Prévision des tassements et gonflements instantanés dans les sols fins proches de la saturation

Abstract

RésuméDes progrès remarquables ont été accomplis ces dernières années dans le domaine des sols non saturés. Cependant, dans la pratique des bureaux d'étude, il est relativement courant de considérer que les sols sont saturés, surtout si le degré de saturation est proche de 1. Cet article montre que, pour les calculs des temps de consolidation ou de gonflement, cette hypothèse peut conduire à des résultats éloignés de la réalité, surtout dans les sols surconsolidés. Une nouvelle approche est proposée pour la prévision des tassements et gonflements instantanés, basée en particulier sur la loi de Henry et la loi des gaz parfaits. Une première validation de la méthode est présentée sur le remblai expérimental D de Cubzac-les-Ponts. Enfin, des abaques sont proposés pour déterminer le coefficient B = Δu/Δo en fonction des caractéristiques cedométriques et de la pression interstitielle. Instant settlement and swelling forecast in fine soils near saturation Mots-clés : AbstractThese last decades, num erous advances have been m ade in the unsaturated soil m echanics. However, it is common use to consider that soils are saturated in engineering practice, even if they are only « near saturation ». This sim plification, when used for consolidation calculations (settlem ent or swelling), can give results far from experimental m easurem ents, particularly for overconsolidated soils. Using Henry's law and perfect gas law, a new theory is proposed for the forecast of instant settlem ent or swelling. The im plem entation of this theory on Cubzac-les-Ponts experimental em bankm ent D is a first validation. Finally, this paper gives abacus to determine coefficient B = Δu /Δo as a function of oedometer characteristics and pore pressure.

A double-structure hydromechanical constitutive model for compacted bentonite

“…The presence of this entrapped air seems to significantly influence the behavior of the soil. Several studies indicate that the entrapped air affects the soil's hydraulic and mechanical properties [11][12][13]. However, at the degree of saturation mentioned above, it appears that neither unsaturated nor saturated formalisms can accurately reproduce the behavior of fine compacted soils.…”

Stress path during pressuremeter test and link between shear modulus and Menard pressuremeter modulus in unsaturated fine soils

“…We will consider two of the unsaturated soil states defined by Boutonnier [2007] ref [3] :  D1 : for this state the gas phase is continuous (suction is over air-entry suction s air (s>s air ) and saturation degree is over air entry saturation S lair (usually between 0,7 to 0,8).Additionally suction has no effect on volumetric forces and his variation effect is limited to inter-grain forces.…”