To estimate the detailed characteristics of the rock around the cavern during excavation, new monitoring technique for dynamic properties of the rock has been applied. In this paper, micro-seismic monitoring and AE monitoring technique are applied to the excavation of large underground rock cavern and the result was discussed to clarify the acutal behavior of EDZ around the cavern.
Zur Einschatzung der Gesteinseigenschaften um die Ausschachtung herum haben die Autoren eine Technik eingesetzt, mit der die physikalischen und dynamischen Änderungen im Gestein um den Schacht wahrend der Ausschachtung beobachtet werden. In der vorliegenden Studie wurde zur mikroseismischen Überwachung ein AE Überwachungsverfahren eingesetzt und die Autoren berichten ueber die Veranderungen in den Gesteinseigenschaften um die Ausschachtung herum.
Dans le but d'evaluer en detail les proprietes des roches qui forment les parois des cavernes creusees, les auteurs ont utilise une technique de mesure permettant d'observer les modifications physico-dynamiques des roches aux alentours de la caverne pendant son excavation. Dans le cadre de cet article, une technique de surveillance de l'agitation et du bruit microseismiques a ete mise en oeuvre et les auteurs font etat de la modification des proprietes de la roche environnante.
As a technical subject in geological disposal of high-level radioactive wastes, the systematization of the evaluation technology of the excavation-disturbed zone of the rock around cavern is required.
For that purpose, the detail monitoring and estimation technology is desired, which the physical and dynamic viewpoint of the rock around the cavern.
The AE method is considered to be useful for estimate the stress condition and change of stress and failure of rock. Moreover, Seismic wave measurement is useful for estimate to change of physical quality of rock.
In this paper, applying borehole type Micro-Seismic technique and AE monitoring technique those were developed to the rock around the cavern, authors report the feature and evaluation of rock behaviors around the cavern.
The AE sensor used for monitoring is shown in Figure 1. The frequency characteristic of AE sensor is 5kHz - 250kHz (the center frequency band is 70kHz) and AE sensor is the piezo-electric element type.
The changes of seismic wave velocity of rock around the cavern were measured by oscillators and receivers. AE sensors were used for receive of seismic wave. Since the frequency of the seismic wave that received is high frequency compare with a usual seismic wave as shown in Figure 2, so it is measurement of Micro-seismic.
AE sensors and receivers were installed and were injected cement milk in the borehole around the cavern before excavation of the cavern.
(Figure in full paper)
The composition of the monitoring system shows in Figure
3. It consists of AE sensor of 12 channels, and two oscillators.
Measured AE signals were amplified to 40dB by the preamplifier, and was amplified to 30dB by the main amplifier, so the total of amplified AE signal is 70dB.
(Figure in full paper)
The cross sectional view and excavation procedure of the rock cavern.