Many large caverns are being constructed in great depths in Korea mainly for the storage of oil and LPG. These caverns are mostly located near the port where rock conditions are reasonably good. In some instances, the horizontal stress is very high and endangers the stability of the cavern. The purpose of this study is to assess the stability of large caverns excavated in a rock mass with high horizontal stress where Ko value is close to 3. Result shows that stress exerted in the shot-crete at crown exceeds allowable value when the 3rd bench is excavated. Also found is the tensile failure of shotcrete near the boundaries between benches.

In Korea werden viele grosse Kaverne fuer Aufbewahrung vom Oel und Fluessiggas in grosser Tiefe gebaut. Am Meisten befinden sich diese Kaverne in der Naehe von Haefen, wo der Fels gute Verhaeltnisse zum Bauen einer Kaverne besitzt. In einigen Faellen ist die Horizontalspannung sehr gross und dadurch wird die Stabilitaet vom Kaverne gefaerdet. Der Zweck dieser Arbeit ist die Stabilitaet des im Fels gebauten grossen Kavernes mit hoher Horiaontalspannung zu schuetzen, wo Ko-Wert sich auf 3 naehrt. Die Ergebnisse zeigen, dass die Spannung im Spritzbeton an der Krone den zulaessigen Wert ueberschreitet, wenn das dritte Bank ausgegraben wird. Im Bereich des Spritzbetons zwischen Baenke wurde das Zugversagen festgestellt.

Des larges cavites nombreuses sont en train d'être construites en grand profondeur en Coree principalement pour le stocage du petrole et LPG. Ces cavites sont pour la plupart situees près de la porte oú les conditions des roches sont resonablement bons. En quelques cas, la contrainte horizontale est tres haute et met en danger la stabilite de la cavite. L'objet de cet etude est d'estimer la stabilite des large cavites excavees dans une masse de roche ayant une haute contrainte horizontale oú la valeur de Ko est proche à 3. Le resultat montre que la contrainte exercee dans le shotcrete à la couronne depasse la valeur admissible quand le troisième banc est excave. En plus une faillite en tension du shotcrete près de la frontière entre des bancs est trouvee

Introduction

For the stable supply of imported energy such as oil and LPG, a lot of storage facilities were already constructed above ground in Korea. But energy demand is increasing rapidly while above ground space is running out. For this reason, many underground storage facilities are being constructed near the port. To store LPG or oil in unlined caverns, it is necessary to locate them in great depths so that the water pressure is big enough to prevent the containing gas or liquid from leaking. In some instances, the horizontal stress is very high and affects the stability of the cavern. In this paper, the stability of oil storage caverns excavated in a granitic rock mass with high horizontal stress was analysed. Due to the high Ko value combined with the vertically long cavern shape, stress concentration at the crown arch was the main concern.

Criterion for Shotcrete Failure

Maximum allowable stress design is based on the assumption that the stress in the shotcrete is linearly proportional to the distance from the neutral axis. In this design method, design stress is determined from the predicted load applied to the structure.

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