Design and analysis of tunnel cross-passage openings: 3D finite element analysis versus 3D shell-spring approach

摘要

Finite element analysis and shell-spring approach are two widely adopted methods to quantify the induced loads in a tunnel lining: for a typical sequential ring, without any openings. This study assesses the effectiveness of utilizing these methods to evaluate cross-passage opening-induced stress redistribution occurring in the segmental lining. For this purpose, member forces were derived using each method based on a case in Bangkok, Thailand, where two cross-passages were being constructed between a bored tunnel and a shaft. The analysis was followed by a comparative study to discuss the effectiveness of using each method in the design of cross-passages. According to the results, it was found that the predicted member forces from both models are in accordance with each other. Hence it was concluded that, for a similar case, one can use more simplistic 3D shell-spring models to examine the lining response rather than carrying out complex 3D finite element models. Furthermore, it was found that the presence of circumferential joints in tunnel lining significantly affects the load transfer mechanism between the opened ring and the adjacent fully enclosed ring. As opposed to the 3D finite element model, the ability to explicitly consider this effect in the calculation was one of the key advantages of conducting the 3D shell-spring model. Moreover, this study concludes that the design of a temporary support system can also be conducted relatively easily and precisely by the 3D shell-spring approach.