To investigate rock breaking mechanisms induced by cutters of tunnel boring machine（TBM） under a biaxial state

TBM indentation tests were conducted on granite specimens using a triaxial testing platform.Then

detailed morphological measurement was carried out to analyze the morphology and volume of the fractured surface using a surface profilometer.It is found that the increase of differential stress results in the increase of consumed energies

the growth of groove volumes and the efficiency of indentation when the Sig

1

（i.e.

the smaller confining pressure） was fixed.The energy of indentations increases as the differential stress decreases

but the groove volumes are decreased

and thus the indentation efficiency is restrained b

y the decline of the differential stress when the Sig

2

（i.e.

the bigger confining pressure） was fixed.