Amplitude and Anisotropy of Apparent Resistivity Changing of Big Models during Shear and Frictional Slipping

Abstract

The models of uniform and non‐uniform media of 1m×1m×0.3m were made with quartz sand and river sand blend cement under mould pressing. The amplitudes and anisotropic features of apparent resistivity changing were observed at different positions and different orientations on measured planes of the model during shear and frictional slipping. The results of experiments are as follows. The resistivity change is related to the position of measurement lines that are combined with four electrodes. The amplitudes of the resistivity change are as big as several percent to tens percent for the lines near the cracks of shear and frictional slipping, and in reverse are small from several percent to zero for the models of uniform media. For the models of non‐uniform media, the amplitudes of the resistivity change are smaller than that of the models of uniform media, which are only several percent. The resistivity change is related to the orientations of lines besides the positions of lines, and the amplitudes are different in four orientations of a measuring point. Some differences of them are very big. The amplitudes of the resistivity change are the same in order of magnitudes for the two loading manners of shear and frictional slipping. For the measuring points located in the zone near the cracks and the places where cracks passes through, the directions of the four anisotropic main axes of the apparent resistivity change coincide with the real orientations of cracks of shear and frictional slipping very well.

Experimental Studies on the Changes in Resistivity and Its Anisotropy Using Electrical Resistivity Tomography

“…For example, Mao et al [7,8] used the resistivity data measured along E-W and N-S trending measuring lines in studying the changes in the degree of earth resistivity anisotropy during the course of earthquake preparation. Chen et al [22][23][24][25] designed four measuring lines in studying the changes of apparent resistivity anisotropy in lab. In this paper, we arranged three measuring lines intersecting at point O (Figure 1), which allowed us to study the changes in apparent resistivity anisotropy at point O with pressure and depth.…”

“…The striking changes in electrical resistivity and its anisotropy were widely observed before earthquake, mine earthquake, volcanic activities, and geologic motions [1][2][3][4][5][6][7][8][9][10][11][12]. In order to address the change characteristics of resistivity and its anisotropy, many investigators conducted a plenty of experiments on rock samples under compression and during fracture, shear, and frictional sliding in lab [13][14][15][16][17][18][19][20][21][22][23][24][25] and theoretic studies [26][27][28][29][30]. Experimental results reported by Brace et al [13] and Brace and Orange [14][15][16] in lab showed that striking changes in electrical resistivity were observed for a variety of igneous and sedimentary crystalline rocks when water-saturated crystalline rocks were stressed to fracture.…”

“…Considering the effects of groundwater, An et al studied the changes in resistivity and its anisotropy with pressure in the presence of feed water [34]. In order to recognize the expansion of fissure with stress, Chen et al [22][23][24][25] studied the water-saturated granite samples and man-made samples under uniaxial compression, triaxial compression with low confining pressure, and frictional sliding. This previous work played very important role in recognizing and understanding the change behaviors of resistivity and its anisotropy with pressure, but they had to analyze the curves of resistivity and its anisotropy with pressure because of only a few electrodes designed on one measuring line.…”