Effects of stress conditions on rheological properties of granular soil in large triaxial rheology laboratory tests

In order to study the rheological properties of red stone granular soil, a series of rheological experiments were executed on large tri-axial rheological apparatus. Under 100, 200 and 300 kPa confining stress conditions, the rheological tests were carried out. These experiment results showed that the stress conditions, especially the stress level were the critical influencing factors of the rheological deformation properties. Under the low stress level (S=0.1), the granular soil showed the elastic properties, and there was no obvious rheological deformation. Under the middle stress level (0.2<S <= 0.6), creep curves showed the linear viscoelastic rheological properties. However, under the high stress level ( S>0.8) creep curves showed the non-linear viscous plastic rheological properties. Especially, under the stress level of S=1.0, the accelerated rheological phase of creep curves occurred at early time with a trend of failure. The stress level had obvious effects on the final rheological deformation of the soil sample, and the final rheological deformation increments nonlinearly increased with stress level. The final rheological deformation increment and step was little under low stress level, while it became large under high stress level, which showed the nonlinearly rheological properties of the granular soil. The confining pressure also had direct effects on final rheological deformation, and the final rheological deformation linearly increased with confining pressure increments.