The coupled hydro-mechanical approach for fluid compressibility problems in porous media

Numerical modeling for geotechnics use formulations which take into consideration simplifying hypotheses for porous media physical behavior. However, these simplifications neglect effects which could contribute in model's accuracy. In this paper, a fully coupled hydro-mechanical formulation considering fluid and solids compressibility is presented. This formulation was tested for a two-dimensional consolidation case. A sensitivity analysis for the fluid compressibility parameter was performed, with comparison of the simulation results to Biot's analytical solution. Results show that the values of vertical displacements are lower to cases with compressible fluids than to those with incompressible fluids. Instantaneously after load application, fluid pressure increases to a maximum value and it dissipates as load is gradually transferred to solid matrix. For compressible fluids, however, there is a delay in fluid pressure dissipation, which makes effective stress lower than expected. Therewith, stress-strain relations are affected, with low soil strain rate values, justifying vertical displacement decrease.