Modelling compacted soils

Abstract

Mechanical and hydraulic compacted soil properties for a given soil mineralogy are essentially controlled by the attained dry density, water content and microstructure. Basic compaction conditions (wet or dry of optimum, higher or lower energy of compaction) result in changes in microstructure. The paper attempts to provide a procedure of increasing accuracy to translate compaction concepts, rooted in common practice, into a modelling framework capable of explaining the behaviour of compacted soils. The approach developed is divided into the following stages: a) The classical compaction variables are interpreted in terms of two stress-like variables. They are regarded as the initial state for a given elasto-plastic constitutive model. The usefulness of this approach is discussed with some examples. b) A proper constitutive framework should introduce explicitly density effects in order to capture a swelling-collapse transition during wetting, a particularly important case in practice since embankments or dams usually experience a wetting increase path after initial compaction. The paper shows how the double structure model introduced by the authors is capable of including density effects in a natural manner. c) Further affects of microstructure are introduced through a different approach namely by defining an appropriate effective stress in terms of a microstructural parameter. This idea enhances the capabilities of previous frameworks.