中文摘要：

通过对二维理想颗粒（圆盘）的直接剪切细观力学机理分析,研究了颗粒受剪时的运动规律,建立了能够描述等径颗粒情况下最密排列颗粒的最大剪应力公式。并通过对另外四种不同级配的圆盘颗粒的直接剪切离散元模拟,探讨了所建立的最大剪应力公式的应用。结果表明：在竖向荷载一定时,最密排列颗粒的最大剪应力取决于边界颗粒影响参数和非边界颗粒影响参数,且这两个参数在最密排列等径颗粒的情况下数值保持一致;对于一般颗粒级配,边界影响参数基本保持不变,非边界影响参数随着d10,d30和d60的增加而线性减小。

英文摘要：

By analyzing the micromechanics of the two-dimensional ideal particles（ disc） under direct shear test,the movement during the shearing is investigated. The formula described the maximum shear stress in the regular dense packing condition is established. In addition,following the direct shear simulations of the four samples with different particle size distributions,application of the formula which could predict the maximum shear stress was discussed. The results show that the maximum shear stress is depending on two parameters namely boundary effect parameter and the non-boundary effect parameters,and these two parameters keep the same under the regular dense packing when the vertical loading is constant. For the general packing,the boundary effect parameters remained unchanged,and the non-boundary effect parameter is linearly decreases with the d10,d30 and d60.