饱和重塑黄土动力反应的数值模拟
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摘要
将具有粉质黏性的马兰黄土重塑后制成饱和试样,进行了一系列的固结不排水动三轴剪切试验,得到不同动应力幅值下的应力应变曲线.以双曲线型骨干曲线为基础,以动态骨干曲线假设为条件,推导了复杂动荷载下用轴向动应力应变表示的卸载、再加载曲线方程.从应力应变曲线和能量消耗两方面对固结不排水动三轴试验进行了数值模拟分析,并与试验结果进行比较,结果表明:当动应力幅值与固结围压之比在一定范围内时,两者的阻尼比接近;当动应力幅值较大时,两者的卸载曲线较为一致.提出的数值方法能较好地模拟重塑饱和马兰黄土的固结不排水动力反应,可为马兰黄土地区的土动力反应分析提供参考.
Saturated soil specimens made of remolded silty clay(malan loess) were tested by undrained dynamic triaxial tests.The stress-strain curves with individual dynamic stress amplitudes were plotted.Based on the hyperbolic backbone curve hypothesis and dynamic backbone curve hypothesis,the equation of unloading and reloading curve was deduced and then the dynamic response of specimens was calculated.The calculated hysteretic loop and dissipated energy were compared with the tests.It is found that the calculated damping ratios agree with the tests as the ratio of dynamic stress amplitude to confining pressure is limited within a certain range,and the calculated unloading curves match test results well under larger dynamic stress.
Saturated soil specimens made of remolded silty clay(malan loess) were tested by undrained dynamic triaxial tests.The stress-strain curves with individual dynamic stress amplitudes were plotted.Based on the hyperbolic backbone curve hypothesis and dynamic backbone curve hypothesis,the equation of unloading and reloading curve was deduced and then the dynamic response of specimens was calculated.The calculated hysteretic loop and dissipated energy were compared with the tests.It is found that the calculated damping ratios agree with the tests as the ratio of dynamic stress amplitude to confining pressure is limited within a certain range,and the calculated unloading curves match test results well under larger dynamic stress.
引文
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[2]IDRISS I M,SEED H B.Seismic response of horizon-tal soil layers[J].Journal of the Soil Mechanics andFoundations Division,ASCE,1968,94(SM4):1003-1031.
[3]刘祖典.黄土力学与工程[M].西安:陕西科学技术出版社,1997.
[4]王兰民.黄土动力学[M].北京:地震出版社,2003.
[5]HARDIN B O,DMEVICH V P.Shear modulus anddamping in soils:measurement and parameter effects[J].Journal of the Soil Mechanics and FoundationsDivision,ASCE,1972,98(SM6):603-624.
[6]李小军,廖振鹏,张克绪.考虑阻尼拟合的动态骨架曲线函数式[J].地震工程与工程振动,1994,14(1):30-35.LI Xiaojun,LIAO Zhenpeng,ZHANG Kexu.A func-tional formula of dynamic skeleton curve taking ac-count of damping effect[J].Earthquake Engineeringand Engineering Vibration,1994,14(1):30-35.
[7]谢定义.土动力学[M].西安:西安交通大学出版社,1988.
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