压头作用下岩石破碎过程分形特性研究

Fractal characteristics of rock fragmentation process induced by indenters

基于Mohr-Coulomb破坏准则,采用有限元方法模拟压头作用下岩石的破碎过程。基于分形理论,采用计盒维数方法计算岩石破碎分形维数。研究表明,压头作用下岩石的破碎具有分形特性。其破碎过程可以分为明显的3个阶段,在3个阶段分形维数的变化趋势有所不同,分形维数可以有效地表征压头作用下岩石的破碎过程。当顶部压头位移达到某个临界值,岩石完全破碎,形成破碎漏斗。此时,分形维数亦达到一个不再变化的临界值,该临界值可以定量表征岩石的破碎程度。

The rock fragmentation process induced by indenters is numerically simulated by using the finite element method based on the Mohr-Coulomb criterion. The fractal dimension is calculated by using the box-counting method based on the fractal theory. The investigation shows that the rock fragmentation process induced by indenters has fractal characteristics. The rock fragmentation process can be classified into three significant stages. In these three stages fractal dimension has different variation trends. The fractal dimension can be used to characterize the rock fragmentation process induced by indenters effectively. When the displacement at the top reaches a critical value, the fragmentation crater appears. At the same time, the fractal dimension reaches a critical value which remains unchanged. The critical value can be used to characterize the fragmentation degree of rock quantitatively.