Midas GTS NX: Progressive Failure Due to Tunnel Misalignment

Osvaldo P. M. Vitali

Lyles School of Civil Engineering, Purdue University, West Lafayette, IN 47907, USA

Tarcisio B. Celestino

Sao Carlos School of Engineering, University of Sao Paulo, Sao Carlos, SP 13566, Brazil
Antonio Bobet

Lyles School of Civil Engineering, Purdue University, West Lafayette, IN 47907, USA

Abstract: "When the axis of the tunnel is not parallel to one of the far-field (geostatic) principal stresses, far-field axial shear stresses are present, which distort the tunnel in the axial direction and affect the stress paths of the ground near the face of the tunnel. The goal of the paper is to investigate the effects of tunnel misalignment with the far-field principal stresses on the progressive failure of the ground around the tunnel. A well-documented experimental tunnel in a massive granite rock mass is used as reference. 3D FEM modelling is conducted to back calculate the tunnel response and to assess the effects of the tunnel misalignment. The misaligned tunnel shows failure at locations not predicted when the tunnel is aligned with the intermediate principal stress. The numerical results suggest that the misalignment may lead to asymmetric spalling of the tunnel walls."