劈裂荷载下的岩石声发射及微观破裂特性  

Acoustic emission and micro-rupture characteristics of rocks under Brazilian splitting load

作　　者：刘希灵[1] 刘周 李夕兵[1] 韩梦思 杨柳青 LIU Xi-ling;LIU Zhou;LI Xi-bing;HAN Meng-si;YANG Liu-qin(School of Resources and Safety Engineering,Central South University,Changsha 410083,China;School of Materials Science and Engineering,Central South University,Changsha 410083,China)

机构地区：[1]中南大学资源与安全工程学院,长沙410083 [2]中南大学材料科学与工程学院,长沙410083

出　　处：《工程科学学报》2019年第11期1422-1432,共11页Chinese Journal of Engineering

基　　金：国家重点研发计划资助项目（2016YFC0600706）;中南大学研究生自由探索创新资助项目（2018zzts757）

摘　　要：通过开展花岗岩和大理岩巴西圆盘声发射试验,结合扫描电镜进行破裂面微观形貌分析,探讨了劈裂荷载下岩石声发射特性与微观破裂机制的关系.结果表明:基于RA(上升时间与幅值的比值)和AF(平均频率)的变化趋势,不同裂纹模式(拉伸裂纹、剪切裂纹以及复合裂纹)的分布和破坏强度受岩石结构影响,但岩石裂纹演化过程不受其影响.相应地,两种岩样破裂信号均以400~499 kHz为主,100~199 kHz的信号次之,但不同破裂阶段的峰值频率变化趋势显著不同.在微观形貌上,花岗岩劈裂面的微观形貌以层叠状、台阶状及平坦状为主;而大理岩以光滑多面体状为主.此外,结合频率-尺度缩放关系可推测,400~499 kHz的信号应主要来自钾长石、大理岩矿物颗粒内部的破裂;100~199 kHz的信号应主要来自石英矿物颗粒内部不连续分离以及压密阶段矿物颗粒之间的滑移.Considering the polycrystalline and anisotropic features of rock, its mechanical failure actually involves the generation,propagation, and penetration of internal micro-cracks until an ultimate macro-fracture is achieved. The nucleation and propagation of cracks emits energy outward as elastic waves referred to as acoustic emission(AE). The close relationship between AE signals and the rock fracture mechanism has been demonstrated. Many instability and failure processes in underground engineering are induced by the effects of tensile stress on tunnels and chambers or local damage to the rock structure. Several compression experiments show that the main fracture mode of rock is tensile failure. Thus, investigations of rock AE characteristics under tensile failure and the effects of the rock fabric on crack propagation patterns are of great significance. This study assesses the signal characteristics AE and its relationship with the micro-rupture mechanisms in granite and marble under tensile stress. Herein, an MTS-322 rock mechanical test system was employed to carry out Brazilian split tests, and a scanning electron microscope was employed to carry out micro-morphological analysis of rupture surfaces. According to the trends of RA and AF, the distribution of crack modes-tensile and shear or mixed patterns in both rock types and its fracture strength depend on the rock fabric. By contrast, the evolution process of crack propagation appears to depend on the softening process. Although the rock fracture signals are mainly in the range of 400-499 kHz and 100-199 kHz, the variation trend of peak frequency shows significant differences at different failure stages. At the microtopographic level, granite mainly shows three micro-morphologies,including laminated,stepwise,and smooth planar patterns.Marble is mostly smooth polyhedrals.The signals at 400-499 kHz may be inferred to be mainly generated by fractures in the k-feldspar and marble minerals,while those at 100-199 kHz are mainly produced by discontinuous separation

关 键 词：巴西劈裂 扫描电镜 RA值 频率特性 微观形貌 

分 类 号：TD76[矿业工程—矿井通风与安全]