Searching for new points of economic efficiency in the implementation of modern tunnelling machines in the context of the digital transformation of underground construction

Abstract

The unit cost of mine roadway driving is conventionally assessed through two parameters – the capital cost of the machine and the face advance rate – while the remaining operating cost contours stay on the periphery of the calculation. The digital transformation of underground construction shifts the sources of efficiency gains beyond this classical frame, yet appraisal methods lag behind the shift, and the effect of introducing modern tunnelling machines is systematically underestimated. The aim of the work was to localise the cost contours in which the efficiency gain concentrates during the transition to digital machine complexes. On an author’s computational model of an underground site, a factor decomposition of the change in unit driving cost was carried out by the chain substitution method and supplemented by a scenario analysis of the project net present value. The calculation showed an 18,8% reduction in unit driving cost alongside a rise in the capital component; about 85% of the gross saving per linear metre is formed by the labour and unplanned-downtime contours, whereas the contribution of advance speed proved partly absorbed by the higher machine cost. More than half of the annual economic effect falls on the reduction of ore losses and dilution, that is, on the extraction quality contour lying outside the speed–capital field. The localisation of the effect in the labour, downtime and quality contours means that digital transformation reconfigures the cost structure of driving rather than merely accelerating the face, and therefore a correct appraisal of its result requires shifting the focus from advance indicators to the full operating cost structure.