<p>The excavation efficiency of TBM and the service life of disc cutters are significantly affected by hard rock geological conditions. Pre-cutting grooves on the rock using the abrasive air jet is a feasible auxiliary method for address this. However, the rock breakage mechanisms in TBM disc cutters cutting with abrasive air jet grooving and the effects of groove depth and spacing should be clarified. This study conducted the linear cutting experiments and the discrete element numerical simulation. The results indicated that with the introduction of grooves created by abrasive air jet, cracks tended to the bottom of grooves but are confined within its boundaries, a pronounced rock ridge with high middles and low sides was formed. When the groove spacing exceeded 95&#xa0;mm, the rock breakage only occurred between the disc cutters. As the groove depth increased, the angle between the cutter blade and the groove bottom decreased, promoted the transfer of stress and long cracks, and caused the larger fracture surfaces inclinations and higher rock ridge. As the groove spacing increased, the angle between the cutter blade and the groove bottom increased, which weakened the transfer of stress and thus inhibited the expansion of long cracks and the rock damage. Arranging the disc cutters along the radial direction of the cutter head can increase the critical spacing to about 115&#xa0;mm, resulting in increasing the installation spacing of the cutters and reducing the number of cutters. The research findings are of great significance for increasing the utilization rate of the cutter, and are conducive to promoting the engineering application of abrasive air jet grooving and TBM cutter rock breaking technology.</p> Graphical Abstract <p></p>