Geoscience Reference
In-Depth Information
Chapter 9
Laboratory Study of Rock Deformation
and Fracture
Abstract
Our primary interest lies in the physics of electromagnetic phenomena
associated with deformation and fracture of rocks. We start with a brief review
of laboratory study of electromagnetic fields resulted from acoustic waves and
shock polarization and magnetization effects in different materials. The vibration of
charged dislocations and piezo-galvanic effect are considered to explain this effect
in metals whereas the production and mobility of point and linear defects of atomic
lattice is treated as a possible cause for the shock polarization effect in dielectrics.
We discuss briefly a variety of electromagnetic phenomena caused by rock fracture.
Among them are radiowave, optical and -radiation, and electron and ion emissions
from fracturing rocks. We study the theories explaining the generation of strong
electric fields in cracks and collapsing pores.
Keywords
Dislocation Piezo-galvanic effect Point defect Rock fracture
Shock magnetization Shock polarization
9.1
Electromagnetic Effects Caused by Dynamic
Deformation of a Solid
It is common knowledge that the dynamic deformation and fracture of solids are
accompanied by a great variety of electromagnetic effects. The basic characteristics
of these phenomena depend on the scales of fracture, intensity and duration of
stress and strain, and a number of other factors. Such effects as generation of low-
frequency electromagnetic fields and radiowaves, emission of charged particles,
light flashes, X-ray emission and micro-discharges inside of cracks have been
observed in laboratory experiments (e.g., see Parrot
1995
; Surkov
2000
).
It has been found experimentally that shock compression of different solids gives
rise to a jump of electric potential at the shock front in all kinds of materials:
metals, semiconductors, and dielectrics (e.g., Mineev and Ivanov
1976
; Freund
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