## 2 Analysis of Ground Support Methods in Unstable Rock Conditions  
Unstable zones include rocks of stability categories IV-V within the mine mass, as well as areas of faults, tectonic disturbances, and metamorphosed rock formations. In category IV zones, combined support structures are predominantly used. These consist of anchors, metal mesh, and shotcrete or arched metal supports of a special SVP profile. The most commonly used anchors include reinforced concrete anchors, SPA (steel-polymer anchor) bolts, Swellex (hydraulic expansion anchors), and KRAs (wedge expansion anchors). The use of reinforced concrete anchors in mines with similar mining and geological conditions, despite their low cost and ease of installation, has revealed certain disadvantages. These include the necessity of using cement- and polymer-based fastening compositions, which can increase installation costs, the risks associated with anchor installation in unsupported areas, and the insufficient flexibility of the support design. This makes these anchors unsuitable for rock-prone deposits and for supporting unstable rocks as part of reinforced combined supports. The use of SPA and Swellex partially addresses the limitations of reinforced concrete in ground support, offering greater flexibility and efficiency under dynamic loading conditions. However, these anchors still require manual installation in unsupported areas, limiting their effectiveness in complex mining environments. Due to increased lateral pressure (resulting in sidewall collapse and floor heaving), steel-polymer anchoring measures were found to be insufficient. Issues such as anchors breaking, support tiles tearing from anchors, and rockfalls between anchors occurred. Additionally, rockfalls and the destruction of shotcrete support on the sides of the workings led to emergency situations, necessitating the bolting of the roof with metal mesh. KRAs, particularly near stopping operations and fixed workings, experience weakening and eventual loss of the locking part, resulting in rockfalls. Concrete supports are prone to cracking during production and operation for several reasons [17; 18; 19]. The primary factors include deformation in hardened concrete, which is mostly caused by tensile or bending loads, environmental exposure, and corrosion. Over time, the development of defects significantly affects the stress-strain state of structural elements. The aforementioned causes of concrete cracking can be mitigated, or their effects minimized, by using dispersed reinforced concrete. Several types of dispersed reinforced concrete are available, being classified mainly by the physical nature of the fibers used. These include steel fiber concrete (with metal fibers made from cold-drawn wires or sheet steel bent into zigzag shapes), glass fiber-reinforced concrete (fiberglass), synthetic fiber-reinforced concrete (polyethylene and polyester), carbon fiber-reinforced concrete (using carbon, aramid, or Kevlar), and fiber-reinforced concrete containing mixed fibers [20; 21; 22]. Despite the variety of dispersed reinforced concrete types used in construction, mixed fiber types play a leading role in preventing crack formation and reducing the rate of crack development. There are two approaches to addressing this issue: the first involves using fibers of the same type but different sizes, while the second involves combining two or more types of fibers, particularly a mixture of steel and synthetic fibers. The simultaneous use of fibers of varying lengths helps reduce the number of both micro- and macro cracks. Short fibers help minimize the formation of microcracks, preventing significant stress dislocations. Long fibers, which can reduce the workability of the concrete mixture, are needed to limit the formation of larger cracks under heavy loads. Importantly, the volume of long fibers should be smaller than that of short fibers.