  Diverging correlation lengths on either side of the jamming transition are
used to formulate a rheological model of granular shear flow, based on the
propagation of stress through force chain networks. The model predicts three
distinct flow regimes, characterized by the shear rate dependence of the stress
tensor, that have been observed in both simulations and experiments. The
boundaries separating the flow regimes are quantitatively determined and
testable. In the limit of jammed granular solids, the model predicts the
observed anomalous scaling of the shear modulus and a new relation for the
shear strain at yield.
