Acoustic Emission Source Precursor Characteristics of Granite Creep Failure under Step Loading Condition
The creep property of rock is the main factor inducing rock failure.It is of great significance to study the pre-cursor characteristics of rock creep failure to ensure the safety of mine production.The creep acoustic emission localization test of rock under different loading conditions was carried out to study the relationship between acoustic emission activity,absolute energy of acoustic emission source and creep stress.The fractal dimension characteristics of Z(i)value and R(i)value of the source in the process of creep failure are analyzed,and the precursor characteristics of granite creep failure are summarized.The results show that when the creep stress is less than the long-term strength,the acoustic emission activity of granite depends on the number of micro-pores when the rock is compacted.The acoustic emission activity decreases with the increase of creep duration,and the absolute energy of the source in the constant creep stage is less than 10 000 aJ.When the creep stress is grea-ter than the long-term strength,the acoustic emission activity is mainly related to the initiation,propagation and coalescence of new microcracks.The acoustic emission activity increases with the increase of the difference between creep stress and long-term strength.The number of seismic sources with absolute energy greater than 25 000 aJ increases in the constant creep stage.In the process of granite creep failure,the fractal dimension of acoustic emission source Z(i)and R(i)increases with the in-crease of creep duration in the middle and late stage of constant creep stage,which can be used as the precursor characteristics of granite creep failure.The research results can provide theoretical and experimental support for exploring the prediction meth-od of rock creep failure.
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