考虑颗粒形态特征的各向异性砂土动力特性及本构模拟

As incompact granular materials, sandy soils are widely used in engineering constructions and their mechanical properties are very complex. The cyclic loading environments owing to traffic, waves, and earthquakes would induce excessive deformation or liquefaction failure of sand, and further inflict heavy casualties and property losses. An important part towards the understanding of anisotropic behavior of sand, which is profoundly influenced by the particle shape and grain size, is the development of experimental investigation and constitutive modeling of cyclic response that accounts for various stress paths. The challenges in the existing work are mainly attributable to that the particle microstructure and the related fabric anisotropy have not been fully concerned in the macroscopic analysis. This project begins with the macroscopic and microscopic mechanical characteristics of granular materials by using the advanced laboratory soil test, microstructure detection, and discrete element method simulations to investigate the cyclic behavior of sand under complex loading conditions. The impacts of particle form characteristics on the deformation, instability, and liquefaction of sandy soils have been addressed. Based on the experimental observations, a cyclic constitutive model is developed to address the particle form and fabric evolution of sand within the framework of anisotropic critical state theory. Through undertaking refined analysis of engineering problems, this research can be successfully applied to improve the liquefaction evaluation and dynamic stability analysis of engineering installation sites, and has great significance in scientific research and engineering application.

作为常见天然地基材料的砂土是一种松散颗粒材料，其工程力学特性十分复杂，在地震、波浪等动力荷载作用下易发生强度衰减、变形过大等灾变，造成人员伤亡和财产损失。砂土最典型的特性是各向异性力学行为，并受到颗粒形状和粒度特征的影响。开展复杂应力路径下砂土材料的液化、失稳等动力特性研究具有重要的学术价值和工程意义，但也面临诸多挑战，其根源在于传统研究忽视了砂土作为颗粒材料的离散特性，未能从细观尺度考虑颗粒形态特征及引起的初始各向异性改变对土体宏观力学行为的影响。本项目拟基于先进室内土工试验、细微观结构探测和离散元数值模拟等，从宏细观尺度系统揭示颗粒形态特征对各向异性砂土变形发展、液化失稳和动力破坏的影响，在各向异性临界状态理论框架下，构建能够描述颗粒形态效应的砂土动力本构模型。项目研究成果可改进复杂工况下场地砂土液化评价与变形计算方法，实现工程问题的精细化分析，具有重要的科学意义和工程应用价值。

作为一种松散颗粒材料，砂土工程力学特性十分复杂，在动力荷载作用下易发生强度衰减、变形过大等灾变，造成人员伤亡和财产损失。砂土最典型的特性是其各向异性力学行为，并受到颗粒粒度特征的影响。开展复杂应力路径下砂土材料的液化、失稳等动力特性研究具有重要的学术价值和工程意义，但面临诸多挑战。本项目开展了不同粒度砂土应力路径试验研究，在实现对室内静、动三轴试验的精细控制与优化分析的基础上，探究了材料组构各向异性和应力各向异性对砂土液化及动力破坏模式的影响，建立基于能量损耗的砂土孔压预测模型和抗液化能力评价方法。同时，本项目采用离散元模拟等细观力学方法研究了颗粒形态对砂性土各向异性力学行为的影响，探明静动力加载条件下材料组构演化规律及其与土体流动、液化等宏观力学响应的内在关联。进一步地，基于各向异性临界状态理论框架，本项目建立了能够描述材料内结构演化的各向异性砂土动力本构模型，实现了对砂土液化后大变形等复杂动力学行为的精确模拟。.项目取得的主要研究进展包括：揭示各向异性砂土在复杂应力路径下的液化特性与动力行为；阐明颗粒粒度特征对各向异性砂性土宏细观力学行为的作用特点；发展基于损耗能的动孔压预测模型并应用于场地砂土流动失稳与液化分析评价；建立各向异性砂土动力本构模型，进行砂性土典型液化破坏和动力变形计算分析。项目研究成果在国际主流期刊上发表7篇SCI收录论文；参加3次学术会议，与国内外同行交流科研成果；培养硕士研究生6名，其中2人已毕业。以上研究成果可揭示颗粒粒度特征对各向异性砂土宏细观力学行为的影响机制，改进复杂工况下砂性土液化评价与动力变形计算方法，具有重要的科学意义和工程应用价值。