ABSTRACT
The deformation model is based on the theory of elasticity, the effective stress principle and the equations of equilibrium. The effective stress for double porosity medium saturated by two fluids is expressed as (Khalili 2008):
d d dp Im M w a
′ + = =
(1)
in which, βαβ is the incremental effective stress parameter, pαβ is the fluid pressure and I is the second-order identity tensor. Symbols m and M represent micro and macro voids, and symbols w and a represent water and air fluids, respectively.
