The shear behavior of rock joints is closely related in a complicated way to some factors, such as the confining condition, the material strength, the joint surface roughness, and the material friction. Therefore, it is necessary to investigate the influence of and/or the relation between the shear behavior and each factor, in order to estimate the shear behavior. In the research described in this paper, direct shear tests were carried out using two types of specimens, namely, smooth joint surface model and a natural joint surface roughness model. Measuring the shear stress, the shear displacement, the dilatancy, and the changes in joint surface roughness, the mechanical properties of the rock joints have been determined. As a conclusion, it is considered that the shear behavior depends on the material friction and the sheared joint asperities.


Le comportement de cisaillement des joints rocheux est relationne d'une facon compliquee avec quelques facteurs, comme les conditions de confinement, la resistance du materiel. la rugosite de la surface du joint et la friction du materiel. Donc, il est necessaire de rechercher la relation et/ou l'influence entre le comportement de cisaillement et ces facteurs, pour forme à estimer le comportement de cisaillement. Dans la recherche decrite dans cette communication, des essais de cisaillement direct ont ete realises avec deux types d'eprouvettes: joint sens rugosite et joint naturel avec une surface rugeuse. En mesurent la tension de cisaillement, le deplacement de cisaillement, la dilatance et les variations de la rugosite de la surface du joint, on a determine les proprietes mecaniques du joint Comme conclusion, on peut considerer que Ie comportement de cisaillement depend de la friction du material et des asperites cisaillees.


Das Scherverhalten von Felsldueften ist auf enge und komplizierte Weise mit bestimmten Faktoren wie zum Beispiel dem Spannungsverhaeltnis, dem Materialwiderstand, der Kluftoberf1aechenrauheit und der Materialreibung verbWlden. Es ist deshalb notwendig, das Verhaeltnis und/oder den Einfluss zwischen dem Scherverhalten und jedem Faktor genau zu untersuchen, um das Scherverhalten zu berechnen. Fuer die in dieser Arbeit beschriebene Untersuchung wurden direkte Schertests an zwei Arten von Spezimen durchgefuehrt: einem glatten Kluftoberflaechenmodell und einem natuerlich rauhen Kluftoberflaechenmodell. Durch die Messung der Scherspannung, der Scherabweichung, der Dilatanz und der Wechsel in der Kluftoberflaechenrauheit wurden die mechanischen Eigenschaften der Felskluft bestimmt. Zusammenfassend kann gesagt werden, dass das Scherverhalten von der Materialreibung und den gescherten Kluftrauheiten abhaengt.


In the excavation of jointed rock masses, the confining pressure on rock joints decreases, and the shear behavior of rock joints can easily occur due to stress relief around underground spaces. In predicting the deformation and the stability of rock structures, therefore, it is important to grasp the shear behavior of rock joints under lower confining conditions. The shear behavior of joints is determined through a complex combination of certain factors, namely, the normal confining condition, the strength of the material (intact rock), joint surface roughness, and the basic friction angle. And, it is necessary to clarify the influence and the relation of each other.

In this study, direct shear tests are carried out using specimens whose joint surfaces are extremely smooth. Performing the tests under a constant normal confining condition, the basic friction angles are determined and discussed On the other hand, direct shear tests are also carried out using specimens which have natural joint surface roughness. Some mechanical parameters are then determined from the experimental results.

In past research works, the peak shear strength was estimated using Barton's empirical equation (Barton,1976), and was compared with the peak shear strength from the experimental results (Kishida, et al.,1996).

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