1482 4.3. Convergence The roadway section between chainages 230 m and 1,040 m included eight stations for convergence measurements, located between approximately 414 m and 1,063 m along the roadway length. Figure 9 presents the maximum values of vertical and horizontal convergence recorded during the development stage as a function of roadway chainage. The highest values of vertical convergence were recorded in the vicinity of chainage 563 m, where the reduction in roadway height reached approximately 29 cm. This location represents a clearly dominant point along the analysed section and indicates locally unfavourable geomechanical conditions. Significant vertical convergence was also observed at chainages 503 m (approximately 19 cm) and 655 m (approximately 13 cm). At these locations, the increase in convergence occurred gradually throughout the entire excavation stage, suggesting long-term stress influence and progressive rock mass deformation. At the remaining measurement stations, vertical convergence was markedly lower and ranged from approximately 3 to 11 cm, which can be considered relatively small values from the perspective of roadway stability maintenance. Areas exhibiting increased vertical convergence correspond well with previously identified zones of greater fractured zone extent and increased roof rock separations, confirming the interrelationship between these phenomena. Analysis of horizontal convergence during roadway development showed that its values were generally lower and more uniform along the entire roadway section. The maximum horizontal convergence occurred in the vicinity of chainage 864 m and reached approximately 11 cm. Notably, this location also exhibited one of the lowest values of vertical convergence (approximately 3 cm), indicating a local change in the deformation mechanism of the roadway. At the remaining stations, the reduction in roadway width did not exceed 8 cm. Figure 9 – Maximum vertical and horizontal convergence 4.4 Axial force in rock bolts The section between chainages 230 m and 1,040 m was characterized by the highest measured axial forces in the rock bolts. At the measurement stations located at 564 m and 936 m, axial forces reached values in the range of 340÷420 kN. It should be noted that the elastic limit, defined for this type of rock bolt as Re = 640 MPa, was exceeded. Nevertheless, for comparative purposes, the recorded values were assumed to correspond to the elastic range. These effects were observed in bolts installed at heights between 0.75 m and 1.0 m. At the 564 m station, compressive forces occurred in the outer bolts at a height of approximately 1.0 m, reaching values of up to 180 kN. In contrast, at the 936 m station, only minor compressive forces were recorded near the bolt base, not exceeding 20 kN (Fig. 10).
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