Hard Rock TBM performance: Preliminary study based on an exploratory tunnel in the Alps

Explorative tunnels are one of the best ways to assess the rock quality in the preliminary stage of a long tunnel excavation project: this strategy allows predictions for evaluating, with good accuracy methods, costs, and technical problems related to the excavation of the main tunnel. The paper presents the first results of a study carried out on a 6.5 m diameter exploratory tunnel excavated in hard rock by TBM. A study of the data taken during the TBM’s advancement is ongoing. The evaluation of the rock cutting effi-ciency, through the excavation specific energy (SE) is performed. A method for the evaluation of the grain size distribution of the muck produced during the excavation is proposed. The development of Matlab code to automatically analyze the machine acquired data in relation with the rock mass characteristics is reported in the paper.