基于精细化数值模拟的EPS轻质土宏细观变形机理研究

Macro-and meso-scopic deformation mechanisms of EPS-mixed soils based on refined numerical simulation

EPS轻质土是双固相组分(水泥土与EPS颗粒)、具有特殊细观结构的混合土。当前对其宏观力学特性研究较多,而对细观力学响应规律研究甚少。为此,分别在Mohr-Coulomb模型和Drucker-Prager模型框架内,基于水泥土和EPS材料试验结果规律总结,发展了二者的简单实用本构模型;基于水泥土和EPS材料界面剪切试验,总结了界面剪切硬化/软化规律;对EPS轻质土三轴剪切试验进行精细化数值模拟,再现了EPS轻质土宏观应力-应变响应规律和试样变形模式。基于精细化模拟分析发现,EPS轻质土的整体剪切、局部鼓胀、整体均匀3种宏观变形模式是细观力学响应的结果,EPS颗粒与水泥土两种材料力学特性的差异引起试样内部应力、应变的非均匀分布,EPS颗粒的非均匀排列强化应力、应变非均匀分布程度,两种因素共同决定试样宏观变形的非均匀性。

The EPS-mixed soils are composed of two solid phases(cemented soils and EPS beads)with the unique mesoscopic structure.The macroscopic behaviour of the EPS-mixed soils has been widely investigated so far,but the focus has seldom been put on the mesoscopic behaviour.In this study,following the frameworks of Mohr-Coulomb model and Drucker-Prager model respectively,the constitutive descriptions of the cemented soils and the EPS materials are developed based on their mechanical test results.Besides,the strain hardening/softening laws of the cemented soil-EPS material interface are summarized based on the interface shear tests.The refined numerical simulations of triaxial shear tests on the EPS-mixed soils are carried out,with which the macroscopic stress-strain behavior and deformation modes of the EPS-mixed soil specimens are replicated.The refined numerical simulations reveal that the three types of deformation modes of the specimens(shear banding,local lateral expansion,overall uniform deformation)can be attributed to the non-uniform mesoscopic mechanical responses.The distinct mechanical behavior of the cemented soils and the EPS materials is the origin of non-uniform stress and strain distributions,and such non-uniformity is enhanced by the non-uniform spatial distribution of the EPS beads.The two factors collaboratively determine the non-uniformity of the macroscopic deformation observed for the EPS-mixed soil specimen.