基于广义塑性理论的堆石料动力本构模型研究

分析了堆石料在等幅与不等幅应力循环荷载作用下的变形特性,以此为基础,确定了不同加载过程中堆石料的剪胀方程,加载方向,切线模量及塑性模量,建立了一个可以考虑堆石料循环加载特性的广义塑性本构模型.模型将所有的加卸载阶段都视为弹塑性过程,并在剪胀方程中引入老化函数来考虑体积应变积累对剪胀(缩)性的影响.模型共有12个参数,均可通过常规室内单调及循环加载试验确定.为验证模型的有效性,依据试验资料确定了两种不同堆石料的本构模型参数,并对等幅循环三轴压缩与不等幅循环三轴压缩试验进行了模拟.两种材料在不同围压下的模型预测结果与试验数据均吻合良好,表明模型可以有效地反映循环荷载作用下堆石料应力应变曲线的滞回特性与永久变形的积累.

Dynamic constitutive model for rockfill materials based on generalized plasticity theory

The stress-strain behaviors of typical rockfill materials under cyclic loading with constant and variable stress amplitudes are analyzed. The stress-dilatancy equations, loading directions, tangential modulus and the representations of plastic modulus are derived based on experimental observations, and a generalized plasticity model is proposed to simulate the dynamic behaviours of rockfill materials. The model treats all the loading-unloading-reloading phases as elastoplastic ones and captures the hardening effects (the influences of the accumulated volumetric strain on the dilatancy and the overall stress strain behaviour) during cyclic loading by incorporating an aging function into the stress-dilatancy equations. There are totally 12 parameters involved in the proposed model, all of which can be determined by the conventional monotonic and cyclic tests. To check the validity of the proposed model, the parameters of two rockfill materials are calibrated based on the experimental data, and the typical cycle triaxial compression tests with constant and variable stress amplitudes are modeled. Satisfactory agreement between the numerical and experimental results under different confining pressures confirms the capability of the proposed model in capturing the hysteretic stress-strain behaviours and the accumulation of permanent deformation under cyclic loading effectively.