Based on results from triaxial compressive tests, an experimental damage model to simulate post-peak behaviours as well as nonlinear behaviours before peak strength was developed. In order to consider pre-peak behaviours, variations of elastic constants at each damage level were regressed by functions of confining pressure. In addition, post-peak behaviours were simulated successfully by using Hoek-Brown constants. As results, the experimental model could predict nonlinear behaviours, peak strengths and stiffness changes observed in experiments.

Base sur des resultats des essais compressifs à trois axes, un modèle experimental de dommages pour simuler des comportements de poteau-crête aussi bien que des comportements non-lineaires avant la force maximale a ete developpe. Afin de considerer des comportements de pre-crête, des variations des constantes elastiques à chaque niveau de dommages ont ete regressees par des fonctions de pression d'emprisonnement. En outre, des comportements de poteau-crête ont ete simules avec succès en employant des constantes de Hoek-Brunes. Comme resultat, le modèle experimental a pu prevoir des comportements non-lineaires, des forces maximales et des changements de rigidite observes dans les experiences.

Auf Basis der Ergebnisse des dreiaxialen Drucktests wurde das experimentelle Schadensmodell, das sowohl das nicht-lineare Verhalten vor der maximalen Starke als auch das Verhalten nach der maximalen Starke simulieren kann, entwickelt. Um das Verhalten vor der maximalen Starke zu beruecksichtigen, wurden die Veranderungen der elastischen Konstante bei dem jeweiligen Schadensniveau durch die Funktionen des begrenzten Drucks zurueckgegangen. Außerdem wurde das Verhalten nach der maximalen Starke unter Benutzung von Hoek-Brown Konstanten erfolgreich simuliert. Schließlich konnte das experimentelle Modell das nicht-lineare Verhalten, die maximale Starke und die Veranderungen bezueglich der Steifigkeit wahrend der Experimente voraussehen.

Introduction

Theoretical models such as micro-mechanical models based on the linear elastic fracture mechanics (LEFM) and damage mechanics models to simulate nonlinear behaviors of rock have some disadvantages that model parameters is difficult to determine from typical laboratory experiments and post-peak behaviours are not simulated well. Other approaches such as statistical models and the bondedparticle model demand many assumptions. From such backgrounds, an experimental model that considers postpeak behaviors and pre-peak damage characteristics was developed in this study.

Experiments
Experimental setup and procedures

Hwangdeung Granite and Yeosan Marble produced in Korea were the main rock types that were used for testing. In previous studies to evaluate deformation characteristics under triaxial compression, triaxial cells with connectors only for strain gauges were used. A few attempts to use AE sensors in triaxial cells were tried. For example, in order to measure AE signals generated in triaxial compression, Butt and Calder (1998) attached AE sensors to outer surfaces of a chamber. However, noise might easily interfere with AE signals even before they migrate to AE sensors. This makes precise analysis of AE data impossible. Therefore, a pressure chamber with 8 single-wire type plugs for strain measurements as well as 14 BNC (Bayonet Neil-Concelman) connectors for AE measurements was developed (Chang, 2002). In this study, in order to minimize noise, BNC connectors were attached directly into the chamber.

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