Frequency fractal feature of microseismic events in the process of immediate rockburst in deep tunnel

摘要

In order to research microseismic (MS) activity rules in the process ofrockburst in deep tunnel,the immediate rockburst induced by TBM and D&B excavation are measured in the field.The attention law of microseismic waveform shows that frequency is a better parameter to reflect the real feature of microseismic source.Then,a calculated method of the main frequency of MS event and its fractal dimension is introduced.The study on the evolution of fractal dimension of the main frequency in the process of immediate rockbursts shows that the distribution of main frequency of MS events is a fractal and has statistical self-similarity.Immediate rockburst induced by different excavation method has different precursory.The lowest fractal dimension of main frequency occurred on the day before major rockburst in the TBM tunnel.But in the D&B tunnel,the fractal dimension gets lowest on the right day of major rockburst.These results can provide references for warning and mechanism study of rockburst in deep tunnel.