Abstract: During shield tunnelling in complex geological conditions, factors such as bedrock protrusions and un? identified boulders can adversely affect tunnelling conditions, resulting in severe cutter damage. Using the shielddriven running tunnelling between Guanren Station and Jimei Entrepreneurship Park Station of Xiamen Metro Line 6 as the engineering background, a 3D numerical model of disc cutters cutting the bedrock after blasting and grouting pretreatment was established to investigate the effects of blasting pretreatment on rock fragmentation mechanisms. The results indicate: (1) During shield tunnelling through the bedrock section after blasting pretreatment, no sudden increases in torque or thrust occurred, the shield attitude deviation remained stable, and the required grouting volume increased by approximately 20%. (2) Blasting and grouting pretreatment altered the rock fragmentation mechanism. Under the disc cutter’s compressive forces, the low-strength grouting materials experienced extensive damage and fragmentation along the periphery of the fractured bedrock. Compared with direct cutting of bedrock,the normal load decreased by approximately fivefold, and the tangential load decreased by approximately threefold.The CSM theoretical model validated the rationality of the simulation results. (3) Increases in the penetration and grouting material strength enhanced the interaction between the cutter and the fractured bedrock, significantly increasing cutting loads. It is recommended in practical engineering to control the penetration at approximately 5 mm and grouting material strength at around 5 MPa.