Rock exfoliation in the unstable formations during underground mine working driving and selection of efficient adhesive compositions for strengthening

Purpose is to identify factors favouring rock exfoliation in roof of underground mine workings while operating Akbakay deposit and determine optimum structure of adhesive reagents for the rock strengthening taking into consideration mineralogical composition of the formation. Methods. The research was carried out in a lab environment. Chemical and ultimate composition of the rock mass samples was determined through x-ray diffraction method; the x-ray phase identification approach helped define their mineralogical composition. The optimum composition of adhesive reagents has been determined based upon the ambient temperature and hardening time. Viscosity durability of the adhesive compounds was assessed using a technique of uniaxial crack of the immovable samples. Statistical data processing involved determination of the required number of the samples to achieve the preset accuracy degree. Findings. Exfoliation of the fragments of both fractured and unstable rocks from Akbakai deposit depends upon availabi-lity of such chemically and mechanically unstable salts as dolomite, albite, and mirror stone. Epoxide reagent in 9 to 1 ratio with polyethylenepolyamine catalyzer has been identified as the most effective adhesive compound. Epoxy adhesives have demonstrated higher cohesive resistance to compare with polyurethane analogues, and better compliance with requirements as for viscosity and hardening time. Originality. Use of epoxy to strengthen both fissured and unstable rocks of Akbakai deposit containing mineral salts, helps increase tensile properties up to three times. Moreover, epoxies also demonstrate high adhesive characteristics; and they are resistant to moisture and temperature attacks being typical for mine environment. New logarithmic dependencies have been identified describing rock mass stability while applying the modified polyurethane with polyethylenepolyamine catalyzer in 9 to 1 ratio. Practical implications. Various types of reagents have been considered for safe and effective strengthening of underground mine workings in the fractured rock masses having a tendency to caving. The proposed adhesive reagents resist efficiently the external share loads and stresses increasing structural stability and safety of rock masses.