Adaptive Strength Criterion of Sandy Gravel Material Based on Large-Scale True Triaxial Tests

Abstract

A series of large-scale true triaxial tests was performed on sandy gravel material from a hydropower station in southwest China. Adopting a special friction-reduction technique, the strength and deformation characteristics of the material were investigated at different stress levels and different intermediate principal stress ratios. The stress, deformation and strength were then analyzed under the framework of generalized deviatoric stress, mean effective stress and Lode angle. The tested strength parameters with the suggested friction-reduction technique were compared with several classic strength criterions, showing a good fitness with the Lade-Duncan criterion and an underestimation by the Mohr-Coulomb criterion. With the increase of coefficient of intermediate principal stress, the material shows an increase of the internal friction angle, but a reduction on the q-p stress ratio. The strength envelope in the π plane shrinks with the increase of stress level.