KEYWORDS In-cycle shotcrete; mine development; underground support; fast-cycle concrete; Inmaculada Mine; cycle time optimization; fiber-reinforced shotcrete; narrow-vein mining; safety INTRODUCTION Underground mines worldwide are looking for optimizations to advance development faster and more safely to meet production targets, especially as orebodies at greater depths present challenging ground conditions. In conventional drill-blast cycles, ground support installation is often a critical path activity that can slow down advance rates. After each blast, crews must scale down loose rock and install supports (such as rock bolts, mesh, or shotcrete) before proceeding to the next round. Traditional practice may delay shotcrete application to a later shift or after other support elements are in place, extending the cycle time per round (Smith and Andrews, 2019). In-cycle shotcrete (ICS) is an innovative (optimized) approach that addresses this bottleneck by applying shotcrete during the development cycle (immediately post-blasting and mucking) rather than at the end or after a delay. By providing near-instantaneous reinforcement of the newly exposed rock, ICS can significantly shorten the re-entry waiting period required for support to gain strength (Ozturk et al., 2016). Previous trials of ICS in mines have reported substantial improvements in heading advance rates and ground stability, making it a promising technique for high-speed development (Jenkins et al., 2005; Garcia et al., 2018). This work focuses on the Inmaculada Mine, operated by Hochschild Mining in southern Peru, exemplifies a scenario where ICS can yield substantial benefits. The mine is a highaltitude (≈4,700 masl) epithermal gold-silver deposit with multiple narrow veins hosted in fractured volcanic rock. Geotechnical assessments classify much of the rock mass as weak to moderately competent (poor quality) (e.g., RMR 0-40), with frequent discontinuities and altered zones that demand timely support after blasting. Maintaining development advance in these conditions is challenging unsupported spans can slough or deteriorate quickly, posing safety risks. Prior to the ICS trial, the mine employed a conventional cycle: drill and blast a round (~3 m advance), exhaust fumes and scale loose rock, then install shotcrete with rock bolts and wire mesh, sometimes followed by shotcrete in a subsequent step. This sequential process meant that shotcrete application often lagged one or more cycles behind the face advance or required waiting for a previous round’s shotcrete to cure adequately before drilling nearby. Consequently, heading cycle times were on the order of 12–14 hours, limiting each development face to perhaps 2 rounds per day at best. The mine identified this support delay as a major constraint on development performance and a contributor to higher costs per meter (Hochschild Mining, 2022). An internal analysis indicated that if the support cycle could be accelerated (without sacrificing safety), additional rounds per month could be achieved, directly translating to more meters of advance and earlier access to ore. The implementation of ICS at Inmaculada aimed to address two main needs: (1) Reduce cycle time per round by enabling quicker re-entry after blasting through rapid support installation, and (2) Ensure ground safety in weak rock by providing immediate reinforcement. A secondary objective was to improve operational efficiency (e.g. reducing
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