Influence du retrait et de la variabilité naturelle des sols argileux sur le comportement des fondations de maisons individuelles

Abstract

Differential movements of wall foundations are a common problem in lot of areas, where residential constructions rest on sensitive clay soils. Young as older structures, without any history of minimal differential movement before, can develop foundations problems in a very short time due to changing soil moisture during an extended dry period. Wall footings for residential construction are usually of dimensions to satisfy local buildings code, nevertheless in many cases, soil investigations are not performed and action due to sensitive clay soil and longitudinal variability of soil properties are not considered in the wall footing design. First, we show the ability of the VLF-R (Very Low Frequency -Resistivity mode) method to provide qualitative resistivity information on the soil variability and the presence of clay soil on a test site. Then, a simple model, based on a beam on an elastic soil foundation, describes the soil-structure interaction. This model is developed through a finite element model in which a 1D structure (wall footing) rests on a spatially varying soil, described with Winkler-type springs. This model is used to study induced effects of soil variations (described by the means of a spatial correlation function), shrinkage, differential settlements and critical bending moment values that cannot be predicted if the soil is assumed homogeneous or shrinkage left out under the wall footing. These different results give some tracks to revise the wall foundation design accordingly.