Consolidation theory for a composite foundation considering radial and vertical flows within the column and the variation of soil permeability within the disturbed soil zone

To remedy ihe coniradielion between lhe equal strain assumption and the flow continuity assumption at a soil-column interface, the traditional flow continuity assumption was abandoned and the radial and vertical flows within a stone column were incorporated to consider the column consolidation and deformation in a coupled fashion. Moreover, two possible variation patterns of the horizontal permeability coefficient of soil within the disturbed soil zone were included, to reflect the detrimental influence on the surrounding soil due to column construction. In addition, a linearly changed total vertical stress along the column depth was assumed, to achieve a more realistic stress distribution in practice. By considering the above mentioned characteristics, the governing equations for this type of consolidation problem were developed. The solutions for the governing equations were subsequently derived by using a new initial condition obtained from the equilibrium condition and equal strain assumption. On the basis of this, the average degree of consolidation of the composite foundation was obtained and discussed. Finally, a parametric study was performed and an application example was introduced to help engineers better utilize the present solution when applied to an actual design. Key words: consolidation, composite foundation, radial flow, coefficient of permeability. Afin de remedier a la contradiction entre les suppositions de deformations egale et de continuite de Tecoulement a (l'interface sol-colonne. la supposition traditionnelle de continuite de I'ecoulement a ete abandonnee pour introduire les ecoulements radiaux et verticaux, dans le but de considerer la consolidation et la deformation de la colonne de maniere couplee. De plus, deux types possibles de variations du coefficient de permeabilite horizontal du sol a 1'interieur de la zone affectee ont ete induits pour refleter 1'impact negatif de la construction de la colonne sur le sol environnent. Une contrainte verticale totale variant lineairement sur la hauteur de la colonne a aussi ete incluse afin d'obtenir une distribution des contraintes plus reahste. En considerant les caracteristiques mentionnees ci-haut, les equations pour des problemes avec ce type de consolidation ont ete developpees. Les solutions des equations sont obtenues en utilisant les nouvelles conditions iniliales derivees des conditions d'equilibre et la supposition de deformation egale. A 1'aide de ces equations, le degre de consolidation moyen pour la Ibndaiion composite est obtenu el discule. Finalemenl. une elude paramefrique a ete effectuee el un exemple d'applicaiion est presenie pour aider les ingenieurs a mieux uliliser la solution developpee pour des conceptions concretes. Mots-ctes : consolidation, fondation composite, ecoulement radial, coefficient de permeabilite. [Traduit par la Redaction]
Introduction Stone columns are one of the most commonly used soil improvement techniques to accelerate the consolidation process and improve the strength and stiffness in soft clay foundations. A number [...]