颗粒材料平面剪切实验与剪切带相关研究

The Plane Shear Test of Granular Materials and Research on Shear Band

根据流体动力学中库爱特流流动的特点,设计了一种新型颗粒材料平面剪切实验装置,并采用数字图像相关方法（DIC）分析了颗粒材料剪切带的形成过程。结果表明：①该实验装置结合DIC方法可以观测到剪切带的形成过程;②剪切开始时,颗粒孔隙率发生变化,颗粒重新分布,形成了漩涡状剪应变区域,随着剪切的进行,剪应变逐渐增大,带状、漩涡状应变区域半径逐渐减小乃至消失,最终融合形成了一条连续的贯穿整个颗粒面的曲线带状区域,即为剪切带;③剪切带位置处于整个颗粒面上部1/4处,其分布区域宽度是颗粒最小粒径的9-12倍,最大粒径的3-4倍,剪切带平均厚度为分布区域宽度的1/2;④对比不同压强下的剪切实验结果,可以发现剪切带最终形成位置变化不大,压强对剪切带的形成位置影响较小,而剪切带处的剪应变大小与剪切带形成位置有关,剪切位置越深,剪应变越大。

According to the flowing characteristics of Couette flow in fluid dynamics, a new plane shear experiment device was designed and bases on digital image correlation method （DIC） the forming process about granular materials shear band was analyzed. The results show that ： ① the formation process of shear band could be observed by using the test device combined with DIC method; ② when shearing began, the porosity of granular materials changed, the granules redistribution happened in order to form a vortex shear strain area; along with the development of the experiment, shear strains increased gradually and strip zones and swirling radius of shearing strains gradually shrank or even disappeared, eventually merged to form a continuous curve strip zone throughout the whole surface of the particle materials, which called shear band ; ③ the shear band, whose distribution areas width is about 9 to 12 times than minimumpartical size,3 to 4 times than maximum, was located at a quarter upper part of the whole particle surface, the average thickness of shear band is a half of shear distribution areas; ④ by comparing the experiments results under different pressures, that final forming positions had few change can be found. Nevertheless , shear strain in the shear band was related to the formation position of the shear band. The deeper shear position, the greater shear strain.