流理性および成層性岩石における水圧破砕き裂進展のＡＥによる標定

Abstract

In this study hydrofracture propagation in discontinuous rocks were investigated by Acoustic Emission (AE) locations. Two kinds of rocks, Inada granite and Tako sandstone, were used in the experiments. Inada granite is an anisotropic rock with rift planes and Tako sandstone has discontinuous planes. AE measurements were carried out by 12 piezoelectric transducers.Hydrofracture propagation in Inada granite were controlled by rift planes. Under unconfined condition hydrofractures were oriented to rift plane. Under confined condition, however, the initiation fracture were caused by the stress condition. In the stage of fracture extension, the fracture changed its direction depending on the rock anisotropy.In the case of Tako sandstone discontinuous plane had a great influence on the propagation of hydrofracture. Discontinuous planes prevented fractures from propagating through these planes. And, the majority of the AE events were located below the discontinuous plane and predominant fracture growth was downwards.