The Penhorwood Talc Mine slope design optimization is based on data collection from drone photogrammetry with resolution capabilities allowing for mapping of major structure and rock fabric (joints). The rock mass at Penhorwood is massive and the slope heights are limited; therefore, the slope design is controlled by major structure and rock fabric which control the interramp slopes and bench catchment. Call & Nicholas Inc. (CNI) developed a drone flight plan program that maximizes resolution with enough precision to map major structural features and rock fabric (joint patterns) in bedrock. Initial mapping of this project focuses on major structures defining structural domain boundaries followed by rock fabric mapping. The rock fabric mapping data confirms the distinct patterns of joints within structural domains and is used for interramp slope catchment design analyses. The design analyses are probabilistic and calibrated to measured bench geometries. Initial analyses show the interramp design can be steepened by approximately two degrees, which would reduce the stripping ratio at Penhorwood. This study demonstrates the potential for utilizing advanced open pit mine-specific drone flight planning and high-resolution point cloud mapping as a means to optimize interramp and catchment designs when pit access is limited or unavailable.
Recent advancements in drone technology have created opportunities for geotechnical analyses using remote sensing in open pit mines. With inexpensive drone hardware and photogrammetry software, high-resolution point clouds of mine highwalls can be generated for geotechnical and geological mapping. Call & Nicholas, Inc. (CNI) created the drone flight planning software, DronePlan3D, because no commercially available software existed that allowed for (1) terrain following using current topography, and (2) optimized gimbal angles over varying terrain (Barkley et al., 2020). Drone surveys conducted using DronePlan3D flight plans provide optimal coverage of mine highwalls, especially on the bench faces where critical geologic and rock fabric data is acquired.