Three-dimensional coupled heat, moisture, and air transfer in a deformableunsaturated soil

A three-dimensional numerical model is presented for three-phase Bow (moist ure, air, and heat) in a deformable partly saturated soil with deformation calculated via a non-linear elastic theory. The present work is an extensio n of a two-dimensional analysis presented by Thomas and He.(1) The objectiv e of this work is the solution of problems of greater geometric complexity. The mathematical formulation of this coupled problem consists of four gove rning equations, developed from the principles of mass and energy conservat ions as well as the stress equilibrium equation. Darcy's flow law is used t o describe the motion of liquid and air in the porous medium, and a Philip and de Vries type vapour flow approach is employed in the formulation. A Ga lerkin finite element method coupled with a finite difference recurrence re lationship is used to obtain simultaneous solutions to the governing equati ons where pore liquid, pore air pressures, temperature and displacements ar e the primary variables. The method allows the non-linear nature of the soi l parameters to be modelled. Three-dimensional 20-noded isoparametric eleme nts are used to simulate different types of cases for the verification of t he work. Results are presented of the application of the new model to four problems, two of which are isothermal and two heating simulations. The thre e-dimensional nature of the results achieved is highlighted. Copyright (C) 1999 John Wiley & Sons, Ltd.