A Novel Rockburst Tendency Index Based on LURR

Abstract

To address the commonly encountered loading and unloading disturbance issues in deep coal resource development, this study analyzes the mechanical properties and deformation characteristics of coal and sandstone. Additionally, a loading and unloading response ratio (LURR) based on crack initiation stress is established to investigate the significance of structural damage and its precursors. Finally, a new rockburst tendency index is defined based on the drop of LURR. The results show that the hysteresis loop of coal and sandstone exhibited three stages of characteristics. The Young’s modulus of both coal and sandstone increased parabolically during loading and unloading process. Sandstone was more prone to larger lateral deformation changes than coal under high confining pressure. LURR of coal could be classified into three stages, while the LURR of sandstone had only two stages. The former could be used as a parameter to evaluate the degradation degree of materials under the collaborative action of coal and sandstone, and the trend of the LURR could be used as a precursor of system failure. it can represent energy dissipation capacity of the mechanical system. The rockburst tendency index based on the drop of LURR effectively reflects the changes in fractal dimension D and surface roughness after material failure, and this index can be classified into three levels: weak, medium, and strong. The research results are expected to improve the understanding of the failure process in underground engineering and system failure.