Multi-fractaland time-varying response characteristics of microseismic waves during the rockburst process

LI Nan; LI Baolin; CHEN Dong; SUN Weichen

Abstract：The multi-fractal characteristics of microseismic waves and their time-varying response law were studied based on the multi-fractal theory.The maximum multi-fractal dimension Dmaxq,multi-fractal spectrum parameters,△α and △f(α),were proposed as the multi-fractal features of the microseismic waves.The results show that multi-fractal feature of microseismic waves induced by rockburst is much stronger than the common microseismic waves before and after the rockburst.The Dmaxq and △α can reflect the degree of heterogeneity and volatility of microseismic waves.The bigger of the Dmaxq and △α,the stronger that the degree of heterogeneity and volatility of microseismic waves will be,and it means that the multi-fractal feature is more obvious.The △f(α) can reflect the relationship between small and large peak frequencies of microseismic waves.The smaller of the △f(α),the greater proportion of large peak in the wave will be,and it means that the energy of the microseismic wave is greater.The timevarying response of the microseismic waves multi-fractal features,Dmaxq,△α and /△f(α),has obvious rules before the rockburst happens.When the Dmaxq or △α is greater than the low critical value,and continuously increases to the high critical value;or when the △f(α) is smaller than the high critical value,and continuously reduces to the low critical value;and particularly when the above three kinds of time-varying response occur at the same time,the severe rockburst is very likely to occur.The time-varying response of the microseismic waves multi-fractal features,Dmaxq,△α and △f(α),can be taken as effective precursor information to monitor and warn the rockburst.