一軸圧縮試験における岩石からの電磁波の発生

1.はじめに

2.実験装置及び試料岩石

 2.1 実験装置

 2.2 試料岩石

3.岩石ごとの特徴

 3.1 稲田花崗岩

 3.2 本小松安山岩・葛生苦灰岩

 3.3 秋芳大理石・来待砂岩・三城目安山岩・モルタル

4.試験条件の影響

 4.1 載荷速度(歪速度)

 4.2 応力帰還制御

 4.3 端面

5.考察

 5.1 電磁波の発生しやすい岩石とそうでない岩石

 5.2 実験条件による電磁波の発生状況

6.可能性のある応用分野の提言とまとめ

参考文献

キーワード:岩石,一軸圧縮試験,電磁波,亀裂, 強度破壊点以降


Electromagnetic Wave Emission in Uniaxial Compression Testing

Abstract

A number of studies on electromagnetic wave emission from fractured rocks have been heretofore carried out. By many authors it was pointed out that rock fracturing or acoustic emission could be concerned with electromagnetic wave emission. However, the origin of electromagnetic wave emission is still not well understood.

In this study electromagnetic wave from rocks was measured with a radio interference measuring apparatus during uniaxial compression testing under several kinds of loading conditions.

Firstly, the uniaxial compression testing under constant strain rate of 10−4 s−1 was conducted for seven rocks. It was found that Inada granite, Honkomatsu andesite and Kuzuu dolomite emit electromagnetic wave. However electromagnetic wave cannot be detected for Sanjome andesite, Akiyoshi marble, Kimachi sandstone and mortar.

Secondly, electromagnetic wave emission was investigated under several experimental conditions. It was found that Inada granite emits electromagnetic wave during uniaxial compression testing under a constant strain rate of 10−5 s−1 and under a constant rate of (stress − strain / Young's modulus).

In most cases, electromagnetic wave emission was accompanied with sudden decrease of stress. By analysis on results of the uniaxial compression testing under constant strain rate, it was found that electromagnetic wave emission is closely related to cracking or crack extension.

The main results in this study can be summarized as follows;
1) Amplitude of electromagnetic wave is relatively large for strong rock.
2) For Inada granite, the larger the stress drop occurred in uniaxial compression test is, the larger the amplitude of electromagnetic wave.

Key Words: Rock, Uniaxial Compression Testing, Electromagnetic Wave, Crack, Post-Failure Region