基于细观唯象分析方法的细粒土本构模型研究

Aiming at a deficiency that the existing soil constitutive models by macroscopic phenomenological analysis difficultly and effectively distinguish the recoverable and unrecoverable constituent parts of soil deformation and then cannot reasonably reflect the stress dependence on soil macroscopic deformation behaviors, a more in-depth study on the constitutive model of fine-grained soils will be again carried out by adopting mesoscopic phenomenological analysis and has an important academic and engineered significance. For this purpose, through seizing a feature that the essence of stress dependence on the macroscopic deformation behaviors of fine-grained soils lies in that fine-grained soils under action of stresses had produced an unrecoverable deformation, a fine-grained soil is abstracted as a recombination of an ideal void material with a ideal compact granular material, thereby, a complex research problem about the fine-grained soil constitutive model is decomposed into several simpler problems as well as their coupling. Secondly, a mesoscopic physical-composition analysis model of fine-grained soils will be studied based on a general feature that the total deformation of fine-grained soils is composed of recoverable and unrecoverable constituent parts, and on this basis, the mesoscopic constitutive models of these two ideal materials and an analysis model for the macro-meso strain coupling relationship of fine-grained soils will be also discussed. Afterwards, through combining with another feature that the recoverable and unrecoverable deformation computed by these mesoscopic constitutive models can be distinctly and effectively distinguished, a new constitutive model of fine-grained soils will be established, which can more wholly describe the macroscopic deformation behaviors of fine-grained soils under complicated stress condition, in particular, can reasonably reflect their stress dependence, and its parameter determination method will be also proposed. Finally, its application method will be discussed.

针对目前基于宏观分析方法的土本构模型因难以有效区分可恢复与不可恢复变形而不能合理反映土宏观变形行为应力依赖性的不足，本项目采用细观唯象分析方法更深入研究细粒土本构模型，具有重要的理论与工程意义。为此，首先抓住细粒土宏观变形行为应力依赖性的本质在于应力作用下细粒土产生了不可恢复变形特点，拟将细粒土抽象为理想空隙材料和紧密土颗粒材料复合形成，将复杂问题分解为简单问题及其耦合进行研究；其次，依据细粒土总变形可视为可恢复和不可恢复变形两部分组成的普遍特征，探讨细粒土细观化物质构成分析模型，并在此基础上，探讨理想材料细观本构模型和细粒土宏细观应变耦合关系模型；然后，利用细观本构模型能有效区分可恢复和不可恢复变形的特点，建立出能全面描述复杂应力条件下尤其是具有应力依赖性的细粒土宏观变形行为的细粒土本构模型，并提出其参数确定方法；最后，探讨拟建模型的应用方法。

本项目依据土体宏观变形可划分为由不可恢复和弹性可恢复两部分变形组成的普遍特点，建立出了可区分不可恢复细观变形和可恢复弹性细观变形的土体宏观变形分析模型。并通过分别探讨细观理想空隙和孔隙骨架两部分材料的细观变形分析方法，建立出了土体侧限初始压缩解析模型，并提出了相应模型参数的确定方法。在此基础上，建立了土体侧限卸载回弹解析模型，进而得出了再压缩模型的初始孔隙比和压缩参数的确定方法，建立出土体侧限再压缩解析模型，它们能够充分反映应力路径和应力历史对土体变形的影响。最后，通过土的侧限压缩试验，并将试验曲线与本项目及现有同类理论模型曲线进行比较分析，表明了本项目模型的合理性。此外，将本项目建立的土的压缩过程分析模型应用于地基沉降计算的分层总和法中，对实际工程的地基基础沉降进行了分析，表明了本项目模型的实用性。同时，考虑细粒土的水力耦合特性，分别导出了全基质吸力下的土水特征曲线模型与流变固结模型。