Thin-layer method for dynamic impedance of isolated foundation with cushions and its parameter analysis
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摘要: 基于半无限弹性地基模型,引入薄层法,推导出层状地基中垫层隔震基础的动力阻抗解答,与黏弹性边界有限元模型进行对比,验证了方法的合理性。针对垫层隔震基础的水平和摇摆动力阻抗,开展了系统的参数分析。模型的计算结果表明:在0~10 Hz,垫层厚度、桩数对摇摆阻抗均有着明显的影响,垫层厚度越大,垫层隔震基础的摇摆阻抗越小;桩数越多,垫层隔震基础的摇摆阻抗越大。此外,相同条件下,桩长越大,垫层隔震基础摇摆阻抗实部越大;垫层剪切波速对基础的水平和摇摆阻抗都有着一定的影响。该方法可用于分析垫层隔震基础在地震荷载作用下的动力特性。Abstract: Based on the semi-infinite elastic foundation model, the dynamic impedance solution of the isolated foundation with cushions in layered soils is deduced by introducing the thin-layer method. The proposed method is verified by the viscoelastic boundary finite element model. A systematic parameter analysis is carried out for the horizontal and rocking dynamic impedances of the isolated foundation with cushions. The calculated results by the model show that within the range of 0~10 Hz, the thickness of the cushions and the number of piles have obvious effects on the rocking impedances: the greater the thickness of the cushions, the smaller the rocking impedance of the isolated foundation with cushions; the more the piles, the greater the rocking impedance of the isolated foundation with cushions. In addition, under the same conditions, the greater the pile length, the greater the real part of the swing impedance of the cushion isolation foundation. The shear wave velocity of the cushion has a certain influence on the horizontal and rocking impedances of the foundation. The proposed method is suitable for analyzing the dynamic characteristics of the isolated foundation with cushions under earthquake loads.
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表 1 3×3群桩基础数值模型参数
Table 1 Numerical model parameters of 3×3 pile groups
参数 量值 参数 量值 土体泊松比 0.4 桩泊松比 0.25 土体阻尼βs 0.05 桩阻尼βp 0.0 土桩弹性模量比(Es/Ep) 10-3 桩间距直径比(s/d) 5 土桩密度比(ρs/ρp) 0.7 桩长细比(L/d) 15 表 2 算例计算参数
Table 2 Parameters of example
参数 量值 参数 量值 土体密度 1800 kg/m3 桩泊松比 0.167 土体泊松比 0.4 剪切波速 150 m/s 土体阻尼比 0.05 桩密度 2500 kg/m3 桩弹性模量 25.5 GPa 表 3 模型参数
Table 3 Parameters of model
因素 量值 垫层厚度 0d, 1d, 2d, 4d 垫层剪切波速/(m·s-1) 150, 200, 250, 300 桩长 10d, 15d, 20d, 25d 桩数 2×2, 3×3, 4×4 -
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