冻土三轴剪切过程中细观损伤演化CT动态试验

A CT-timely experimental study on meso-scopic structural damage development of frozen soil under triaxial shearing

对冻结粉质粘土在三轴剪切过程中的结构损伤进行了CT技术动态测试。通过对CT图像及CT数的分析发现:在受载之前冻土结构已经存在孔隙、管状孔隙和低密度区等初始缺陷;变形过程中冻土结构的弹性损伤只占总损伤的比例很小,而结构粘塑性损伤的比例则很大;在三轴剪切过程中和蠕变过程一样存在结构损伤的弱化和强化现象,孔洞几何特征的改变和孔洞的长大、联合,颗粒之间的相互错动及滑移是冻土结构粘塑性损伤发展的重要特征。冻土的结构损伤主要发生在冻土屈服之后,这部分损伤不能用CT数的变化来定量计算。

Meso-scopic structural damage development during the triaxial shearing process of frozen soil was studied by computerized tomography (CT) technique. Analysis of CT-images and values during deformation shows that there is already a variety of initial structural damages, such as micro-holes, pipe-shaped holes and low-density regions before loading. The elastic damage only accounts for a very small scale in total damage, but viscoplastic damage for a great scale. There also exist the phenomena of structural strengthening and softening during triaxial shearing, similar to those during creep of frozen soil. The viscoplastic damage, which can not be determined by CT-values, behaves mainly in the forms of the changes of size and shape and unification of microscopic cavities, the slippages between soil particles and/or cemented ice particles.