9. Poromechanics and Deformation

The chapter deals with cases of transport of mass and energy in which the solid matrix, as the entire porous medium domain, undergoes deformation. Models of consolidation as a consequence of construction, and models of land subsidence due to heavy pumping, are developed and presented. Also, the propagation of waves in a porous medium domain, in which soil deformability plays an essential role, is briefly discussed. Models of consolidation as a consequence of construction, and models of land subsidence due to heavy groundwater pumping, are developed and presented. Also, the propagation of waves in a porous medium domain, in which soil deformability plays an essential role, is briefly discussed. The chapter focusses on cases in which fluids are extracted from or injected into geological formations, possibly under non-isothermal conditions. The presented models describe phenomena of deformation of porous medium domains in aquifers in response to imposed stresses. Examples are: (1) Land subsidence as a consequence of pumping water from aquifers, (2) ground surface upheaval, as a consequence of injection, (3) development of fractures as a consequence of injecting fluids into a tight geological formation (4) induced seismicity as a result of fluid injection into confined formations, and (5) soil liquefaction. Change in the flow regime, associated with fluid pressure changes, causes changes within a considered porous medium domain causing formation deformation. The chapter starts by introducing the concepts of stress and strain in a single phase continuum-first at the microscopic level and then at the macroscopic one. Then, following the phenomenological approach, the complete model for stress-strain analysis is developed for the saturated (or multiphase) elastic porous medium, leading to the strain and deformation within the considered porous medium domain.