A Unified Approach To The Modelling of Liquefaction And Cyclic Mobility Of Sands

Abstract

In this paper the problem of liquefaction of sand under either monotonic or cyclic loading is tackled from the point of view of continuum mechanics. It is shown that a suitable constitutive model may explain, in a phenomenological sense, the generation of pore pressure in an undrained test either when the load is monotonically increased to failure or when sand is cyclically sheared at constant stress or strain amplitudes. It is demonstrated that in the former case liquefaction of loose samples amy be described if a convenient set of constitutive parameters is chosen. It is also shown that liquefaction under cyclic loading may occur even for very dense sands, and that the essential features revealed by experiments, such as progressive pore pressure build-up accompanied by small shear strains followed by a sudden pore pressure increase with large strains, are correctly modelled by the theory. The constitutive model employed is a combination of a classical elastoplastic constitutive law, which proved to be successful in modelling the behaviour of sand under monotonic loading, and of a law allowing for hysteresis, which applies to loading processes within the yield locus, especially conceived to interpret the behaviour of soils under cyclic loading. (Author/TRRL)