Place & Date: Kyoto, Japan, November 30 - December 02, 2004
Conference: Proceedings of 3rd Asian Rock Mechanics Symposium "Contribution of Rock Mechanics to the New Century"
Title: Evaluation of Excavation-Induced Microcracks during Construction of an Underground Power Plant Using Acoustic Emission
Authors: Tomoki Shiotani*, Koki KUmagai*, Kazunobu Matsumoto*, kaoru Kobayashi*, and Hiroshi Chikahisa*
*Research Institute of Technology, Tobishima Corporation, Japan

ABSTRACT
Rock deforms unexpectedly although careful geological surveys were performed in advance of construction. During construction of caverns, for example, and therefore monitoring should be conducted to feedback the construction design. During the construction, such measurement as deformation, stress are conventionally performed, however, since resulting measurements are from 'averaged or pinpoint monitoring,' spatial distribution of damage due to excavation could not be readily or precisely obtained. In the paper, acoustic emission monitoring is carried out not only to know the spatial or temporal evolution of crack but to ensure the safe construction. With wave-guide, the monitoring area of AE is expanded even for less numbers of sensors. Evolution of cracks is estimated using AE sources as well as improved b-value. The findings are further discussed in combination with other measurements. Through the monitoring, it was suggested that AE monitoring could provide both information on spatial and temporal behavior of microcracking, and the findings obtained from AE monitoring was in good accordance with evaluated rock behavior by other measurements.

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