Experimental Study on Rockburst and Spalling Failure in Circular Openings for Deep Underground Engineering.

This study aims to simulate the process of rockburst and spalling failure of roadway surrounding rock under three-dimensional stress in deep rock engineering. Utilizing an independently developed true triaxial rockburst experimental setup, the failure process of a circular tunnel under initial in-situ stress at a depth of 500 m was investigated using red sandstone with prefabricated holes. A miniature camera device and acoustic emission (AE) monitoring system were used to monitor and record the experimental process in real time. Using the collected data, the process of rockburst and spalling failure of the circular tunnel was reproduced. Finally, the difference between rockburst and spalling failure was analyzed and compared based on four aspects of stress characteristics, acoustic emission characteristics, fragment characteristics, and V-shaped notch morphology characteristics. The experimental results show that the failure of surrounding rock was more likely to occur under dynamic disturbance load, resulting in particle ejection. The spalling failure was found to be a slow and gradual static failure process. The mechanism of rockburst was more complex involving tension-shear coupling failure, whereas, the mechanism of spalling failure was simple involving a tensile failure. Compared with spalling failure, rockburst was more intense, producing more debris, and the V-shaped notch was narrow and deep. Highlights: Failure process of rockburst and spalling is reproduced in a laboratory. The stress characteristics of rockburst and spalling failure are calculated based on elastic theory. Frequency-amplitude characteristics and crack types based on acoustic emission are analyzed. The failure intensity of rockburst and spalling is investigated based on the rock fragments and morphology of V-shaped notch. The failure process of rockburst and spalling is discussed along with strain energy. [ABSTRACT FROM AUTHOR]