Implicit Finite Difference Formulation for Treating Multiphase Flow in Wet Porous Soils

摘要

A one dimensional implicit multiphase finite difference formulation which calculates the relative flow and dynamic stress behavior in wet porous soils has been developed and incorporated into a computer code called CRIME. Various 1-D test cases are presented which demonstrate the ability of CRIME to efficiently calculate to very late times with time steps much larger (factors > 1000) than permitted by standard explicit techniques. The loading and subsequent consolidation of a realistic layered geology of varying saturation has been successfully simulated. The basic approach is to characterize the geologic materials in terms of both solid (soil lattice) and pore-fluid properties. A variety of constitutive models can be used to describe the effective stress behavior of the soil lattice. The pore-fluid properties are those of water and/or air with separate hydrodynamic equations of state (EOS) for each. In the case of partially saturated soils, a pressure equilibrium condition is used for the water-air mixture EOS in the soil pores. Soil permeability, the pore-fluid pressure and effective stress gradients, and the pore-fluid viscosity all determine the relative flow velocity.