Abstract
In order to clarify the mechanism of microcracking due to thermal attack in inhomogeneous granite, AE (Acoustic Emission) was monitored during the small scale insitu heater test in an old quarry of Inada granite. An 2m long electric heater was inserted at the depth from 3.3m to 5.3m in a bored hole of the 100mm diameter, and the temperature of the heater was increased to 800°C. AE was monitored for 60 hours with 12 sensors buried in 4 holes bored 1m distant from the hole with the heater, and thus 636 AE hypocenters were located. AE hypocenters clustered in pegmatite intruded into granite and pre-existing joints. In addition, it was observed that the temperature in which AE started to occur was about 60°C in granite, which is the same temperature as other researchers previously reported on their laboratory experiments, while the temperature of AE generation was lower than 60°C in pegmatite.
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