The brittle failure induced by high in-site stress occurring at the tunnel face significantly affect the TBM performance. To study the rock mass failure mechanism under the combined effect of high stress and TBM cutters, three groups of true-triaxial rockburst tests were conducted, simulating the failure processes using the loading scheme “one-single face free and the remaining five surfaces loaded”. Conditioned granite specimens previously cut by the TBM cutter were prepared, and the different stressed conditions were determined based on the in-situ stress field of the Yinhan water conveyance tunnel. As the confining stress increased, the peak strength of the rock specimen also increased, and the final rupture was more violent, leading to a rockburst. The failure process recorded by the high-speed camera and the failure pattern showed a clear change. The rock conditioned by the TBM cutter was more susceptible to brittle failure under high stress, and the failure depth was greater. The stress-strain curves in the σ1 direction and the AE characteristics indicated that as the loading stress increased, the damage in the rock changed from a dominant tensile failure to a dominant shear failure, gradually extending to deeper areas of the rock. This alteration changed the rock mass mechanical behavior of the tunnel face, i.e., its stability and boreability, consequently influencing the rock breakage process by TBM cutters. As the severity of failure increased, the TBM performance shifted from a low efficiency rock-breaking performance limited by the cutter thrust to a high efficiency rock-breaking performance limited by the muck capacity and safety control.