3D numerical simulation of a large span double-arch tunnel construction

This paper presents a numerical simulation of double-arch tunnel excavation process by means of elasto-plastic finite element method. To perform a fully 3D numerical analysis of the whole excavating and supporting process, a FEM model including the surrounding rock and supporting structure was developed, and the whole process is divided into 20 construction steps according to the actual construction sequence. The results were satisfactory and were reasonably close to the displacement data monitored in the construction field. In the second part of the article, the redistribution of stress in shotcrete, lining and anchor against each excavation step was studied to understand the interaction between rock and the supporting structure. Furthermore, the load pattern in surrounding rock and the supporting structure were studied to analyze the influence of excavation in adjacent tunnel and find out the reasonable distance between adjacent excavation surfaces. The results obtained provide a better understanding of excavation process of double-arch tunnel, and is helpful for guiding design and construction.