3D numerical simulation of reinforced concrete lining's cracking behavior in tunnels

Longitudinal cracks in actual tunnel linings are 3D semi-embedded. The fracture properties of lining are influenced by numerous factors, such as steel bar, fracture geometry, and boundary conditions. A 3D numerical model for analyzing the cracking behavior of reinforced concrete lining was proposed in this study. This model was used to investigate the fracture characteristics of 3D semi-embedded cracks on reinforced concrete lining in mountain tunnels. The approximation formula for stress intensity factors (SIFs) of the crack tip in reinforced concrete tunnel lining was deduced. Moreover, the numerical models of 3D semi-embedded and 2D edge cracks were constructed on the basis of the finite element method. The outcomes of the 2D and 3D models were compared via case study. The effects of tensile reinforcement ratio, position of reinforcing bars, and the relative height and angle of the cracks on SIF were discussed. Results demonstrate that the SIF of 3D semi-embedded cracks is less than 50% of that of 2D edge cracks. The SIF of the crack tip decreases significantly after considering the effect of steel bars, and it is negatively related to the tensile reinforcement ratio and longitudinal propagation of lining crack prior to vertical propagation. This study serves as a reference for designing secondary linings in tunnels. © 2019 School of Science, IHU.