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In-situ ground motion parameters test for silty clay and back analysis of model parameters
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摘要: 为解决目前现场原位地震动参数较难获取的问题，自行研发了土体地震动参数原位试验测试系统，该系统包括可移动系统、荷载伺服系统、动力反应系统和数据采集系统四部分，利用该系统对南京某工程场地进行了土的现场非线性剪切模量试验，得到了粉质黏土的现场非线性剪切模量G-logγ曲线和G/Gmax-logγ曲线，发现当剪应变γ超过0. 1%时，动剪切模量G减小的速度愈来愈快，反映了土在动荷载作用下非线性及应变累积性的特点。此外，基于Martin-Davidenkov模型，采用遗传算法对现场试验结果进行了反演分析，得到了该试验地区较浅土层内的模型参数取值范围。Abstract: In order to solve the problem that in-situ ground motion parameters are difficult to obtain, the in-situ ground motion parameters test system, which includes a mobile system, a load servo system, a dynamic response system, and a data acquisition system and has a wide range of applications, strong controllability and high reliability, was developed to carry out the test of field nonlinear shear modulus of silty clay in Nanjing and obtain the field G-logγ curve and G/Gmax-logγ curve. It is found that when the γ exceeds 0.1%, the G decreases faster and faster, reflecting the nonlinearity and strain accumulation of soil under dynamic loading. In addition, the back analysis of model parameters by genetic algorithm was conducted based on the Martin-Davidenkov model to get the range of model parameters in the shallow soil layer of the test area.
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Key words:
- ground motion parameters /
- in-situ test /
- shear modulus /
- back analysis /
- seismic safety evaluation
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图 2 桩基础和传感器布置（单位：mm，S代表检波器）
Figure 2. The layout of pile foundation and sensor (unit: mm)
图 6 S1-S2土层目标函数值与迭代次数的关系曲线
Figure 6. Objective function values with iterations in S1-S2
图 7 S3-S4土层目标函数值与迭代次数的关系曲线
Figure 7. Objective function values with iterations in S3-S4
表 1 现场测试的加载方案
Table 1. Field loading plan
序号 静荷载/kN 动荷载/kN 序号 静荷载/kN 动荷载/kN 1 10 0.8 11 18 0.8 2 10 1.0 12 18 2.7 3 10 1.6 13 18 5.4 4 10 2.0 14 18 6.5 5 10 2.7 15 18 8.0 6 10 3.2 16 18 11.0 7 10 3.8 17 36 0.8 8 10 4.4 18 36 5.4 9 10 4.9 19 36 16.3 10 10 5.4 20 36 27.2 
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表 2 两土层G/Gmax-γ模型参数及目标函数值
Table 2. G/Gmax-γ model parameters and objective function values in two soil layers
埋深/m A B γ0/10−4 min f 1-2 1.150 1 0.609 5 68.589 7 0.0431 2-3 1.075 0 0.502 4 68.668 8 0.0433 3-4 1.053 4 0.534 2 68.613 5 0.0310 4-5 1.047 7 0.578 6 68.592 2 0.0432
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