可液化土层的位置对土层-地下结构地震反应的影响

为了研究不同位置的液化土层对地下结构地震反应的影响,采用PL-Fin土体液化本构模型,使用FLAC3D进行了研究,总结了液化土层发生液化大变形时刻液化区分布、孔隙水压力与超静孔隙水压力比变化规律及差异、地下结构的位移及差异沉降规律,并与非液化场地下的地下结构地震反应进行了对比.主要结论有:当结构底部存在液化土层时,引起的结构位移最大,使结构下沉;结构两侧的土体液化会引起结构上浮,并使侧墙水平向向层间位移和顶底板竖向层间位移增加;结构整体位于液化土层中时,土体位移、结构位移和结构层间位移差都不是最大值,仅研究结构整体位于液化土层的规律存在不足;结构周围、两侧、底部、底部45°位置、左右两侧和底部45°位置以及底部和底部45°位置存在液化土层(B+C)位置共计6种工况下结构顶板y向层间位移变化规律基本一致,但车站不同位置存在液化土层,土层液化的反应和对结构的影响存在一定差异;液化大变形发生在孔隙水压力和超孔压比突增后的1~3s后,因此可由孔隙水压力和超孔压比的突变判断是否发生液化大变形.

Research on Seismic Response of the Soil and Underground Structure Caused by Liquefiable Soil in Different Positions

In order to study the seismic response of underground structures when liquefied soil layer is located in different positions, the PL-Fin constitutive model proposed and developed in FLAC3D was used in this paper. The time when large deformation occurred, liquefied area distribution, the law and difference of pore water pressure and excess pore water pressure ratio, the law of the displacement characteristics, and differential settlement of structure were summarized. Their differences were also compared and analyzed when the structure is on non-liquefied soil layer. The primary conclusions are as follows: the displacement of structure was the largest when liquefied soil layer was under structure and caused the structure sink; the liquefied soil on both sides of the structure caused the structure float upward, and increased the displacement between the layers of side walls in the horizontal direction as well as between the roofs and floors in the vertical direction; the soil displacement and the displacement and differential settlement of structure were all not the largest when structure was all located over the liquefied soil, so it was not enough to only study the law when structure was embedded in liquefied soil; the law of the y-displacement of story drift on top plate was similar when the liquefied soil was located at six different positions including around the structure, on its two sides, in its bottom, in 45 degrees at the bottom of the location, on its two sides and 45 degrees at the bottom of the location, and in its bottom and 45 degrees at the bottom of the location, but the response of liquefied soil and the influence on the structure performance were different; and the large deformation caused by liquefaction occurred in 1 to 3 seconds after the jump of pore water pressure and the excess pore water pressure ratio, so their mutation can be considered as judgement on whether the large deformation occurred or not.