Three-dimensional mineral grade distribution modelling and longwall mining of an underground bauxite seam

A multi-step interpolation approach was proposed to model the three-dimensional grade distribution and to demarcate orebody in a thin and anfractuous bauxite seam. A pre-mining demonstration procedure was established to virtually perform fully mechanized longwall mining in the modelled bauxite seam. Meanwhile, a comprehensive evaluation function expressed by the sum of dilution and loss rates of bauxite was utilized to determine the optimal cutting heights (1.71-2.69 m) and a suitable diameter (1.5 m) for the cutting drums mounted on a double-drum shearer to achieve no-waste and high-recovery mining of the demarcated 106,026 m3 bauxite orebody. In addition, a numerical model of strata containing geological defects (a karst cave and fault), discontinuities (joints and stratifications) and a mountain was established to simulate the discontinuous motion and overburden fracturing disturbed by the longwall mining in the modelled bauxite seam. The results indicated that the overburden presented reliable stability and impermeability, in which no large-scale caving in goaf, no water influx, no cave collapse, no fault slip, and no mountain slope landslide occurred. This was due to arched roofs above the Karst cave and the mining-induced fractured zone, the subcritical condition of the longwall panel in the dip section, and support from the protective pillar between two adjacent panels.