218 / 2018-07-07 14:41:29

Loading rate effect on rock damage evolution and acoustic emission characteristic under uniaxial compression

acoustic emission (AE),damage evolution,strain rate,damage variable,rock mass,stress-strain

矿山动力灾害 > 岩爆冲击

To accurately understand rock damage mechanisms under loading and evaluate rock burst danger during coal mining, uniaxial compression tests of rock samples at different loading rates were carried out. The strain rate effect on rock mechanical properties, AE parameters response and damage evolution law have been analyzed systematically. The results show that with the increase of loading rate, rock peak strength increases, peak strain value decreases, dynamic failure duration at post-peak decreases, and elastic modulus increases slightly. Meanwhile, AE hits, counts and events all decrease significantly by power function as loading rate increases, but AE energy increases obviously. Peak frequencies of AE events are mostly located between 95~125 kHz and 270~310 kHz. Additionally, there exits well-defined correspondence between AE count curve and rock stress-strain curve. Rock damage variable was derived based on accumulative AE count, while the damage evolution at different loading rates can be divided into three stages, including initial damage, steady evolution, and accelerated development. Moreover, the constitutive damage equation has been established on the basis of equivalent strain hypothesis and AE count. Calculated results can basically reflect the characteristics of rock stress-strain curves loaded at different strain rates. The conclusions of this paper can provide references for the issues of strain rate effect and seismic pre-warning of rock burst danger.