非饱和黏土变形和强度特性试验研究

 利用双压力室非饱和三轴仪，进行非饱和黏土脱湿、等吸力固结和排水剪切试验，研究非饱和黏土的体变、屈服和强度特性，结果表明：在低吸力范围内，非饱和黏土在脱湿过程中的体积收缩呈弹塑性体变性状，验证了非饱和土本构模型中SI屈服曲线的存在；在等吸力固结试验中，黏土固结屈服应力随着吸力增加而增加，LC屈服曲线呈二次抛物线变化，固结压力的增长比基质吸力的增长对体变性状的影响效应要大。在剪切试验中，非饱和黏土应力应变关系依赖于净围压和基质吸力的不同组合，基质吸力增强土体应力–应变关系的硬化特性；在不同的吸力条件下，固结排水剪的有效内摩擦角基本不变，黏聚力的增长与吸力的增长基本呈线性关系。

EXPERIMENTAL STUDY ON CHARACTERISTICS OF DEFORMATION AND STRENGTH OF UNSATURATED CLAY

A series of triaxial tests were carried out using double-cell triaxial system for unsaturated soils to investigate the behavior of volume change,yield and strength of unsaturated clays. The stress paths included drying with isotropic stress,isotropic compression and shearing with controlled suction. The results show that the clay exhibited an elasto-plastic shrinkage upon drying with low suction,indicating the existence of the suction- increase(SI) yield locus. During isotropic compression,the yield stress increases with increase of suction and the loading collapse(LC) yield curve changes parabolically. Increasement of net normal stress has more significant effect on the behavior of volumetric change than that of matric suction. The stress-strain relationship depends on the combinational style of net normal stress and matric suction,and suction enhances the stress-strain stiffness feature during triaxial shear test. Under conditions of different values of constant suctions,the effective friction angle is approximate a constant,and cohesion coefficient versus suction relationship is approximately linear.