基于CT扫描研究颗粒形状对砂土力学性质的影响

Influence of Particle Shape on the Mechanical Properties of Sand Based on CT Scanning

为了探究颗粒形状对砂土力学性质的影响,选取玻璃珠、石英砂、玻璃渣3种颗粒形状差异较大的砂土作为研究对象。首先通过计算机断层(computed tomography,CT)扫描重构了3种砂土的三维结构,选取了伸长率(EI)、扁度(FI)、球度(S)3个表征颗粒形状参数的均值作为砂土颗粒整体形状参数(overall regularity,OR),并对整体形状参数OR进行统计分析。然后配制7种不同形状参数的砂土进行了常规三轴压缩试验得到了其力学强度参数,研究砂土颗粒形状对其力学强度的影响规律。结果表明:7种砂土的应力-应变曲线均为应变软化型,都呈现出先剪缩后剪胀的特性;整体形状参数OR能较好反映砂土的力学特征,即随着整体形状参数OR的减小,应变软化现象变得不明显,但其峰值偏应力呈增大的趋势;砂土的内摩擦角随整体形状参数OR的减小呈线性增长,表观黏聚力急剧增大,但最大剪胀角随OR的减小而减小。此外,将临界内摩擦角与整体形状参数OR进行线性拟合,得到了两者较好的线性关系。

In order to explore the influence of particle shape on the mechanical properties of sand,three kinds of sand with different particle shapes,glass bead,quartz sand and glass slag were selected as the research objects.Firstly,the three-dimensional structure of three types of sand was reconstructed through CT scanning.The mean of three characteristic particle shape parameters,namely elongation(EI),flatness(FI),and sphericity(S)was selected as the overall regularity(OR)of sand particles.Statistical analysis was conducted to determine the feasibility of evaluating the shape of sand particles using the overall regularity OR.Then,the mechanical strength parameters of sand with 7 different overall regularity were obtained by conventional triaxial comprehension test,and the influence of sand particle shape on its mechanical strength was studied.The results show that the stress-strain curves of 7 kinds of sand are strain softening type,showing the characteristics of first shear shrinkage and then dilatancy.The overall regularity OR can reflect the mechanical characteristics of sand well,that is,with the decrease of the overall regularity OR,the strain softening becomes less obvious,but the peak-state deviatoric stress increases.The angle of internal friction of sand increases linearly with the decrease of the overall regularity OR,the apparent cohesion increases sharply,but the maximum dilatancy angle decreases with the decrease of OR.In addition,a good linear relationship between the critical internal friction angle and the overall regularity OR was obtained by linear fitting.