1968 1. Proximity to sensitive infrastructure (e.g., administrative facilities, water dam) requiring high confidence in design and execution to protect assets and maintain operational continuity. 2. High production targets, demanding efficient drill and blast practices to maintain throughput and cost control. 3. Orebody complexity, with carbonaceous domains that increase dilution risk and affect metallurgical recovery, requiring tighter control of dig boundaries and blends. 3. TECHNICAL APPROACH AND IMPLEMENTATION Approach consists of implementing technical projects to address each of the challenges presented. 1. Controlled blasting near sensitive areas, combining electronic initiation systems, predictive vibration modeling, and real-time QA/QC to maintain structural integrity and operational continuity. 2. Optimization of drilling and blasting through the application of high-energy explosives to expand patterns and reduce powder factor without compromising fragmentation quality. 3. Ore dilution control using three-dimensional blast movement modeling to improve dig-layer boundaries, reducing dilution and increasing blend reliability. 3.1 Controlled Blasting Near Sensitive Infrastructure 3.1.1 Context and Objectives Antas is a newly incorporated orebody in the Santa Luz mine plan and a key source of ore required to meet near‑term production targets. The Antas area consists of a series of small‑to‑medium pits, including Antas 3 North (A3N), which lies unusually close to sensitive infrastructure: administrative facilities at approximately 50 m and a water dam at roughly 300 m. Early planning considered relocating the administrative buildings; however, the time required to construct replacement facilities was incompatible with production schedules. The objective, therefore, was to deliver safe, compliant production blasting at A3N without relocation, preserving the integrity of nearby structures and ensuring continuity of ore supply. Three fundamental controls were established for blasting at A3N to ensure both blast quality and operating cost management: vibration control, flyrock control, and powder factor adherence. For administrative structures, the vibration limit adopted was based on local regulation (ABNT NBR 9653); for the dam, a stricter limit of 5 mm/s was applied. Flyrock control targeted the elimination of any fragment landing in the administrative area. Powder factor was defined as a critical indicator because it influences both blast quality and operating costs, increasing the level of analysis and control for A3N blasting outcomes. 3.1.2 Design and Implementation A3N presented an unprecedented challenge, as the required controlled blasting differed significantly from conventional practice elsewhere at Santa Luz. To address this complexity, the team first conducted a detailed review of references on controlled blasting, analyzing methodologies and technologies applicable to A3N’s conditions. Before commencing operations at A3N, a field validation campaign was carried out in Antas 2, a surrogate area with similar lithology but greater distance to sensitive structures. Signature holes and monitored blasts were used to calibrate the baseline vibration model, confirm maximum instantaneous charge (MIC) limits, and optimize stemming dimensions derived from Scaled Depth of Burial (SDOB) and cratering test results. Figure 124 presents the initial vibration model for A3N obtained from signature holes executed during this stage in the Antas 2 pit.
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