Numerical Modeling of Steady-State Plow/Soil Interaction.

A numerical model of steady-state plowsoil interaction in support of cable burial operations on the seafloor was developed. Coupled field equations for equilibrium of an elasto-plastic medium and pore water diffusion in the presence of rigid surfaces contacting and sliding through fully saturated soil were solved in two dimensions. Time histories of unit plow forces contained distinct transient and steady-state phases reminiscent of total plow force histories recorded in the laboratory. The computed relationship between unit plow force and velocity was linear, although no critical velocity was evident in the results. Permanent soil deformation in the wake of the plow tip replicated observed behavior. Stress concentrations in the soil and contact forces distributed over the plow blade were consistent with patterns of severe wear on plow blades observed after usage in the field. Soil dilatation response was reasonable, and negative pore pressures were representative of measured response, although a modeling provision for pore water cavitation did not present itself. Moreover, the model explains how the mean pressure stress builds forward of the plow tip strengthening the pressure sensitive soil through which it penetrates, and suggests why past field measurements of resistance exceeded predictions from conventional analysis procedures.