复杂应力状态下湿陷性黄土水理性及强度特性研究与应用

There are a wide range of special soils in China. Among them, Collapsible loess’ stress-strain appearance can be easily affected by engineering construction, which may result in geological disasters in loess area. It’s significant for the safety of engineering construction to study the water retention capacity and strength behaviors of unsaturated loess under complex stress condition. This project focuses on loess in west of China, explores the moisture state and its migration law of typical loess ground based on massive field and laboratory experiment, twin shear unified strength theory and unsaturated soil theory. By studying the influence of pore structure on water retention capacity from the angle of mesoscopic, the influence law of soil’s moisture state affected by meso-structure and its failure mechanism. The moisture state of loess can be described on mesoscopic scale by SEM and discrete element analysis. Thus the measurement and evaluation system of pore distribution law can be proposed. The unified strength theory of unsaturated soil can be established rely on twin shear unified strength theory. The calculation method of earth pressure under seepage is proposed, which takes intermediate principal stress into consideration. The relationship between strength of loess and its moisture state is revealed and a nonlinear unified damage constitutive model is established. It can provide evidence to judge the strength and deformation of loess under the affection of water. The achievement of this project can provide the important basis to regionalize and prevent the geological disasters in the western region.

我国地域辽阔分布着种类繁多的特殊土体，其中湿陷性黄土的应力应变状态受工程建设影响极易发生重大灾害。深入研究复杂应力状态下非饱和黄土的水理特性及强度特性，对保证黄土工程安全具有重要科学意义和研究价值。项目以西北黄土为研究对象，基于大量的现场和室内试验，运用非饱和土理论和双剪统一强度理论，深入探索典型黄土场地含水状态和时空运移范围；从细观分析孔径结构影响土体持水特性内在机理，揭示黄土细观组成对含水状态影响规律及破坏机制；基于扫描电子显微术和离散元分析，进行黄土含水状态细观描述，提出土中孔隙分布规律的测定、评价方法；基于双剪统一强度理论，建立非饱和土统一强度理论和考虑中间主应力渗流土压力计算方法；从细观损伤揭示黄土强度和本构关系与含水状态关系，建立非线性统一损伤本构模型并验证，为预测黄土遇水湿陷变形和强度提供依据。研究成果具有创新性和广泛的应用前景，可为西部岩土工程建设和灾害防治提供重要依据。

我国地域辽阔分布着种类繁多的特殊土体，其中湿陷性黄土的应力应变状态受工程建设影响极易发生重大灾害。深入研究复杂应力状态下非饱和黄土的水理特性及强度特性，对保证黄土工程安全具有重要科学意义和研究价值。本项目以西北黄土为研究对象，基于大量的现场和室内试验，运用非饱和土理论和双剪统一强度理论，深入探索典型黄土场地含水状态和时空运移范围。首先进行了黄土场地滑坡易发区、基坑工程、高填方区实地调研和现场实测及室内试验研究。针对黄土场地的现场浸水渗透试验数据，分析了原状黄土中水的下渗规律，揭示含水率、饱和度、密度、干密度、孔隙比随深度的变化规律，确定水在黄土中时空运移范围以及产生的湿陷变形。然后从现场取回黄土试样，进行了一系列室内物理力学特性试验，压力膜仪土-水特征曲线试验，三轴渗透试验，湿陷试验，饱和、非饱和黄土的静、动三轴试验，不同含水率的介电常数测试，土水接触角试验以及电镜扫描测试和压汞试验等。分析了黄土的矿物成分和微细观结构特征，系统分析了原状、重塑、压实黄土试样干湿循环下的持水特性，从细观分析了孔径结构影响土体持水特性内在机理，揭示了黄土细观组成对含水状态影响规律及破坏机制。基于电镜扫描和离散元分析，进行黄土含水状态细观描述，提出土中孔隙分布规律的测定、评价方法。建立了考虑滞回特性可反映孔隙比、颗粒平均半径及接触角等细观参数对非饱和土的强度、变形、渗透等性质影响的土水特征曲线模型并进行验证。基于双剪统一强度理论，结合损伤理论和边界面塑性理论，提出基于统一强度理论反映粒间胶结损伤破坏的非饱和黄土结构性衰减规律，建立了非饱和土统一强度理论和考虑中间主应力渗流土压力计算方法，从细观损伤揭示黄土强度和本构关系与含水状态关系，建立了非线性统一损伤本构模型并进行试验验证。为预测黄土遇水湿陷变形和强度提供依据。研究成果具有创新性和广泛的应用前景，可为西部岩土工程建设和灾害防治提供重要依据。