Evaluation Of The Structural And Waterproof Performance Of A Precast And Assembly Underpass Under Long-Term Surface Dynamic Loads

With the development of rapid underground construction, precast assembly underpass (PAU) has been used as an alternative way to replace the traditional cast-in-place underpass. However, only limited research was conducted to investigate the behaviour of longitudinal joints on the ultra-shallow buried structure under long-term surface dynamic loads. Although the underpass segments may not be damaged under dynamic loads, the unexpected deformation of longitudinal joints can lead to the safety risk of connecting bolts and waterproofing. This paper aims to evaluate the mechanical behaviour and waterproof performance of PAU under dynamic loads. Firstly, the full-scale numerical model was carried out, and a relative circumferential deformation index of longitudinal joints is proposed on the basis of the yield strength of connecting bolts. Then, a 1/10 scaled physical model test is designed to evaluate the long-term accumulative deformation by simplifying the ground surface vehicle loads into a simple cosine wave. Moreover, based on the results of the scaled model test, a relative radial deformation index is suggested by conducting the waterproof strip shear tests. The relative circumferential and radial deformation values at the longitudinal joints are recommended less than 15 and 30 mm, respectively, which is to satisfy the standards of both structural safety and waterproof. The results were also applied successfully to a tunnelling project.