Dem analysis of bonded granular geomaterials

In this paper, the application of the distinct element method (DEM) to frictional cohesive (c,) geomaterials is described. A new contact bond model based on the Mohr-Coulomb failure criterion has been implemented in PFC2D. According to this model, the bond strength can be clearly divided into two distinct micromechanical contributions: an intergranular friction angle and a cohesive bond force. A parametric analysis, based on several biaxial tests, has been run to validate the proposed model and to calibrate the micromechanical parameters. Simple relationships between the macromechanical strength parameters (c,) and the corresponding micromechanical quantities have been obtained so that they can be used to model boundary value problems with the DEM without need of further calibration. As an example application, the evolution of natural cliffs subject to weathering has been studied. Different weathering scenarios have been considered for an initially vertical cliff. Firstly, the case of uniform weathering has been studied. Although unrealistic, this case has been considered in order to validate the DEM approach by comparison against analytical predictions available from limit analysis. Secondly, nonuniform weathering has been studied. The results obtained clearly show that with the DEM it is possible to realistically model boundary value problems of bonded geomaterials, which would be overwhelmingly difficult to do with other numerical techniques.