Abstract: This study elucidates the effects of rockbolt support in modern tunnel via a numerical simulation which based on a threedimensional nonlinear constitutive model. The constitutive model takes the mechanical behavior of intact rock, the orientations of joint sets, and the mechanical behavior of joint planes into account, and therefore is capable of describing complete stressstrain relationship and strength and deformability anisotropies of rock masses induced by joint sets. Numerical simulation results show that rockbolts increase the normal stress acting on joints in specific locations and thus enhance their shear strength, resulting in constraining shear displacement and dilation of the joints. The support effects of rockbolt on tunnel are then mobilized and elucidated qualitatively.

Key words: jointed rock masses, tunnel, support, rockbolt, joint shear displacement, dilation