某越江综合管廊河谷场地液化流滑侧向扩展研究∗

液化引起河流阶地横向流滑会对长江下游的自然环境和建筑环境造成巨大破坏。然而，长江下游宽河谷场地尺寸达几千米，场地存在厚且松软的沉积层，土层分布极不均匀。土壤的非线性和千米级横向变形限制了该类场地数值模拟的可计算性。针对长江下游宽河谷场地地形的复杂性和地层的特殊性，并结合实际工程所在场地地质剖面，建立了长江下游宽河谷场地精细化模型。采用已建立的砂土液化大变形粘弹塑性本构模型和 ALE 方法， 解决了该类场地流滑大变形模拟困难。考虑地震波类型和强度的影响，分析了宽河谷微倾斜场地液化分布特征和侧向流滑规律。结果表明：微倾斜可液化场地坡底处土层的液化程度最为严重，微倾斜岸坡场地河床发生了明显的液化侧向扩展地震破坏，揭示了宽河谷微倾斜可液化岸坡场地侧向扩展的空间变位特征，上述原因主要是由于宽河谷不同位置处土单元应力状态差异性所造成；通过与场地液化侧向扩展震害等级评价标准进行对比，进一步明确了该长江下游宽河谷微倾斜岸坡场地液化流滑侧向扩展的震害特征及其程度。

Research on Liquefaction-induced Lateral Spreading in the Valley Site of the Utility Tunnel Crossing the Yangzi River

Liquefaction-induced lateral spreading on river terraces presents significant threats to the natural and built environments in the lower Yangtze River region. However, the extensive valley sites in the lower Yangtze River, spanning several kilometers, are characterized by thick, loose sediment layers with highly uneven distribution. The nonlinear behavior of soil and kilometer-scale lateral deformations pose challenges to numerical simulations of such sites. In this study, considering the complexity of the terrain and the specificity of the strata in wide valley sites of the lower Yangtze River, a refined model was developed based on geological profiles of actual engineering sites. Utilizing a sand liquefaction large deformation viscoelastic-plastic constitutive model and the ALE method, the study over-came the simulation challenges associated with large deformation flow sliding in these sites. Considering the influence of seismic wave types and intensities, the liquefaction distribution characteristics and lateral spread patterns of slightly inclined wide valley sites were analyzed. The results indicate that liquefaction was most severe at the base of the slope in slightly inclined liquefiable sites, and significant lateral spread seismic damage occurred in the riverbed of slightly inclined slope sites, revealing spatial displacement characteristics of lateral spread in slightly inclined liquefiable slope sites of wide valleys. This displacement is primarily attributed to variations in stress states of soil units across different positions within wide valleys. By comparing with evaluation criteria for liquefaction-induced lateral spread damage levels, the characteristics and extent of liquefaction-induced lateral spread damage in slightly inclined slope sites of wide valleys in the lower Yangtze River were further clarified.