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为获取岩石力学试验碎片表面的分形特征,特别是码尺在亚毫米级以下的二维分形特征,利用投影覆盖法对大理岩岩爆试验碎片表面特征进行研究。首先,利用岩爆试验模拟隧洞开挖时洞腰的卸载破坏现象并分析大理岩试件破坏特征。然后,利用激光共聚焦扫描显微镜对碎片进行表面测量,获取其三维表面数据,并使用三角剖分法求取不同码尺所对应的表面积,分析表面积随码尺变化的规律即碎片的二维分形特征。最后,论证使用投影覆盖法计算大理岩碎片表面积的码尺下限。试验结果表明:(1)碎片表面积在0.625~639.375μm范围内具有多重分形特征;(2)表面积增长率的分布在0.625~319.688μm范围内类似于正态分布,在0.625μm范围以下,碎片表面积的增长极为有限,故分形规律计算碎片表面积的码尺下限可以取0.625μm;(3)基于扫描电镜的断口分析进一步证实碎片表面积计算中的码尺下限及其二维多重分形特征。
In order to obtain the fractal characteristics of the surface of rock mechanics test fragments, especially the two-dimensional fractal features of subscripts below sub-millimeter scale, the surface coverage characteristics of marble rock fragments in marble were studied by using projection overlay method. First of all, the rock burst test is used to simulate the unloading failure of the tunnel waist and analyze the failure characteristics of the marble specimen. Then, the surface of the debris was measured by laser confocal scanning microscope to obtain the three-dimensional surface data, and the triangulation method was used to determine the surface area corresponding to different yardstick. The change of surface area with yardstick was analyzed. feature. Finally, the projection of the lower bound of yardstick on the surface area of marble fragments is demonstrated using projection overlay method. The experimental results show that: (1) the surface area of the fragments has multifractal characteristics in the range of 0.625 ~ 639.375μm; (2) the surface area growth rate distribution is similar to the normal distribution in the range of 0.625 ~ 319.688μm; The limit of the code size of fractal surface area calculated by fractal rule can be 0.625μm. (3) The lower limit of the code size and the two-dimensional multifractal characteristics in the calculation of fragment surface area are further confirmed by the fracture analysis based on SEM.