OJAppS  Vol.2 No.2 , June 2012
Using AC Conductivity Measurements to Study the Influence of Mechanical Stress on the Strength of Geomaterials
ABSTRACT
The Dielectric Spectroscopy technique is a tool that can be used to provide information regarding the physical and chemical properties of materials. In this work Dielectric Spectroscopy (DS) measurements were conducted on marble specimens that were previously subjected to uniaxial compressive stress up to fracture in order to investigate the influence of the mechanical stress on the dielectric properties of the specimens. Specifically, the ac conductivity (σac) was measured when an ac electric field in the frequency range 1 kHz - 1 MHz was applied upon dry and saturated specimens which were subjected successively to higher levels of mechanical stress. The experimental results indicate that there are systematic variations in the values of the ac conductivity after each stress application at a higher stress level. Such variations become more intense at higher stress values and can be used to indicate the upcoming fracture since significant increase of conductivity is recorded when microcracks formations appear and propagate in the sample bulk.

Cite this paper
nullI. Stavrakas, K. Moutzouris, K. Ninos, N. Mitritsakis, Z. Agioutantis and D. Triantis, "Using AC Conductivity Measurements to Study the Influence of Mechanical Stress on the Strength of Geomaterials," Open Journal of Applied Sciences, Vol. 2 No. 2, 2012, pp. 61-65. doi: 10.4236/ojapps.2012.22007.
References
[1]   F. G. Bell, “Engineering Properties of Soils and Rocks,” Blackwell Science Publishers, Hoboken, 2000.

[2]   J. C. Jaeger and N. G. W. Cook, “Fundamentals of Rock Mechanics,” Chapman and Hall Publishers, London, 1979. doi:10.1017/CBO9780511735349

[3]   D. L. Turcotte, W. I. Newman and R. Shcherbakov, “Micro and Macroscopic Models of Rock Fracture,” Geo- physical Journal International, Vol. 152, No. 3, 2003, pp. 718-728. doi:10.1046/j.1365-246X.2003.01884.x

[4]   D. Triantis, C. Anastasiadis, I. Stavrakas and F. Vallianatos, “Dielectric Characteristics of Marble Rocks after the Application of Various Stress Modes before Fracture,” WSEAS Transactions on Systems, Vol. 3, 2004, pp. 102- 106.

[5]   C. Anastasiadis, I. Stavrakas, D. Triantis, A. Kyriazopoulos and K. Ninos, “Rock Damage Estimation with Dielec- tric Loss (tanδ) Measurements,” International Journal of Microstructure and Materials Properties, Vol. 1, No. 3-4, 2006, pp. 421-429.

[6]   I. Stavrakas, D. Triantis and C. Anastasiadis, “The Influ- ence of Externally Applied Uniaxial Stress on Isothermal Depolarization Current Mechanisms in Rock Samples,” Journal of Material Science, Vol. 40, No. 17, 2005, pp. 4593-4596. doi:10.1007/s10853-005-1152-3

[7]   T. L. Chelidze, Y. Gueguen and C. Ruffet, “Electrical Spectroscopy of Porous Rocks: A Review—II. Experimental Results and Interpretation,” Geophysical Journal Interna- tional, Vol. 137, No. 1, 1999, pp. 16-34. doi:10.1046/j.1365-246x.1999.00800.x

[8]   T. L. Chelidze and Y. Gueguen, “Electrical spectroscopy of Porous Rocks: A Review—I. Theoretical Model,” Geophysical Journal International, Vol. 137, No. 1, 1999, pp. 1-15. doi:10.1046/j.1365-246x.1999.00799.x

[9]   A. Kyritsis, M. Siakantari, A. Vassilikou-Dova, P. Pissis, and P. Varotsos, “Dielectric and Electrical Properties of Polycrystalline Rocks at Various Hydration Levels,” IEEE Transactions on Dielectrics and Electrical Insulation, Vol. 7, No. 4, 2000, pp. 493-497.

[10]   A. K. Jonscher, “Dielectric Relaxation in Solids,” Chelsea Dielectric Press, London, 1983.

[11]   J. Dyre, “Some Remarks on ac Conduction in Disordered Solids,” Journal of Non-Crystalline Solids, Vol. 135, No. 2-3, 1991, pp. 219-226. doi:10.1016/0022-3093(91)90423-4

[12]   C. Anastasiadis, D. Triantis, I. Stavrakas, A. Kyriazo-poulos and F. Vallianatos, “Ac Conductivity Measurements of Rock Samples after the Application of Stress Up to Fracture. Correlation with the Damage Variable,” WSEAS Transactions on Systems, Vol. 4, No. 3, 2005, pp. 185- 190.

 
 
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