The challenge of tool consumption prediction in TBM excavation: The micro-hardness approach

Wear and tool consumption in rock tunnel boring machine (TBM) significantly impact costs and downtimes. Understanding the factors that affect tool service life is crucial for optimising tool usage and maintenance. This practical understanding is not just theoretical, but it has real-world implications for the industry. For instance, the well-known and theorised dependence of the disc replacement on its position (centre, mid, periphery) on the TBM head can be explained simply by the different amounts of excavation work allocated to the different discs. This understanding can directly influence the design and operation of TBM machines. Apart from that, tool service life depends on the ‘sensitivity’ of the tool, which refers to the amount of metal loss tolerated without severe impairment of its efficiency. Lastly, service life depends jointly on the rock excavated and the metal employed to make the tools, which is the subject of this article. The research investigates these factors through a) a comprehensive literature review linking rock abrasivity theories with experimental studies, b) the presentation of real-life cases of TBM use in hydropower tunnel construction in Italy, and c) the analysis of real-world data on rock types, metal composition, tool consumption and machine performance. The primary objective of the present study is to identify correlations to develop a predictive model for tool durability, which will be validated using field data.