Constitutive models for geomaterials considering induced anisotropy and density of soils and their application, to bearing capacity problems of foundation under various loading conditions

在前人基于tij概念的模型的基础上，提出了新的砂土和粘土的各向同性硬化和随动硬化弹塑性模型，分别命名为次加载tij模型和运动次加载tij模型。这些模型适当地考虑了密度和围压对土体变形和强度的影响。此外，在随动硬化模型中考虑了应力诱导各向异性。利用砂土的三轴压缩和拉伸试验、真三轴试验、平面应变试验和空心圆柱试验资料对模型的有效性进行了检验。所建模型的预测结果能较好地模拟砂土的应力应变特性和强度特性，包括破坏后的应变软化。这些模型的材料参数数量较少，不受密度和围压的影响。因此，本模型适用于 关于我们 本文介绍了地基材料在变形过程中密度发生变化的岩土工程问题，并将本构模型应用到有限元程序中，分析了浅基础承载力等岩土工程问题。分析了浅基础在偏心荷载、倾斜荷载、复合荷载和集中荷载作用下的性状。利用自行研制的可施加多种荷载的试验装置，进行了相应的浅基础模型试验。尽管模型试验的应力水平很低，但在各种加载条件下，试验结果与分析结果之间有很好的定性一致性。也就是说，承载力的尺度效应、荷载沉降曲线、基础的竖向和水平位移（包括旋转）等。结果表明，适当考虑岩土材料典型力学特性的有限单元法能给出符合实际的岩土工程问题的解，是岩土工程实际设计的有力工具。少

New isotropic hardening and kinematic hardening elastoplastic models for sand and clay, which are named subloading tij-model and kinematic subloading tij-model respectively, are developed, referring to the previous models based on tij concept. In these models, the influence of density and confining pressure on the deformation and strength of soils are properly considered. Furthermore, Stress induced anisotropy is taken into account in the kinematic hardening model. The validity of proposed models is checked using the experimental data of triaxial compression and extension tests, true triaxial tests, plane strain tests and hollow cylinder tests on sand and clay. The results predicted by the proposed models can simulate well the stress-strain behavior and strength of sand and clay including strain softening after failure. The material parameters of these models are small in number and are not influenced by the density and confining pressure. Therefore the present models are applicable to … More the geotechnical problems in which the density of the ground materials is changed during their deformation.The constitutive models are implemented into the finite element program and applied to the analyzes of some geotechnical problems such as bearing capacity problems of shallow foundations. The behavior of shallow foundation under eccentric load, inclined loading combined loading as well as concentric loading is analyzed. The corresponding model tests of shallow foundation are also carried out with a new developed device that can impose various kinds of loads. Even though the stress levels of model tests are very low, there are good qualitative agreements between the tests results and the analytical results under various loading conditions? I.e., scale effect of bearing capacity, load settlements curves, vertical and horizontal movements of the foundation including its rotation and others. It is shown that the finite element method in which typical mechanical characteristics of geomaterial are properly taken into consideration can give realistic solutions of geotechnical problems and is a powerful tool for the practical design of geotechnics. Less