光弹颗粒材料的直剪实验研究

Direct shear experiments of photoelastic granular materials

对颗粒材料中的力链分布特征的了解,有助于从根本上了解颗粒材料基本性质。借助光弹实验,对两种直径混合的颗粒材料在二维直剪作用下的平均强度力链分布和几何结构变化进行了初步的探索。光弹实验方法是目前能够直观观察到力链分布的唯一有效的实验方法,在进行光弹实验前,设计研制了光弹直剪仪并进行了多次光弹圆盘颗粒材料退火实验。利用数字图像技术对光弹实验结果进行处理,并尝试用彩色梯度算法表征颗粒材料的平均受力情况,并获得平均强度力链。结果表明,二元颗粒材料集合体的几何结构具有各向异性。对力链方向统计分析表明,平均强度力链出现了局部化。

It has been realized that,the force chain is crucial to the fundamentals of granular materials.The photoelastic granular material of bi-disperse discs was employed to investigate the evolution of the packing and the force chain when subject to 2D direct shearing.Photoelastic experiments of granular materials were employed for the first time in the study of force chains of granular materials in China.Experimental techniques were dealt with including the development of a photoelastic direct shear apparatus as well as the manufacturing and annealing of Polycarbonate discs.The photoelastic direct shear experiments results as obtained were processed using the digital image processing methods,in which the average color gradient method was introduced to extract the force chain information developed.Anisotropy of the packing of the bi-disperse granular material was observed.The equally important was the localization of intermediate strong force chains based on the statistical analysis.