Influence of Weak Dynamic Disturbances on Rockburst Occurring in the Borehole Containing a Small-Scale Single Structural Plane: An Experimental Study

Structural plane plays an important role in affecting the rockburst, especially when it is subjected to an external dynamic disturbance. To investigate the influence of weak dynamic disturbances on a structural rockburst, a series of rockburst tests were conducted using a true triaxial rockburst testing machine enhanced by a video monitoring system. The granite specimens were thin squares (200 mm × 200 mm × 30 mm) with a circular hole (diameter of 50 mm) in the center. These specimens were used to simulate the occurrence of structural rockbursts in tunnels. The structural rockburst process and the corresponding acoustic emission (AE) and energy release were systematically investigated. The results indicated that weak dynamic disturbance decreased the stress level and made the rockburst occur more easily. The type of structural plane changed the influence of the weak dynamic disturbance on the structural rockburst. For the specimens with unexposed structural planes, more rock split and collapsed but fewer local rockbursts occurred, the intensity of the final rockburst was smaller than that of the static loading, and the stress when the final rockburst occurred was approximately 9% lower compared with those without a weak dynamic disturbance. For the specimens with exposed structural planes, the stress when the final rockburst occurred was approximately 10% lower but with a higher rockburst intensity compared with those without a weak dynamic disturbance. The AE characteristics indicated that tensile fractures dominated the rock failure process during the weak dynamic disturbance. The proportion of shear fractures increased with the increasing number of weak dynamic disturbances. In addition, the characteristics of the energy release indicated that weak dynamic disturbance decreased the local energy release rate ( LERR ) of the unexposed structural planes but increased the LERR of the exposed structural planes. The dip angle of the structural plane had an obvious effect on the rockburst. As the dip angle of the unexposed structural planes increased, the rockburst intensity, variation in the AE parameters, and LERR initially increased and then decreased which indicated that the rockburst was more intense under the dip angles of 30° and 45°. For exposed structural planes, the rockburst intensity, variation of the AE parameters, and LERR increased with increasing dip angle (0°–60°), which indicated that the 60° dip angle was more dangerous. Highlights The physi