Review of current coal rib control practices

The instability of coal ribs in underground mines continues to result in the injuries and fatalities of mine workers. The proper esti-mation and evaluation of primary and secondary support for coal ribs is still a challenging problem in the field of ground control science and requires further research and study. Although mining operations have various support design criteria and support methodologies for strata control, most rib support designs are still based on experience and local practices. This review study is intended to summarize the currently applied practices for rib support and control in various countries and mining conditions. Firstly, critical parameters that con-trol the amount and type of required rib support are considered and evaluated. The study revealed that among these parameters that control the stability of coal ribs, mining depth, rib height, cleat orientation/condition, and coal strength are the most significant param-eters. Secondly, current rib support application methods were also summarized. Similar to rock mass classification systems, some studies proposed a rib control rating system for practical estimation of the current rib condition and to estimate primary support requirements. These studies are classified and summarized into two groups (categorical and empirical) based on the required inputs and methodologies. Empirically based coal rib rating systems were closely examined, and the usefulness and intuitive aspects of each rating system were com-pared. This comprehensive literature review demonstrates that the Australian rating system, Analysis and Design of Rib Support (ADRS), and the new U.S. rating system, Coal Pillar Rib Rating (CPRR), are highly applicable for their regions.