原状黄土的结构性与渗气特性的关联性初探

Correlation between structure of intact loess and gas permeability

对3个地区的不同含水率原状黄土进行了等向压缩与渗气性同步测定试验,分析了原状黄土等向压缩过程中变形特性与渗气特性,探讨了压缩特性与渗气性之间的关联性通过引入用渗气性定义的结构性参数,提出了描述湿载耦合作用时原状黄土压缩变形的表达式。研究结果表明:原状黄土的渗气性变化与压缩特性的变化过程呈良好的关联性,渗气性可反映原状黄土组构与湿度不同而引起结构势差异及其应力作用引起黄土结构势的损伤过程;把结构屈服时某一含水率与参考含水率土的渗气系数之比定义为结构比参数,通过将不同含水率下结构比参数引入到等向应力变量中而得到了具有归一性的压缩曲线;据此,提出了以参考含水率的原状黄土的压缩曲线为基础,统一、连续描述非饱和原状黄土屈服前后压缩变形模式,其计算与试验结果皆吻合较好。

The isotropic compression tests with simultaneous gas permeability measurements are performed for intact loess with various water contents in three regions. The behaviours of compression deformation and change of induced gas permeability of intact loess are analyzed. The correlation between gas permeability and compression deformation is discussed. The formula of compression curve of intact loess is proposed to characterize the compressive deformation under the coupling of moisture and stress, in which the structural parameter defined by gas permeability is included as a known parameter. The results suggest that changes of gas permeability of intact loess are found to have a good correlation with volumetric deformation during isotropic compression tests. The structural potential difference of intact loess caused by the fabric and moisture and its damage induced by the stress can be reflected by the change in gas permeability. The gas permeability ratio corresponding to the yield stress at the ratio of a certain water content to the reference water content is defined as the structureal ratio parameter, and it is introduced into the isotropic stress variable to lead to a normalized compression curve of intact loess with various water contents. Regarding the compression curve at the reference water content as the reference state, a unified and continued description of the compression deformation before and after yielding for unsaturated intact loess is proposed, and the calculated results agree well with the test ones.