Method for calculating the parameters of combined support for mine workings in an unstable rock mass

Abstract

Relevance. The study is driven by the fact that current regulatory documents do not provide adequate calculation methods for supporting development and preparatory mine workings in unstable rock masses of stability categories IV–V and within zones affected by stoping operations. This leads either to collapse risks due to insufficient support strength or to significant cost overruns due to unjustified over-reinforcement. Aim. To develop an improved, comprehensive methodology for calculating the parameters of a combined support system comprising rock bolting, shotcrete, and steel arch (SVP) support. The methodology should ensure structural reliability with a specified safety factor and optimize material costs. Methods. Key correlations were established based on the analysis of rock physico-mechanical properties and sclerometric data. The load calculation employed a brittle-fracturing medium model, while the influence of stoping operations was accounted for using 3D numerical modeling methods and GEP analysis to determine the stress concentration factor. The combined support calculation is performed in stages: first, rock mass strengthening from bolting is determined using empirical dependencies; then, the load is calculated; and finally, the parameters of the ground support (shotcrete, SVP arches) are selected using the finite element method. Results. The methodologyʼs effectiveness was demonstrated through calculations for 5 m and 6 m wide workings under various mining and geological conditions. It enables a well-founded selection of combined support parameters, ensuring its stability with a safety factor and optimizing support costs. Current limitations of the method are noted, related to the maximum cable bolt length (5 m) and the use of characteristics for B25 class concrete, which are planned to be addressed in future research.