Viscous Behaviour of Unbound Granular Materials in Direct Shear

Modelling of Ageing Effects on the Elasto-Viscoplastic Behaviour of Geomaterial

“…The ‰ow characteristic (i.e., the irreversible volumetric and shear strain relation) is basically free from the viscous property and can be expressed as part of the properties of P body in Fig. 2(a) Duttine et al, 2008). More study on the ageing eŠect on the ‰ow characteritics is necessary.…”

Viscous Property of Toyoura Sand Over a Wide Range of Shear Deformation Rate and its Model Simulation

“…2 and 5 imply that the following behaviour trends should be observed in ML tests at diŠerent constant · s values: 1) With dense specimens, the peak shear strength is rather independent of · s, while the residual shear strength decreases with an increase in · s. 2) With loose specimens, the peak shear strength noticeably decreases with an increase in · s, while the residual shear strength decreases more signiˆcantly with an increase in · s. As shown below, these behaviour trends are actually observed in ML at constant but diŠerent values of · s. The increasing and decreasing rate in the shear stress ratio, RDS, upon a step increase and decrease by a factor of 10 and 1/10 is deˆned as the rate sensitivity coe‹cient, bDS. The value of b DS is rather independent of void ratio and shear displacement (Duttine et al, 2008a). The bDS values obtained from these tests presented in Figs.…”

“…Study of the viscous properties also provides valuable information of the internal deformation mechanism of geomaterial. Recent studies have revealed that the type of viscous property (i.e., the viscosity type) of geomaterial is not unique but diŠerent depending on geomaterial type while it is much more complicated than had been considered (e.g., Di Benedetto et al, , 2005Tatsuoka, 2007;Tatsuoka et al, 2002Tatsuoka et al, , 2008Duttine et al, 2008a). Figure 1 schematically illustrates the stress-strain behaviours for the four basic viscosity types that have been found by various recently performed laboratory stress-strain tests on a wide variety of geomaterials.…”

“…The general trend of the viscosity of geomaterials is that, as the geomaterial becomes less coherent and/or as the interlocking among particles becomes weaker, the viscosity type tends to change from the Isotach to the Combined; then to the TESRA; and nally to the P&N (Tatsuoka, 2007;Tatsuoka et al, 2008). Furthermore, the viscosity type tends to change with an increase in the shear strain (or the shear deformation) in a single shear test (Duttine et al, 2008a), as typically seen from Fig. 2.…”

“…On the other hand, Duttine et al (2008a) evaluated the viscous properties of dense specimens of a number of unbound granular materials over a very wide range of shear displacement (i.e., a wide range of shear deformation of the shear zone) before and after having reached the residual state by performing drained DS tests under constant pressure (as shown in Fig. 2).…”