Comparison of characteristics of excavation process and characteristics of acoustic signal in TBM excavation

Excavation of various underground structures, such as tunnels, caverns and linear mining structures using the tunnel boring machines (TBMs) has become an ultimate technology in underground construction in recent decades. Construction of TBMs has been improved over the years and still is being refined by introducing novel progressive materials. Technological processes of excavation have passed through many changes as well. The research teams at the Institute of Geotechnics, Slovak Academy of Sciences in Kosice have investigated the issues of optimization of TBM´s performance. The outcomes confirmed existence of a pair of regime parameters values, where the specific cutting energy achieves the minimum value. Further experiments with accessory vibro-acoustic signal that accompanies the rock cutting process showed that the vibro-acoustic signal contains the information on the interaction between the cutting tool and the rock. Acoustic signal was recorded during the full-face excavation of the exploratory adit for Branisko tunnel. The signal was evaluated in relation to the regime parameters, i.e. thrust force and revolutions of the TBM´s cutterhead.