单轴压缩下多裂隙含水岩样电阻率变化与体积应变
THE ELECTRICAL RESISTIVITY CHANGES AND VOLUMETRIC STRAIN OF WATER-BEARING CRACKED ROCK SAMPLES UNDER UNIAXIAL COMPRESSION
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摘要: 在单轴压缩下,对经过高温焙烧的含水辉长岩进行了轴向和径向电阻率变化以及体积应变的同时连续测量.结果表明,在完全饱和前的非弹性压缩阶段,电阻率随压应力增高而降低;在完全饱和的弹性压缩阶段,电阻率升高;在非弹性的体积膨胀阶段,电阻率继续上升.从Archie 公式出发,通过近似分析,导出了电阻率变化和体积应变的关系式.实验结果和近似分析定性上相附.本文的主要结果是发现含水岩样在膨胀阶段电阻率的升高,初步认为这是由于热开裂的张开,降低了饱和度的结果.Abstract: The axial and transversal electrical resistivity changes in water-bearing, and high temperature baked gabbro rock samples together with their volumetric strain have been measured simultaneously and continuously under uniaxial compression. The measurement shows that the value of resistivity decreases at first before complete water saturation in the stage of non-elastic compression, then it begins to increase in the stage of complete water saturation and elastic compression. Finally the resistivity increases again during the last non-elastic dilatancy stage. According to Archies law, an approximate relationship between the resistivity change and volumetric strain has been obtained through mathematical analysis. Qualitatively, our experimental results are in agreement with it, but not quantitatively. The main result obtained is that the electrical resistivity of water-saturated rock samples increases during the dilatancy stage under uniaxial compression. It may be explained by decrease of water saturation as caused by reopening of the heated cracks.
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[1] 钱复业、赵玉林,地震前地电阻变化十例,地震学报,2, 2, 1980,
[2] A. Mazzella and' Morrison, Electrical resistivity variations associated with earthquakes on the San Andreas fault, Science, 185, 855——857, 1974.
[3] V. I. Mjachkin, et al., Two models for earthquake forerunners, Petrc 9ppl. Geoplay., 113, 169——181,1975.
[4] M. D. Zoback and J. D. Byerlee. The effect of micro——crack dilatancy on the permeability of wes——terly granite, J. Geophys. Res., 80,, 752——755, 1975.
[5] E. I. Parkhomenko and A. J. Bondarenko, Effect of uniaxial pressure on electrical resistivity of rocks, Bull.A cad. S., USSR, Geophysics, Ser, 2, 326, 1960.
[6] N. Fujii ands Y. Iiamano, Anisotropic changes in resistivity and velocity dluring rock deformation, High——pressure research applications in geophysics, Edited by Murlih. Manghnani and Syun——
[7] iti Akimote, Academic press, New York, 53——63, 1977.
[8] W. F. Brance, A. S. Orange, and T. M.’Madden, The effect of pressure on the electrical resistivity of water——saturated crystalline rocks, J. Geophys. Res., 70(22), 5669——5678, 1965.
[9] W. F. Brace and A. S. orange, Further studies of the effects of pressure on electrical resistivity of rocks, J. Geophys. Res., 73(16). 5407——5420, 1968.
[10] W. F. Brance, Dilatancy——related electrical resistivity changes in rocks, Pure Appl. Geophys., 113, 207——217, 1975[1] 钱复业、赵玉林,地震前地电阻变化十例,地震学报,2, 2, 1980,
[2] A. Mazzella and' Morrison, Electrical resistivity variations associated with earthquakes on the San Andreas fault, Science, 185, 855——857, 1974.
[3] V. I. Mjachkin, et al., Two models for earthquake forerunners, Petrc 9ppl. Geoplay., 113, 169——181,1975.
[4] M. D. Zoback and J. D. Byerlee. The effect of micro——crack dilatancy on the permeability of wes——terly granite, J. Geophys. Res., 80,, 752——755, 1975.
[5] E. I. Parkhomenko and A. J. Bondarenko, Effect of uniaxial pressure on electrical resistivity of rocks, Bull.A cad. S., USSR, Geophysics, Ser, 2, 326, 1960.
[6] N. Fujii ands Y. Iiamano, Anisotropic changes in resistivity and velocity dluring rock deformation, High——pressure research applications in geophysics, Edited by Murlih. Manghnani and Syun——
[7] iti Akimote, Academic press, New York, 53——63, 1977.
[8] W. F. Brance, A. S. Orange, and T. M.’Madden, The effect of pressure on the electrical resistivity of water——saturated crystalline rocks, J. Geophys. Res., 70(22), 5669——5678, 1965.
[9] W. F. Brace and A. S. orange, Further studies of the effects of pressure on electrical resistivity of rocks, J. Geophys. Res., 73(16). 5407——5420, 1968.
[10] W. F. Brance, Dilatancy——related electrical resistivity changes in rocks, Pure Appl. Geophys., 113, 207——217, 1975
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