4. HYPOTHESES 4.1 General Hypothesis Negative operational elasticity between mechanical availability and jumbo utilization reflects that operational delay times, beyond mechanical aspects, limit the proportional increase of utilization when availability improves. 4.2 Specific Hypotheses ● There is negative operational elasticity between mechanical availability and utilization, showing that an increase in availability does not necessarily generate a proportional increase in equipment utilization. ● Drilling performance (m/h) varies between day and night shifts; however, these variations are not exclusively attributable to mechanical availability, but also to operational and management conditions. ● Operational delays not associated with the mechanical condition of equipment (such as operator absence, planning, work organization, and coordination) represent the most influential factors in reducing effective utilization. 5. BACKGROUND Mining productivity depends on multiple factors including equipment reliability, operational planning, infrastructure, and human resources. While maintenance strategies aim to improve mechanical availability, productivity improvements require that operational conditions allow equipment to be effectively used (Bernaola, 2012). Studies on underground mining operations have shown that reducing unproductive times significantly improves equipment utilization and operational efficiency (Apaza, 2017; Martínez, 2016). Long-hole drilling is a highly mechanized mining method used in sublevel stoping operations, where long holes are drilled toward the orebody and blasted to extract large volumes of material. This method offers high productivity but depends strongly on continuous operational support, such as adequate ventilation, access to the work face, energy supply, and operator availability (Arniel et al., 2016). Time management is critical in drilling operations, as equipment performance is determined not only by mechanical failures but also by operational delays that reduce productive drilling time. Previous research has identified that operational delays, auxiliary equipment availability, and coordination inefficiencies are among the main factors affecting productivity in underground mining operations (Gómez, 2017). 6. CONCEPTUAL FRAMEWORK Mechanical availability is defined as the percentage of scheduled time during which the equipment is mechanically capable of operating.
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