Mining-induced static and dynamic loading rate effect on rock damage and acoustic emission characteristic under uniaxial compression

Abstract

To further understand rock damage mechanisms under loading, evaluate coal burst danger and ensure stopping safety during coal mining, uniaxial compression tests of rock samples at different mining-induced loading rates were carried out. A systematical analysis has been conducted on strain rate effect on rock mechanical properties, AE parameters response and damage evolution law. The results show that along with the increase of mining-induced loading rate, an increase of peak strength and elastic modulus of rock together with a decrease of peak strain and dynamic failure duration in post-peak period are shown. Several acoustic characteristics are found decreasing in power function when loading rate increases such as AE hits, counts and events, but an obvious increase of AE energy is shown. Peak frequencies of AE events are mostly between 95 ∼ 125 kHz and 270 ∼ 310 kHz. A well-defined correspondence between AE count curve and rock stress-strain curve is presented. Rock damage variable was derived based on accumulative AE count, and three stages of rock damage evolution at different loading rates can be divided: initial damage, steady evolution, and accelerated development. A 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 at different strain rates. The conclusions of this paper can provide references for the issues of coal burst control and hazard assessment.