不同冲击荷载下花岗岩力学和能量耗散特性

为探究不同冲击荷载条件下花岗岩的动力学特性,采用分离式霍普金森压杆分别对花岗岩试样进行单次和重复冲击荷载试验,并对试样的应力-应变响应、应变率曲线特征、能量耗散特性以及破坏形态进行综合分析.结果表明:单次冲击下,试样动态抗压强度与比能量呈现对数函数关系,试样破坏程度随着比能量的增加而逐渐增大;随着入射波峰值应力的增加,应力-应变曲线峰后段的回弹现象逐渐减弱,应变率曲线呈现出愈加明显的“双峰”特征,其第2波峰逐渐高于第1波峰.重复冲击作用下,当试样未破坏时,应力-应变曲线基本经历弹性加载、损伤演化和峰后回弹3个阶段,当试样经历最后一次冲击时,应力-应变曲线峰后段形状与试样的破坏程度有关.此外,试样破坏时的累积比能量越大,其破坏越严重,应变率曲线由“单峰”逐渐向“双峰”过渡.

Mechanical and energy dissipation characteristics of granite under different impact loads

To explore the dynamic characteristics of granite under different impact loading conditions, single and repeated impact tests of granite samples were carried out by the split Hopkinson pressure bar respectively. The stress-strain response, strain rate curve, energy dissipation characteristics, and the failure modes of the samples were analyzed. Results show that in the single impact test, the relationship between the dynamic compressive strength and the specific energy presented a logarithmic function. The damage degree of the granite sample aggravated gradually with the increase of the specific energy. With the increase of the incident peak stress, the curve of the strain rate showed a "double-peak" form, and the second peak gradually became larger than the first peak. The rebound phenomenon of the stress-strain curve in the post-peak phase tapered off. In the repeated impact test, when the sample did not fail, the stress-strain curve generally experienced three stages, i.e., elastic loading, damage evolution, and post-peak rebound. When the sample underwent the last impact, the post-peak shape of the stress-strain curve was related to the failure degree of the sample. In addition, it was found that as the accumulative specific energy increased, the damage degree of the granite samples increased, and the curve of the strain rate gradually transited from "single-peak" to "double-peak".