This technical note investigates the shear behavior of loess using a specifically designed triaxial test scheme, in which five different drainage conditions of loess were controlled by a strain increment ratio (dε_v/dε_a) in the shear stage. It was established that with an increase in the strain increment ratio, the behavior of the loess samples changed from strain-softening to strain-hardening behaviors in the triaxial test. When dε_v/dε_a was less than zero, a strong contractive strain-softening behavior was revealed with a large collapsibility index. In the shear stage of a partially drained condition, the loess sample yielded a ‘limited flow’ behavior, which was marked by an occurrence of phase transformation from contractive to dilative response in the q-p’ diagram. More importantly, a unique relationship between the strain increment ratio and stress ratio (q/p’) was established for the test materials. The experimental results suggest a pressing need to thoroughly consider the drainage conditions of loess and the associated impacts on shear.

本技术说明使用专门设计的三轴试验方案研究黄土的剪切行为，其中黄土的五种不同排水条件由剪切阶段的应变增量比 ( dε _v / dε _a ) 控制。确定了随着应变增量比的增加，黄土样品在三轴试验中的行为从应变软化行为转变为应变硬化行为。当dε _v / dε _a小于零，则显示出强烈的收缩应变软化行为，并具有大的塌陷指数。在部分排水条件下的剪切阶段，黄土样品产生了“有限流动”行为，其标志是在q - p'图中发生了从收缩响应到膨胀响应的相变。更重要的是，为测试材料建立了应变增量比和应力比 ( q / p' )之间的独特关系。实验结果表明迫切需要彻底考虑黄土的排水条件及其对剪切的相关影响。