We present a unified framework for understanding the compaction of colloidal gels under their own weight. The dynamics of the collapse are determined by the value of the gravitational stress ${\sigma }_g$, as compared to the yield stress ${\sigma }_Y$ of the network. For ${\sigma }_g<{\sigma }_Y$, gels collapse poroelastically, and their rate of compression decays exponentially in time. For ${\sigma }_g>{\sigma }_Y$, the network eventually yields, leading to rapid settling. In both cases, the rate of collapse is backflow limited, while its overall magnitude is determined by a balance between gravitational stress and network elastic stress.

• Received 13 December 2004

DOI:https://doi.org/10.1103/PhysRevLett.94.218302