SUMMARY:

The present paper reports the results of combined investigations of rock pressure manifestation and of rock mass stresses and deformation as well as the engineering measures on tunneling in complicated geotechnical situations. Investigations were carried out under natural conditions in the course of years, at the same time a cycle of the rock laboratory tests was performed. The pressure intensive manifestations laws operating deep down Under the surface were found due to the investigation results. During the tunnel construction they allowed to realise new lining designs providing the rock mass stability, high rates of tunneling and the operation reliability of the underground construction.

ZUSAMMENFASSUNG:

Im Vortrag sind Ergebnisse einer komplexen Untersuchung der Erscheinungen des Bergdrucks, des Gesteinzustandes bei Spannung-Verformung sowie die ingenieurtechnischen Massnahmen zum Tunnelvortrieb unter aussert komplizierten geotechnischen Bedingungen gezeigt. Die Untersuchungen wurden unter Naturbedingungen jahrelang vorgenommen. Das schloss jedoch keinen Zyklus der Laborprufuengen des Gesteins aus. Nach den Ergebnissen der komplexen Untersuchungen sind die Gesetzmassigkeiten einer intensiven Druckerscheinung in den grossen Tiefen festgestellt werden. Sie ermöglichten u.a. wahrend des Tunnelbaus eine neue Ummantelungskonstruktion zu realisieren die jeweilige Stabilitat des Gesteins, hohe Schnelligkeit des Vortriebs und Sicherheit des unterirdisches Bauwerks im Betrieb absicherte.

RESUME:

L''expose fait etat des resultats des investigations complexes de la pression des roches, de l''etat de contrainte et de deformation des massifs rocheux, ainsi que de la technique de percement du tunnel dans des conditions geotechniques fort compliquees. Les recherches s''echelonnant sur plusieurs annees ont ete menees dans des conditions naturelles, sans exclure, pour autant, tout un cycle d''essais des roches en laboratoire. Les resultats des recherches complexes ont permis d''etablir les lois regissant les manifestations intensives de la pression en grande profondeur. Ces lois ont permis de trouver, au cours de la construction du tunnel, une nouvelle forme de blindage assurant la stabilite du massif rocheux, une vitesse de percement accrue et la fiabilite de fonctionnement de l''ouvrage Souterrain.

INTRODUCTION

Up to the end of the 50s the waters OF the highland lake Sevan stored in the course of centuries were used tor irrigation and power needs of Armenia. It reduced its level by 18m. In order to preserve the flora and fauna of the lake Sevan basin, of this pearl of nature, in the period between the 60s and the 80s a number of irrigation and power measures were realised, the river Arpa diversion to the lake Sevan being one of them.

The construction complex for diverting the river Arpa to the lake Sevan is presented as Follows. Due to the 47 m high barrage on the river Arpa, a water storage is created with available capacity of 25 mln m3. Prom the storage the water is directed to the lake Sevan through two powerless (pressureless) tunnels with 48.3 km of total length. On its way the tunnel includes the waters of the tributary Elegis. The tunnel capacity along the tributary Elegis is 18 m3/sec and after it it is 25 m3/sec. The diverted flow volume is defined as 250 mln m3(Hydraulic Power Engineering of Armenia, 1979.

GEOTECHNICAL CONDITIONS

The Arpa-Sevan tunnel route passes through large rock masses presented by separate lithologic and stratigraphical formations. Upper Cretaceous conglomerates, sandstones, limestones and porphyrites forming the anticlinal fold nucleus of Hayotsdzor (Armenian Valley) synclinarium serve as the basis for the whole complex of the highland rocks. Within the diversion route boundaries they occur than the tunnel level mark and are crossed by separate fragments of other tunnels. The upper part of the complex is presented by volcanogenic-sedimentary rocks of the Middle Eocene, mainly by tuff stone of various bedding, by tuffites, and by tuff aleurites with porphyrite subordinate inter-layers. Thickness of this formation lies within 200 - 2000 m. Volcanogenic rocks of the Upper Eocene, Miocene and Pliocene formations also occur in the described deposits. They are presented by porphyrites and andesites, by their tuffs and tuffobrecias, by pumice-liparite tuffs of psephitic structure intermitted with members of andesite tuff-brecias, with tuffite lentils, with dark-brown clays and with clayey conglomerates. Within the described region intrusive rocks are presented by granodiorites. Their intrusive bodies in the form of stocks and sills broke through the thickness of volcanogenic-sedimentary rocks and occurred all along the tunnel route.

Volcanogenic-sedimentary Eocene rocks are highly dislocated and folded, with numerous cracks and breaking zones due to the rock hydrothermal hydrothermal changes.

It was just in these zones that underground waters of different temperature and mineral composition found their way out at separate points. In doing so, spring-like waters escaping through the craks with the temperature less than 10°C were distributed along the tunnel route, their total discharge being no more than 670 1/sec.

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