页岩单轴压缩破坏过程中声发射能量分布的统计分析

Statistical analysis of acoustic emission energy distribution during uniaxial compression of shale

脆性岩石受载荷作用发生破裂的过程其能量释放具有临界性,为了更加清楚了解脆性岩石破坏过程及能量变化规律,对页岩进行单轴状态下的压缩试验,加载速率分别为0.01,0.1,0.5 mm/min。在加载过程中同步采集全过程声发射参数,计算绝对能量的概率密度函数并采用最大似然估计法计算表征概率密度函数的临界指数。结果表明:(1)每个加载速率下的能量概率密度函数在7个数量级范围符合幂定律分布。(2)最大似然估计得到的临界指数r具有一个最优的平坦稳定范围,能准确表征能量分布的幂定律。(3)子时间区间与全过程区间具有相同的临界指数r,因此可以通过试验前期的声发射情况了解破裂和破裂中能量释放的状态。

The energy release of brittle rock＇s failure under loading is critical process. In order to have a more clear understanding about the brittle rock＇s failure process and the rule of energy release,shale under uniaxial compression test has been carried in laboratory,and the loading rates were 0.01,0.1,0.5 mm/min respectively. During the whole loading process, acoustic emission（AE） parameters have been collected,and the probability density function（PDF） of absolute AE energy was calculated. PDF＇s critical exponents were estimated by the maximum likelihood estimation method. The results showed：（1） The PDF of absolute AE energy under different loading rate in seven orders of magnitude ranges conformed to the power law distribution.（2） The critical exponent r calculated by the maximum likelihood estimates method had an optimal range of stability,which characterized the power law distribution accurately.（3） The critical exponents of one span and the whole process were similar with each other,which allowed one use the AE information in the preliminary stage to study the energy release during final collapse.