Stochastic compressibility for land subsidence modelling

Numerical models for predicting land subsidence due to fluid withdrawal require the correct evaluation of representative mechanical properties of the deforming porous medium. One such property is the vertical uniaxial compressibility cM which is obtained through either lab oedometer tests or in situ measurements, and typically exhibits a marked scattering. The present communication addresses the influence of the cM uncertainty for the predicted land settlement using a stochastic approach where cM is regarded as a random variable. A compressibility law, characterized by a log-normal distribution with depth-dependent mean and constant variance, is implemented into a Finite Element poroelastic model and used in a preliminary study based on the Monte Carlo method. The results show how the cM variance affects the reliability of the expected land subsidence and point out the impact of the cM uncertainty on the quality of prediction.