DFN modelling has been widely applied to the design of rock excavations in the civil engineering space. The paper explores design solutions for bearing capacity of rock ledges in Hawkesbury Sandstone. The paper presents stochastic DFN models to generate typical rock defects for distinct classes of sandstone in the Sydney region. A summary of defect trace length study (i.e. proxy for joint length) for the Hawkesbury Sandstone is also included as this DFN parameter has an important influence on the creation of rock blocks/ wedges for the model. The bearing capacity of rock ledges are examined using discontinuum numerical analysis utilizing 3DECTM. The assessment parametrically alters the orientation and geometry of the excavation through referenced DFN models for Class II Sandstone. The results of the study provide a numerical perspective to the typical recommended values for ultimate and serviceability bearing capacities and highlight the influence of adverse rock defects on bearing capacities specially for particular excavation face orientations relative to dominant joint set orientations.
DFN modelling for rock excavation design is becoming common practice in the civil engineering space. This paper presents a case study integrating DFN modeling and discontinuum analysis using 3DECTM Version 7.0 to parametrically assess the bearing capacities of rock ledges. This works outcome provides a numerical perspective to the typical adopted bearing capacity values for sandstone in the Sydney region. Specific example has been taken from Class II sandstone. The summary workflow for this research is presented in Figure 1.
Ledges are a natural product of rock excavations. The bearing capacity of rock ledges are a particular case where the confinement of the rock mass on one side is removed. The stability of the rock face and thus the overall bearing capacity of the rock ledge is influenced by the increased kinematic freedom of rock blocks and wedges.