MINERÍA la mejor puerta de acceso al sector minero MINERÍA / SEPTIEMBRE 2022 / EDICIÓN 540 66 de pilares simplificadas decrecientes, 1-4-7 y 1-5-9 para un total de 144 tajos. Se usa una combinación del criterio BSR y el análisis volumétrico para proporcionar información sobre la ubicación, el momento y la duración del macizo rocoso inestable dentro del cuerpo mineralizado, el techo y el piso en todos los niveles del bloque minero. Metodología Configuración del modelo El modelo simplificado de un cuerpo mineralizado típico en el Escudo Canadiense se construyó usando FLAC3D, con una extensión de 360 m a lo largo de un rumbo EO y una inclinación de 80° hacia el sur. Las formaciones hospedantes comprendían metavolcánicas con una formación de roca verde dominante, una formación de norita rígida al norte y metasedimentos dúctiles al sur. Un enjambre de intrusiones ígneas en la to the north, and ductile metasediments to the south. A swarm of igneous intrusions in the region were represented by two dykes striking WNW-ESE to the north and south of the orebody. The model dimensions were 840 m along the EW axis, 390 m along the NS one, and 300 m in depth. A total of 862,400 zones were used with a higher mesh density in the zones of interest. Based on commonly used intervals in sublevel open stoping, vertical distances between levels were set at 30 m. Stopes were dimensioned at 20 m along the strike length, 15 m in width, and 30 m in height, translating into 18 stopes longitudinally and 2 transversely for 36 on each level. Mining was simulated from the bottom up on four active levels – L1550, L1520, L1490, and L1460 – from a depth of 1550 m to 1430 m. Each stope was designed with a volume of 9,000 m3 for a total of 324,000 m3 per level and 1,296,000 m3 for four active levels. Haulage drifts were excavated in the footwall at 30 m from the ore- body, in addition to three crosscuts – western, cen- tral, and eastern – per level. Drift and crosscut di- mensions were based on those typically used in Canadian mines with a 5 m × 5 m cross-section and a 1-m arch in the back. Figure 1 presents an isometric view of the model. The mining block from L1580 to L1430 is shown in detail in Figure 2a, while details of the haulage drifts and crosscuts are presented in Figure 2b. Rock Mass Properties and Pre-mining Stresses The rock mass properties used in the model were based on a previous case study mine in the Canadian Shield. Laboratory test results on intact rock samples were combined with borehole logs indicating the rock mass rating (RMR) to derive the required rock mass properties, which are summarized in Table 1 and were used as input properties. The model was simulated in linear elastic mode to maximize induced stress magnitudes and provide a more conservative estimate of potential instability. Based on the rock mass properties of the geologic units, the BSR criterion was selected to gauge the potential for instability in the orebody and greenstone formation. The generation of pre-mining stresses in homogeneous (McKinnon, 2001) and heterogeneous rock mass (Shnorhokian et al., 2014) was achieved using boundary tractions applied on all sides of the model. Calibration was conducted to obtain model readings on L1490 within the norite formation comparable to in-situ measurements obtained at the previous case study mine. Additional model readings on L1400 and L1580 were compared to typical stress Figura 3. Números de secuencia de extracción por tajeo para los enfoques de pilares 1-4-7 y 1-5-9.
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