Stochastic poromechanical modeling of anthopogenic land subsidence
M. Ferronato, G. Gambolati, P. Teatini
Dept. Mathematical Methods and Models for Scientific
Applications, University of Padova, Padova, Italy
D. Bau'
Department of Geological Engineering and Sciences, Michigan Technological
University, Houghton, MI, USA
ABSTRACT
A key issue in poromechanical modeling, e.g. for predicting anthropogenic land
subsidence due to fluid withdrawal, is the evaluation and use of representative
mechanical properties for the deforming porous medium at a regional scale.
One such property is the vertical uniaxial rock compressibility
cM which can be obtained through either laboratory
oedometer tests or in situ measurements, and typically exhibits quite a marked
scattering. This paper addresses the influence of the cM
uncertainty on the predicted land settlement using a stochastic simulation
approach where cM is regarded as a random variable and a
large number of equally likely cM realizations are generated
and implemented into a poroelastic finite element model. A compressibility law,
characterized by a log-normal distribution with depth-dependent mean, constant
variance and exponential covariance, is assumed. The Monte Carlo simulation
provides a set of responses which can be analyzed statistically. The results
from a number of numerical experiments show how the cM
variance and covariance affect the reliability of the simulated land subsidence
and provide a quantitative evaluation of the intrinsic uncertainty of the model
prediction.
