Theoretical study of lateral reaction mechanism of piles

Abstract

The mechanism of the lateral reaction of piles in an elastic-plastic medium is examined. Plane strain is first assumed. The analytical solution for a circular section in an elastic medium is given. The influence of pile section (square pile), disturbance of a soil ring around the pile, plastic yield of soil in undrained behaviour (Tresca's criterion) are studied by means of the finite element method. All these factors affect strains and stresses only in the vicinity of the pile. Graphs are given making it possible to calculate the corresponding corrective terms to be applied to the analytical solution. In a second step, which defines the value of the outside radius of this two-dimensional model, the simplified three-dimensional problem of a horizontally-loaded vertical axis in a semi-infinite elastic solid is studied using Mindlin's solution for a point force. The influence of the relative soil-pile rigidity, head loading and fixing conditions, which have an effect especially on distant fields, are taken into account and quantified by simple rules for determining this outside radius. Finally, a specific numerical application of the results is made and the solution is very satisfactory compared with experimental measurements. On étudie le mécanisme de réaction latérale des pieux en milieu élasto-plastique. On suppose tout d'abord que la déformation est plane. La solution analytique pour une section circulaire dans un milieu élastique est donnée. Les influences de la forme de la section du pieu (pieu carré), du remaniement d'un anneau de sol autour du pieu, de la plastification du sol en comportement non drainé (critère de Tresca) sont étudiées à l'aide de la méthode des éléments finis. Tous ces facteurs ne jouent sur le champ des déformations et des contraintes que dans le voisinage du pieu. Des abaques sont donnés, permettant de calculer les termes correctifs correspondants, à appliquer à la solution analytique. Dans un deuxième temps, pour préciser la valeur à prendre en compte du rayon extérieur de ce modèle bidimensionnel, on étudie le problème tridimensionnel simplifié d'un axe vertical chargé horizontalement dans un massif élastique semi-infini, en sommant la solution de Mindlin pour une force ponctuelle. Les influences de la rigidité relative sol-pieu, des conditions de chargement et d'encastrement en tête, qui affectent surtout les champs au loin, sont ainsi prises en compte et quantifiées par des règles simples de détermination de ce rayon extérieur. Enfin une application numérique concrète des résultats est faite et la solution est très satisfaisante, comparée aux mesures expérimentales.

Stabilisation of excavated slopes in strain-softening materials with piles

“…The p-y method uses the expected soil displacements to calculate pile reaction (e.g. Baguelin et al, 1977;Lee et al, 1995;Georgiadis & Georgiadis, 2010;Galli & di Prisco, 2013). In a limit equilibrium (e.g.…”

Tubular Piles – Buckling Design in a Complex Situation

“…Therefore, Scott suggested to use a bi-linear load-displacement behaviour with an initial stiffness corresponding to a value of C = 1 for equation (7.4). The suggested value is based on results by Baguelin et al (1977) which come from theoretical studies of a rigid cylinder which is moved horizontally in an elastic continuum. These approaches are very sensitive to the applied boundary conditions, as the distance of the pile from the support significantly influences the load-displacement behaviour and thus the coefficient of subgrade reaction.…”

“…The solution proposed by Baguelin et al (1977) uses a two-dimensional plane strain system with a rigid cylinder which is displaced laterally. The load applied to the pile causes a uniform translation of the corresponding circular boundary, i.e.…”

“…perfect adhesion between soil and pile. Baguelin et al (1977) solved the problem analytically by deriving the stresses from a single Airy function. The maximum radial displacements u R of the pile per unit thickness can be calculated as follows: By relating the applied load P to the radial displacements u R the coefficient of subgrade reaction k S can be calculated as a function of the Poisson ratio µ and the outside boundary r out .…”

Ultimate lateral load of slope-stabilising piles

“…A number of contributions dealt with pile-soil interaction, by means of Winkler approach (e.g. Baguelin et al, 1977;Fukuoka, 1977;Guo, 2006) or continuum models (e.g. Poulos, 1973Poulos, , 1995Poulos, , 1999Hull, 1993).…”