Joint induced anisotropic deformation and supporting effects of rockbolts for tunnels excavated in regularly jointed rock masses

Based on a three-dimensional non-linear constitutive model, this study investigates the anisotropic deformation of a tunnel excavated in jointed rock masses and associate supporting effects of rockbolts. Using a numerical model capable of describing the influence of mechanical behavior of intact rock, the spatial configuration of joint sets, and mechanical behavior of the joint plane on the non-linear behavior of a rock mass, this manuscript reveals the joint-induced anisotropy in failure zone and deformation surrounding a tunnel. The support effects of a rockbolt are generally limited. However, when the rockbolt is pre-stressed and acts perpendicular to a joint plane, the shear displacement and associated dilation of the plane is constrained. And the joint sliding failure caused by tunnel excavation can be reduced. The rockbolt provides a beaming effect. Such an effect is significant in locations where the joint planes parallel to tunnel wall and influenced by the numbers of joint sets and joint strength.