Examining Coal Rib Stability Using Mechanical Bolts: Experimental and Numerical Study

Abstract

In the underground coal mines of US, mechanical bolts are employed alongside other bolt types to mitigate rib deformation and enhance the stability of coal ribs. The performance of mechanical bolts within coal ribs has received limited research attention to date. This paper presents an integrative approach that combines numerical modeling and experimental methods to propose a comprehensive methodology for supporting coal ribs using mechanical bolts. Standard pullout tests were conducted to establish the load–response behavior of mechanical rib bolts. Subsequently, these load–response characteristics were calibrated through numerical models and applied to larger-scale supported coal rib simulations. The coal rib models were compared and validated with a case study to pursue the studies with more realistic numerical models. The validated models serve as the foundation for the models employed in parametric studies. A support approach tailored to mechanical bolt applications was developed based on these comprehensive studies. The key findings of this paper are as follows: Mechanical bolts exhibit a trilinear force–displacement response with critical points providing crucial insights into their characteristics, such as stiffness and yield capacity of the bolt. Bolt length was found to be less influential than the number of bolts during the design of the mechanical bolts. The bolts’ placement within the rib structure arose as another critical factor. Generally, stronger coal units do not necessitate additional support, whereas medium-strength and weaker coal require support in most scenarios. Specific support design approaches were proposed for various mining conditions, including coal strength, overburden depth, and mining height. The combined results of numerical simulations and experimental tests underscore the pivotal role of proper mechanical bolt application in ensuring stable coal rib conditions, with several noteworthy contributions setting this study apart.