Modeling of granular media submitted to internal underpressure

A conglomerate, composed of granular materials encapsulated in a tight, flexible envelope, and submitted to an internal underpressure is investigated experimentally and modelled numerically. The underpressure level, controlled by a vacuum pump, has a great influence on the properties of the media. The structures filled up with plastic grains and submitted to uniaxial compression tests are examined in this study. The nonlinear behaviour is simulated using the viscoplastic constitutive law of Chaboche. The identification of material parameters is formulated as an optimization problem and solved by means of the evolutionary algorithm. The numerical examples present the robustness of the proposed approach. Possible improvements of the method are discussed.