Citation: Bohanek, V.; Su´ ceska, M.; Dobrilovi´ c, M.; Hartlieb, P. Effect of Confinement on Detonation Velocity and Plate Dent Test Results for ANFO Explosive. Energies 2022, 15, 4404. https://doi.org/10.3390/en15124404 Academic Editor: Albert Ratner Received: 14 May 2022 Accepted: 14 June 2022 Published: 16 June 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). energies Article Effect of Confinement on Detonation Velocity and Plate Dent Test Results for ANFO Explosive Vjeˇ cislav Bohanek 1, * , Muhamed Su´ ceska 1 , Mario Dobrilovi´ c 1 and Philipp Hartlieb 2 1 Faculty of Mining, Geology and Petroleum Engineering, University of Zagreb, 10000 Zagreb, Croatia; muhamed.suceska@rgn.hr (M.S.); mario.dobrilovic@rgn.hr (M.D.) 2 Mining Engineering and Mineral Economics, Montanuniversitaet Leoben, 8700 Leoben, Austria; philipp.hartlieb@unileoben.ac.at * Correspondence: vjecislav.bohanek@rgn.hr; Tel.: +385-913113456 Abstract: The detonation properties of nonideal explosives are highly dependent on charge diameter and existence and properties of confinement. In this study, the effect of different confinements on the detonation velocity of ANFO explosives was experimentally determined along with the results of the plate dent test. ANFO explosive was selected as one of the most commonly used nonideal explosives. Following the measurement results, we found that the detonation velocity increased with increasing wall thickness, and the velocity increase was different for different confinement materials. A strong correlation existed between the ratio of the mass of confiner and explosive (M/C) and the detonation velocity (R = 0.995), and between (M/C) and the depth of the dent (δ) (R = 0.975). The data presented in this paper represent preliminary findings in developing a confinement model required for reliable numerical modeling of nonideal explosives. Keywords: ANFO; confinement; detonation velocity; plate dent test 1. Introduction Nonideal high explosives are typically highly porous, low-density materials, where the fuel and oxidizer are not mixed on a molecular level, with a low detonation velocity (3–5 km/s) and a long detonation reaction zone (approximately centimeters) [1]. Due to its safety characteristics, simple manufacturing process, low price, and satisfactory blasting and technical properties, ANFO explosive is one of the most commonly used nonideal explosives in mining, construction work, and even for explosive welding of metal. Apart from its wide use, ANFO explosive is interesting from a scientific point of view, i.e., the numerous factors that affect the degree of nonideal behavior [2]. Several authors have presented their research on the influence of various parameters on the detonation velocity of ANFO, such as: • Grain size, density, and porosity of ammonium nitrate [3–6]; • The influence of the addition of aluminum powder of different particle sizes and in different proportions [7–9]; • Method of initiation [10,11]; • ANFO temperature [12]. The relationships between the ANFO density, radius of the charge, oil fraction, and detonation velocity are already well-known [13]. One of the research interests related to the nonideal detonation of ANFO explosives is the influence of confinement on the detonation velocity and the shape of the detonation front. This article presents research conducted on small-diameter pipes made of different metals and wall thicknesses, and the influence of confinement on the measured detonation velocity, with the results of the plate dent expressed by a linear equation. Energies 2022, 15, 4404. https://doi.org/10.3390/en15124404 https://www.mdpi.com/journal/energies