Abstract
A constitutive model for sands and clays by which the general strain increments (dεx, dεy and dγxy) are directly related to the general stress increments (dσx, dσy and dτxy) is proposed. This model is derived from the hyperbolic relationship between the general shear-normal stress ratio (τxy/σx or τxy/σy) and the general shear strain (γxy), and the "stress-dilatancy relation" expressed in general coordinates. In order to evaluate the influence of rotation of the principal stress axes on strains, "rotation tests", in which the stress path is the circumference of a Mohr's circle, have been carried out by a "two-dimensional general stress apparatus" using a stack of aluminium rods (mixture of φ 1.6 mm and φ 3.0 mm). The test results agree well with the analytical ones based on the proposed model. Simple shear tests and liquefaction tests with rotation of the principal stress axes are also analyzed by the proposed model. The model is extended to a three-dimensional one using the superposition of the "two-dimensional" principal strain increments. The three-dimensional model can analyze all the results of triaxial compression and extension tests under constant mean, major and minor principal stresses, and constant principal stress ratios, and "stress probe" tests in triaxial compression and extension conditions. The stress-strain parameters in the proposed model are determined from a conventional triaxial test and an oedometer test.
