湿陷性黄土与膨胀土的分级增湿变形特性试验研究

对陕西张桥的湿陷性黄土和安康的膨胀土分别进行了分级增湿变形试验。根据试验结果分析了这两种土的应力应变关系曲线、增湿变形过程中基质吸力变化特点及增湿变形类型。分析表明，其两者的增湿变形应力应变曲线形态完全不同，湿陷性黄土的应力应变曲线明显分为压缩、湿陷变形和固结压密3段，并且在湿陷变形转变为固结压密时有一个明显的转点。膨胀土的应力则随变形增加呈衰减趋势，并且在增湿变形中以体积变形为主，剪切变形较少。湿陷性黄土和膨胀土在增湿过程中基质吸力变化亦表现出明显的差异，前者随含水率明显变化，随应力变化较小，而后者随含水率和应力的增加均有较大变化。最后提出湿陷性黄土的湿陷起始应力和膨胀土的膨胀应力两个概念，进一步合理分析了两者的特征力。

Deformation characteristics of collapsible loess and expansive soil under the condition of wetted in stages

The deformation characteristics of collapsible and expansive soil under the condition of wetted in stages are experimentally studied by triaxial compression test.The relationships between stress and strain of both soils and the variation of suction in the process of deformation are analyzed.It is found that the difference of the stress-strain relationship between these two kinds of soil is remarkable.The stress-strain curve of collapsible loess consists of three phases: compression,collapse deformation due to wetting and compressive consolidation. A distinct turning exists at the changing from collapse deformation to compressive consolidation.Whereas,a descending tendency of stress-strain curve happen in the process of wetting which shows the volume deformation is more than the shear deformation.The suctions of both unsaturated soils during wetted in stages are also distinctly different.The suction of loess is little sensitive to stress level,and is more sensitive to water content.The suction of expansive soil is greatly sensitive to both water content and stress.The concept of initial stress of loess due to deformation of wetting and the concept of swelling stress of expansive soil are suggested which are more precisely expressing the characteristics of these two kinds of soil.