Q_2黄土调整吸力的非饱和三轴压缩试验研究

Experimental Research on Q_2 Loess by Unsaturated Triaxial Compression Tests with Suction Change

通过对Q2黄土进行调整吸力的非饱和三轴压缩试验,研究了浸水湿化程度对Q2黄土力学特性的影响。试验表明:不同浸水湿化程度的Q2黄土,其应力应变曲线为弱软化型,浸水湿化程度越高,软化程度越弱,浸水湿化至饱和时可近似看作理想硬化型;轴向应变较小时,Q2黄土的天然结构保持良好,应力随应变的增大而增大,随着轴向应变进一步增大,其天然结构逐渐被破坏,应力随之先缓慢上升后逐渐减小直至稳定;浸水湿化会同时引起土体应力状态和土体结构的改变,屈服应力随浸水湿化程度的提高而减小,在浸水湿化接近饱和时屈服应力变化最快,土体结构变化最大;形成年代早的Q2黄土细粒质量分数高,结构特征区别于Q3黄土,因而呈现出不同的力学特征。

Unsaturated triaxial compression tests is carried out by applying suction changes to investigate influences of mois-ture content on mechanical behavior of Q2 loess. The results show that stress-strain curves of Q2 loess at different moisture contentare strain-softening, i.e. the higher the moisture content is, the flatter the curves after yielding are. The stress-strain curve is close tostrain-hardening as the loess is saturated. The initial parts of the stress-strain curves are steep for the presence of the natural fabricwhile with the progressive destruction of the fabric, deviator stress increases moderately with the axial strain and then decreasessteadily to a constant. Wetting brings changes both in stress state and fabric of Q2 loess. Yielding stress decreases with the rise ofmoisture content, changing rapidly as it comes to saturation, as is with the structure. Fabric of Q2 loess is different from that of Q3loess, and more fine particles lead to its different mechanical behavior.