考虑组构演化的砂砾土弹塑性本构模型

Elastoplastic constitutive model of sand-gravel composites accounting for fabric evolution effects

考虑组构演化效应对于真实、准确地描述无黏性土在循环加载过程中的宏观力学行为具有重要意义。在砂砾土单调加载条件下构建的非线性剪胀方程的基础上,引入反映其循环荷载条件下剪胀阶段组构演化的剪胀内变量,基于广义塑性理论框架建立了反映砂砾土静力及液化全过程力学特性的弹塑性本构模型。对比考虑组构演化效应前后砂砾土液化变形、应力路径和超孔隙水压力发展规律,说明了组构演化效应对于模拟砂砾土液化响应的重要影响。通过开展一系列砂砾土静、动力大型三轴试验并结合相关文献试验结果对模型性能进行了验证。结果表明该模型总体上能够合理反映砂砾土在静力排水条件下应力-应变-体变特性以及在液化过程中超孔隙水压力的累积与消散、应力路径演化和液化变形发展情况,可为砂砾土工程数值模拟提供有力的本构工具。

Considering fabric evolution effects is crucial for accurately describing the macroscopic mechanical behavior of cohesionless soil under cyclic loading.Building upon the nonlinear dilatancy equation established for sand-gravel composites under monotonic loading,a fabric-dilatancy internal variable,which accounts for fabric evolution during the dilatancy stage under cyclic loading,is introduced.An elastoplastic constitutive model based on the generalized plasticity framework is proposed to capture the full range of mechanical behaviors of sand-gravel composites under both static and liquefaction conditions.By comparing the liquefaction deformation,stress paths,and excess pore water pressure development of sand-gravel composites before and after considering fabric evolution effects,the significance of fabric evolution effects in simulating the liquefaction response of sand-gravel composites is demonstrated.The model's performance is validated through a series of large-scale triaxial tests on sand-gravel composites under both static and dynamic loading conditions,as well as by comparing with test results from relevant literature.The results show that the model generally provides a reasonable representation of the stress-strain-volume behavior of sand-gravel composites under static drained conditions,as well as the accumulation and dissipation of excess pore water pressure,stress path evolution,and liquefaction deformation during liquefaction.This model can serve as a powerful tool for numerical simulation in sand-gravel composites engineering.