影响结构地震反应破坏耗能比的因素分析

文章采用结构地震能量反应分析方法，通过对结构等延性破坏耗能比例谱的分析，讨论了影响结构破坏耗能在总耗能中所占比例的主要因素。

Mechanical and energy dissipation characteristics of granite under cyclic impact loading

This study investigated the effect of repeated blasting on the stability of surrounding rock during the construction of a tunnel or city underground engineering.The split Hopkinson pressure bar(SHPB)was used to carry out cyclic impact tests on granite samples,each having a circular hole,under different axial pressures,and the cumulative specific energy was proposed to characterize the damage characteristics of the rock during the cyclic impact.The mechanical properties and the energy absorbed by the granite samples under cyclic impact loads were analyzed.The results showed that under different axial pressures,the reflected waveform from the samples was characterized by“double-peak”phenomenon,which gradually changed to“single-peak”wi th the increase in damage value.The dynamic peak stress of the sample first increased and then decreased with an increase in impact times.The damage value criterion established based on the energy dissipation could well characterize the relationship between the damage and the number of impacts,which showed a slow increase,steady increase,and high-speed increase,and the damage value depended mainly on the last impact.Under the action of different axial pressures,all the failure modes of the samples were axial splitting failures.As the strain rate increased,with an increase in the dimension of the block,the sizes of the rock fragments decreased,and the fragmentation became more severe.

加卸载条件下冲击性岩石动态力学特性研究

为探究矿井基本顶周期来压路径对冲击性矿柱动力学特性的影响,借助分离式霍普金森压杆冲击加载设备,对不同循环加卸载预处理的冲击性砂岩开展动态压缩实验。探讨不同循环加卸载路径、冲击气压对岩样断裂强度、破坏耗能、碎块分布的影响。结果表明:动态应力–应变曲线分为弹性变形阶段、非稳定断裂发展阶段、断裂后阶段。在非稳定断裂发展阶段,应变硬化现象和跃进特性明显。在断裂后阶段,岩样破坏程度与冲击气压呈正相关。反射能、透射能、耗散能密度与入射能线性增长关系显著。平均反射能、平均耗散能密度随循环上限应力增大呈先下降后上升的“U”型变化特性。岩样密实度越高,冲击破坏时反射能、耗散能密度越小,透射能越大。冲击荷载下,岩样主要表现为粉碎破坏、岩块碎裂、岩块侧面剥落脱离、岩块劈裂。冲击扰动越剧烈,岩样平均碎块粒径越小,平均分形维数越大,破坏越彻底,岩屑分布越均匀。