脆性岩石破裂演化过程的三维细胞自动机模拟

Failure evolution processes of brittle rocks using 3D cellular automaton method

在三维条件下定义了实体细胞自动机的基本组件,综合运用弹塑性理论、细胞自动机自组织演化理论、统计原理以及岩石力学理论等,建立了模拟岩石三维破裂过程的张量型细胞自动机模型,并开发了相应的数值模拟软件EPCA3D。利用EPCA3D对脆性岩石进行单轴压缩破裂过程模拟,通过破裂模式、岩样内部破裂情况、全应力-应变曲线和声发射曲线等的分析,揭示岩石破裂的机制。结果表明,EPCA3D能够较好地模拟非均质岩石在载荷作用下微裂纹的萌生、扩展和贯通的全过程。利用该模拟系统,采用应力-应变线性组合的加载控制方式,研究了不同围压对岩石全应力-应变曲线的影响。研究结果表明:对于脆性非均质岩石,低围压下容易表现为II类行为,且强度较低;高围压下容易表现为I类变形行为,且强度较高。

The basic components of solid cellular automaton were defined in three-dimensional condition. The theories of elastoplasticity, cellular automaton, statistics and rock mechanics are integrated to develop an elastoplastic cellular automaton model to simulate the failure processes of heterogeneous rocks under three-dimensional condition and the associated numerical code EPCA^3D was compiled in Visual C＋＋ environment. The EPCA^3D code was used to simulate the failure processes of heterogeneous rocks under uniaxial compression. The failure mechanism was well explained by analyzing failure pattern, inner failure position, complete stress-strain curves as well as the acoustic emission. It is found that the EPCA^3D has the ability to simulate crack initiation, propagation and coalescence in the failure processes of rocks. Using the developed model, the effect of confinement on the complete stress-strain curves is investigated by using the linear combination of stress and strain loading control method. It is concluded that brittle heterogeneous rock is prone to behave Class Ⅱ with small confinement and behave Class Ⅰ with big confinement. The strength of the rock is lower with smaller confinement and vise versa, which is consistent with the results obtained from physical experiments.