The role of gravity in the state of stress and pore pressure of poroelastic rocks

SUMMARY The response of porous rocks to fluid flow and external loads is critical to a wide range of geophysical and geotechnical problems, and is described by the long-established theory of poroelasticity. Despite the wealth of literature existing on the subject, little investigation has been devoted to the analysis of the state of stress and pore pressure regimes within porous media under the action of gravity force. Here, we present analytical solutions for the effective stress and pore pressure in gravitationally loaded porous rocks, in both drained and undrained conditions, and compare them with results from Finite Element numerical models. We also apply our models to a ground deformation episode observed in the Campi Flegrei Caldera, Italy. We find that the numerical results accurately reproduce our analytical solutions and show how accounting for gravity-induced stress and pore pressure regimes is critical to model stress and deformation in poroelastic media accurately. Specifically, we highlight how failing to assign realistic initial conditions, or neglecting gravity altogether, may lead to misleading results and interpretations of geophysical observables, such as ground deformation and rock failure.