Numerical study of the effect of soil-atmosphere interaction on the stability and serviceability of cut slopes in London clay

The stability of cut slopes is greatly influenced by seasonal pore-water pressure variations under the combined effect of rainfall and vegetation. However, predicting soil-atmosphere interaction is not straightforward, due to the complexity of both the boundary conditions involved and the hydromechanical behaviour of soils, which is coupled and highly nonlinear, rendering the use of numerical tools, such as finite element analysis, necessary. This paper discusses the numerical modelling of soil-atmosphere interaction and presents the analysis of a slope cut in London clay in a highly vegetated area. The whole life cycle of the slope is considered with phases of low and high water demand vegetation and vegetation clearance. The analysis results indicate that dense vegetation is associated with high factors of safety, but may induce large differential displacements, which are likely to affect the serviceability of the slope. Vegetation clearance, however, may initiate instability, highlighting the need for effective vegetation management to achieve a balance between serviceability and ultimate limit states. Although the case considered is representative of southeast England, it introduces the necessary tools for realistic numerical analysis of soil-atmosphere interaction. Key words: slope stability, serviceability, vegetation, precipitation, soil-atmosphere interaction. La stabilite des pentes entaillees est fortement influencee par les variations de pression de l'eau interstitielle saison nieres sous l'effet combine des precipitations et de la vegetation. Cependant, predire l'interaction sol-atmosphere n'est pas si simple, en raison de la complexite des deux conditions aux limites en cause et le comportement hydromecanique des sols, qui est couple et fortement non lineaire, ce qui rend l'utilisation d'outils numeriques, tels que l'analyse des elements finis neces saire. Cet article traite la modelisation numerique de l'interaction sol-atmosphere et presente l'analyse d'une pente entaillee dans l'argile de Londres dans une zone tres vegetalisee. L'ensemble du cycle de vie de la pente est considere avec des phases de demande en eau basse et haute de la vegetation et la clairance de la vegetation. Les resultats de l'analyse indiquent que la vegetation dense est associee a des facteurs eleves de securite, mais peut induire des deplacements differentiels qui sont susceptibles d'affecter l'etat de fonctionnement de la pente. L'enlevement de la vegetation, cependant, peut declencher l'instabilite, soulignant la necessite d'une gestion efficace de la vegetation afin de parvenir a un equilibre entre la fonctionnalite et les etats limites ultimes. Bien que le cas considere est representatif du Sud est de l'Angleterre, il presente les outils necessaires a l'analyse numerique realiste de l'interaction sol-atmosphere. [Traduit par la Redaction] Mots-cles: stabilite des pentes, facilite d'entretien, vegetation, precipitations, interaction sol-atmosphere.
Introduction It has long been established that one of the main factors affecting the performance of infrastructure slopes (cut and embankment slopes) is the magnitude and variation of pore-water pressures [...]