Lining Crack Patterns Corresponding with 3D Displacements for Rock Tunnels in Operation Revealed by Numerical Simulation

In this stage, the analysis of tunnels is based on the study of “stress-strain relationship around a hole in an elasto-plasticity media” and “closed convergence curve concept”. These theories of underground excavation are mostly proposed by European and American countries. Because of their old geological ages and high strength and excellent cement of rock mass, the tunnels there can be operated stably as long as the construction is fully completed. However, the tunnels constructed in Japan and Taiwan, are deformed to give some impacts to their operation, due to the young geological ages of Japan and Taiwan. Thus, the theories above cannot be fully applied in the cases in Taiwan, and how to keep the operation of tunnels stable becomes one important issue in tunnel engineering of Taiwan. In the tunnel, there are different kinds of defect can be observed on the lining, for the reason that there are various kinds of way to detect the tunnel. The most common issue in the operation of tunnels is how to deal with cracks on the linings. Since the patterns of cracks seem related to the relevant causes, it is generally viewed as an effective way to deal with the cracks for maintaining tunnels in operation by observing, recording and explaining the pattern and development of cracks. In this study, one finite element model with one tunnel and the surrounding rock mass is proposed to survey the relationship between the patterns of cracks and different conditions of displacements of lining induced by the movements of surrounding rock mass. Besides, the impacts of different cross-section geometry and length of tunnels, different number of construction joints and stiffness of surrounding rock mass to the development of cracks are investigated, and one case study is demonstrated. The results show that the different conditions of displacements of surrounding rock mass would induce distinct patterns of cracks of linings, and the crack patterns would not alter caused by different condition of tunnels. The case study also shows that the patterns and the positions of cracks on the model in this study are consistent with the in-situ record.