Mixed-Reality Geotechnical Cell Mapping for Slope Stability Assessment at Rio Tinto Bingham Canyon Mine
Authors: Nilufer K. B. A. , Karen B. , Lukas F. , Chad W. , Emre O. 
Published: August 2024

ABSTRACT:
In this paper, the applicability of Mixed Reality (MR) in combination with Uncrewed Aerial Vehicle (UAV) photogrammetry data is investigated to aid the cell mapping process at Rio Tinto's Bingham Canyon Mine. Cell mapping is critical for evaluating slope stability in mining operations but is traditionally time-consuming and poses safety risks to mappers. These challenges are tried to be addressed through hybrid methods, by collecting orientation data remotely from UAV-based photogrammetry and by integrating the Microsoft HoloLens 2 headset with pre-processed high-resolution UAV-based photogrammetry scans. The proposed methodology showcases the incorporation of EasyMineXR Desktop and EasyMineXR-MR with Microsoft HoloLens 2. Measuring orientation using MR and photogrammetry data helped us obtain comparable or enhanced-quality data in a digitized format. In the future, it is planned to incorporate an Augmented Reality (AR) technology for orientation measurements with merged UAV photogrammetry scans as the hardware technology improves. The trial of the proposed methodology underscores the potential of combining MR with UAV photogrammetry in geotechnical mapping applications for openpit mines, paving the way for safer and more efficient field data collection practices.

1. INTRODUCTION
Cell mapping is a data collection method for geotechnical characterization and is used to determine parameters such as Rock Mass Rating (RMR) (Bieniawski, 1988) and Geological Strength Index (GSI) (Marinos, 2005). These parameters along with other data can then be used as inputs for slope stability analysis. The most common approach to cell map areas is to take a cell-– nominally 50'X50' and describe the geotechnical characteristics of the rock, including rock mass and discontinuity parameters. Rock mass parameters include lithology, weathering, strength, rock defects, rock quality (RQD), and the number and fabric of the structure sets. Discontinuity information collected includes the structure type, persistence, fracture count spacing, infill type and thickness, joint alteration strength, seepage, roughness, waviness, and orientation.
Geotechnical engineers at Rio Tinto's Bingham Canyon Mine (BCM) utilize a similar cell mapping approach (Bakken, 2023). Collecting this information on mine high walls can be time-consuming and hazardous. Safety hazards include rockfall off the high wall, trips, slips, and falls, and prolonged exposure to thermal extremes. Limiting the time personnel are exposed to these hazards is one way the safety risk around collecting this data can be reduced. BCM operates 24/7 365 days a year. This limits the accessibility for cell mapping as the area must be segregated from haul traffic and the cell mapping process must not impact production. Therefore, the geotechnical team at the BCM has tested two methods that integrate innovative technologies with traditional mapping: (i) digital mapping using UAV-based photogrammetry data, and (ii) Mixed Reality (MR) for in-field mapping. These hybrid approaches, integration of digital mapping and MR to traditional mapping increase the overall safety of mappers by minimizing exposure near high walls while reducing the time for collecting data sets, such as structure orientation measurements. These methods also have the potential to increase the amount of data collected in a cell.