浸湿对原状Q2黄土微观结构与力学性质的影响研究

改进了非饱和三轴浸水试验系统，通过调整吸力控制土样的浸湿程度；进行了环境电镜扫描和非饱和三轴压缩试验，研究了浸湿引起的Q2黄土微观结构变化和力学性质变化。微观结构测试表明，Q2黄土集粒间孔隙以引起中等或弱湿陷的中等孔隙为主；围压不变，随着浸湿程度的加深，孔径较大的集粒间孔隙相对含量逐渐减少，而孔径为10～20 ?m的孔隙相对含量逐渐增大。三轴压缩试验结果显示，不同浸湿程度的Q2黄土应力-应变关系均呈弱软化型，可分为偏应力随轴向应变快速上升、缓慢上升和缓慢下降至平稳3个阶段。分析了浸湿后Q2黄土的力学性质与微观结构特征之间的关系。引入微观结构参数，将微观结构特征与宏观力学性质联系起来，初步建立了考虑微观结构影响的Q2黄土本构模型。

Research on influence of soaking on microstructure and mechanical behavior of Q_2 loess

Triaxial soaking test system is developed; and test samples could be soaked to different saturations. Microstructures of Q2 loess of different saturations are observed by environmental scanning electron microscope (ESEM) and their mechanical behaviors are investigated through unsaturated triaxial tests. ESEM tests show that inter-aggregate pores of Q2 loess mainly consist of those that induce moderate or slight hydro-collapse. Confining pressure held constant, ration of inter-aggregate pores of larger size decreases with saturation; while that of inter-aggregate pores of 10-20 ?m increases. Results of unsaturated triaxial test show that stress-strain curves of Q2 loess of different saturations are all slightly strain-softening, and could be divided into three phases: rapid increase of deviatoric stress with axial strain, slight increase and slight decrease of deviatoric stress to a constant with axial strain. Relation between microstructure and mechanical behavior of Q2 loess after soaking is analyzed. A microstructural parameter is introduced that relates microstructure and mechanical behavior. A constitutive model of Q2 loess is established preliminarily considering influence of microstructure.