Abstract: For studying the variation law of strength,deformation and model parameters of Duncan-Chang E-B model induced by shrinking scale of rockfilling materials,super-large triaxial and large-scale triaxial shear tests were carried out for rockfilling material with the sample sizes of φ500 × 1000 mm(maximum test particle size was 100 mm)andφ300 × 700 mm(test maximum particle size was 60 mm)respectively.The results showed that the internal friction angle and peak stress of dmax =60 mm sample were larger than those of dmax=100 mm sample.The parameters k and Kb of Duncan-Chang model for dmax =60 mm sample were 16.92% and 9.44% larger than those of dmax=100 mm sample respectively.There was a good power function relationship between the initial deformation modulus and the confining pressure of the two tests.The initial Poisson's ratio showed a quadratic polynomial relationship with confining pressure.