常吸力下非饱和土水-力耦合循环塑性的模拟

Simulation of hydro-mechanical coupling cyclic plasticity of unsaturated soils under constant suction condition

为描述非饱和黏性土在静、动态荷载作用下的应力-应变特征及水-力耦合效应,在塑性增量流动理论的框架内建立一个描述常吸力条件下非饱和黏性土水-力耦合效应的弹塑性双面模型.基于BBM(Barcelona basic model)及Li和Meissner提出的一种塑性硬化准则,并考虑非饱和土的典型土水特征,通过边界面和加载面在应力空间中的演化表征非饱和土在循环荷载作用下的应力-应变特征及水-力耦合效应.考虑不同初始饱和度、初始孔隙比、吸力、净围压和动应力幅值等因素影响,采用相关研究者室内各向等压和静、动态三轴试验结果对所建模型进行验证,模拟结果与试验数据的对比显示模型具有良好的模拟能力.此外,为检验模型的合理性,在室内试验的基础上采用该模型预测非饱和土在循环荷载下的一些典型水-力耦合行为.结果表明,模型能够较好地模拟和预测非饱和黏性土在常吸力静态和循环动态加载作用下的水-力耦合特性.

To investigate the stress-strain characteristics and hydro-mechanical coupling behaviors of unsaturated cohesive soils under static and cyclic loading,an elastoplastic two-surface model for describing the hydro-mechanical coupling behaviors of unsaturated cohesive soils under constant matric suction was established in the framework of plastic incremental flow theory.Considering the typical soil-water characteristics of unsaturated soils,based on the Barcelona basic model(BBM)and the plastic hardening rule suggested by Li and Meissner,the stress-strain characteristics and hydro-mechanical coupling behaviors of unsaturated cohesive soils under cyclic loading were described through the evolution of bounding surface and loading surface in stress space.Taking into account of the influences of initial degree of saturation,initial pore ratio,matric suction,net confining pressure,and dynamic stress amplitude,the model was verified by utilizing the previous research results of isotropic compression and static and cyclic triaxial tests.Comparisons between simulation results and experimental data show that the proposed model performed well in simulation.In addition,in order to examine the rationality of the model,several typical hydro-mechanical coupling behaviors of unsaturated soils under cyclic loading were predicted based on the test data.Results show that the proposed model could properly simulate and predict the hydro-mechanical coupling behaviors of unsaturated cohesive soils under static and cyclic loading with constant suction.