Numerical simulation of true triaxial tests on mechanical behaviors of rockfill based on stochastic granule model

The three-dimensional deformable discrete element method is employed to study the strength and deformation characteristics of rockfill under three-dimensional unequal stress states by means of true triaxial numerical tests. In addition, the six-rigid-plate loading and the constant value of the intermediate principal stress ratio loading paths are adopted. The simulated results show that the true triaxial numerical tests can preferably reflect the stress and deformation of rockfill under the three-dimensional unequal stress states, and the numerical results are the same as the test ones. The stress ratio parameters significantly affect the stress intensity of rockfill under the three-dimensional stress state and the three-dimensional strain also changes with the increase of the ratio parameters. To be more specifical, when the intermediate principal stress ratio parameter b increases from 0 to 1, the second principal strain direction changes from compression to expansion while the third principal strain direction has always been in the state of compression, and the the internal friction angle of rockfill increases with the increase of b, which basically conforms to the Lade-Duncan failure criterion. In the mesoscopic level, the higher the confining pressure is, the larger the value of b and coordination number of particles are. In the loading process, the anisotropy degree of contact normal orientation and contact normal force are strengthened, the main direction of contact force turns to the loading direction, the anisotropic coefficient evolution curve is similar to the stength curve, in other words, the strength of the rockfill samlpes has some relationship with the normal contact.