可液化场地下盾构扩挖地铁车站结构地震破坏机制振动台试验

发布时间：2018-07-17 06:47

【摘要】：开展近远场水平地震动作用下可液化地层中盾构扩挖地铁车站结构振动台试验,分析模型地基土层的侧向变形、孔压比、加速度、宏观现象和动土压力以及结构的加速度、应变等物理量。研究结果表明,可液化模型地基在激振时经历先震密而后上浮的物理过程,震后有明显的喷砂冒水现象;地基土层侧向发生的是剪切型变形,其左摆与右摆过程中的峰值位移出现明显的不对称现象;小震时,模型地基中的加速度放大系数从下部到表层逐渐增大,中震及大震时,表现出先减小后增大的趋势;地震波沿模型地基向上传播的过程中,出现明显的高频滤波、低频放大的现象;可液化地基的孔压在地震作用下经历"急增长、慢消散"的变化过程;地下结构的存在对其周围地基孔隙水压力的增长(砂土液化)有明显的抑制作用。随着输入地震动强度的增加,动土压力明显增大,地下结构上、下方的土压力差值是结构发生液化上浮的内因,结构本身在强震过程中逐渐从弹性状态向弹塑性转化;液化场地条件下的结构侧方动土压力有随着埋置深度的增加而增加的趋势;可液化场地条件下盾构扩挖地铁车站结构的地震破坏机制是:中柱率先发生剪压破坏,而后是隧道开口部位与拱肩破坏,随后是侧墙与顶板的连接部位受拉破坏,最终形成机构而发生倒塌。
[Abstract]:The shaking table test of shield tunneling subway station structure in liquefiable stratum under the action of horizontal ground motion near far field is carried out. The lateral deformation, pore pressure ratio, acceleration, macroscopic phenomenon, dynamic earth pressure and acceleration of the model foundation soil layer are analyzed. Strain, etc. The results show that the liquefiable model foundation experienced the physical process of first shock density and then floatation, and there was obvious phenomenon of sand blasting and water rising after the earthquake, and the lateral deformation of the foundation soil layer was shear type. The peak displacement of the left pendulum and the right pendulum is asymmetrical obviously, the acceleration magnification coefficient in the model foundation increases gradually from the lower part to the surface layer during the small earthquake, and decreases first and then increases with the moderate earthquake and the large earthquake. In the process of seismic wave propagating upward along the model foundation, the phenomenon of high frequency filtering and low frequency amplification appears, and the pore pressure of liquefiable foundation goes through the process of "rapid growth, slow dissipation" under earthquake action. The existence of underground structure can inhibit the increase of pore water pressure (sand liquefaction). With the increase of the intensity of the input ground motion, the dynamic earth pressure increases obviously. The difference of the earth pressure under the underground structure is the internal cause of the liquefaction and floating of the structure, and the structure itself gradually changes from elastic state to elastic-plastic state during the strong earthquake. Under liquefaction site condition, the lateral dynamic earth pressure of the structure increases with the increase of buried depth, and the seismic failure mechanism of shield expanded excavated subway station structure under liquefiable site condition is as follows: the first shear compression failure occurs in the middle column, Then the opening of the tunnel and the arch shoulder are destroyed, and then the connection between the side wall and the roof is damaged by tension, and finally the mechanism collapses.
【作者单位】：北京工业大学城市与工程安全减灾省部共建教育部重点实验室;北京城市交通协同创新中心;中国建筑工程总公司技术中心;
【基金】：国家自然科学基金资助项目(41572276,41272337) 北京市教育委员会科技计划重点项目(KZ200910005009)~~
【分类号】：TU93;U231

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