Nonlinear Seismic Response Analysis of Two-dimensional Depositional Basins
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摘要: 沉积盆地对地震动具有明显的放大效应。利用ABAQUS软件及二次开发平台，编写了基于Davidenkov骨架曲线的VUMAT子程序，对饱和沉积盆地进行了非线性反应模拟。建立不同基岩面坡度的二维T型沉积盆地，输入4条不同频谱特性及幅值的近断层地震波，研究不同盆地基岩面坡度、饱和介质特性、地震波强度等因素对沉积盆地非线性反应规律的影响。研究结果表明，地震波作用可造成饱和沉积盆地发生局部液化，地震波强度越大，液化区分布范围越广，地表处出现了永久塑性变形；地震波强度的增大导致地表土层发生液化的时间提前，且下层土的液化会减弱地震波的传播速度，导致上层地表土发生液化的时间延后；盆地内地表最不利位置随着基岩面坡度的增大逐渐向中心处移动，不同工况下速度峰值放大系数为1.18～3.33。
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关键词:
- Davidenkov本构模型 /
- VUMAT /
- 二维非线性分析 /
- 近断层沉积盆地 /
- 场地反应
Abstract: Near fault seismic motion can lead to significant seismic disasters in the near field area, particularly in regions with sedimentary terrain, exacerbating the potential disaster. In this paper, ABAQUS software and secondary development platform are employed to compile VUMAT subroutine based on Davidenkov skeleton curve, to conduct nonlinear simulation of saturated sedimentary basin, and to establish two-dimensional T-shaped Sedimentary basin with different bedrock surface slopes. Four near fault Seismic wave with different spectral characteristics are selected to input the site with different amplitudes, and the nonlinear response of the site under the action of different basin slopes and seismic wave intensities is studied. It is found that seismic wave can cause liquefaction in saturated sedimentary basin. The greater the strength of seismic wave is, the wider the distribution range of liquefaction area is, and permanent plastic deformation occurs on the surface; The increase of seismic wave strength can lead to the advance of liquefaction time of surface soil layer, and the liquefaction of subsoil will weaken the propagation strength of Seismic wave, resulting in the delay of liquefaction time of upper surface soil layer.As the bedrock surface slope increases, the most vulnerable location on the basin's surface shifts toward the center. Furthermore, the amplification coefficient of peak velocity ranges from 1.18 to 3.33 under various working conditions. -
图 7 试验与仿真孔压时程曲线对比
Figure 7. Comparison of experimental and simulated pore pressure time-histories
图 10 基岩面坡度为30°时孔压比分布
Figure 10. Distribution of pore pressure ratio with the slope of the bedrock surface of 30°
图 11 基岩面坡度为45°时孔压比分布
Figure 11. Distribution map of pore pressure ratio with the slope of the bedrock surface of 45°
图 12 基岩面坡度为60°时孔压比分布
Figure 12. Distribution map of pore pressure ratio with the slope of the bedrock surface of 60°
图 13 测点水平向反应谱（集集WGK0.2 g，5%阻尼比）
Figure 13. Response spectrum of measurement points ①~⑦ in horizontal direction（Jiji WGK0.2 g, 5% damping ratio）
图 14 测点竖向加速度反应谱（集集WGK0.2 g，5%阻尼比）
Figure 14. Measurement points ①~⑦ vertical direction acceleration response spectrum (Jiji WGK0.2 g, 5% damping ratio)
表 1 场地模型参数
Table 1. Site model parameters
位置 层数 厚度/m S波波速/（m·s−1） 网格类型 密度/（kg·m−3） 弹性模量E/MPa 静泊松比$ \mathrm{\vartheta } $ 动泊松比$ {\mathrm{\vartheta }}_{\mathrm{d}} $ 盆地内 第1层 30 205.8 CPE4 R 2 120 231 0.444 0.49 第2层 40 300 1 800 453 0.4 — 第3层 30 400 1 900 851 0.4 — 盆地外 200 600 2 000 1 920 0.334 — 
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表 2 模型参数
Table 2. Model parameter
直径D/m 高度H/m 相对密度Dr 网格类型 单元数/个 天然孔隙比 初始有效围压/kPa 动剪应力比 0.0391 0.08 0.5 C3 D8 R 96 0.885 100 1.05
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表 3 子程序参数
Table 3. Subprogram parameters
$ \rho $/（kg·m−3） ${V}_{{\rm{s}}}$/（m·s−1） A/B $ {\mathrm{\vartheta }}_{\mathrm{d}} $/$ \mathrm{\vartheta } $ $ {\gamma }_{0} $ a C1/C2 m/n k/b 2 120 0.08 1.02/0.36 0.49/0.444 0.000 38 0.5 0.73/0.475 0.43/0.62 0.002 5/0.5
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表 4 仿真与试验对比
Table 4. Comparison between simulation and experiment
对比结果 试验 仿真 轴向应变峰/% 3.2 2.9 破坏时间/s 70 71.4
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