岩石のＡＥカイザー効果と３次元ＡＥ震源分布からみたマイクロクラッキングとの関係

Abstract

Two kinds of uniaxial cyclic loading experiments of sandstone were conducted, together with measurements of AE (Acoustic Emission), in order to know the relation between the Kaiser effect of AE and microcracking in the rock. One loading pattern is the cyclic loading shown in Fig. 1, and the other loading pattern is the loading shown in Fig. 2. In these experiments, 8 AE sensors were attached to the surface of the rock in order to determine the spatial distribution of AE hypocenters.The Kaiser effect of rock was closely related to the microcracking occurring in the rock during the loading of pre-stress. In the case of the loading shown in Fig. 1, Kaiser effect was not clear. This is because the microcracking region in the rock did not grow into the saturated microfractures' condition which was equivalent to the pre-stress. In the case of the loading shown in Fig. 2, however, the Kaiser effect was clearly observed during the loading up to 25 MPa. The result of the spatial distribution of AE hypocenters suggest that the rapid increase of AE over the pre-stress was regarded as the microcracking from the region where AE clusters were formed by the previous cyclic loading.