Quartz mica schist collected from Nathpa-Jhakri Hydropower Project, Himachal Pradesh, North India is tested under triaxial loading using a servo-controlled loading system. Complete stress-strain-volume change behaviour including post peak softening behaviour of the samples, are presented. Strength and deformation parameters are given.

Quarz mica schist, der von Nathpa Jhakri Hydropower Projekt, Himachal Pradesh gesammelt wird, wird Nördlich Indien unter triaxial geprueft, der von Gebrauch eines servo kontrollierten Ladesystems beladung. Vollstandiges Spannung-Spannung-Band Änderung Verhalten Postens Spitze Erweichung Verhaltens der Proben, wird ueberreicht. Kraft und Verformung Parameter werden gegeben.

Mica à quartz schist recueilli du Projet de Hydropower de Nathpa Jhakri, Himachal Pradesh, l'Inde du nord est essaye sous l'utilisation de chargement de triaxial un système chargeant servo regle. La tension complète-la tension-comportement de changement de volume y compris la poste sommet amollir le comportement des echantillons, sont presente. Les paramètres de force et deformation sont donnes.


The behaviour of rocks is affected by a number of factors such as origin, mineralogical composition, stress history, joints and loading condition. Most of the rocks exhibit strain-softening behaviour. Wawersik (1968) distinguished stable and unstable failures in rocks. The post-peak behaviour of rocks, in which the strain-softening occurs, can be captured by utilising a special set up in which the failure of the sample is controlled. This has been achieved using two methods, viz.

  1. by using a testing machine with a relatively high longitudinal stiffness (control of axial stiffness only), and

  2. by using a closed loop servo-controlled testing machine (control of any function of one or more displacement or other experimental variables).

The first method is based on the equilibrium of the machine-specimen system. The stiffnesses of the machine and the specimen are estimated and compared. Some investigators (Hudson et. al, 1971, 1972, Brady et. al., 1973 and Hallbauer et. al. 1973) studied the effect of size and length / diameter ratio in the uniaxial tests using stiff testing machines. The second method is based on the control of deformation, load or their combination with any other experimental parameters. The method utilises a feedback control system to control an experimental variable automatically, continuously and precisely. Various aspects of servo-controlled system such as end friction, strain rate, geometry of specimen and choice of feedback system have been investigated by some investigators (Yumlu and Ozbay, 1995, Okubo and Fukui, 1996, Haied and and Kondo, 1997 and Vardoulakis et. al, 1998). Majority of the investigations have been based on the uniaxial testing of rocks. This paper presents the study of the behaviour of quartz mica schist rock samples under triaxial stress condition. The servo-controlled testing system is used for testing.

Rock Samples

For the study, rock samples collected from Nathpa- Jhakri Hydropower Project, a run-of-the-river hydropower project constructed in the middle reaches of the river Satluj in the Himachal Pradesh State, Northeren India has been used. The rocks in the project site are metamorphic type and they consist of gneissose schists and basic intrusives (amphibolites), granite and pegmites.

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