Loading...

Numerical modeling of multiphase fluid flow in deforming porous media: A comparison between two- and three-phase models for seismic analysis of earth and rockfill dams

Khoei, A. R ; Sharif University of Technology

1478 Viewed
  1. Type of Document: Article
  2. DOI: 10.1016/j.compgeo.2010.10.010
  3. Abstract:
  4. In this paper, a fully coupled numerical model is presented for the finite element analysis of the deforming porous medium interacting with the flow of two immiscible compressible wetting and non-wetting pore fluids. The governing equations involving coupled fluid flow and deformation processes in unsaturated soils are derived within the framework of the generalized Biot theory. The displacements of the solid phase, the pressure of the wetting phase and the capillary pressure are taken as the primary unknowns of the present formulation. The other variables are incorporated into the model using the experimentally determined functions that define the relationship between the hydraulic properties of the porous medium, i.e. saturation, relative permeability and capillary pressure. It is worth mentioning that the imposition of various boundary conditions is feasible notwithstanding the choice of the primary variables. The modified Pastor-Zienkiewicz generalized constitutive model is introduced into the mathematical formulation to simulate the mechanical behavior of the unsaturated soil. The accuracy of the proposed mathematical model for analyzing coupled fluid flows in porous media is verified by the resolution of several numerical examples for which previous solutions are known. Finally, the performance of the computational algorithm in modeling of large-scale porous media problems including the large elasto-plastic deformations is demonstrated through the fully coupled analysis of the failure of two earth and rockfill dams. Furthermore, the three-phase model is compared to its simplified one which simulates the unsaturated porous medium as a two-phase one with static air phase. The paper illustrates the shortcomings of the commonly used simplified approach in the context of seismic analysis of two earth and rockfill dams. It is shown that accounting the pore air as an independent phase significantly influences the unsaturated soil behavior
  5. Keywords:
  6. Fully coupled model ; Multiphase fluid flow ; Seismic analysis ; Deformable porous media ; Partially saturated soils ; Capillarity ; Capillary tubes ; Fluids ; Geologic models ; Hydraulic structures ; Mathematical models ; Numerical methods ; Porous materials ; Rock mechanics ; Seismology ; Soils ; Wetting ; Algorithm ; Boundary condition ; Capillary pressure ; Deformation ; Displacement ; Earth dam ; Elastoplasticity ; Finite element method ; Flow modeling ; Fluid flow ; Hydraulic property ; Immiscible fluid ; Numerical model ; Porous medium ; Rockfill dam ; Seismic method ; Three-dimensional flow ; Two-dimensional flow ; Multiphase flow
  7. Source: Computers and Geotechnics ; Volume 38, Issue 2 , March , 2011 , Pages 142-166 ; 0266352X (ISSN)
  8. URL: http://www.sciencedirect.com/science/article/pii/S0266352X10001400