基于阻尼的地震循环荷载作用下黏土非线性模型

Nonlinear model based on damping ratio for clays under seismic loading

提出一种基于阻尼比的黏土动应力应变模型,通过在滞回曲线中显示地引入代表阻尼比大小的形状系数,使得理论滞回曲线真实地反应土体的滞回阻尼性能。首先推导在等幅对称荷载下滞回曲线的理论方程。然后,为将该模型应用于随机地震荷载的情况,对扩展的曼辛不规则加卸载准则进行了改造,提出当沿小圈加载时,滞回曲线奔向曾经到达过的最大加卸载点。最后,介绍对一种粉质黏土进行的等幅循环荷载和不规则荷载作用下的循环单剪试验。试验结果表明,模型能够较好地模拟土在地震循环荷载作用下的滞回特性。

A dynamic stress-strain model based on the damping ratio of clays is proposed. Importing of the shape coefficient, which represents the soil＇s damping ratio, into the hysteretic loop curve function, makes that the theoretical hysteretic stress-strain loop reflect the actual damping characteristics of the soil. The theoretical functions of the hysteretic loops under symmetrical constant amplitude loading are deduced first. Theri for the usage of the hysteretic loop model based on damping ratio under seismic loading, the rebuilding of the expanded Masing＇s rules is discussed. It is proposed that when the loading or unloading path is on the so-called ＂small loops＂, the loop curve points to the maximum or minimum loading point ever reached in the history. Finally, a cyclic simple shear testing of silt clay is introduced, under both constant amplitude loadings and irregular loadings. The test results indicate that the proposed model can simulate the hysteretic behavior of soils well.