Parameter identification methodology for unsaturated soils

The main objective of this paper is to present a direct automatic identification and uncertainty estimation methodology that can be applied satisfactory to obtain the best matching parameters of geotechnical models for unsaturated clay soils. Basically, in geotechnical engineering, the denomination of inverse problem or parametric calibration refers to an iterative process of comparison between the measured data and numerically predicted data both data sets define the objective function obtained from the numerical model, which allows determining the best fitting parameters of the model. This methodology is useful to define soil engineering standards for geotechnical applications, like radioactive waste repositories. In this work we describe the behaviour of a clay soil by means of a three-dimensional elasto-plastic model for unsaturated soils. This constitutive model is within the framework of the global mechanical problem of the unsaturated soils, regarding the volume deformations, pre-consolidation stress and shear states. The influence of suction on the mechanical behaviour of unsaturated soil is taken into account by using a principle of stress that is obtained adding a function of the suction to the net mean stress. (authors)