Acoustic emission energy statistical properties of sandstone during uniaxial creep and its fracture surfaces morphology

In order to investigate the statistical characteristics of acoustic emission (AE) of sandstone during uniaxial creep,the AE signals have been captured both in long-time and step loading creep tests. Histogram analysis and maxi- mum likelihood method were used to study the statistical characteristics of AE absolute energy respectively. The results show that the AE jerks of long-time and step loading creep tests have similar shape,but the AE rate of step loading was higher than that of long-time test;Both the probability density functions ( PDF) of long-time and step loading creep tests satisfied the power law well,and the exponents came from histogram analysis and maximum likelihood method were very similar. These exponents were much closer to the earthquake results than to the exponent of uniaxial com- pression. Unlike the smooth fracture surfaces of sandstone sample in uniaxial compression,the fracture surfaces in- duced by creep were much coarser and with stepped fractures. These results agreed with the assumptions and results of fiber bundle model with time dependence fiber elements.