Directional Characteristics of Resistivity Changes in Rock of Original Resistivity Anisotropy

Abstract

AbstractAccording to pre‐designed patterns, multiple electrodes are arranged on the surfaces of four samples. Among them three samples have the original resistivity anisotropy which was not formed by ingredient of rock and one sample has that formed by ingredient of rock. The samples are fully saturated with water. The multiple electrodes are combined form arrays of resistivity changing anisotropy in different directions and spacing. The experiments of dynamic rock resistivity change are done with uniaxial compression, low confining triaxial compression and shear, and the variation of resistivity during the whole loading process is observed. The experimental results show that the samples of original resistivity anisotropy are essentially accordant with that of original resistivity isotropy in resistivity changing anisotropy. Namely, for the measuring‐points that are located at cracks or rupture bands, the results of resistivity changing anisotropy are good. The four directions deduced from four kinds of combinatorial equation sets of resistivity are essentially identical with each other and coincide with the orientations of cracks or main rupture bands approximately. For the measuring‐points without cracks or rupture bands passing through, either the four directions calculated by different combinatorial arrays of resistivity are inconsistent with each other, or the direction can not be determined, especially in the case that the crack plane is parallel to the measuring‐surface.