Longitudinal seismic response of shield tunnel: A multi-scale numerical analysis

Developing a rational and efficient numerical model to analyze the longitudinal earthquake response of shield tunnel has become a hot topic in the field of underground structure seismic research in recent years. Based on the idea of scale coupling, this study proposed a multi-scale numerical model that can capture the dynamic response of ring joint in the vulnerable part of shield tunnel precisely. In this multi-scale model, the non-focused part of structure is described by the Timoshenko beam & nonlinear spring, while the focused part is described by the three-dimensional "refined ring joint". The multi-scale model is subsequently utilized to calculate the longitudinal seismic response of the shield tunnel through a typical site with a soft-hard stratum junction. In addition, the influence of earthquake wave parameters on the seismic response of the tunnel structure is also discussed in this study. Some inspiring conclusions are as follows. The dynamic response of the shield tunnel rises dramatically near the soft-hard stratum interface because of the non-uniform deformation of the soil in that area. Strong earthquake waves (with high PGA or PGV) may cause nonlinear increase in the opening deformation of a ring joint and the yielding of several joint bolts. Under high intensity seismic load, the service state of joint bolts varies widely, and the damage is concentrated in one region of the ring joint.