原状Q_3黄土在加载和湿陷过程中细观结构动态演化的CT–三轴试验研究

Experimental study on dynamic evolution of meso-structure of intact Q_3 loess during loading and collapse using CT and triaxial apparatus

为了揭示原状Q3黄土在加载和湿陷过程中的细观结构变化,将湿陷三轴仪与医用CT机相配套,进行了一系列控制吸力的CT-三轴湿陷试验,不仅得到了加载过程和湿陷过程中的宏观反应曲线,而且得到了相对应的CT扫描图像。结果表明:原状湿陷性黄土具有较强的初始结构性;加载过程中,较大的孔洞先扩展后闭合,小孔洞逐渐闭合;湿陷过程中,大部分孔洞逐渐闭合且断面的密度分布趋于均匀;湿陷过程中大孔洞闭合与否取决于浸水时的应力状态。通过宏细观试验资料的分析,确定了原状湿陷性黄土的结构屈服应力,提出了一个基于CT数均值的结构性参数,分别定义了加载和湿陷过程中的结构损伤变量,研究了它们的变化规律,建立了结构损伤演化方程。

To disclose the variation of meso-structure of intact Q3 loess during loading and collapse, a series of CT scanning-triaxial collapsible tests with controlled suction are done using triaxial apparatus for collapsible soils combined with computer tomography. Not only the macro response curves but also the corresponding images of CT scanning are obtained. It is indicated that the intact collapsible loess has apparent fabric; bigger holes expand, then close; smaller holes gradually close during loading; most of holes gradually close and the distribution of density of scanning section becomes homogeneous in the process of collapse; and whether the bigger holes close or not is decided by the stress condition of immersion. On the basis of analysis of macro and meso experimental materials, the yielding stress of fabric of the intact collapsible loess is determined, a structural parameter is developed based on the mean of CT values, structural damage variables in the process of loading and collapsing are individually defined, the changing law of variables is studied and equations of structural damage evolution are established.