交通荷载作用下土体黏弹塑性疲劳本构模型

路基工后沉降是路基填土在车辆动荷载及其自重作用下发生蠕变引起的,因此研究土体在交通荷载作用下的蠕变特性对预测路基工后沉降有较大意义。为利用流变力学理论成果,将车辆动荷载和路基土自重荷载简化的组合荷载做等效处理。基于分数阶微积分构建分数阶黏壶,将分数阶黏壶替换西原模型黏塑性体中常值黏性元件,即得到一种土体黏弹塑性疲劳本构模型。当组合荷载上限应力大于土体临界动应力时,模型为分数阶西原模型,可反映土体破坏型疲劳变形规律;反之,则为反映土体稳定型疲劳变形规律的广义Kelvin模型。结果表明:该模型能较好地描述交通荷载作用下土体疲劳变形特性,对试验数据拟合的相关系数在0.91以上。

Visco-elastic-plastic Fatigue Constitutive Model for Soil under Traffic Loading

The post settlement of subgrade is caused by subgrade creep under self-weight and vehicle dynamic loading,and it is of great significance to study soil creep properties under traffic loading for subgrade settlement prediction. Based on the theoretical achievements of rheological mechanics,the combined loading simplified by vehicle dynamic loading and self-weight loading of subgrade soil is processed equivalently. A fractional-order dashpot based on fractional calculus is constructed,constant dashpot in the visco-plastic body of nishihara 's model is replaced with fractional-order dashpot,a visco-elastic-plastic fatigue constitutive model for soil under traffic loading is obtained by doing so.When the upper stress of combined loading is larger than critical dynamic stress of soil, the model is fractional-order nishihara 's model,which can reflect the destructive deformation law of soil; otherwise,it is a generalized Kelvin model,which can reflect stable deformation law of soil. Results show that this model can better reflect the creep behavior of soil under traffic loading and its fitted correlation coefficient of test data is above 0. 91.