Particle contacts and granular suspension rheology

Concentrated suspensions of athermal grains shear thicken easily. Until recently, this has been explained by the formation of ’hydroclusters’ due to lubrication forces. I review recent evidence pointing instead to the stress-driven formation of inter-particle contacts. I show that by careful consideration of the different kinds of possible constraints to motion at such contacts, it is possible to give a comprehensive phenomenological description of the flow of a large range of granular suspensions