花岗岩晶粒尺寸对岩爆影响的试验研究

Experimental study on influence of granite grain size on rockburst

为探究晶粒尺寸对硬脆性岩石岩爆的影响,利用真三轴岩爆试验系统,对细中、中粗两种不同晶粒尺寸的含预制圆孔花岗岩开展了岩爆模拟试验。试验结果表明:在相同的加载过程中,细中晶粒花岗岩出现板裂静态脆性破坏,而中粗晶粒花岗岩出现岩爆动力破坏;细中晶粒花岗岩早期声发射活动较弱,大破裂、低主频事件在时空分布上较集中,特征应力较大,而中粗晶粒花岗岩早期声发射活动较活跃,大破裂、低主频事件在时空分布上较离散,特征应力较小,碎屑破碎程度更高。晶粒尺寸对花岗岩的岩爆倾向性具有重要影响,晶粒尺寸较大的硬脆性岩石的岩爆倾向性更强。深部地下岩体工程的岩爆倾向性评价中,除强度和脆性外,晶粒尺寸也是需要考虑的重要因素。

In order to explore the influence of granite grain size on rockburst,cubic granite specimens with an opening and different grain sizes(fine to medium and medium to coarse)were used to conduct the rockburst tests using the true triaxial rockburst testing system.The experimental results show that the failure process of the fine to medium-grained granite is mainly composed of brittle failure.However,rockburst failure(dynamic failure)dominates the failure for the medium to coarse-grained granite.The acoustic emission(AE)activity in the early loading stage is weak for the fine to medium-grained granite,and the lowfrequency large-rupture events are concentrated in time and space,and the characteristic stress is higher.However,the AE activity in the early loading stage is stronger for the medium to coarse-grained granite,and the low-frequency,large-rupture events are more discrete in time and space,and the characteristic stress is lower,and the fragments are broken more.The grain size has an important influence on the rockburst proneness of granites.The hard-brittle rock with coarser grain size has a stronger rockburst proneness.In addition to strength and brittleness,grain size is an important factor to be considered in rockburst proneness evaluation of deep underground rock mass engineering.