Longitudinal seismic response characteristics of seabed shield tunnels using submodeling analysis

Considering the spatial inhomogeneity and dynamic nonlinearity of seabed soil and longitudinal bolt connection at the seabed shield tunnel intersegments, a new approach coupling the generalized response displacement method and submodeling technique is proposed to analyze the longitudinal seismic response of long and large-scale seabed tunnels. The opening widths at the ring intersegments and the seismic stress distribution characteristics of segments under different bedrock motions are given. The results show that: (1) The modeling of the proposed new approach is simple, and it can reasonably consider the effects of dynamic interaction between soil and tunnel on the longitudinal seismic response of long and large-scale shield tunnels. The pressure-overclosure model and surface-based cohesive behavior are used to characterize the influences of the bolted intersegmental joints, which can reasonably describe the discontinuous deformation characteristics between adjacent ring segments. (2) The opening widths of intersegments are larger in the transition zone of soft and hard soils; under the same peak accelerations of bedrock motions, the opening widths of intersegments caused by Darfield seismic records with rich low frequency components are larger than those caused by Iwate seismic records with rich high frequency components, and the opening widths of intersegments at some local locations exceed the allowable limit of waterproofing for Darfield seismic records with the peak accelerations of 0.2g and 0.4g. (3) The seismic stress distribution of segments varies greatly under different bedrock motions. The seismic stresses of segments in the upheaval zone of bedrock and near the top of the ring segments are larger for Iwate seismic records, and those in the transition zone of soft and hard soils and near sandy soil lenses are larger for Darfield seismic records.