土的统一硬化模型及其发展

土的统一硬化模型是以修正剑桥模型为理论基础,以采用统一硬化参数使其简明反映土的剪胀性、以采用变换应力方法使其合理反映土的三维特性为标志性特征,可针对不同类型土的特性,通过对统一硬化参数作适当调整,来建立与其相应的模型。统一硬化模型被发展为黏土和砂土的统一硬化模型、统一硬化超固结土模型、统一硬化K0超固结土模型、考虑砂土软化的模型、考虑土的材料各向异性的模型等十余种模型。这些模型能分别描述土的剪缩、剪胀、硬化、软化、超固结性、初始应力各向异性、材料各向异性、结构性、蠕变压缩和渐进状态等特性以及大应力条件下颗粒破碎和循环加载条件下土的变形特性等。

UNIFIED HARDENING MODEL FOR SOILS AND ITS DEVELOPMENT

Based on the Cam-clay model,the outstanding characteristics of the unified hardening model(UH model) are that the UH parameter is used to describe the stress dilatancy and the transformed stress tensors is used to exhibit the behaviour of clays in the three-dimensional stress space.The different models corresponding to the different soils are proposed modifying the hardening parameter appropriately.The UH model includes more than 10 models,which are the UH model for clays and sands,the UH model for overconsolidated clays,UH model for K_0 overconsolidated clays,the critical state model for sands dependent on stress and density,the model for soils with inherited anisotropy and so on.These models can describe the stress dilation/contraction,hardening/softening,overconsolidation,stress induced anisotropy,inherited anisotropy,creep,asymptotic state,rotational hardening,crushing under great stress and other characteristics of soils,respectively.