Estrada Nicolas, Taboada Alfredo, Radjaï Farhang
Géosciences Montpellier, Université de Montpellier II and CNRS, cc060, Place Eugène Bataillon, 34095 Montpellier cédex 5, France.
Phys Rev E Stat Nonlin Soft Matter Phys. 2008 Aug;78(2 Pt 1):021301. doi: 10.1103/PhysRevE.78.021301. Epub 2008 Aug 1.
We investigate a class of granular materials characterized by the possibility of interlocking between the particles. The interlocking is modeled by its effect through rolling resistance depending on relative rotation and normal force at the contact points and involving a single parameter analogous to the sliding friction coefficient. The model, which is introduced in the framework of the contact dynamics method, is applied to simulate the simple shear of a large granular sample. We present a detailed analysis regarding the influence of rolling and sliding friction parameters on the macroscopic response in terms of shear strength, fabric properties, and force transmission. Interestingly, two distinct regimes can be distinguished in which the steady-state shear strength is controlled by either rolling resistance or sliding friction. The relative contributions of rolling and sliding contacts to the shear strength are consistent with the same two regimes. Interlocking strongly affects the force network by enhancing the arching effect and thus increasing the relative importance of weak contact forces and torques, which is reflected in a decreasing power-law probability distribution of the contact forces and torques below the mean. Due to the combined effect of friction and interlocking, the force-carrying backbone takes an increasingly columnar aspect involving a low fraction of particles. Our data suggest that the nature of the weak contact network is strongly affected by the formation of these columns of particles which do not need to be propped laterally. In particular, in the limit of high rolling resistance and sliding friction, the role of the weak network of contacts is no longer to prop the force chains, but, like the strong contact network, to actively sustain the deviatoric load imposed on the system.
我们研究了一类颗粒材料，其特征在于颗粒之间存在相互锁定的可能性。这种相互锁定通过滚动阻力来建模，滚动阻力取决于接触点处的相对旋转和法向力，并涉及一个类似于滑动摩擦系数的单一参数。该模型是在接触动力学方法的框架内引入的，用于模拟大型颗粒样本的简单剪切。我们针对滚动和滑动摩擦参数对宏观响应（包括抗剪强度、结构特性和力传递）的影响进行了详细分析。有趣的是，可以区分出两种不同的状态，其中稳态抗剪强度由滚动阻力或滑动摩擦控制。滚动和滑动接触对抗剪强度的相对贡献与这两种状态一致。相互锁定通过增强拱效应，从而增加弱接触力和扭矩的相对重要性，强烈影响力网络。这反映在接触力和扭矩低于平均值时幂律概率分布的减小。由于摩擦和相互锁定的综合作用，承载力的骨架呈现出越来越柱状的形态，涉及的颗粒比例较低。我们的数据表明，弱接触网络的性质受到这些无需侧向支撑的颗粒柱形成的强烈影响。特别是，在高滚动阻力和滑动摩擦的极限情况下，弱接触网络的作用不再是支撑力链，而是像强接触网络一样，积极承受施加在系统上的偏应力载荷。
