Critical state of rockfill materials and a constitutive model considering grain crushing

The grain crushing of rockfill materials with high stress level has significant influence on its strength and deformation mechanisms. The soil mechanics theory based on critical state concept can describe the stress-strain relationship of reconstituted soils successfully, but currently for rockfill materials, few studies are conducted on influence of grain crushing on critical state and its mathematical description. The consolidation drained and undrained triaxial compression tests of 18 sets with consolidation stress ranging from 0.4 MPa to 4 MPa and isotropic compression tests of 6 sets were conducted on rockfill materials. The experimental results show that: for all the consolidation confining pressures, the samples tended to critical state under drained and undrained conditions; and the critical states of rockfill materials in q-p' plane and e-lgp' plane all behave nonlinear. Based on these experimental results and by introducing state parameter, a new constitutive model for rockfill materials is formulated under the framework of generalized plasticity; and the determination of model parameters is provided as well. Finally, the constitutive model is used to simulate the test results of rockfill materials from Changhe Dam; and it is verified that the proposed constitutive model could simulate well the stress-strain features of rockfill materials with the consolidated confining pressures ranging from 0.4 MPa to 3.5 MPa.