Experimental study on the failure characteristics of naturally jointed granite with locking segment and failure forecast under truly 3D-stress conditions

• The effects of natural joint angle on rockburst behavior is investigated using true triaxial unloading tests. • A multi-physics monitoring approach combining acoustic, optical, and mechanical measurements is employed to track the progression of rock failure. • The four-stage rock failure process has been clearly characterized. • A new precursor indicator for failure prediction is identified, and its predictive performance is compared with two conventional indicators. The natural joint inclination angle is vital for assessing the stability of underground engineering structures. However, the influence of joint inclination angle on failure characteristics remains poorly understood due to the relative scarcity of effective simulation experiments. To this end, true triaxial tests with a free face with a synchronous acoustic emission (AE) monitoring system, and a digital image correlation (DIC) system are carried out. Results show that the failure process involves calm stage, process zone nucleation stage, local static splitting failure stage, and strength failure and post-peak softening stage. Typical delamination fracture in the intermediate principal stress ( σ 2 ) direction is faithfully documented, as well as the rockburst. More importantly, the inclination angle of natural joint has a significant influence on rockburst. Furthermore, The minimum principal strain ( ε 3 ) has been demonstrated to have the capability to predict dynamic failure time, and its predictive performance has been compared with that of conventional prediction parameters, which underlies the active control of the rockburst in deep underground engineering.