基于微震信号多重分形特征的岩石边坡变形预警研究

依托白鹤滩水电站左岸岩石边坡工程,引入多重分形去趋势波动分析法(MF-DFA)估算微震波形多重分形谱,以岩石破裂微震波形多重分形时变响应特征为基础,揭示岩石边坡变形预警信号。研究表明,左岸边坡岩石微破裂与爆破振动波形多重分形特征明显,且爆破振动波形多重分形谱宽度远大于岩石微破裂波形多重分形谱宽度。边坡裂缝增大前,岩石微破裂波形多重分形时变响应特征表现出很强的规律性,可作为变形预警信号,即:岩体在发生变形破坏前,多重分形谱宽度△α呈现增大趋势,微震波形多重分形谱△f(α)呈现减小趋势,可视为变形预警前兆信号;发生变形破坏时,△α呈现减小趋势,△f(α)呈现增大趋势,可视为变形破坏期;发生变形破坏后,△α和△f(α)均呈现平稳趋势,△f(α)整体将处于零线附近,可视为稳定期。

Study on deformation pre-warning of rock slopes based on multi-fractal characteristics of microseismic signals

Based on the rock slope engineering of the left bank of Baihetan hydropower station,Multi-fractal Detrended Fluctuation Analysis(MF-DFA)is used to estimate the multi-fractal spectrum of microseismic waveforms,and the pre-warning signs of rock slope deformation are pointed out on the basis of the time-varying response characteristics of multi-fractal time series of microseismic waveforms.The results show that the multi-fractal characteristics of rock microcracking and blasting waveform time series in the left bank slope are obvious,and that the multi-fractal spectrum width of the blasting waveform is much larger than that of the rock microcracking waveform.Before the slope cracks increase,the multi-fractal time-varying response characteristics of rock microcracking waveforms show strong regularity,which can be viewed as pre-warning signals for deformation.Before the deformation and failure of the rock mass,the multi-fractal spectrum width△αshows an increasing trend while the multi-fractal spectrum of microseismic waveforms△f(α)presents a decreasing trend,which can be regarded as precursor signals of deformation pre-warning.When deformation and failure occur,△αshows a decreasing trend while△f(α)presents an increasing trend,which can be regarded as a deformation failure period.After deformation and failure,both△αand△f(α)show a steady trend and△f(α)as a whole will be near the zero line,which can be regarded as a stable period.