花岗岩在固体围压三轴压缩下破裂，然后沿主破裂面摩擦滑动（粘滑或稳滑），实验后我们将样品从围压介质铅中剥出来，做成显微薄片，在２０倍显微投影仪下观测其主破裂及裂纹系分布，用尺度法统计并计算裂纹系分维。结果表明，８个样品的无标度区（Ｒ）都相同，但是随尺度变化，分维值表现出分段线性的特征。当０．０５＜Ｒ＜０．１５ｍｍ时，裂纹系分维在１．１２－１．４１之间，主破裂分维在１．０８－１．１５之间；当０．１５＜Ｒ＜７．５ｍｍ时，裂纹系分维在１．４６－１．８３之间，主破裂分维在１．２２－１．５３之间。主破裂和裂纹系分维值都和围压、应变率等实验条件及破裂强度有关。随围压和应变率不同，主破裂和裂纹系发育成不同形态。在实验的８个样品中，可以用分数维来识别裂纹系的形态和微裂纹的多少。 The granite fractures under the triaxial compression of the confining pressure of the solid, and then slides along the main rupture surface (sticky or slippery). After the experiment, we strip the sample from the confining medium lead to make a thin slice of microscopic material. Under the micro projector, the main crack and the crack system were observed. The fractal dimension of the crack system was calculated and calculated by the scale method. The results show that the scaleless regions (R) of the eight samples are all the same, but the fractal dimension shows a piecewise linear feature as the scale changes. When 0.05