剪切和摩擦滑动大模型的视电阻率变化幅度和各向异性

用石英砂、河砂和水泥模压制成1m×1m×0.3m的均匀和非均匀介质模型，对模型进行剪切和摩擦滑动实验，观测模型不同位置和不同方位的视电阻率变化幅度和各向异性特征. 均匀介质模型实验结果为：电阻率变化与测线的位置有关，距裂隙近的测线，电阻率变化幅度大，从百分之几到百分之几十；距裂隙远的测线，电阻率变化幅度小，从百分之几到不变. 对于非均匀介质模型，电阻率变化幅度要小一些，最大也只有百分之几. 电阻率变化除与测线的位置有关外，还与测线的方位有关，同一测点不同方位的测线，电阻率变化幅度不同，有的差别很大. 剪切与摩擦滑动两种加载方式的电阻率变化幅度数量级相同. 裂隙穿过部位及其附近测点的电阻率变化各向异性主轴方位解与剪切和摩擦滑动的实际裂隙方位吻合较好.

AMPLITUDE AND ANISOTROPY OF APPARENT RESISTIVITY CHANGE IN BIG MODELS DURING SHEAR AND FRICTIONAL SLIPPING

Models of uniform and non uniform media of 1m×1m×0.3m size are made with quartz sand and river sand blended with cement under mould pressure. The amplitudes and anisotropic features of apparent resistivity changing are measured at different positions and in different orientations on measured plane of the mode ls during shear and frictional slipping. The results of experiments for the models of uniform media show that the resistivity change is related to the position of measurement array that consists of four electrodes. The amplitudes of the resistivity change are large ranging from several percent to tens percent for the arrays near cracks of shear and frictional slipping, and are small from several percent to zero for the arrays far from cracks. 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 at most. The resistivity change is related to the orientations of arrays besides the positions of arrays. The amplitudes of the resistivity change are different in four orientations at the same measuring point. Some differences of amplitudes are very large. The amplitudes of the resistivity change have the same order of magnitudes for the two loading manners of shear and frictional slipping. For the measuring points located in the zone which are close to cracks or penetrated by cracks, the directions of the four anisotropic main axes of the apparent resistivity change coincide very well with the real orientations ofcracks produced by shear and frictional slipping.