A generalized Cambridge-type constitutive model for sand is developed from the fundamental axioms of critical state theory. An infinity of normal consolidation loci for sand prevents the direct cou...

Nor-sand: a simple critical state model for sand

Angles of friction and dilatancy of sand

A fabric tensor \IF\di\dj\N for three-dimensional assemblies of granular soils is introduced as an index showing the anisotropy due to the preferred orientation of constituent particles and is actually determined by using data derived from a material science approach of soils. Using the fabric tensor, a Drucker–Prager type of yield function is extended so as to take into account the anisotropic yielding behavior of granular soils. Plane strain tests on Toyoura sand are analyzed with a result that the anisotropic shear strength is well fitted by the extended Drucker–Prager yield function. Based on this, it is concluded that this study provides a step to link the material science approach of soils, in which the spatial arrangement of particles and associated voids plays an important role, to the continuum theory of plasticity.

Yield Function for Soil with Anisotropic Fabric

Synopsis A theoretical relation is derived between the peak Coulomb φ values for saturated drained sands measured in the direct shear test and the plane strain compression test using the stress-dilatancy equation and the assumption that the directions of principal strain increment and principal stress coincide. Limiting dilatancy rates in triaxial compression allow an overall comparison of the φ values to be expected in these three types of test. Present available experimental data indicate quite close agreement over the range φu = 17°–39° for cohesion-less soils. On derive une relation theorique entre les valeurs φ de pointe de Coulomb pour des sables draines satures mesurees dans l'essai de cisaillement direct et l'essai de compression a deformation en plan en utilisant 1'equation de contrainte-dilatabilite et la supposition que les directions de l'accroissement de deformation principale et de la contrainte principale coincident. Des taux limites de dilatabilite en compression tr axiale permettent de fa...

The Relationship Between the Shear Strength of Sands in Triaxial Compression, Plane Strain and Direct Shear

Synopsis Certain design problems in soil mechanics should be treated as deformation rather than failure problems and to this end incremental stress-strain relations must be developed for different types of soil. The incremental strain rate ratio given by the stress-dilatancy relation may prove valuable in such studies. A short account is given of the stress-dilatancy theory with particular reference to the concepts of the upper ocv and lower oμ, limits. The main object of the Paper is to investigate the conditions under which these limits are approached employing stress paths involving both loading and unloading in triaxial compression and extension. A major part of the Paper is devoted to a critical discussion of errors involved in drained triaxial tests on sand and to certain modifications developed to minimize these errors. The peak or failure points in the various tests have been studied to assess the failure criteria commonly applied to soils. It is shown that the extended Von Mises and Tresca criter...

J Khayatt Amir

Papers

Incremental strain rate ratios and strength of sand in the triaxial test