220 rockbolts, support, monitoring, coal mine 1. INTRODUCTION Long-term hard coal exploitation, as is the case in Poland, necessitates mining operations at increasingly greater depths and in areas located farther from shafts, which results in a significant increase in production costs. This is caused, among other factors, by the need to extend transportation routes, develop and maintain a larger number of roadway workings, and apply increasingly complex and costly methods of natural hazard prevention (Ratajczak et al., 2015). Mining depths reaching up to 1300 m also lead to an increase in primary and secondary stresses around underground openings, resulting in support deformation and difficulties in maintaining the functionality of roadways. In response to these conditions, heavy steel supports with reduced frame spacing are commonly applied (Caban et al., 2020). Such solutions significantly increase operating costs. Consequently, these conditions differ substantially from those encountered in underground hard coal mining in many other countries, where mining depths typically range from 400 to 600 m and rock bolting systems are predominant (Craig et al., 2021; Li, 2017). Rock bolt support systems are characterized by lower steel consumption, easier underground transportation, and lower costs compared to traditional steel supports. When appropriately mechanized, they also enable higher advance rates (Masny & Ficek, 2021). Additional advantages include improved safety and working conditions, as well as the possibility of full mechanization of the installation process (Ma et al., 2020; Korski & Majcher, 2021). To verify the design assumptions and the effectiveness of the support system, in situ monitoring is typically conducted (Małkowski et al., 2020). For these reasons, roadway development using a self-supporting rock bolt system installed with a Bolter Miner was implemented at the “Budryk” hard coal mine in Poland. This represented a global first, as the roadway was driven at a depth of approximately 900 m. The aim of this study is to demonstrate how the roadway was successfully maintained using ongoing in-mine investigations of rock mass properties and continuous monitoring of roof strata behavior and installed rock bolts. 2. DESIGN OF A SELF-SUPPORTING ROCK BOLT SYSTEM Proper support design is crucial to ensuring the stability and functionality of underground mine workings throughout their entire service life. Regardless of the design approach applied—analytical, empirical, or numerical—it is essential to consider a comprehensive set of data encompassing natural, technological, and mining-related factors. Of particular importance is the identification of the in situ stress state of the rock mass, resulting from overburden weight, rock properties, and tectonic processes. This stress state determines the secondary stress redistribution after excavation and, consequently, the extent of the rock damage zone surrounding the opening as well as the intensity of deformations. Studies have shown that at greater depths, horizontal stresses may reach values comparable to or even exceeding vertical stresses, which has a significant impact on roadway stability and support
RkJQdWJsaXNoZXIy MTM0Mzk2