Rock mass properties and TBM performance in the Central Gneiss unit of the Brenner Base Exploratory Tunnel (Italy)

Rock mass characteristics, including uniaxial compressive strength and quartz content of the intact rock material, as well as the number, spacing, and orientation of joints, play a pivotal role in the performance of tunnel boring machines (TBMs). Various researchers have proposed TBM performance prediction models that have gained widespread acceptance in the literature and have been extensively utilised over the years. This study aims to analyse data collected from the hard rock TBM excavation of the Northern Italian stretch of the Brenner Base Exploratory Tunnel within the Central Gneiss unit. To this end, statistical analyses were conducted to explore relationships between intact rock and rock mass properties and the actual TBM data recorded during the excavation. Furthermore, the study compared penetration rates derived from performance prediction models based on rock and rock mass properties with actual penetration data, highlighting the extent to which the models align with real observations.