Numerical simulation of effect of joint dip angle on displacement around the tunnel

In the present study, we studied the displacement around the tunnel in a transversely isotropic rock mass with the scenario of tunneling direction parallel to joint strike. The effect of dip angle in tunneling on the displacement distribution around the tunnel was simulated by the three-dimensional (3D) bonded-particle discrete element method (PFC3D). The seven dip angles (β) of the joint covering the range of 0° to 90° with an interval of 15° were used. The numerical results showed that the dip angle had a significant effect on the distribution of the displacement zone and displacement magnitude around the tunnel. For small dip angles (i.e., β = 0°- 15°), the displacement zone at the crown was symmetric. For medium dip angles (i.e., β = 30°- 45°), the displacement zone extended significantly at the tunnel's crown. The extent of displacement zone was the largest. For high dip angles (i.e., β = 60°- 90°), the displacement at the crown is minimal and limited strongly by the joints. Four displacement field types represented the movement around the tunnel as: Tensile displacement field (Type-I); Shear displacement field in intact rock (Type-II); Shear and tensile displacement field (Type-III); Shear displacement along the joint (Type-IV).