从非饱和土力学角度探讨黄土湿陷机制

Discussion on the mechanism of loess collapsibility from the perspective of unsaturated soil mechanics theory

本文回顾了黄土湿陷概念的由来及其基于其微结构湿陷机制研究现状。对从非饱和土力学角度开展黄土湿陷机理研究的有关问题进行了讨论和分析,提出了广义湿陷性概念。黄土湿陷机制研究应根据具体湿陷路径针对性开展非饱和土应力路径试验研究,从而进一步建立黄土广义湿陷本构模型,为工程问题的定量分析和数值计算提供科学依据。非饱和黄土常剪应力增湿试验表明,黄土湿陷破坏之前发生了一定的微小变形,随后应变速率突然增加,偏应力也不再维持为常数。同时,观察到孔压突然上升1-2kPa,表明黄土湿陷过程发生了不完全排水剪缩破坏。

The paper reviews the concept origin of loess collapsibility and the research status of collapsibility mechanism based on its microstructure, and discusses on the collapsibility mechanism from the perspective of unsaturated soil mechanics, then puts forward the concept of generalized collapsibility. It is suggested that research of loess collapsibility includes the laboratory investigations based on field collapsibility stress-path and then building of constitutive model, as a base for engineering quantitative analysis and numerical simulation. One series （3 samples） loess moistening test under dead load shows that collapse occurs so suddenly at less than 1% of axial strain that deviatoric stress can not retain. Meanwhile, about 1 - 2kPa pore pressure raise is observed, indicating incompletion drained shear failure occurring in the collapse process.