花岗岩晶体粒径分布对声发射特性影响的颗粒流模拟

Particle flow simulation of the influence of granite crystal size distribution on acoustic emission characteristics

基于离散元理论和PFC软件,将等效晶质模型和矩张量理论相结合,模拟了单轴压缩实验中细观结构的非均质性对岩石声发射特性的影响,揭示了晶体粒径分布所造成的非均质性对岩石破裂过程中声发射事件的空间定位分形维数、破裂强度、b值等的影响规律。主要研究结论:(1)细观结构的非均质性对岩石的声发射活动存在较大影响。随着组成声发射事件的微裂纹数的增加,声发射事件数迅速下降,两者符合负指数函数关系。(2)当晶体粒径分布越不均匀,其岩石的非均质性越大,应力场分布均匀性越差,岩石的声发射活动开始越早,微裂纹形成的越早,起裂应力越低。晶体粒径、应力场分布、微裂纹和声发射事件是一条影响链。(3)随着非均质性因子的增加,声发射活动的b值逐渐减小,岩石中大尺度微破裂所占比例增加。声发射b值和非均质性因子H之间呈现出良好的线性关系。(4)当非均质性因子较大时,破裂强度大的声发射事件倾向于集中在主破裂面。随着非均质性因子的增加,声发射事件的空间定位的自相似性增强,声发射空间定位的分形维数逐渐降低。分形维数与非均质性因子呈现幂函数关系。该研究方法有效弥补了室内声发射试验的不足,为揭示细观结构的非均质性对岩石声发射活动的内在影响提供了一种有效的技术手段。

Based on the discrete element theory and PFCsoftware,the grain-based model and the moment tensor theory are combined to simulate the influence of the heterogeneity of the microstructure in the uniaxial compression experiment on the acoustic emission characteristics of the rock.It reveals the inhomogeneity caused by the distribution of crystal sizes affects the fractal dimension,fracture strength and b value of the spatial location of the acoustic emission event in the rock fracture process.The main research conclusions are as follows:(1)the heterogeneity of the mesostructure has a great influence on the acoustic emission activity of the rock.With the increase of the number of micro-cracks that constitute an acoustic emission event,the number of acoustic emission events rapidly decreased,and the two parameters above have a negative exponential function relationship.(2)The more uneven the crystal particle size distribution,the greater the heterogeneity of the rock and the worse the uniformity of the stress field distribution,the earlier the acoustic emission activity of the rock and the earlier the formation of micro-cracks,the lower the initiation stress.Crystal size,stress field distribution,micro-cracks and acoustic emission events are an influence chain.(3)As the heterogeneity factor increases,the b value of acoustic emission activity gradually decreases,and the proportion of large-scale micro-fractures in the rock increases.There is a good linear relationship between the acoustic emission b value and the heterogeneity factor H.(4)When the heterogeneity factor is large,the acoustic emission events with large fracture strength tend to concentrate on the main fracture surface.As the heterogeneity factor increases,the self-similarity of the spatial location of acoustic emission events increases,and the fractal dimension of the spatial location of acoustic emission gradually decreases.The fractal dimension and the heterogeneity factor have a power function relationship.This research method effectively makes up for the shortcomings of indoor acoustic emission tests,and provides an effective technical means for revealing the intrinsic effect of mesostructure heterogeneity on rock acoustic emission activities.