循环动载下大理岩的力学响应及裂隙扩展规律

Mechanical response and fracture propagation law of marble under cyclic dynamic load

为研究大理岩在循环冲击载荷下的动态力学性能,利用分离式霍普金森压杆装置(SHPB)及核磁共振装置(NMR),研究循环动载(1~10 s^-1)冲击下岩石内部的裂隙发展规律.结果表明:岩石在循环动载冲击下,峰值应力随应变率的增大变化很小,但是随着冲击次数增加,存在一个临界应变率或冲击次数,当达到该临界值时,峰值应变快速增大;岩石在最初冲击时,表现出明显的弹性后效,随着冲击次数增加,岩石内部裂纹起裂时间越来越早,且裂纹扩展越来越快,应变幅值增大;通过核磁共振成像发现,随着冲击次数的增加,裂隙集中发育(白色亮点)愈来愈明显,呈条带状分布,并逐渐贯通.从最终破坏形态来看,大理岩在动载下为轴向劈裂破坏,大块较多.

In order to study the dynamic mechanical properties of marble under weak impact load,the fracture development law of rock under low strain rate(1-10 s^-1)impact is studied by split Hopkinson pressure bar device(SHPB)and nuclear magnetic resonance(NMR).The results show that under the impact of low strain rate,the peak stress changes little with the increase of strain rate,but with the increase of impact times,there is a critical strain rate or impact times,when it reaches the critical value,the peak strain increases rapidly.And when the rock is impacted initially,it shows obvious elastic aftereffect,with the increase of impact times,the internal crack of rock starts to crack with the increase of the impact times,the fracture concentrated development(white light spots)are more and more obvious,distributed in strips,and gradually penetrated.According to the final failure mode,the marble is axially split under dynamic load,and there are many large blocks.