ABSTRACT
Starting from a symmetric triangular pile with a horizontal basis and rotating the basis in the vertical plane, we have determined the evolution of the stress distribution as a function of the basis inclination using Finite Elements method with an elastic-perfectly plastic constitutive model, defined by its friction angle φ , without cohesion. It is found that stress distribution satisfying equilibrium can be found even when one of the free-surface slopes θ is larger than φ. This means that piles with θ>φ can be (at least) marginally stable and that slope rotation is not always a destabilising perturbation direction. These numerical computations enlighten the avalanche process; they show that no dynamical angle φdyn^φ is needed to understand avalanching. It is in agreement with previous experimental results. Furthermore, we show that the maximum angle of repose θ M can be modified using cyclic rotations; θ M =φ can be achieved.
