## 2 Analysis of Ground Support Methods in Unstable Rock Conditions
The presence of fibers in the range of 1 to 2% increases the tensile strength, resistance to crack development, and impact resistance, making this composite suitable for shotcreting applications. Concrete reinforced with steel fibers of various lengths is characterized by enhanced fire resistance, low creep, and high deformation properties. Overall, dispersed reinforcement with 1 to 3% steel fibers can increase the compressive strength by up to 40% and flexural strength by up to 150%, significantly improving the resistance to mechanical and thermal shocks, as well as wear resistance. Frames made from the special SVP-22 profile are used as arched metal supports in the form of 27-metal, three-bar (or five-bar) arches (referred to as SP at the mine). The roof and sidewalls of the workings are tightened between the support frames using timber. Backfilling of the voids created after roof collapse is carried out using either timber supports or modern chemical materials that expand in volume (Figure 1). In \"very weak\" and \"exceptionally weak\" rock formations, the distance between arches should be no greater than 0.5 and 0.3 m, respectively. These distances can be confirmed through regulatory documentation when using arched metal supports. The use of arched metal supports in rocks of stability category IV ensures the preservation of their load-bearing capacity and has a positive effect on the geomechanical state of the rock mass, thereby enhancing work safety. However, it was observed that in certain areas of the mine, the metal frame support was unable to withstand the loads, leading to support deformation. In rocks of stability category V, the safe use of arched metal supports is not always possible due to the development of metasomatic processes and rockfalls within 0.5-1 work shifts. To improve rock stability under these conditions, advance supports are implemented. Advance supports are used during workings in unstable rocks. These supports have a length of 3 m and a working width of 3.5 m, with 8 supports mounted on the roof of a working, and up to 12 supports for wider workings (with a width of 4.5 m) (Figure 2). Figure 1: Support scheme with a special arched profile and tightening of the roof and sidewalls with SPA-P-12.9. Drive-in supports are employed in soft or crushed rock formations. The driving depth of the advance supports should be at least 1.5 times the depth of the face per cycle. The use of this type of advance support has demonstrated excellent results in highly fractured cohesive masses. However, the spillage of crushed rock between the supports has been observed. In such conditions, advance supports and injection hardening of the rock mass are used. To increase rock mass stability during workings in very challenging mining and geological conditions, drill-injection anchors are used to inject polyurethane resin [23; 24; 25; 26; 27]. Organomineral and polyurethane resins, including Geoflex, Bevedol VFA-Bevedan, and Bevedol S-Bevedan, were tested to reinforce disturbed or unstable zones in the rock mass. A large number of options for stabilizing mine workings in unstable zones have been tested under mining conditions. While they ensure the stability and functionality of the workings according to their intended purpose, they significantly reduce the excavation speed and increase the cost of support.