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

Viscous Properties of Granular Materials Having Different Particle Shapes in Direct Shear

“…For example, in drained DS tests on medium dense to dense air-dried specimens of uniform relatively angular sands (i.e., Hostun and Toyoura sands), the viscosity type in the pre-peak regime is TESRA, which gradually changes to P&N in the post-peak regime and remains so at the residual state (Duttine et al, 2008). This trend was also observed in ML DS tests for a wide range of constant shear displacement rates, diŠerent by a factor of 100,000 (Duttine et al, 2009). d) The viscous properties for a given geomaterial type can be properly quantiˆed by the rate-sensitivity coe‹cient ( b13) deˆned as:…”

“…The DS tests were performed at a constant average normal pressure sv of 50 or 100 kPa. In the study of Duttine et al (2008Duttine et al ( , 2009, the initial opening before consolidation was systematically set between 10 and 20･D50 of the respective materials (i.e., natural sands and glass beads). In case of Chiba gravel-a, the opening was limited to 5 mm, as 10･D50 comes to about 20 mm, which is as high as about one third of the height of a half DS box (60 mm) and it was considered that this large opening would provoke signiˆcant stress release at the specimen edges.…”

“…Despite the signiˆcantˆndings mentioned above, it is very di‹cult to evaluate the viscous properties for a wide range of shear loading state, from the pre-peak regime to the full residual state, using TC and PSC tests and torsional shear tests. Duttine et al (2008Duttine et al ( , 2009 showed that the direct shear (DS) tests are more relevant to this end. As the viscosity type tends to change with shear strain and due to this limitation of the TC tests mentioned above, Enomoto et al (2009) could not su‹ciently quantify the in‰uence of particle shape on the viscous properties of granular materials.…”

Effects of Particle Characteristics on the Viscous Properties of Granular Materials in Shear

“…The features of the developments of inelastic strain described in this paper are summarized in Table 4. The eŠect of void ratio indicated in this table is after Duttine et al (2008b).…”

“…Firstly, the r1 value re‰ects the viscosity type in that r1 is equal to 1.0 with Isotach type, while it decreases as the viscosity type changes from Isotach toward P&N. Secondly, more coherent geomaterials (e.g., sedimentary soft rock and cement-mixed soil as well as highly plastic clay) exhibit the Isotach type viscosity (with r1＝1.0). With unbound GMs, the viscosity type changes from Isotach toward P&N as the microstructure becomes less stable associated with; a) a decrease in the coordination number (i.e., the average number of contact points between particles per particle) due to a decrease in Uc and a dry density (Duttine et al, 2008b); and b) a decrease in the inter-particle interlocking due to a decrease in A * (i.e., with a decrease in the particle angularity).…”