An integrated approach for rockfall analysis with drapery systems

The rockfall hazard in mining environments needs to be rigorously managed in order to ensure safe mining operations, in particular when designing portal entries for punch longwalls. The installation of drapery systems is a common practice to mitigate the rockfall hazard at the base of highwalls. However, the hazard is not completely eliminated since blocks can still detach and fall in between the drapery and the highwall. This contribution shows how geostructural modelling and 3D rockfall analysis can be combined in order to accurately map and assess the rockfall hazard at the base of such highwalls. The study entails the estimation of the size distribution of unstable blocks and the simulation of their trajectories and velocities for highwalls without and with drapery. First, 3D photogrammetry is combined with discrete fracture network modelling in order to generate polyhedral models of the rock mass structure. Polyhedral modelling and kinematic analyses are combined to estimate the volume and shape distribution of unstable blocks. Unstable blocks are then classified according their shape. Second, a 3D discrete element rockfall model is presented which allows for an accurate prediction of velocities and run‐out distances for rock slopes with and without drapery. The 3D model is used to predict trajectories and velocities for blocks representative of a highwall, i.e. block size and shape according the results from the polyhedral modelling. The focus is to investigate the efficiency of the drapery and to quantify the residual rockfall hazard at the base of a highwall