Experimental observation and an empirical model of enhanced heap stability resulting from the mixing of granular materials

We report the existence of enhanced heap stability as a result of the mixing of granular materials. Our setup consists of a rectangular container, filled with a binary mixture of granular matter up to some height h , that is rapidly opened at one wall to allow repose angle (θ c ) formation. We develop an empirical model for θ c based on the Mohr–Coulomb failure criterion. The model is parameterized by an effective cohesion c and an effective coefficient of friction μ that depend on: (1) the granular proportions and (2) the c and μ for pure cases. Good agreement is achieved between the experiment and the model. We note that even the experimental fluctuations of θ c as a function of granular proportions are well correlated (<2% deviation) with the computed uncertainty of the empirical model.