STRESS PROPAGATION IN SAND

We describe a new continuum approach to the modelling of stress propag ation in static granular media, focussing on the conical sandpile crea ted from a point source. We argue that the stress continuity equations should be closed by means of scale-free, local constitutive relations between different components of the stress tensor, encoding the const ruction history of the pile: this history determines the organization of the grains, and thereby the local relationship between stresses. Ou r preferred model fixed principle axes (FPA) assumes that the eigendir ections (but not the eigenvalues) of the stress tensor are determined forever when a material element is first buried. Stresses propagate al ong a nested set of arch-like structures within the medium; the result s are in good quantitative agreement with published experimental data. The FPA model is. one of a larger class, called oriented stress linea rity (OSL) models, in which the direction of the characteristics for s tress propagation are fixed at burial. We speculate on the connection between these characteristics and the stress paths observed microscopi cally. (C) 1998 Elsevier Science B.V. All rights reserved.