OFFICIAL IMPACT OF LOAD DIAMETER AND SPACING ON PRESPLIT DESIGN: FINITE ELEMENT ANALYSIS *H.A. Espinoza, M.G. Torres, J.F. Vergara Orica, Peru - Chile, (*Presenting author: Hector.espinoza@orica.com) ABSTRACT Numerical Modeling applied to presplit design allows evaluating the behavior of fragmentation and the formation of the cutting plane, considering variables such as load diameter, and spacing between holes. Unlike traditional models, this methodology incorporates real properties of the rock mass such as strength, elasticity, presence of geological structures and stress and deformation parameters, which improves the analysis and allows simulating conditions closer to the real behavior of the rock mass. The simulation technique used in this study is the Finite Element Model (FEM), which uses a plan view configuration, which allows simulating the formation of presplit cracks by means of a plane deformation study that incorporates the interaction of shock waves coming from the nearest holes. This work compares the behavior of the presplit filter in two types of load diameter configurations: 1 1/2 inches and 1 1/4 inches, evaluated with spacing of 1.2 m, 1.5 m, and 1.8 m. With this modelling it is possible to visualize the development of the fragmented planes, i.e. the cracks generated in the rock mass, which allows us to understand how the cut plane is formed and what is the real impact of each configuration on the rock mass. It was observed that larger diameters generate wider fracture radii, favoring the interconnection of cracks, likewise, it is confirmed that shorter spacings improve the continuity of the presplit filter, but require a careful design to avoid over-fracturing. The results allow us to establish more robust technical criteria for presplit design, contributing to more efficient geotechnical management in drilling and blasting operations. INTRODUCTION Within the set of controlled blasting techniques, presplitting has established itself as the most widely used solution to accurately define the excavation limit and the final quality of the slope. Its purpose is to generate, before the main shot, a plane of discontinuity faithful to the design profile, so that the subsequent energy stops at that limit. This approach seeks to minimize fracturing within the rock mass, improve slope stability, and reduce structural damage to the final wall. The resulting slopes comply with mining designs and ensure safer operations; furthermore, they align with sustainability criteria and generate a positive economic impact, fostering business continuity through reduced support costs and enhanced mining process performance. Presplit blasting consists of drilling a row of close and lightly loaded holes along the final excavation limits. These holes are fired prior to the main production blast to create a tensile fracture plane that stops the propagation of blast energy beyond the designed
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