabebindekraft und die innere Reibungswinkel waren unge-fahr 0.12–0.22, 0.6–0.87 von unversehrtem Felsenkraftsparametern, jeweilig.

En Coree, la sixieme centrale souterraine de la pompe d'accumulation dans la caverne est en construction. La methode d'element fini a ete utilisee pour analyser la stabilite de cinq dernieres centrales en service. Dans cette analyse, la reaction de la roche sur place etait mesuree par la methode d'overcoring et celle du rapport horizontal-vertical etait calculee de 1.07–1.32 en quatre places. L'intensite et l'elasticite de la masse de roche ont ete estimees de la roche intacte. Quant a l'elasticite, sa masse de roche etait 0.16–0.55 fois que celle de la roche intacte. En general, elasto-plasticite avec le critere de defaut Mohr-Coulomb etait utilisee et sa cohesion d'energie et son angle de friction interieure etaient supposees respectivement 0.12–0.22, 0.6–0.87 fois que la parametre de l'intensite de roche intacte.


The first pumped powerhouse was constructed during 1973–1980 in Korea. After that, several pumped powerhouses were planned or constructed in a row for 30 years. As a consequence of several experiences from planning to construction for pumped powerhouses, engineering technology on pumped powerhouse has been developed in Korea.

As of 2003, four pumped powerhouses are in operation and another two pumped powerhouses are under construction. Table 1 and Figure 1 show the general specifications and the location of the underground pumped powerhouses in Korea.

In this paper, geological and rock mechanical condition, initial rock stress, stress analysis on main cavern, reinforcement pattern design and construction result during pumped underground powerhouses excavation are presented. Especially, softwares for stability analysis, input parameters and result like displacements, stresses and rockbolt axial forces are compared, additionally.

Geology and in-situ rock stress
Geological condition and rock property

Table 2 shows regional and local geological condition around the caverns. Physical and mechanical tests on rock cores were carried out, but the results are not presented in this report.

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