This paper evaluates today's knowledge regarding prediction of the rock mass properties using existing rock mass classification systems. The paper illustrates a case where back calculation of convergence measurements has been used for estimating rock mass properties. The work is based on observations made at the Uri project, Kashmir, India, The result is compared with estimates which are based on commonly used classification systems. The result shows that convergence measurements in a tunnel give a solid ground for reliable predictions of the rock mass properties.
Les connaissances actulles concernant les previsions des proprietes d'une masse rocheuses en s'appuyant sur la classification des masses rocheuses sont exposees dans cet article. Ce dernier presente une etude oú des calculs anterieurs bases sur des mesures de convergence ont permis d'estimer les proprietes rocheuses.Ce travail fut acheve à l'aide d'observations effectuees sur un chantier au Cachemire en Inde, le Projet Uri. Les resultats sont compares aux previsions obtenues selon les systèmes de classification classiques. Ces resultats montrent que seules les mesures de convergences faites dans un tunnel apportent une prevision valable des proprietes de la masse rocheuse.
Diese Arbeit ist eine Auswertung der heutigen Kentnis wie man die Eigenschaften einer Steinmasse durch Klassifisierung voraussieht. Hier wird ein Fall beschrieben wo man die Eigenschaften einer Steinmasse durch Nachrechnungen der Konvergierung in einem Tunneln geschatzt hat. Die Arbeit gruendet sich auf Beobachtungen und Erfahrungen bei dem Uri Project, in Kashmir, India. Das Ergebnis wird mit anderen Ergebnissen verglichen, die sich auf bewahrten Klassifisierungssystemen gruenden.Es wird gezeigt, daβ das Messen von Konvergierungen die einzige Methode fuer eine zuverlassige Voraussage des Benehmens einer Steinmassse ist,
Rock mass classification systems are at present used to estimate the rock mass properties of a rock mass. Such properties are used as input parameters for predictions of the rock mass behaviour. In this paper some existing classification systems are evaluated regarding their possibility to predict rock mass properties. The evaluation is limited to one case study and the results must therefore be considered as indications only, rather than as general statements. The field studies for the work presented here were carried out at the Uri Project which is a 480 MW hydropower project situated in the State of Jammu and Kashmir in north-western India. The power plant is supplied with water from the Jhelum River which has its springs in Kashmir and flows through the Kashmir. Valley into Pakistan, where it becomes a tributary of the Indus River. The project is designed as a run-of-the-river scheme. The water is diverted from the river and leads from the head regulator and desilting basins into an l l-km long headrace tunnel and two 210-m high pressure shafts. After passing through the four turbines in the machinery hall the water is lead through the draft tubes and the 2-km long tailrace tunnel back into the river. The headrace and tailrace tunnels are of horseshoe shape with a diameter of 9 m.
The tailrace tunnel intersects the Panjal thrust, which is one of the major thrust zones in this part of the Himalayas. The tunnel runs from Panjal Volcanics, a competent basaltic rock in which the power station is located, through a thrust zone, ending in red shale at the outlet side. At the Upstream end of the tailrace tunnel, after about 30 m of Panjal volcanic, a 290-m wide strata consisting of a mixture of sheared and crushed mica, talc, chlorite and graphite schists and phyllites with some limestone bands was encountered. A notable amount of clayey gouge was also present.
