Concerning the excavation of rock cavern, it is one of the most important issues to evaluate the behavior of rock joints. But few detailed measurements for joint behavior had been conducted. Therefore, in order to evaluate the stability of rock cavern, effective approach for monitoring and analyzing the joint behavior needs to be developed. In this paper, authors described the results of analysis for joint behavior during the excavation by comparing with both results of the in-situ measurement by BTV and the numerical analysis by MBC model.

Bei Ausschachten von Gesteinshöhlen ist es von besonderer Bedeutung, das stark von den Verbindungsteilen beeinflusste Gesteinsverhalten zu bewerten. Jedoch wurden bisher nur wenige Beobachtungen ueber das Öffnungsverhalten von Verbindungen durchgefuehrt. Daher muss ein effizientes Verfahren zur Überwachung der Stabilitat unterirdischer Höhlen und der Analyse des Verhaltens von Verbindungsstellen entwickelt werden. In der vorliegenden Studie beschreiben die Autoren das Verhalten von Verbindungsstellen wahrend der Ausschachtung durch Vergleiche sowohl mit den Ergebnissen von in situ Messungen mittels BTV als auch numerische Simulation mit dem MBC Modell, welches auch Diskontinuitaten beruecksichtigen kann.

Quand il s'agit d'excaver une caverne dans une roche ayant des joints très developpes, il importe fort d'evaluer le comportement de la roche. Cependant, le nombre d'observations du comportement des roches effectuees au niveau de joints est loin d'être suffisant. Par consequent, pour s'assurer de la stabilite des parois des cavernes souterraines, il a fallu mettre au point une methode fiable de detection et d'analyse du mouvement des joints. Dans cet article, les auteurs decrivent leurs etudes de comportement des joints pendant l'excavation, en comparant les resultats des mesures effectuees in-situ, dans un chantier d'excavation par BTV, avec ceux d'analyse de la simulation numerique par MBC permettant de tenir compte des discontinuites.

Introduction

The rock mass usually includes a number of joints, which strongly affect the behavior of the rock cavern. For example, in case of excavation the rock cavern, the opening and the shear sliding of existing joints and newly generated joints, which are initially closed under the earth pressure, influenced to the rock cavern behaviors.

As one of the joint observation methods, BTV (Borehole TV) is often used, and the observation and measurement of joint behaviors in the large rock cavern was carried out with whole excavating steps from initial state to final excavation.

As for analytical approach, the simulation analysis for excavating the rock cavern was conducted and predicted the joint opening distribution by using the MBC model which is suggested by Horii and Yoshida and can consider the joint opening behavior. In this paper, authors describes the consideration for joint behavior under excavation by comparing with both results of the in-situ measurement by BTV and the numerical simulation analysis by MBC model, which can consider the discontinuities.

(Figure in full paper)

Joint opening behavior by BTV monitoring

Using BTV apparatus shown in Figure 1, the number of joints and the joint opening displacement were respectively monitored around the large cavern.

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