Geological and mechanical rock mass conditions for TBM performance prediction. The case of “La Maddalena” exploratory tunnel, Chiomonte (Italy)

The Tunnel Boring Machine (TBM) performance prediction is fundamental both to select the most effective tunnel construction methods and to estimate the condition of excavation, in terms of time and economic costs of the infrastructure. Many researchers have developed several empirical and theoretical models, mainly based on the comparison between geological-geotechnical rock masses characteristics and TBM data. However, these models are specific-site and hardly applicable to different contexts. The aim of this work is to carry out easy models utilizable during early stage of tunnel planning and realization; for this purpose singular rock mass parameters (Uniaxial Compressive Strength, quartz content, spacing between fractures, etc.) have been related to TBM performance indices, as the Rate of Penetration (ROP) and the Field Penetration Index (FPI). In particular, this study focuses on “La Maddalena” exploratory tunnel (Tunnel Euroalpin Lyon-Turin), situated in northern Italy, where geological, geotechnical and TBM performance data have been continuously collected during tunnel construction.