原状Q_2黄土三轴剪切细观结构演化定量研究

Quantitative study of meso-structure evolution of intact Q_2 loess during triaxial shear test

基于非饱和原状Q2黄土CT-三轴剪切试验得到的结构演化清晰的CT图像及CT数据,提出利用CT数随偏应力的关系确定屈服应力的新方法。基于CT数定义了结构性参数和结构演化变量;分析了结构演化变量与净围压和吸力的关系,相对于应变(包括偏应变和体应变),当吸力相同时,净围压越大,结构演化变量值越大;当净围压相同时,吸力越大,结构演化变量值越小。建立了非饱和原状Q2黄土三轴剪切过程的结构演化方程,该方程为结构演化变量与偏应变和体应变的关系,能同时反映净围压和吸力等对结构演化的影响。利用提出的结构演化方程对试验数据进行拟合,拟合结果较理想。

A series of triaxial shear tests on intact unsaturated Q2 loess were conducted using computerized tomography （CT）-multi-function triaxial apparatus developed in Logistical Engineering University. The distinct CT images and detailed CT data of the evolution of meso-structure were obtained during loading. A new method is proposed to identify the yield stress of intact Q2 loess using curves of CT-number versus deviatoric stress. A structure parameter and a structure evolution variable are defined based on CT data. The variable of structure evolution increases with the increase in net confining pressure under the same suction; while the variable of structure evolution decreases with the increase in suction under the same net confining pressure. An equation describing the evolution of structure is developed. In the equation, deviatoric strain and volumetric strain are included. The equation reflects the influences of net confining pressure and suction on the evolution of meso-structure during loading. The structure evolution equation successfully simulates the laboratory tests of unsaturated intact Q2 loess.