Comparison of multidisciplinary approaches and unification of concepts on the movement of water and soil in deformable porous media

A theoretical review is presented on different approaches used for mathematical equations describing water and soil movement associated with transient pore water flow and soil deformation. Through a careful analysis of the governing equations, concepts used in different fields of engineering are found to be exactly equivalent. The comparison of soil water flow equation applicable to non-rigid porous media with the equation for consolidation reveals that under saturated conditions, both the compression index C_c and the coefficient of compressibility a_v are equivalent to the slope of soil moisture retention characteristic (MRC) and differential moisture capacity (dΘ/dΨ). Further, the coefficient of consolidation C_v is found to have the same physical meaning as the soil moisture diffusivity (D). Although both approaches originate from the same physical basis, practical applications have been limited to specific fields of soil engineering. It appears, however, that the approach used in soil physics retains wider applicability because it provides solutions of soil deformation (i) even under no external load, (ii) for unsaturated flow, and (iii) in a two-dimensional mode.