论文部分内容阅读
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。
Shaking table test of metro station structure with shield expansion in liquefiable stratum under horizontal ground motion is carried out. Lateral deformation, pore pressure ratio, acceleration, macroscopic phenomena and earth pressure and acceleration of structure are analyzed. Strain and other physical quantities. The results show that the liquefiable model foundation undergoes a physical process of first compacting and then floating when it is excited, and there is obvious sandblasting and water-taking phenomenon after the earthquake; lateral deformation of the foundation soil occurs by shear deformation, In the small earthquakes, the magnification of acceleration in the model foundation gradually increases from the lower part to the surface and shows the tendency of first decreasing and then increasing when the earthquakes and the large earthquakes occur. The phenomenon of high frequency filtering and low frequency amplification appears when the seismic waves propagate upward along the foundation of the model. The pore pressure of the liquefiable ground undergoes the process of “rapid growth and slow dissipation” under the action of earthquake. The existence of underground structures The pore water pressure around the growth of the ground (sand liquefaction) have a significant inhibitory effect. With the increase of earthquake input intensity, the earth pressure increases obviously. The difference of earth pressure above and below the subsurface structure is the internal cause of structural liquefaction. The structure itself gradually transforms from elastic state to elasto-plasticity during strong earthquakes. The earth moving pressure under the site conditions tends to increase with the depth of embedment. The earthquake damage mechanism of the metro station structure under shield liquefiable conditions under liquefiable conditions is that shear failure occurs first in the center column and then The opening of the tunnel and the shoulder of the arch are destroyed, and then the connecting parts of the side wall and the roof are damaged by the pull and eventually form a mechanism and collapses.