The main objectives of this project are the study of the thermodynamics of granular materials and the distribution of forces in granular packings. We intend to study a class of lattice gas models, with frustrated interactions, whose static and dynamical properties exhibit interesting features that are common to granular packings, structural glasses and spin glasses. These models can be studied using renormalization group methods together with extensive computer simulations. We will also apply a novel real space renormalization group approach recently introduced in the study of Self-Organized Criticality for Sandpile and Forest-Fire models. The Reynolds transition has also important consequences on the acoustic properties due to the complicated networks on which stresses are transmitted. We will investigate the problem of the distribution of forces in granular media, which shows interesting and unintuitive results. We will also try to clarify the relationship the phenomenology of granular media and the concept of Self-Organized Criticality.