Influence of intermediate principal stress on deformation and strength of gravel

True triaxial tests on specimens of gravel were performed,in which σ3 was invariable,and σ1,σ2 were loaded at the same time in a certain proportion b [=(σ2-σ3)/(σ1-σ3)].The influences of the intermediate principal stress on three principal strains and strength were studied separately.Mohr-Coulomb Criterion,Lade-Duncan Criterion,Matsuoka-Nakai Criterion and Fang Kai-ze Criterion were compared with the true triaxial test results of gravel.It was found that the relationships between friction angle and b reflected by Matsuoka-Nakai Criterion and Fang Kai-ze Criterion were different from those of the experimental results,and the laws reflected by Lade-Duncan Criterion were close to those of the experimental results,while it overrated the influence of b on the friction angle.Hence a criterion was proposed,and the relationship between the friction angle and b was deduced and verified using several true triaxial test results.It was indicated that the proposed criterion could reflect the relationship between the friction angle and b more accurately than Lade-Duncan Criterion and Matsuoka-Nakai Criterion.