Abstract:

The distribution rules of stress and displacement of grade III surrounding rock during excavation of tunnels with circular crosssection, rectangular crosssection, straight wall and arch crosssection and curved wall crosssection are analyzed by FLAC3D software respectively. The tunnel with circular crosssection has the smallest displacement, stress concentration coefficient and plastic zone, while the tunnel with rectangular crosssection has the largest displacement, stress concentration coefficient and plastic zone. The point with maximal stress concentration coefficient has the farthest distance from working face of tunnel with circular crosssection, which means the support structure bears the minimal surrounding rock pressure. The numerical value of displacement, stress concentration coefficient and plastic zone for the tunnel with curved wall crosssection and straight wall and arch crosssection ranges between that of tunnel with circular crosssection and rectangular crosssection. So the circular crosssection and curved wall crosssection are practicable tunnel crosssection shapes, rectangular crosssection and straight wall arch crosssection are not.

Key words:  tunnel, crosssection shapedisplacementplastic zonestress concentrationFLAC3D