不同粒径花岗岩断裂力学行为及声发射特征研究

Fracture mechanical behaviors and acoustic emission characteristics of Beishan granites with different particle sizes

利用MTS815 Flex Test GT岩石力学试验系统及声发射(AE)三维定位实时监测系统,对4种不同粒径北山花岗岩进行断裂韧度试验,系统研究了不同粒度北山花岗岩的断裂力学行为及声发射特征。在三点弯曲试验条件下,北山花岗岩峰值过后断面还具有较大的承载面积。粒径越大,其峰值载荷越低,且屈服载荷所占峰值荷载百分比越小,断裂韧度值越小;粒径越大其破坏过程中的总变形量越大,且加载末期承载能力越高。细粒及中细粒岩样声发射事件最早出现于拉应力较大的尖端下部,而强度相对较小的粗粒及中粗粒岩样声发射事件最早出现于受点荷载的上端部。声发射事件集中出现于裂纹稳定扩张阶段,这一阶段为岩石断裂的最主要阶段。粒径越大,声发射事件越多,且整个断面分布越广泛。

To investigate the fracture mechanical behaviors and acoustic emission characteristics of of Beishan granites with different particle sizes,we used the MTS815 Flex Test GT rock mechanics testing system and acoustic emission three-dimensional positioning monitoring system to conduct three-point bending tests on the four different particle sizes of Beishan granites.The experimetal results show that under the condition of three-point bending test,there is still comparative large bearing area in the section of specimen after the peak.The bigger is the particle size,the lower is the peak load is,the lower is the yield load＇s percentage of peak load,and the smaller is the fracture toughness value.But the bigger particle size allows larger total deformation,and the residual strength is also higher.For the fine-grained or medium-fine grained specimens with a relatively low strength,the acoustic emission events firstly appear near the tip of notch,where tensile stress is larger.In the coarse-grained or medium-coarse grained specimens,acoustic emission events initially emerge in the upper part in which point load is applied.Regardless of the fine-grained or coarse-grained granite,the acoustic emission events concentrated in the stable stage of crack extension which is the main stage of rock fracture.The statistical results indicate that the bigger the particle size of granite,the more the acoustic emission events is,and the broader the distribution of acoustic emission events is.