考虑微细观组构影响的高吸力非饱和土持水和力学特性研究

In the arid and semi-arid regions, various civil and geological engineering projects are related to the water retention and mechanical behavior of unsaturated soils at high suctions. In the current study, there are not clear about the relation between the evolution of micro- and meso-pore structures and the macro-mechanical behavior of unsaturated soils and its quantitative description at high suctions. This project proposes to investigate the water retention and mechanical behavior of unsaturated soils with different micro- and meso-fabrics at high suctions using the vapor equilibrium method and the triaxial shear test under constant water content. Combined with the test results from the micro- and meso-structural analyses, the macro-mechanical behavior and the evolutional mechanism of micro- and meso-pore structures for unsaturated soils in a high suction range will be investigated in detail. The influence of key factors on the micro- and meso-pore structures and mechanical behavior of unsaturated soils will be clarified. The strengthening mechanism for unsaturated soil of different micro- and meso-fabrics due to suction at high suctions will be revealed. On this basis, a prediction method will be proposed for the strength of unsaturated soils considering the effect of micro- and meso-fabric in a high suction range. This project can provide some useful research results for geotechnical engineering problem with unsaturated soils at high suctions.

在干旱和半干旱地区，许多土木和地质工程涉及到高吸力下的非饱和土持水和力学问题。现有研究尚未探明高吸力下的结构性非饱和土微细观孔隙结构的演化与宏观力学特性的关系及其定量化描述等科学问题。为此，本项目拟采用饱和盐溶液蒸汽平衡法和等含水率下的三轴剪切试验，对不同微细观组构的非饱和土试样进行系统的持水和力学特性试验研究；并结合微细观分析手段得到的试验结果，着重对高吸力范围内非饱和土宏观力学特性与微细观孔隙结构的演化机理进行深入研究；阐明其关键因素的影响规律，揭示不同微细观组构的高吸力非饱和土试样因吸力引起非饱和强度增强的微细观机理。在此基础上，提出适用于高吸力下考虑微细观组构影响的非饱和土强度预测方法。本项目可为高吸力非饱和土相关的岩土工程问题提供有用的研究成果。

高吸力下的非饱和土是普遍存在的，尤其是在干旱和半干旱地区。持水和力学特性研究是非饱和土渗流、变形与强度研究的基础。本项目采用饱和盐溶液蒸汽平衡法和等吸力的三轴剪切试验，对高吸力下不同孔隙结构的非饱和土进行系统的持水和力学特性试验与理论研究。主要成果如下：1）详细研究了初始孔隙比和孔隙结构对高吸力下非饱和土持水特性的影响，提出了高吸力下等吸力控制的三轴剪切试验方法；其次，结合试验结果探讨了高吸力下非饱和土的滞回特性，并指出在高吸力下非饱和土的滞回特性主要与比表面积等相关。2）采用开发的高吸力下吸力控制的三轴剪切试验，量测了压实粉土、黏土和膨胀土试样在高吸力下的强度特性，分析了不同类型非饱和土在高吸力下强度特性的变化规律；3）提出了归一化处理全吸力范围内不同初始孔隙比影响的主脱湿/吸湿持水曲线方法；在归一化处理方法的基础上，提出了考虑初始孔隙比影响的非饱和土滞回特性的模拟方法。4）对常用的非饱和土强度预测方程在广吸力范围内的适用性进行了详细地分析和讨论。在此基础上提出了一个能较好预测广吸力范围内非饱和粉土或粉质黏土的强度计算方程。