孔洞形状对大理岩渐进破坏力学特性影响研究

Research on the Effect of Cavity Shapes for the Progressive Failure and Mechanical Behavior of Marble

为研究孔洞形状对岩石破坏特性的影响,对含不同形状孔洞大理岩进行单轴压缩实验,利用高速摄像仪记录孔洞周边裂纹的萌生、扩展和贯通直至试样破坏的过程,分析孔洞形状对大理岩力学特性、破坏模式、裂纹扩展特性的影响规律,以及试样所储存的能量与岩石变形破坏的关系。研究发现,孔洞形状对大理岩的力学特性有明显影响,且不同边界类型的孔洞有不同的裂纹扩展特性。另外,试样的宏观破坏是由远场裂纹迅速扩展的结果,而初始裂纹对材料破坏没起到关键作用。从能量的角度提出一个可判别岩石脆性破坏的能量跌落系数,还发现岩块弹射烈度与单位体积吸收能量的大小有关。通过FLAC3D对不同孔洞形状大理岩进行数值模拟,得到不同孔洞形状大理岩的应力分布和应力集中系数特征,其应力分布特征较好地反映了室内试验的破坏特征。

In order to study the effect of cavity shapes on failure properties of rocks,uniaxial compressive tests have been carried out on marbles with different types of single hole in specimens＇ central. The process of crack initiation,propagation,and coalescence of the marble specimens are recorded by a high speed video camera. The influence of the cavity shapes of specimen on rock mechanics parameters,failure mode and crack propagation characteristics are analyzed,as well as the relationship of specimen between stored energy and deformation and failure. It is found that the mechanical characteristics of marbles are obviously influenced by cavity shapes with approximately identical cavity size and space position,and cavities with different boundary types have different crack growth characteristics. In addition,the macroscopic failure of specimens is mainly the result of rapid expansion of far field cracks,while initial cracks don＇t play a key role in the final material failure. On the viewpoint of energy,the coefficient of energy-drop is proposed,which can distinguishes brittle failure of rock. Additionally,there is a correlation between the size of energy absorbed per unit volume and intensity of rock block ejection. Numerical simulations of marbles with different cavity shapes are carried out by using FLAC3 D. The characteristics of stress distribution and stress concentration coefficient of marbles with different cavity shapes are obtained,which can reflect the failure characteristics of laboratory test well.