Abstract: The traditional rock-breaking mode of mechanical-rock interaction can no meet the requirement of large improvement of tunneling efficiency of TBM. Innovative rock-breaking technology and its rock-breaking mechanism have gradually been paid more and more attention. On the premise of not changing the main structure of TBM, the penetration test using TBM constant cross-section hob indenter has been carried out on rock samples with three different lithology under lateral constraint conditions. The influence of pre-cutting groove on rock-breaking mode of mechanical cutter are studied. The results show that: (1) Pre-cutting groove can reduce the normal load of indenter when the rock sample is broken, and the normal load of the rock sample with pre-cutting groove is reduced by 44.13%-53.05% compared with that without groove. The lower the uniaxial compressive strength of the rock is, the larger the reduction ratio of normal load will be. (2) There is a critical value for the influence of pre-cutting groove depth on the normal load when the rock sample is broken. Beyond this critical value, the influence of pre-cutting groove depth on the failure behavior of the rock sample is weakened. Based on the above investigations, a new combined rock-breaking mode of pre-cutting groove and mechanical cutter is proposed, and an innovative rock breaking technology that can realize pre-cutting groove is discussed. The combined rock-breaking mode can break through the bottleneck of rock-breaking efficiency and is of great significance for TBM equipment upgrading and major engineering project construction.

Key words: pre-cutting, TBM mechanical cutter, rock-breaking mode, rock-breaking technology, combined rock breaking