We propose a model to describe the quasistatic shearing of dry granularmaterials, which notably captures the differences in velocity profiles recentlyobserved in 2 and 3-D Couette flow experiments. In our scheme, the steady-stateflow is due to the intermittent motion of particle clusters moving togetherwith the wall. The motion of a cluster is associated with the transientformation of a fracture inside the sheared pack. The model is based on theexistence of a persistence length for the fractures, which imposes aself-similar structure on the clusters. Through a probabilistic approach, wecan evaluate the rate of appearance of a cluster of a given size and obtain aprediction for the average velocity profiles. We also predict the existence oflarge stress fluctuations at the moving wall, which characteristics are in goodagreement with experimental data.
展开▼
