3-D numerical analysis of large subsoil liquefaction distortion influence resulted from earthquake on bridge pile foundation
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摘要: 为研究地震地基液化大变形对桥梁桩基的危害性, 建立了含液化层的二层与三层土体系计算模型, 考虑桩土共同作用的非线性关系, 利用FLAC-3D有限差分软件对液化侧扩地基中的单桩、群桩进行了动力有限差分分析, 探讨了地基液化大变形条件下桩基位移与内力变化分布规律。分析结果表明: 二层与三层土体中, 液化土层和非液化土层交界面处产生的桩身弯矩极值是控制桩身破坏的关键因素, 液化土层本身对桩身弯矩的影响很小; 桩帽对桩顶的侧移有一定制约作用, 但对桩身弯矩极值的影响不显著; 群桩中上坡桩与下坡桩的侧向位移与桩身弯矩分布模式相似, 但上坡桩发生的侧向位移和桩身弯矩要略大于下坡桩情况。Abstract: In order to study large subsoil liquefaction distortion influence resulted from earthquake on bridge pile foundation, typical computation models in two and three soil layers were set up, the interaction nonlinearity relation between pile and soil was analyzed, the dynamic finite difference analysis of single pile and group piles was carried out by using FLAC-3D, and the characteristics of displacement and inner force of pile foundation were studied in detail. Analysis result shows that the bending moment extremum at the interface between liquefaction layer and non-liquefaction layer controls the failure of pile in the two and three soil layers, liquefaction layer has little effect on the bending moment of pile; the pile cap limits pile lateral displacement to a certain extent, and has little effect on its bending moment extremum; according to group piles, the lateral displacement and the bending moment distribution of upgrade pile are similar to that of downgrade pile, but the values of upgrade pile are larger.
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表 1 土体参数
Table 1. Soil parameters
土层种类 体积模量K/MPa 剪切模量G/MPa 粘聚力C/kPa 内摩擦角φ/(°) 密度ρ/(kg·m-3) 非液化土 26.70 16.00 15 24 2 000 可液化土 6.70 4.00 — 30 1 880 
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表 2 桩体参数
Table 2. Pile parameters
体积模量K/MPa 剪切模量G/MPa 弹性模量E/GPa 泊松比μ 桩径d/m 内摩擦角φ/(°) 密度ρ/(kg·m-3) 15.02 12.85 21.0 0.20 1.0 24 2 500
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表 3 桩土相互作用参数
Table 3. Interaction parameters between pile and soil
作用方向 连接弹簧刚度/GPa 连接弹簧粘聚力/GPa 连接弹簧摩擦角/(°) 剪切 130 10 30 法向 130 10 30
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