Numerical simulation of vibroflotation compaction – application of dynamic boundary conditions
The stabilization of open cast mine dumps by vibroflotation compaction has been numerically simulated using a Particle Flow model. The main aspects of modeling have been the vibration of the compaction unit and the definition of non-reflecting boundary conditions besides the calibration of the micromechanical material behavior of the investigated soil. As compaction depends not only on the frequency but also on the amplitude of the compaction unit, for a given frequency the amplitude has been variably defined depending on the evoked reaction force of the surrounding soil. To prevent vibrations from being reflected at the model boundaries, so-called “quiet boundaries” were introduced. Therefore boundary particles are not restricted concerning the displacement but damping forces, depending on the actual velocity components, are applied, allowing the absorption of arriving shock waves. Some simulation results of vibration cycles lasting 30 seconds are shown, which prove the efficacy of the implemented features but also reveal remaining problems.