海底盾构隧道纵向地震反应特征的子模型分析

Longitudinal seismic response characteristics of seabed shield tunnels using submodeling analysis

考虑海床土体的空间不均匀性、动力非线性特性和海底盾构隧道管环间纵向螺栓连接等因素,提出了基于子模型技术的长大隧道纵向地震反应广义反应位移法,研究了不同地震动作用下隧道管环间的张开量和地震应力分布特征。结果表明:①基于子模型技术的广义反应位移法建模简单,能合理地考虑土与隧道结构的动力相互作用效应对长大隧道结构纵向地震反应的影响;采用压力–过盈模型和黏结模型表征管环间纵向连接螺栓的作用,可较合理地描述相邻管环间的非连续变形特性。②隧道穿越软硬土层交界处的管环张开量较大;基岩峰值加速度相同时,低频发育的Darfield地震动作用引起的管环张开量明显较之高频发育的Iwate地震动作用时的大,且基岩峰值加速度为0.2g和0.4g的Darfield地震动作用下局部位置的管环间张开量超过防水允许限值。③不同频谱特性的基岩地震动作用下管环地震应力分布差异较大,Iwate地震动作用时基岩隆起区域靠近管环顶部处的地震应力较大;Darfield地震动作用时隧道穿越软硬土层交界处及砂土透镜体附近的管环地震应力较大。

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 0.2 g and 0.4 g.(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.