A pore network approach to estimate the soil water retention curve of a granular material

Abstract

Pore network modelling (PNM) is used to estimate the soil water retention curve (SWRC) of a granular soil, based on its grading properties. The ball and stick geometry is adopted, which considers the pores to be spherical, and the throats tubular. The topological characteristics of this geometry are evaluated based on the grain size distribution of the medium, and its grading properties. The pore size distribution is constructed based on the geometrical properties of the grading, and approached by a statistical distribution (normal or Weibull distributions). Additional hypotheses are proposed to establish the throat size distribution based on the neighboring pores. An invasion percolation algorithm is then applied to a saturated pore network, to simulate the introduction of air and the expulsion of water, thus mimicking the desorption of the sample. When analyzing the test data of uniformly graded sand, a reasonable agreement is observed between the experimental data and the numerical predictions.