【摘要】 开展了近、远场地震动作用下可液化场地上三拱立柱式地铁地下车站结构大型振动台模型试验。分析了模型地基的加速度、孔压、地表震陷及模型结构的加速度、应变。结果表明:模型地基的孔压累积经历了缓发展、急增长两个阶段;模型地基的加速度Arias强度释放时刻与孔压急增长阶段的起点时刻相对应,加速度Arias强度峰值较大的工况,模型地基孔压比峰值也较大;模型地基孔压场分布呈现出小震时模型结构底部液化程度较低、大震时场地底部液化程度较低的现象。强地震动作用下,模型结构发生了显著的上浮;模型地基、模型结构均表现出对低频相对发育的地震动反应更为强烈的现象。强震作用下,浅层可液化土在循环流动过程中发生了由于剪切刚度瞬态突增而导致峰值加速度瞬时急增的现象。模型结构中柱为此类型车站的最不利构件,附拱在与竖向成±(30°~60°)区域内应变反应较大,中庭上拱在45°位置处应变反应较大;随着模型结构拉应变幅值的增加,模型结构自振频率不断衰减。主观测面测点和次观测面测点的拉应变幅值均存在不同程度的差异,模型结构的应变反应存在空间效应。更多还原

【Abstract】 A series of large-scale shaking table experiments was conducted on three-arch type underground structure in liquefiable ground subjected to the near field earthquake and the far field earthquake. Experimental results are discussed in items of pore water pressure, earthquake-induced ground settlement, acceleration response of soil and structure and the deformation of model structure. The measured data substantiate that, the buildup of pore water pressure mainly experiences two stages, at the first stage, the pore water pressure increases slowly, at the second stage, the pore water pressure rises sharply. Good agreement is found between the development of pore water pressure and Arias intensity. A larger peak of Arias intensity corresponds a higher peak of pore water pressure ratio. The distribution of pore water pressure field implies a lower degree of liquefaction at the bottom of model structure as result of a low intensity earthquake; while for the high intensity earthquake, the lower degree of liquefaction occurs at the bottom of ground. Subjected to the high intensity earthquake, the model structure generates an upward movement relative to the foundation. Both model structure and model soil present intense response to the ground motion with low frequency, the peak acceleration of ground motion in shallower fine sand layer shows some ‘spikes’ during the shallower liquefied soil cyclic mobility. Moreover, the low frequency components appear more at the upper soil than deeper soil. For the structure, the strain response of center column is larger than that of subarch, and the strain recorded at atrium arch is the smallest. With the increase of tensile strain amplitude, the natural frequency of the model structure decreases. The tensile strain recorded at the primary observation plane is distinctly different from that at secondary observation plane, implying that remarkable spatial effects of model structure.更多还原