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A number of studies on electromagnetic wave
emission from fractured rocks have
been heretofore
carried out. By many authors it was
pointed
out that jock fracturing or acoustic
emission
could be concerned with electromagnetic
wave
emission. However, the origin of electromagnetic
wave emission is still, not wel.1 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 10-4s-1
s 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.
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