In　tunnel　construction　by　tunnel　boring　machine　(TBM),　the　excavation　efficiency　is　highly　related　to　cutter　spacing.　Due　to　the　inhomogeneous,　discontinuous　and　anisotropic　characteristics　in　rocks,　there　are　limitations　to　study　rock　fragmentation　process　by　using　numerical　simulation.　The　purpose　of　in-situ　penetration　tests　is　to　optimize　the　operational　parameters　for　a　specific　TBM,　thus　this　kind　of　tests　cannot　consider　the　effect　of　different　cutter　spacings　on　rock　breaking　process.　The　full-scale　cutting　experiment　can　minimize　the　size　effect　by　using　a　large　rock　sample　and　the　cutter　spacing　is　able　to　be　adjusted　during　the　experiment,　therefore　the　full-scale　cutting　experiment　has　been　widely　used　in　recent　years.　In　order　to　study　the　influence　of　different　cutter　spacings　on　excavation　efficiency　by　TBM　cutter,　the　mechanical　rock　fragmentation　experimental　platform　of　Beijing　University　of　Technology　is　used　to　conduct　a　series　of　rock　cutting　tests　with　five　sets　of　cutter　spacings.　In　these　tests,　the　diameter　of　the　disc　cutter　with　a　constant　cross　section　is　432　mm.　The　size　of　test　granite　rock　sample　is　1000　mm　×　1000　mm　×　600　mm,　taken　from　Beishan,　Gansu　Province　of　China.　During　the　experiments,　the　three　dimensional　forces　acting　on　the　rolling　cutter　are　recorded,　and　the　rock　chips　collected　after　each　cutting　pass　are　weighed　respectively.　The　impact　of　cutter　spacing　on　excavation　efficiency　is　analyzed　by　use　of　the　obtained　average　normal　force,　average　rolling　force　and　specific　energy.　The　results　show　that　when　penetration　is　small,　the　cutter　spacing　has　no　obvious　effect　on　the　average　normal　force　and　rolling　force.　However,　with　the　increasing　penetration,　the　cutter　spacing　has　significant　impact　on　both　the　average　normal　force　and　the　rolling　force.　For　all　of　the　cutter　spacings　arranged　in　the　tests,　the　increase　in　penetration　will　produce　more　rock　chips　but　not　always　improve　the　efficiency　of　rock　fragmentation　at　the　same　time.　For　Beishan　intact　granite,　when　the　ratio　of　spacing　to　penetration　is　around　30,　the　specific　energy　reaches　the　minimum　value,　which　means　that　the　highest　rock　fragmentation　efficiency　can　be　expected　under　this　condition.　©,　2014,　Yantu　Gongcheng　Xuebao/Chinese　Journal　of　Geotechnical　Engineering.　All　right　reserved.