砂岩单轴压缩声发射和纤维束模型模拟

Acoustic emission of sandstone under uniaxial compression and simulation of fiber bundle model

利用纤维束模型(FBM)模拟非均质材料破坏动力学行为,在实验室内进行了砂岩力控制单轴压缩声发射(AE)试验。将纤维束模型纤维断裂与砂岩声发射类比分析发现,低应力阶段纤维束模型对偶发的雪崩过程敏感性低,但在高应力阶段纤维束模型能够很好地表征应力控制单轴压缩砂岩声发射特征;雪崩尺寸的模拟和试验结果都呈现双幂形式,具有相似的双幂指数和转换点;模拟和试验结果都以纤维束模型为基础和声发射反映固体内部损伤为前提,固体的破裂失稳满足二阶相变特征,且分叉率ξ是符合描述二阶相变的连续序参量;在临界点附近针对分支率演化(固体破裂相变)过程概率理论、纤维束模拟与声发射试验结果一致,可见纤维束模型能较好地模拟岩石声发射行为进而反映岩石损伤断裂过程。

The fiber bundle model(FBM) and acoustic emission(AE) tests of sandstone under uniaxial force controlled compression are carried out to study the fracture characteristics of heterogeneous materials. The failure of fiber elements in fiber bundle model is analogous to the acoustic emission signal. The results show that: At low stress stage, FBM ignored the occasional avalanche processes, but FBM characterized acoustic emission characteristics well in high stress stage. The distribution of avalanche sizes and AE events both had double power-law behavior, and the probability distribution function(PDF) of simulations and tests share the similar power exponents and inflection points. Simulation and experimental results show a behavior analogous to the second-order phase transitions, and branching ratio ξ could be as a suitable order parameter to describe this transition. Moreover, near to the critical point, the evolution of branching ratio came from FBM and AE tests are consistent.