单轴压力下有补给水岩石电阻率变化各向异性研究

将两种规格的长方体水饱和花岗岩标本，以标本一个面的中心点为中心，对称布置成互成４５°角的４条对称四极法电阻率测线。标本电极面和相邻面的一小部分用防水环氧胶密封，使标本在装有水的承压水箱中，沿标本长轴方向受压，观测标本视电阻率随压力的变化。实验结果为：（１）有补给水实验与无补给水实验，电阻率变化整体形态相似，即电阻率随压力的变化先上升，后下降，但有补给水实验的电阻率下降幅度要大一些。（２）电阻率变化出现明显的方向性，可以用电阻率变化最大的各向异性主轴方向表示；实验中，用４条测线、４种组合（每３条测线组合可以确定１个视电阻率变化各向异性主轴方向）方法确定的４个电阻率变化各向异性主轴方向基本一致。（３）加压期间，电阻率各向异性主轴方向随压力增加发生变化，这种变化不是渐变和乱变，而是有规律的跃变，即整个实验过程，多数标本只跃变１—３次，每次跃变形成一个主方向，在主方向内，角度变化不大。（４）有补给水岩石电阻率变化整体形态与美国Ｂｒａｃｅ等（１９６８）所作的围压和孔隙压的岩石电阻率变化形态相似。

Anisotropy Studies of Rock Resistivity Changes under Uniaxial Pressure and Water Replenishment

Two differet kinds of rectangular granite samples with saturated water were used for test.From the center of one plane of the samples, symmetric four electrode arrangments were installed in four directions on the samples (Wenner method), which were settled symmetricaly four measure-lines of the apparent resistivity with an angle of 45 degrees between one and another. The electrode plane and a fraction of its two linked up planes were sealed up with waterproof epoxylite. The sample were placed in pressure vessel wich is full of water, and we measured the changes of the apparent resistivity loading pressure along the longest dimension. The resules of the experiment are as foils: (1) the whole shape of the apparent resistivity changes of both experiments with water replenishment or not are similar, that is, the resistivity increases at first, then decreases with the increease of pressure, but the resistivity amplitude with water replenishment decreases much faster. (2) the directivity of the change of resistivity is obvious. That shows the direction of anisotropic main axis of the resistivity change determined with the method of four meaxure-lines, and four kinds of combinations (every three combined measure-lines can determine the direction of the anisotropic main axis of the resistivity change ). (3) during loading pressure, the anisoeropic main axis direction of the resistivity varies with the increase of the pressure. Such varies are not gradual and chaotic, but regular jump change. Within the whole duration of loading pressure, most samples jump 1-3 times, and every jump produce one main direction, in wich the changes of the angle are small.