STUDY ON SHEAR BEHAVIORS OF ROCKFILL IN LARGE-SCALE TRIAXIAL TESTS UNDER DIFFERENT STRESS PATHS

According to the original gradation of the upstream main rockfill in the Yixing Pumped-storage Power Station,the rockfill samples are conducted with combining the similar gradation and equivalent weight modeling techniques.Some large-scale triaxial tests are performed on the samples with YS–30 large-scale triaxial test machine to investigate their shear behaviors under the different stress paths.It is shown that the stress paths together with the consolidation stress σc are the main external influential factors on the shear behaviors of the rockfill.The shear strength of the rockfill is of high nonlinearity,but the stress path almost does not influence the shear strength.With the increases of σc and the stress ratio k,the relationship of stress and strain changes from strain-softening(when σc is low) and the strain-hardening(when σc is high) to entire strain-hardening,but the relationship of volumetric strain and axial strain changes from the shear dilatancy(when σc is low) and shear shrinkage(when σc is high) to entire shear shrinkage.With the increase of stress ratio k,most of the plastic deformation of the rockfill changes from shear plastic deformation to compression plastic deformation;and the failure mode also changes from shear failure to compression failure.The transformation between shear dilatancy and shear shrinkage depends upon a critical stress ratio kcrit and consolidation stress(σc)crit.