Development and Underground Validation of an In-Stope Hard Rock Cutting and Vacuum Extraction System for Narrow Tabular Platinum Mining

Deep-level South African platinum mining is constrained by narrow tabular orebodies, geotechnical complexity, heat and declining drill-and-blast productivity. Continuous non-explosive extraction remains a strategic mechanisation objective, but a practical system must combine efficient hard rock breakage with reliable removal of cuttings in a severely constrained excavation. This paper presents the development and underground validation of an integrated in-stope system comprising an undercutting hard rock cutting unit and a vacuum rock transportation system. Development progressed through component testing and modelling, integrated original equipment manufacturer testing, underground assembly, and a seven-month on-mine validation programme against twenty-one cutting-system and fifteen vacuum-system key performance indicators agreed before the trial. The system achieved a stable 50 mm depth of cut at 12 mm per cutter per revolution, an average advance rate of 1.20 m per cutting hour against a 1.05 m/h business-case target, and a peak of 1.4 m per cutting hour. The vacuum system achieved extraction efficiencies of 88% for fragments smaller than 20 mm and 95% for fines smaller than 10 mm. Cutting occurred predominantly in anorthosite with an average uniaxial compressive strength of 237 MPa, outside the 100 to 130 MPa design envelope. During the evaluated productive cutting periods, material removal rather than rock-breakage capability constrained the sustainable operating setting. Hose friction, conveying distance and rock density contributed to residual fines that affected gripper stability and navigation. The trial establishes technical feasibility and identifies engineering controls required before extended production evaluation.