In-situ　stress　is　one　of　the　important　geological　factors　affecting　Tunnel　Boring　Machine　(TBM)　performance.　Meanwhile,　cutter　wear　is　also　a　nonnegligible　issue　in　TBM　tunneling.　In　this　work,　a　continuum-discontinuum　approach,　the　finite-discrete　element　method　(FDEM)　is　employed　to　explore　the　impact　of　confining　stress　on　rock　breaking　and　optimum　cutter　spacing.　Firstly,　the　evolution　of　system　kinetic　energy　and　rock　surface　displacement　during　confining　stress　equilibrium　is　revealed.　Then,　a　series　of　adjacent　cutter-indentation　tests　are　performed　to　analyze　the　rock　fracture　pattern　and　its　transformation　law,　cutter　force　and　the　vertical　extent　of　the　fracture　zone,　which　is　compared　with　the　existing　experimental　and　numerical　results.　Finally,　a　fragment　extraction　algorithm　is　adopted　to　count　fragment　shape　and　area,　and　the　specific　energy　(SE)　is　quantitatively　analyzed　according　to　fragment　area　and　cutter　work.　Besides,　the　cutter　force　and　cutting　performance　with　different　existing　wear　are　discussed.　Results　indicate　that　the　maximum　cutter　force　increases　and　the　vertical　crack　propagation　is　more　suppressed　as　confining　stress　increases.　Overall,　the　rock　fragment　area　increases　first　and　then　decreases　with　the　increase　of　cutter　spacing　under　all　confining　stresses,　while　the　optimum　cutter　spacing　increases　as　confining　stress　increases.　Moreover,　the　rock　breaking　efficiency　is　the　highest　with　a　confining　stress　of　3　MPa　and　a　cutter　spacing　of　114　mm.　The　existing　wear　increases　the　cutter　work　and　reduces　TBM　performance.　The　findings　are　helpful　in　the　design　of　TBM　cutterhead　in　tunnel　excavation　under　different　in-situ　stress　conditions.　©　2024　Elsevier　Ltd