Protocol for the assessment of unsaturated soil properties in geotechnical engineering practice

The implementation of unsaturated soil mechanics into routine geotechnical engineering practice requires an evaluation of methodologies that may be used for the assessment of 'unsaturated soil property functions.' Guidelines and recommendations need to be provided to practicing engineers. The guidelines need to take the form of 'engineering protocols' that define acceptable standards for engineering practice. 'Engineering protocols' for unsaturated soils engineering practice can be divided into 'preliminary design' protocols and 'final design' protocols. Both design levels involve the use of a variety of estimation procedures that have been proposed for various classes of geotechnical problems (e.g., unsaturated flow, shear strength, volume change, and distortion). The hierarchy in methodologies is based mainly on the costs and risks associated with a particular engineering project. In this paper, 'hierarchical levels' are suggested that take into consideration the cost of various direct and indirect methodologies for the determination of unsaturated soil properties. Recommendations and suggestions are provided for methods for the determination and use of the soil-water characteristic curves (SWCC) and consequently, for the computation of unsaturated soil property functions (USPFs). Primary attention is given to estimation procedures best known to the authors and most appropriate for geotechnical engineering practice. Key words: unsaturated soil mechanics, soil-water characteristic curves, unsaturated soil property functions, soil suction, engineering protocols, hierarchical levels. L'implementation de la mecanique des sols non satures dans la pratique de routine de la geotechnique implique une evaluation des methodologies qui peuvent etre utilisees pour la determination des >> fonctions des proprietes du sol non sature >>. Les ingenieurs praticiens doivent avoir acce's aux lignes directrices et aux recommandations. Les lignes directrices doivent prendre la forme de << protocoles d'ingenierie >> qui definissent les standards acceptables dans la pratique de l'ingenierie. Les protocoles d'ingenierie peuvent etre divises en protocoles de conception preliminaire et en protocoles de conception finale. Ces deux niveaux de conception impliquent l'utilisation d'une variete de procedures d'estimation qui ont ete proposees pour differentes categories de proble'mes geotechniques (ex : ecoulement non sature, resistance au cisaillement, changement de volume et distorsion). La hierarchie des methodologies est basee principalement sur les couts et les risques associes a' un projet d'ingenierie specifique. Dans cet article, des >> niveaux hierarchiques << sont suggeres qui tiennent compte des couts de plusieurs methodologies directes et indirectes servant a determiner les proprietes des sols non sature s. Des recommandations et suggestions sont presentees a propos desmethodes de determination et d'utilisation des courbes caracteristiques sol-eau << SWCC >>, ainsi que sur les calculs des fonctions des proprietes du sol non sature << USPFs >>. Une attention particuliere est donnee aux procedures d'estimation les mieux connues par les auteurs et les plus appropriees pour la pratique de la geotechnique. Mots-cles : mecanique des sols non satures, courbes caracteristiques sol-eau, fonctions des proprietes du sol non sature, succion du sol, protocoles d'ingenierie, niveaux hierarchique. [Traduit par la Redaction]
Introduction The development of infrastructure to meet the needs of society commonly involves soils from above the groundwater table. These soils have negative pore-water pressures and are referred to as [...]