153 prediction of TBM performance in hard rock conditions has been subject to extensive research, including empirical and analytical models for penetration rate and advance rate estimation (Rostami, 2016). Beyond technical differences, this transition represents a system-level change in underground development. Continuous excavation generates uniform tunnel geometries, reduces reliance on diesel-intensive operations, and creates a more stable energy demand profile. These structural characteristics directly influence safety performance, ventilation requirements, and schedule predictability. For underground mining, this shift is not merely technological but strategic. Development performance increasingly affects capital exposure, early cash flow, and regulatory compliance. Evaluating excavation systems therefore requires consideration of safety metrics, energy intensity, and schedule reliability in addition to conventional cost-per-meter comparisons. 2. PERFORMANCE METRICS FOR SUSTAINABLE UNDERGROUND DEVELOPMENT The transition toward lower-emission and higher-safety underground operations requires excavation systems to be evaluated using measurable performance indicators. Traditional comparisons based primarily on cost per meter or advance rate no longer capture the broader operational and regulatory context of modern mining projects. Mechanized excavation systems have increasingly been described in mining literature as integrated production systems rather than isolated excavation tools (Asche and Mather, 2014). To assess excavation methods from a sustainability and risk perspective, two key dimensions are particularly relevant: safety performance and energy intensity. 2.1 Safety Performance: Exposure and Lost Time Injury (LTI) Safety in underground development is strongly influenced by personnel exposure at the excavation face and the frequency of high-risk activities. Conventional drill-and-blast operations involve repeated cycles of drilling, explosive charging, blasting, ventilation clearance, scaling, and re-entry. Each cycle requires personnel to return to the face under changing ground conditions, contributing to cumulative exposure. Lost Time Injury (LTI) rate is widely used as a standardized safety indicator in the mining industry. While project-specific datasets vary, structural differences in process architecture directly influence exposure profiles. Continuous mechanized excavation reduces or eliminates activities such as explosive handling and repeated face re-entry, thereby modifying the risk structure of the development process.
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