In this study

large-scale triaxial consolidation drained（CD） shear tests under 0.2-3.5 MPa confining pressure for the rockfill of Shuibuya Dam were performed to investigate the stress-strain behaviors of rockfill

i.e.

deviatoric stress-axial strain relationship and volume strain-axial strain relationship.Stress-strain relationships under different confining pressure conditions are determined using relationships of failure strength and volume strain to confining pressure.Critical deviatoric stress σ

cre

and critical deviatoric strain ε

vcre

normalize the stress-strain relation

ships of experimental results and verifies the proposed equation.The experimental results show that

for the dense rockfill

a certain elastic stage occurs in the initial deformation

and its slope is strongly dependent on confining pressure.More strain softening is observed under low the confining pressure.The rockfill presents strain hardening and shear contraction within 0.8≤σ

3

≤3.0 MPa of confining pressure.Dilatancy behavior occurs depends on the critical confining pressure（between 0.45 and 0.8 MPa）.The deformation of rockfill under σ

3

>3.0 MPa presents strain softening and shear contraction.Analysis show that the rockfill strength decrement caused by particle breakage is greater than the increase caused by confining pressure increment.The relative breakage rate is above 15%.Peak principal stress ratio is reduced as the confining pressure increases

consistent with the increase of axial strain.The fracture strength is observed linear with confining pressure.Predictions by proposed equation show that the formula given in this paper is correct.