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Published on: May 20, 2018
Electrical Resistivity Changes in Saturated Rock under Stress
Science (New York, N.Y.)
|September 23, 1966
Summary
Electrical resistivity in water-saturated rocks like granite drops significantly before fracturing under compression. This occurs due to microcrack formation, even at high pressures, offering insights into rock mechanics.
Area of Science:
- Geophysics
- Rock Mechanics
- Materials Science
Background:
- Electrical resistivity is a key property for understanding subsurface processes.
- Rock fracture mechanics is crucial for geological engineering and resource exploration.
- Previous studies have explored rock properties under stress, but pre-fracture resistivity changes require further investigation.
Purpose of the Study:
- To investigate the changes in electrical resistivity of crystalline rocks before compressive fracture.
- To determine the relationship between crack formation and resistivity variations.
- To assess the influence of confining pressure on these pre-fracture phenomena.
Main Methods:
- Compressive stress tests were performed on water-saturated crystalline rock samples (granite, diabase, dunite, quartzite).
- Electrical resistivity was measured in situ during the compression tests.
- Microscopic observations were used to identify crack formation and propagation.
Main Results:
- Electrical resistivity decreased by an order of magnitude in all tested rocks prior to fracture.
- Significant resistivity changes were observed even under high confining pressures.
- Open crack formation, initiated at one-third to two-thirds of the fracture stress, correlated with resistivity drops.
Conclusions:
- Pre-fracture electrical resistivity changes are a sensitive indicator of impending rock failure.
- Crack formation significantly impacts the electrical properties of saturated crystalline rocks.
- This phenomenon has implications for monitoring rock mass integrity in geological applications.
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