为研究黄土的增湿变形问题,通过常规三轴剪切试验、等向压缩试验,分别研究了不同初始含水率原状黄土试样的应力-应变关系。通过三轴剪切试验发现,原状黄土的临界状态线近似一条直线且不通过p-q平面的坐标原点,随初始含水率变化沿q轴上下平移。通过三轴压缩试验发现,原状黄土的e-lnp曲线不是一条直线而是折线,且折点处对应的球应力随初始含水率的增大而减小。采用椭圆形屈服轨迹的假设,结合试验规律得出原状黄土试样的起始屈服函数,通过该起始屈服函数可以得出各应力路径下的起始屈服应力和起始含水率。该研究成果是后续建立原状黄土增湿变形本构模型的基础。

The stress-strain relation of undisturbed loess with varied initial moisture content was examined via conventional triaxial shear test and isotropic compression test. Shear test revealed that the critical state lines of undisturbed loess approximated to be straight lines which shifted along the q axis up and down horizontally with the variation of moisture content but do not pass through the coordinate origin of the p-q plane. Triaxial compression test demonstrated that the e-lnp curve of undisturbed loess was a broken line rather than a straight line, and the spherical stress at the fold point declined with the increase of initial moisture content. Under the hypothesis of ellipse yield locus, the initial yield function of undisturbed loess was acquired, according to which the initial yield stress and initial moisture content in different stress paths can be predicted. The present research lays a foundation for establishing the constitutive model of undisturbed loess during the process of moistening deformation.