摘要
本文采用在粉质粘土中掺入水泥和冰粒的方法，人工制备成结构性粘土，对其进行了较为深入的试验研究。包括等向压缩试验、等球应力剪切试验，不同应变速率下的三轴CD和CU试验，以及等围压循环剪切和等球应力循环剪切等试验。着重探讨了结构性和粘滞性、固结压力和排水条件以及应力路径等对结构性土变形特性和力学特性的影响，并结合重塑土作了平行对比试验研究。在此基础上，建议了2个用于描述结构性粘土在单调荷载作用下各向异性的粘弹塑性损伤模型：参照时间面粘弹塑性损伤模型及参照时间线粘弹塑性损伤模型；以及2个用于描述结构性土在复杂荷载作用下各向异性的弹塑性损伤模型：边界面砌块体弹塑性损伤模型和次塑性扰动状态弹塑性损伤模型。所建立的模型可以通过简单应力路径下的试验测定模型参数。其中，按照传统的方法把粘滞变形和瞬时塑性变形(包括损伤变形)分开来建立参照时间面粘弹塑性损伤模型；而在建立参照时间线粘弹塑性损伤模型时则认为粘滞性存在于变形的任一时刻，不再人为地把粘滞变形和瞬时塑性变形(包括损伤变形)分开，而是作为一个整体来建模。把滑移屈服面看作为等向硬化和旋转硬化的边界面，从而合理地把砌块体模型从单调荷载推广到复杂荷载情况，建立了边界面砌块体模型；通过定义与应力偏转角相关的归一化应力比η，反映结构性土在复杂荷载作用下塑性模量场各向异性的变形特性，包括卸荷剪缩特性，基于扰动状态概念和次塑性理论，建立了次塑性扰动状态模型。通过与试验结果相比较，验证了上述模型的合理性。重点检验了次塑性扰动状态模型对几种典型复杂应力路径例如应力路径偏转、旋转剪切、主应力轴旋转等的数值模拟能力。
为了使建议的模型能够用于实际问题，本文导出了可用于有限元数值计算的参照时间线粘弹塑性损伤模型的粘弹塑性损伤矩阵，以及次塑性扰动状态模型的弹塑性损伤矩阵，并分别给出了耦合求解比奥静力和动力固结方程的数值解法。对于静力问题，针对芬兰一个国际竞赛试验堤进行了数值分析并与实测数据作了较好的比较，分析了结构性、粘滞性和固结特性的耦合作用。对于动力问题，采用异步交叉
迭代显式有限元解法，对典型的地基算例进行了固液耦合的有限元动力弹塑性反应
分析，结果定性符合土力学的一般规律。
最后，利用流体动力学理论和动力有限元方法对一爆震问题的离心机模型试验
进行了数值分析并与实测数据作了较好的比较，得出了一些有益的结论。
In this paper, cement and ice are mixed with silty clay in freezing room to make artificial structured soil samples for a series of tests, including isotropic compression, constant-sphere-stress triaxial compression, drained and undrained triaxial compression at several strain rates, and cyclic triaxial compression under constant confining pressure and constant sphere stress. The influence of structure, viscosity, consolidation pressure, drainage condition and stress path, on the mechanic and deformation characteristic of structured soil is studied. The same study is conducted parallely on remoulded soil for comparision. Based on experimental investigation, two anisotropic elastic visco-plastic damaging (EVPD) models-reference time surface model and reference time line model, are proposed for simulation of time-dependent deformation of structured soil under monotonic loading. Two anisotropic elasto-plastic and damaging(EPD) models梑ounding surface masonry model and hypoplasticity disturbed state concept(DSC)
model, are presented for simulation of deformation of structured soil under complex loading. These four models' parameters can be determined conveniently by tests with simple stress path. The reference time surface EVPD model is developed traditionally, seperating viscous deformation from instant plastic deformation (including damaging deformation); while in the reference time line EVPD model, it is considered that viscous deformation occurs at any stage of loading, so the viscous deformation and instant plastic deformation (including damaging deformation) are not seperated but modelled as a whole. In the bounding surface masonry model, the sliding yield surface is considered as isotropic hardening and rotating hardening bounding surface, and the masonry model is expanded from monotonic loading to complex loading. In the hypoplasticity DSC model, the scalar normalized stress ratio r| is defined relevant to stress turning angle, and based on disturbed state concept and hypoplasticity theory, the anisotropic p
lastic modulus is derived to describe the deformation
characteristic of structured soil under complex loading, including unloading extraction. The validity of the four models has been verified through the comparison between predicted results and the experimental data under monotonic and complex loading. In addition, the capability of the hypoplasticity DSC model is emphaticly studied to simulate complex loading such as stress path turning, rotating shear, rotation of the axis of principal stress, etc.
In order to make the proposed models applicable to practice, the matrix of the reference time line EVPD model and hypoplasticity DSC model are derived for FEM numerical analysis. The decoupling solution methods for static and dynamic Biot consolidation equation are proposed. For the static problem, EVPD FEM analysis is performed for a test embankment in an international competition in Finland. The computed results are compared with measured data, and the coupling effect of structure, viscosity and consolidation is discussed. For dynamic problem, the unsimultaneous staggered iteration FEM method with explicit central difference scheme is used for the elasto-plastic analysis of the dynamic response of a soil foundation. The computed results show good agreement with soil mechanic knowledge.
At last, fluid dynamic mechanics theory and wave propagation dynamic FEM method are used to analysize a blast centrifuge model test, and the computed results agree well with the measured data. Some useful conclusions are drawn from the analysis.
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