Failure characteristics and physical signals of jointed rock: an experimental investigation

Jointed rock mass stability is a constant focus in underground engineering applications. In this study, the uniaxial compression test is carried out on defective red sandstone with different defect angles by using cement to simulate the defects. The physical characteristics of the strain and the acoustic emission energy released during the failure of the jointed rock mass are monitored by means of strain and acoustic emission methods. The experimental results indicate that with the difference in the defect angle, the failure mode of the jointed rock sample changes, and the instability signal released during the failure process is also different. When the angle of the defective part is small, within 15 degrees, the failure modes of the defects are similar to those of the intact rock sample. When the defect angle is between 15 degrees and 60 degrees, the failure modes of the defects begin to transition from tensile failure to shear failure. With the increase in the defect angle, the failure process of the jointed rock sample becomes faster and it becomes more difficult to capture the instability signal. When the angle of the defect part is smaller than 45 degrees, the overall instability of the jointed rock sample can be determined by measuring the physical signal released in the static sub-instability stage. When the angle of the defect part increases, the instability can only be determined based on the physical signal released from the previous stage, that is, the strong deviation from the linear stage. The experimental method used in this paper could be used to identify failure precursors of jointed rock masses and to develop technology for disaster prevention in rock engineering.