NUMERICAL MODELING OF TRANSIENT PORE PRESSURE AS A TRIGGER MECHANISM OF SEDIMENT FAILURE

The stability of sediments is a function of the mechanical strength of the material and applied forces counteracting this strength, most prominently pore pressure. Sediment failure occurs if the applied forces exceed the shear strength of the slope material in a short time. The most efficient way to decrease the shear strength is the increase of pore pressure by destroying the particle network. However, up to now less is known about the specific interplay between sediment matrix and pore pressure changes on a grain scaled level immediately before destabilization.

We use three-dimensional numerical models involving particle-fluid coupling in fully saturated granular materials at a small scale to analyse the transient changes of pore pressure and mechanical behavior of sediment. The numerical models are based on a fixed coarse-grid fluid scheme implemented in the Particle Flow Code (PFC3D). The scheme solves the continuity and Navier-Stokes equations in an Eularian Cartesian coordinate system to calculate pressure and velocity of fluid within each grid including the influence of particles. The movement of particles is described by force-displacement law.

Results quantifying sediment strength and fluid pressure as counteracting factors that control sediment stability are discussed.