Performance of an alternative tool for rock cutting: the case of Luserna Stone

This study presents an overview of the Luserna Stone Basin, located in the region of the Cozie Alps in Piedmont, northwest Italy. It covers an area of approximately 50 km2 between the Pellice and the Po Valleys, where numerous quarries have been developed over the years. The commercial term "Luserna Stone" refers to a gray-blue gneiss with small clear feldspar eyes and high lamination. The area of interest is known as "Tube Medie" and "Tube Superiori" and is located in the municipality of Bagnolo Piemonte, west of the village of Montoso and near the border with the municipality of Luserna San Giovanni. The Luserna Stone quarries have always been a source of employment for the local population and beyond since ancient times. Currently, the commercialization of this material has expanded nationally and internationally, becoming a strength for the economy of this region, which is not always prosperous but remains significant, especially due to the stone's durability over time. After outlining the geology and petrography of this specific gneiss, the Luserna-Rorà and Bagnolo basins are analysed within the context of the PRAE, the Regional Plan for Exploitation Activities of Piedmont which is a tool adopted to plan and manage the extraction of natural resources. This study describes the main geomechanical characteristics of the rock under investigation, obtained through laboratory tests conducted on samples coming from the Tube Medie and Superiori quarries. In particular, the more compact samples, suitable for sawing and known as the massive formation, belong to the Tube Medie area, while those characterised by distinct schistosity and suitable for splitting, known as the schistose formation, come from the Tube Superiori quarries. The geostructural arrangement of the quarries under exam, referring to the layout and orientation of geological structures, is analysed in detail, together with the recovery and block yield of the stone. Furthermore, the quarrying method employed, which involves the organization in horizontal descending benches, is assessed, followed by an analysis of stone-cutting technologies. The three techniques commonly used for the detachment of gneiss blocks are: dynamic splitting with detonating cord, diamond wire sawing and the expansive mortar. Finally, the results of the tests performed with an innovative product aimed at rock cutting, called Minax, are presented. Minax is a compound used in mining activities for bench blasting, block squaring, and rock fragmentation, as well as in the civil sector for trench excavation and similar applications. This substance, which aims to become an alternative to conventional explosives, was developed and produced in Brazil in 2020. The technical characteristics and performance of Minax are presented in detail, together with a critical analysis of the results obtained from the experimental campaign.