A series of uniaxial compression tests was performed with a stiff and servo-controlled machine. At the same time, acoustic emission events were monitored. The circumferential strain rate was used as a feed back signal to control the servo system. From the post-peak behavior of test results, marble and sandstone are Class I rocks. Granite, andesite, tuff, siltstone, quartzite and serpentinite are Class II rocks. The failure modes observed include spalling, axial splitting and shear failure along filling material. The growth, interaction and coalescence of cracks can be clearly identified by acoustic emission activity. There usually exists a higher amplitude emission activity for the precursor of rock failure.
Des essaies de compression uni-axialle sont effectues dans un système auto-controle. L'effet d'emission acoustique a aussi ete observe pendant les essaies. La vitesse de deformation est utilisee pour contrôler Ie système. Selon Ie resultat, marbre, grès sont classifie comme "Type I", granite, andesite, tuff, argile, quartzite et serpentinite sont "Type II". Les styles de fissures observes incluent "spalling", "splitting" axial et cisaillement sur les materiaux remplis. La croissance, l'interaction et Ie coalescence de fissures peuvent être clairement identifies par l'activite d'emission acoustique. II y a souvent un grand amplitude d'activite d'emission comme Ie presurseur des fissures de roches.
Eine Reihe von einaxialen Druckversuchen wurde mittels einer Servoanlage durchgefuehrt. Gleichzeitig wurde das Geschehen der akustichen Ausstrahlung ueberwacht. Als Kontrolle des Servosystems dient die Verformungsrate. Die Versuchsergebnisse zeigen, dass Marmor und Sanstein als Felsklasse I einzustufen sind. Granite, Andesite, Tuff, Siltstone, Quartzite sowie Serpentinite als Felsklasse II. Fuer die Beobachtung des Versagensmodells sind die Absplitterung, die axiale Spalte und das Scherversagen entlang des Fuellermaterials heranzuziehen. Die Entwicklung, die Weckselwirkung sowie die Verbindung des Risses kann durch das Geschehen der akustischen Ausstrahlung deutlich identifiziert werden. 1m allgemeinen ist die Entstehung einer grosseren Ausstahlungsamplitude ein Indiz fuer das Felsversagen.
In the last three decades, one of the most important advances in rock mechanics is the study of the complete stress-strain curve of rocks under incremental compression. In general, the knowledge of post peak behavior of rocks was vague prior to 1965 (Cook, 1965). This behavior is now considered to be closely related to the stability of many underground structures in tunnelling and mining. Due to the fact that the post -peak behavior of rocks is often in unstable state, the complete stress-strain curve is not so easy to obtain. However, the development of stiff, servo-controlled loading system and the sophisticated control method aided by micro computer make it possible to investigate the post-peak behavior of rocks (Hudson, et aI., 1972). On the other hand, the progresses in the measurement of acoustic emission technique also make it possible to understand the microfracturing process of rocks in deformation (Hardy, 1981). In this study, both of the servo-controlled test machine and acoustic emission measuring system are utilized to make a comprehensive study on the behavior of rocks under uniaxial compression. Wawersik (1968) classified rocks into Class I and Class II based on their post-peak behaviors. The stress-strain curve of Class I rocks is characterized by a negative slope in the post-failure region. In contrast to Class I, that of Class II rocks is characterized by a positive slope. Deformation of Class II rocks is self-sustaining beyond the ultimate strength. Thus, the complete stress-strain curves of Class II rocks cannot be attained only by stiffening the test machine. Many attempts have been made to study the Class II rock behavior using servo-controlled machine. A linear combination of stress and strain function has been successfully used as a control feed back signal to obtain the complete stress-strain curve of rocks (Okubo and Nishimatsu, 1986). It has been recognized that the growth and coalescence of microcracks are responsible for the complete stress-strain behavior of rocks under compression (Bieniawski, 1967; Kranz, 1983). The process from microcracks to macrocracks can be observed by optical techniques or by acoustic emission measuring techniques. The optical observation is an indirect and static method, while the acoustic emission measurement is direct, real time and remote sensing method.