自由场边界效应对港珠澳大桥工程人工岛地震反应的影响

发布时间：2018-09-12 08:51

【摘要】：以港珠澳大桥工程西人工岛为研究对象,首先针对自由场分析模型讨论了自由场边界效应对场地地震反应的影响。在此基础上,采用闫静茹建立的人工岛数值模型,分析了自由场边界效应对人工岛场地的地震反应的影响,进而对比分析了在水平单向输入、水平双向输入和三向输入地震动时,人工岛的三维非线性地震反应。主要工作和成果如下:1.对比分析了自由场边界效应对人工岛下卧层自由场及人工岛场地的动力反应的影响,发现考虑自由场边界效应后,自由场地及人工岛场地沿地表观测线的峰值加速度会偏大,沿深度方向峰值加速度呈现逐渐增大的趋势,而不考虑自由场边界效应时,自由场地基人工岛场地沿深度方向峰值加速度出现先增大后减小的现象,这与实际情况是不相符的。修筑人工岛后,人工岛地表的峰值加速度小于相应的自由场地情况,其傅氏谱值也小于自由场地,因此人工岛的加固效应使场地的振动能量减小了。同时发现,软土场地会过滤掉大部分高频成分,仅保留低频成分,并且对低频地震动放大效应要较为明显一些。2.对比分析了不同工况下,自由场边界效应对人工岛场地的峰值位移及震陷的影响,发现自由场边界效应对人工岛场地水平X向影响不明显,但对Z向峰值位移分布规律影响较大。考虑自由场边界效应时,人工岛场地的水平峰值位移会偏大。自由场边界效应对人工岛场地的震陷分布影响较大。并且,考虑自由场边界效应后场地的震陷量会偏大。3.考虑自由场边界效应后,桩墙产生最大应力的位置与不考虑自由场边界效应时基本一致,都是出现在桩墙椭圆柱长轴两端曲率较大的位置,并且,考虑自由场边界效应后,桩墙的最大应力值会偏大,这种效应对水平双向输入时尤其明显。三种工况下,自由场边界效应对桩墙X向峰值位移影响较大。其中,考虑自由场边界效应后,桩墙沿桩身深度方向,X向的位移变化较小;不考虑自由场边界效应时,桩墙沿桩身深度方向,X向的位移变化较大。同时发现,桩墙沿短轴方向整体变形较大,易失稳,应加强人工岛的护坡设置,保证人工岛的稳定性。
[Abstract]:Taking the west artificial island of Hongkong-Zhuhai-Macao Bridge as the research object, the influence of the free field boundary effect on the site seismic response is discussed for the free field analysis model. On this basis, using the artificial island numerical model established by Yan Jinru, the effect of free field boundary effect on seismic response of artificial island site is analyzed, and then the horizontal one-way input is compared and analyzed. Three-dimensional nonlinear seismic response of artificial islands under horizontal and three-direction input ground motion. The main work and results are as follows: 1. The effect of free field boundary effect on the dynamic response of free field and artificial island site is analyzed. It is found that when the free field boundary effect is considered, the peak acceleration of free field and artificial island site along the observation line will be larger. The peak acceleration increases gradually along the depth direction, but without considering the free field boundary effect, the peak acceleration of the artificial island site increases first and then decreases along the depth direction, which is inconsistent with the actual situation. After the artificial island is built, the peak acceleration of the artificial island surface is less than the corresponding free site, and its Fourier spectrum is also smaller than the free site, so the reinforcement effect of the artificial island reduces the vibration energy of the site. At the same time, it is found that the soft soil site will filter out most of the high-frequency components and retain only the low-frequency components, and the amplification effect of low-frequency ground motion will be more obvious. The effects of free field boundary effect on the peak displacement and earthquake subsidence of artificial island site under different working conditions are analyzed. It is found that the free field boundary effect has no obvious effect on the horizontal X direction of artificial island site. But it has a great influence on the distribution of Z-direction peak displacement. Considering the boundary effect of free field, the horizontal peak displacement of artificial island site will be larger. The free field boundary effect has great influence on the seismic subsidence distribution of artificial island site. Moreover, considering the boundary effect of free field, the seismic subsidence of the site will be larger. 3. Considering the free field boundary effect, the position of the maximum stress of the pile wall is basically the same as that of the pile wall without considering the free field boundary effect. Both of them appear in the position with large curvature at both ends of the elliptic column of the pile wall, and the free field boundary effect is taken into account. The maximum stress value of the pile wall is larger than that of the pile wall. This effect is especially obvious for the horizontal and bidirectional input. Under three conditions, the free field boundary effect has a great effect on the X-direction peak displacement of pile wall. Considering the free field boundary effect, the displacement of pile wall along the depth direction of pile body is smaller, and the displacement of pile wall along the depth direction of pile body is larger than that of pile wall with the consideration of free field boundary effect. At the same time, it is found that the pile wall has a large deformation along the short axis and is prone to instability, so the slope protection of artificial island should be strengthened to ensure the stability of artificial island.
【学位授予单位】：北京工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU311.3;P756.8

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