花岗岩在单轴冲击压缩荷载下的动态断裂分析

利用脉冲整形器改进后的分离式Hopkinson压杆(SHPB)系统,对新加坡Bukit Timah地区的花岗岩圆柱形试样进行了高应变率下的单轴压缩实验。实验结果发现:随着应变率的增加,不仅花岗岩材料的抗压强度增大,而且以轴向拉伸劈裂为主要破坏形式的破碎程度也有所提高,表现为碎块的尺寸减小和数量增加。针对上述花岗岩的动态特性,采用多裂纹相互作用的动态滑移型裂纹模型定量的分析了不同应变率下,材料的微裂纹的初始长度、角度、初始裂纹间距以及裂纹面的摩擦系数等微裂纹特征对材料动态强度及破碎的影响,将岩石类材料的宏观动力学特性与其细观微结构联系起来,合理地解释了花岗岩的动态强度及破碎程度的应变率相关性。

Dynamic failure analysis on granite under uniaxial impact compressive load

High strain-rate uniaxial compressive loading tests were produced in the modified split Hopkinson pressure bar(SHPB) with pulse shaper on granite samples.It was shown that the failure of the granite cylinder was typical tensile splitting failure mode by sudden splitting parallel with the direction of uniaxial compressive loading at different strain rates.Besides,it was concluded not only the strength of granite increased,but also the fragment size decreased and fragment numbers increased with the increasing strain rate.To analyze quantitatirely the failure phenomena,the numerical calculation based on a dynamic interacting sliding microcrack model was adopted to investigate the influence of microcracks with the different initial crack length,crack angle,crack space and friction coefficient on the macro-mechanical properties of granite under different strain rates.Accordingly,the strain-dependency of the compression strength and the fragmentation degree of granite was explained reasonably.