## 3 Indices of Roadways Stability
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Rock Mass Mass Class** & **Rock Mass Description** & **Number of Cracks I\({}_{k}\) [-]** & **Total Declination\({}_{r}\)** & **Range of Intense Cracks\({}_{is}\) [m]** & **Recommended Method of Reinforcing the Steel Yielding Arch Support** \\ \hline I & Perfect & Intact & \(\leq\)5 & \(\leq\)15 & \(\leq\)0.5 & Increase the number of arches \\ \hline II & Very good & Block & 6–15 & 16–40 & 0.5–1.5 & Bolting the roof arches + increase the number of arches \\ \hline III & Good & Weakly cracked & 16–25 & 41–60 & 1.5–2.5 & Increase the number of arches; bolting the roof arches; or bolting between steel arches \\ \hline IV & Average & Cracked & 26–40 & 61–80 & 1.5–4.0 & Hoisting just fixed to the roof by long cable strand bolts + rock bolts; Bullflex bags recommended \\ \hline V & Weak & Strongly cracked & 41–60 & 81–100 & 4.0-6.0 & Two hosting joists fixed to the roof by long cable strand bolts, pre-tension and fully ground bolts recommended; rock bolts; Bullflex bags recommended \\ \hline VI & Very weak & Damaged & \(>\)60 & \(>\)100 & \(>\)6.0 & Bolting between steel arches using injection; cable bolts with pre-tension; Bullflex bags recommended; reinforcement may be ineffective to maintain the roadway \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Description of rock mass classes according to the ERMF index, along with suggested reinforcements. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Roadway** & **Tested Section [m]** & **Geological Factors** & \begin{tabular}{c} **Geomechanical Rock** \\ **Properties** \\ \end{tabular} & **Mining Factors** & **RDE** & \
\begin{tabular}{c} **MDE** \\ **Class** \\ \end{tabular} & **RFM** &
\begin{tabular}{c} **RFM** \\ **Class** \\ \end{tabular} \\ \hline \multirow{3}{*}{Bw-4} & 200–400 & 77.68 & 62.48 & 62.96 & 203.1 & III & 81.98 & 56 & III \\ \cline{2-10}  & 400–600 & 81.76 & 53.98 & 62.96 & 198.7 & III & 90.24 & 60 & III \\ \cline{2-10}  & 600–800 & 87.34 & 53.98 & 62.96 & 204.3 & III & 86.28 & 59 & III \\ \hline \multirow{3}{*}{PW-1} & 100–329 & 84.00 & 62.48 & 35.80 & 182.3 & III & 81.00 & 49 & IV \\ \cline{2-10}  & 350–451 & 84.00 & 55.26 & 35.80 & 175.1 & IV & 90.24 & 53 & IV \\ \cline{1-1} \cline{2-10}  & 451–808 & 84.00 & 59.76 & 35.80 & 179.6 & IV & 81.00 & 48 & IV \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Comparison of the Roadway Design Efficiency index (RDE) and the Roadway Functionality Maintenance index (RFM) for the analysed roadways. High-intensity crack zones were observed in the roof of Bw-4. The total separation largely determined the class, and hence the rock mass class was classified as I, II, or III (Table 6). Due to the various roof conditions in Bw-4, bolting between steel arches was recommended to ensure stability. A significantly weaker rock mass class was determined for PW-1. Excavating the roadway directly under the seam edge, about 20 m above, resulted in a very extensive crack zone, reaching a height of over 10 m above the roadway. Intensive cracks were also observed up to \(2\div 3\) m above the roof contour. The rock mass was severely damaged at the first two research stations, as the cumulative total separation reached almost 100 cm, with nearly 100 registered discontinuities. For all the tested stations, a rock mass of class V was determined. In this roadway type, which is classified as \"weak\" according to the ERMF classification, the steel arch support should be reinforced with two rows of hoisting joists fixed to the roof with the help of long cable strand bolts, preferably with pre-tensioning and Bullflex bags (Table 7).