ABSTRACT
ABSTRACT: This paper presents a recent advancement in laboratory experimental investigations on rockbursts at China University of Mining and Technology Beijing’s (CUMTB’s) State Key Laboratory for Geomechanics & Deep Underground Engineering. The innovative modified true triaxial apparatus (MTTA), which has a single face unloading device (SFUD), can implement in-situ analog tests on rockbursts using cubical specimens by loading in three principal stress directions independently, abruptly unloading the specimen on one surface and exposing this surface to air, thus simulating the excavated boundary and subsequent rockbursts. The findings on the mechanisms that trigger a rockburst, the evolution of the rockburst process, the experimental setup and the measuring approaches are detailed. Based on more than 200 rockburst tests using the MTTA with rock specimens of different properties sampled from different mines from both at home and abroad, the last unloading rate (LUR) at the instant of bursting, the critical time (CTI) at the instant of bursting, the critical maximum principal stress (CMPS) at the instant of bursting and their inter-relationships were thoroughly analyzed. The experimental results from the experiment on a sandstone rockburst, as an example, was documented regarding the high-speed failure process, the acoustic emission (AE) energy release characteristics, the 3-D map of the time-frequency (t-f) spectrum and the structural features of the microscopic cracks in different burst phases. These attainments form a theoretical foundation for advancing the study of the mechanisms of rockbursts and provide experimental grounds for predicting and forewarning rockburst events.
