## 6 Results and Discussion  
### Monitoring of Bw-4 Roadway  
Monitoring of Bw-4 was conducted at six research stations--two for each tested support section (Figure 11). Based on the results analysis, it can be concluded that the first test section of the roadway (gauges installed at 249 m and 349 m of Bw-4) was, in the period before mining, stable. The maximum loads were 23.5 kN and 25.6 kN, consistent with the average load values of 22.3 kN and 24.7 kN. This was below the yielding value,  
Figure 10: Monitoring station scheme: u—roof beds separation, P\({}_{\rm k}\)—the bolt load, Q—the load on a sensor. which for the applied load cell was approximately 64 kN. During the longwall exploitation period, the frame maximum load values increased to 57.1 kN and 90.9 kN, respectively, indicating that it was yielding at the second station. Nevertheless, the average load values increased slightly to a maximum of 32 kN. From the curves presented in Figure 6, it can also be inferred that there was frame yielding, indicated by sudden drops in the recorded force. This situation occurred at 580, 660, and 758 m of the roadway ahead of the longwall face. However, when the longwall face passed the monitoring station, there was a sudden drop in force several times at every measurement station. An interesting observation is that the loads on the wooden chips (Figure 12) during the longwall exploitation were very low, ranging from 3 \(\div\) 15 kN. This indicates that the designed support systems successfully absorbed the loads from the rocks bending towards the goat. This also applies to the load cell installed on base No. 4 on the second test section, for which the maximum value was 101.9 kN. This was also below the crib's capacity, which was approximately 121 kN for the applied gauge. Unfortunately, the continuity of measurements was not maintained, due to some interruptions in electrical connectivity and the fact that the monitoring was conducted during the COVID-19 pandemic. Figure 11: Measurement results obtained from the load cells installed on the steel arch support in Bw-4 roadway. Even before the start of longwall exploitation, the cable strand bolts (Figure 13) were already transmitting high force values, reaching up to 175 kN. However, when subjected to abutment pressure, they were further loaded, reaching up to 235 kN. Consequently, in the case using 9 m strand bolts with significant deformability (the deformability of strand bolts is ca. 5%), the steel arch support was generally relieved. The yield of arches occurred only sporadically. The displacement chart of the roof rocks indicates that separation took place at test Section 1, while periodic compaction took place at Sections 2 and 3 (Figure 14). So extendable strand bolts not fixed directly to the roof allowed for roof separation, but a roof bolted tightly by fully grouted bolts and cables and steel arches adjoined to the roof rocks, with the help of Bullflex bags, even lifted roof rocks a few centimetres upwards (this generally prevents arch slide). Then, the highest load was applied to cable bolts, while support frames were relieved. Figure 14: Total displacement of rock layers in Bw-4 roadway. Figure 13: Total load along the bolt in Bw-4 roadway. Figure 15a-i present the results of Bw-4 cross-section scanning. The depicted graphs compare the shape of the excavation when the longwall both started (blue colour) and finished its run. The convergence of Bw-4 in test section I was minimal and mainly occurred on the longwall panel side. The width change averaged \(50\div 60\) cm, the roof lowering was \(10\div 20\) cm, and the average floor uplift was around 30 cm. Consequently, the cross-section decreased by approximately 21%. In test section II at chainage 500, the excavation contour was most deformed ahead of the longwall face, and the cross-section was the smallest.