ABSTRACT
A torsional hollow cylinder device called “T4CstaDy” was developed to study the behaviour of sand in a wide range of strains (from approx. 10−6 to 10−2). Experimental data have shown the existence of delayed or viscous effects for Hostun dry sand. A general framework based on a three component element is explained to model the viscous and non-viscous behaviour. As regards the non-viscous part, eight terms for compliance tensor may be determined and the existence of a limit tensor has been observed for very small amplitude cycles. A new hypoelastic model for this limit tensor is proposed to take into account some experimental observations (symmetry of this tensor, anisotropy, etc.). Simulations of moduli are presented for different tests, with and without rotation of axes, performed at a confining pressure of 300 kPa. For the viscous part, a new component named “viscous evanescent” is described. It allows the modelling of the viscous properties of Hostun sand, for example, when sharp strain rate changes or creep periods occur. A simulation of a typical test is presented.
