Experimental Study of Strainbursts Caused by Stress Concentration and Local Mine Stiffness Decrease as Mining Proceeds

The important role of local mine stiffness (LMS) on rock strainbursts has been extensively recognized. Understanding the evolution of LMS as mining proceeds is of significance to rockburst prevention. Existing studies on this topic, however, are limited to theoretical and numerical methods. In this study, an experimental study is performed using in-house built equipment to produce strainbursts resulting from excavation-induced stress concentration and LMS decreasing. The process of excavations and their resultant disturbance is produced using real coal blocks in the laboratory. A novel method is proposed for calculating LMS, based on which the evolution of LMS with excavations is quantitatively evaluated. The influence of initial LMS on the strainbursts is also investigated. The experimental result demonstrated that there is a critical threshold value of LMS below which the coal pillar fails with a bursting pattern. The threshold is related to the post-peak stiffness of the coal pillar. The experimental study proposes a novel method for producing strainbursts and evaluating LMS in the laboratory.