粗粒土的颗粒破碎规律与本构模拟研究

Granular soils, such as sands, gravels and rockfills are commonly used as construction materials in civil and hydraulic engineering. These materials often exhibit very complicated mechanical behaviour. When applied stress is raised over to a high level, particle breakage and crushing effects will become significant, which can cause a change in material deformation and strength properties. The proposed research will be focused on the particle crushing behaviour and constitutive modelling of granular soils in a wide stress range and engineering applications. Concerning the irreversibility of particle crushing induced deformation and material property change, a constitutive framework of mixed conventional plasticity-hypoplasticity will be developed. Laboratory tests and DEM numerical simulation will be conducted to reveal the mechanism and pattern of grain breakage and crushing in different stressing paths, to explore the relationship of the characteristic void ratios, the critical state line with the degree of grain crushing. Following that, a specific stress-strain relation, taking into account of the grain crushing effects, will be formulated and validated. Application of the model will be oriented to the analysis of grain crushing effects in high concrete-faced rockfill dams.

砂土、砂砾料、堆石料等粗粒土是土木、水利工程中的常用建筑材料，具有复杂的力学行为特征。这类材料在较高应力作用下，会出现显著的颗粒破损和破碎现象，使材料的变形和强度特性发生改变。本项目主要研究粗粒土在应力变化范围较大的情况下，颗粒破损破碎规律、颗粒破碎对材料基本特性和力学行为的影响，考虑破碎效应的土体本构模拟以及工程应用。将根据颗粒破碎引起不可逆变形和材料特性改变的特点，在亚塑性理论基础上提出一个新型的混合塑性模型框架。在本构理论的引领下，通过实验、DEM数值模拟和细观力学分析等手段，揭示不同加载应力路径下颗粒破碎的规律、颗粒破碎效应的形成机理，确定特征孔隙比、临界状态线、临界状态强度与颗粒破碎的关系，在此基础上建立一个能考虑颗粒破碎效应的粗粒土应力应变关系，并加以验证。进一步的应用研究将把本构模型用于分析高面板堆石坝中的颗粒破碎效应。

本项目的主要背景是岩土工程中粗颗粒在高应力或冲击荷载作用下会发生颗粒破碎现象，对粗粒土的工程力学特性有显著影响。项目组围绕这一问题开展了实验、数值仿真模拟以及理论研究，揭示了粗粒土在压缩条件下的颗粒破碎发展过程和级配演化规律，提出了一个与试样初始粒径分布相关的粗粒土破碎指标，阐明了粗粒土的压缩性与颗粒破碎的关系以及影响粗粒土破碎“屈服”的主要因素；在亚塑性理论框架中，通过引入由颗粒破碎诱发的塑性体积应变，建立了一个能体现颗粒破碎效应的亚塑性-常规塑性混合本构模型，可应用于堆石坝的变形分析；发展了光滑粒子数值分析方法，并自主开发了可应用与流体运动、固体大变形及流-固相互作用等问题的光滑粒子数值分析软件（SParSim）。