A few assumptions suggested by the mechanism of anthropogenic land settlement due to fluid withdrawal lead to the development of a simplied subsidence model relying on one anisotropic diusion equation for the vertical displacement only. The model can be used in a generally heterogeneous porous medium, possibly with a non linear or plastic mechanical behavior, and subject to an arbitrary pore pressure variation. The present communication investigates the conditions under which such a model provides an outcome of comparable accuracy with respect to the solution of the classical equilibrium equations. The results show that the diusion model of subsidence gives a good prediction above the producing eld especially in case of a thin depleted reservoir embedded within weakly heterogeneous porous media with a Poisson ratio between 0.20 and 0.30, i.e. the vast majority of real applications. The above model allows also for a novel interpretation of the volumetric locking phenomenon occurring for a Poisson ratio close to its limiting value of 0.50 and helps gain a new insight in terms of equivalent mechanical conductivities into the propagation of the deep compaction to the land surface.
A diffusion model for land subsidence
FERRONATO, MASSIMILIANO;GAMBOLATI, GIUSEPPE;PUTTI, MARIO;TEATINI, PIETRO
2006
Abstract
A few assumptions suggested by the mechanism of anthropogenic land settlement due to fluid withdrawal lead to the development of a simplied subsidence model relying on one anisotropic diusion equation for the vertical displacement only. The model can be used in a generally heterogeneous porous medium, possibly with a non linear or plastic mechanical behavior, and subject to an arbitrary pore pressure variation. The present communication investigates the conditions under which such a model provides an outcome of comparable accuracy with respect to the solution of the classical equilibrium equations. The results show that the diusion model of subsidence gives a good prediction above the producing eld especially in case of a thin depleted reservoir embedded within weakly heterogeneous porous media with a Poisson ratio between 0.20 and 0.30, i.e. the vast majority of real applications. The above model allows also for a novel interpretation of the volumetric locking phenomenon occurring for a Poisson ratio close to its limiting value of 0.50 and helps gain a new insight in terms of equivalent mechanical conductivities into the propagation of the deep compaction to the land surface.Pubblicazioni consigliate
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