Breaching is a style of retrogressive subaqueous slope failure controlled by dilation and consequent pore pressure drop; it has the potential to generate turbidity currents that build thick successions of turbidites. We present pore pressure measurements made during breaching failure, as well as a physical model that shows how the pore pressure field within the failing deposit is connected to the erosion rate associated with the failure surface. We show that breaching can occur in any dilative granular material. Conditions for breaching could be common on the continental shelf, making it an important mechanism in transferring sediment into the deep ocean. A dynamic equilibrium exists between the slope failure and the pore pressure dissipation during breaching. This equilibrium leads to a way to estimate the rate of sediment release from breaching using a simple material property, the coefficient of consolidation. Contrary to previous work, we find that the erosion rate is independent of the dilation of the deposit due to the coupling between erosion and pore pressure dissipation. The equilibrium between the erosion and pore pressure dissipation decouples the steady-state pore pressure field from the permeability of the deposit; this is the first time this behavior has been recognized in sediment failures.
- Received 23 September 2011.
- Revision received 13 February 2012.
- Accepted 15 February 2012.
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