The piezoelectric effect of quartz rich rock has been investigated both in the laboratory and a subterranean environment.
In the laboratory experiment, rock specimens from the Con Mine, Northwest Territories, were examined for crystal alignment and cut into oriented 3.81 cm (1.5 in) sided cubes. The specimens were clamped, together with the measuring electrodes, between parallel plates of a compression cage designed to apply a consistent and uniform pressure distribution across the samples. A solenoid device applied a stress pulse of highly repeatable amplitude and form to the specimen and an instrumentation amplifier measured the differential
piezoelectric voltage between opposite faces of the specimen.
The massive samples with random fabrics were expected to yield a net "statistical effect". The measured voltage variations between orthogonal directions were attributed to signal domination by large crystals within the matrix, limited sample volume, microfracturing, and the distribution of non-piezoelectric mineral components within the matrixes of some specimens. The greatest piezoelectric responses were obtained from samples containing large crystals in their matrix.
The cubic aggregates which clearly exhibited quartz crystal alignment displayed the theoretically predicted minimum piezoelectric response parallel to the preferred crystal elongation direction. The specimens exhibiting greatest alignment produced the largest piezoelectric responses. The limited experimental evidence indicated that the signal magnitude was also proportional to quartz content and crystal size. Underground trials of two exploration systems were conducted at the Con Mine
In the first trial, during periods of low industrial electrical interference, clear piezoelectric signals were observed for source-target distances as large as 55 m and electrode-target distances out to 20 m. Piezoelectric signals were generated by impact of both compressional and shear seismic waves with the exposed quartz vein. While this exploration system operated quite effectively during periods of low electrical noise, a superior filter system was required for the normal conditions.
For the second fields test, a more portable, DC powered, instrumentation amplifier with an extensive filter system was designed. Despite the improved filtering, noise levels were significantly higher during this trial and beyond 10 m the initial arrival of the piezoelectric signal was obscured. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/21377 |
| Date | January 1979 |
| Creators | Jose, Barrie Frederick |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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