可液化地基-非规则截面地铁车站地震变形研究

Taking the metro underground station structure with an irregular cross-section, having five spans on the upper layer and three spans on the lower layer as a prototype, a shaking table test on the dynamic interaction between soil and metro underground structure was carried out under the condition of a liquefiable site. The test proposed a model foundation preparation method combining a flexible sensing chain and a water-sinking method, which is applicable to the shaking table model test of a liquefied foundation - underground structure. The horizontal deformation of the foundation was tested using an array of displacement meters; the development, dissipation and spatial distribution laws of pore pressure, the relationship between the seismic intensity and pore pressure, and the surface settlement and foundation deformation were analyzed. The results show that: the vibration pore pressure of saturated sand mainly completes the accumulation process during the earthquake process, and there is a significant correlation between the vibration pore pressure ratio and the Arias intensity of the ground motion; the existence of the underground structure under strong earthquake action changes the spatial distribution pattern of the foundation pore pressure; during the earthquake process of the model structure, a significant floating phenomenon occurred, and the floating not only occurred in the pore pressure accumulation section, but also an inertial floating effect still existed in the pore pressure dissipation section. With the expansion of the liquefied area and the increase in the liquefaction degree of saturated sand, the uneven settlement and inclination phenomena of the variable cross-section underground structure are significant, and the difference in the cross-section structure form should be considered in the anti-floating design of the underground structure.

以上层为五跨和下层为三跨的非规则截面地铁地下车站结构为原型,在可液化场地条件下进行土与地铁地下结构动力相互作用振动台试验。试验提出适用于液化地基-地下结构振动台模型试验的柔性传感链结合水沉法的模型地基制备方法,采用阵列式位移计测试了地基水平变形;分析了孔压发展、消散及空间分布规律,地震动强度与孔压关系,地表震陷与地基变形等。结果表明:饱和砂土振动孔压主要在地震过程中完成累积过程,振动孔压比与地震动Arias强度表现出显著的相关性;强震作用下地下结构存在改变了地基孔压空间分布模式;模型结构地震过程中出现了显著上浮现象,上浮不仅仅发生在孔压累积段,孔压消散段仍存在惯性上浮效应。随着液化区的扩展以及饱和砂土液化程度的增大,变截面地下结构不均匀沉降和倾斜现象显著,地下结构抗浮设计中应考虑截面结构形式差异性。