Influence of the fluid-dynamic and rheological properties of sediments on the process of viscoelastic compaction at different rates of sedimentation

The problem of compaction of depositing sediments is studied for different geophysical characteristics of the process of sedimentation. A model is proposed for describing the compaction of sediments with growing thickness. The model is based on the modern concepts of the viscoelastic rheology of accumulating sediments; and, in terms of mathematics, it is a system of nonlinear differential equations in partial derivatives, which describe the processes of compaction and filtration with an increasing thickness of sediments. I have studied numerically the dependence of the regimes of compaction on the formulated characteristic criteria of similarity in the system of equations. Fluid-dynamic criterion, which characterizes the ratio of the rate of sedimentation to the rate of the filtration of a fluid (the rate of fluidization), and the rheological criterion of compaction, which characterizes the proportion between the viscous and elastic strains on the time scale of the process of compaction, i.e., the ratio of the two time scales—the time scale of the elastic strains’ relaxation and the time scale of the viscous compaction. The complex modeling of the mechanics and hydrodynamics of the interrelated processes of compaction and movement to the surface of the saturating fluids with an increase in the thickness of sediments reproduces the mechanism of the formation of different regimes of compaction, including those, which lead to an anomalously high pore pressure and to significant, in some circumstances step-like rise in the pressure of the saturating fluid, frequently observed at depths of 2–3 km.