Limit equilibrium approach to study the evolution of shear band systems insoils

The paper is concerned with the analysis of shear band systems appearing in dry soil behind flexible retaining walls under plane strain conditions. Th e experimental problem studied is that of an initially vertical, plane reta ining wall, deforming because of the gradual excavation of sand from one si de of the wall, The aim of the paper is to clarify some of the possible phy sical reasons for multiple shear bands developing behind such walls. The pr oblem of shear band arrangement in a regular pattern, and their possible se quence, are also considered. The behaviour of soil adjacent to the wall is modelled by a set of rigid blocks, cut off from the soil body by lines para llel to the classical Coulomb wedge 'slip line' and sliding subsequently on each other. The distance between subsequent shear bands is calculated from the equilibrium of an actual soil wedge, which may contain previously acti vated wedges. An elastic behaviour of the wall is taken into account in a s implified way when equilibrium is verified. The plastic softening of soil i s expressed in terms of the angle of internal friction or cohesion decreasi ng linearly with soil wedge displacement. The present simplified analysis i s aimed as an explanation of shear band patterns, and constitutes a first s tep towards more refined treatments.