单轴压缩条件下花岗岩声发射事件空间分布的分维特征研究

基于声发射事件空间分布的柱覆盖分形模型，利用MTS815 Flex Test GT岩石力学试验系统和PCI-2声发射（AE）三维定位实时监测系统，对瀑布沟水电站地下厂房花岗岩单轴压缩损伤破坏过程中声发射事件空间分布的分形特征进行了研究。结果表明，声发射事件随应力增加逐渐活跃，加载初期声发射数量较少，应力接近峰值强度时，声发射事件累计数曲线呈指数上升。声发射事件的空间分布随应力增加是一个降维过程，其空间分维D在3~2内变化，峰值强度时，其值最小。弹性阶段后期，岩石内部微破裂开始向破坏面集聚，声发射空间分维D下降幅度明显增大。声发射空间分维恰当地表征了声发射事件空间分布的复杂程度。研究结论揭示了岩石声发射事件空间分布的分形特征，室内试验结果与文献对岩爆研究结果相吻合，可为现场监测应用提供理论指导。

Fractal Study on Spatial Distribution of Acoustic Emission Events of Granite Specimens Under Uniaxial Compression

The granite samples collected from the underground powerhouse of Pubugou Hydropower Station were tested on MTS815 Flex Test GT rock mechanics test system under uniaxial compression condition. During the whole test process, the acoustic emission events were monitored by PCI-2 based AE system. Based on the cylinder-covering spatial fractal model, the spatial distribution features of AE events and the changing law of spatial fractal dimensions at different stress levels were studied. The experimental results show that there are little AE events at low stress stage. The AE events become gradually active as the stress increasing and the cumulative number of AE events raises exponentially when the stress is close to the peak strength. The fractal dimension values gradually decrease from 3 to 2 with increasing stress and reach the minimum value when the loading is equal to the peak strength. At the later stage of elastic deformation, the spatial fractal dimension values decrease obviously with the microcracks in granite sample gathering in the nearby field of failure surface. The complexity of AE events spatial distribution can be characterized properly by its fractal dimension; and these results are agreed with the research results of rock burst in references. So the study provides theoretical basis and research means for in-situ rock mass monitoring by acoustic emission parameter.