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THE MECHANIZED MINING OF AGGRESSIVE ROCK: THE INDUSTRIAL APPLICATION WITH SPECIAL REFERENCE TO IN SITU CUTTING MEASUREMENTS

Objective

To define an industrial testing tool that will provide all the characteristics of a cutting machine for mechanical mining in places traditionally reserved for blasting because of the hardness and the abrasivity of the rock.

The research will comprise the following stages.

Stage 1 is the adaptation of the cutting tools and machines to aggressive rocks. This will involve the following work.
Based on previous research, a theoretical model will be established accounting for the complexity of the rock failure mode and its change when the wear appears and develops. The theoretical predictions will be compared to the in situ data and the laboratory data. The model will be used to predict the advantage and limitations of various tools cutters, depending on rock type and general conditions.
In the improvement of aggressive rock cutting tools, the solutions will be search for in 2 directions: the research of the best tip well adapted to the aggressive rock cutting and the use of activated tools (diamond tipped tools, water jet assisted, and vibration assisted tools). A comparison of the lifetime and the performance of the classical tools (picks and disc cutters) and activated ones will be established.
The effect of wear on tools will be studiied. Practical applications of cutting process are limited because of the rapid wear on tools cutting in abrasive rocks. For the kinetic investigation of the tool wear an abrasivity index of the rock and a wear index of cutting tools will be defined, and then the correlations between the wear index and the cutting parameters, such as time of tool use, rock abrasivity and cutting speed, will be investigated and factors influencing the wear process.
In the previous EC project, a computer program was developed for roadheaders in order to compare performances of different kinds of machines and to evaluate their energy consumption. This program will be improved to simulate the dynamic performances of the cutting machine in aggressive rocks and extended to tunnel boring machines for allowing realistic comparisons between picks and disc cutters (classical and activated) for the mechanized mining of aggressive rocks. The computer simulation will be linked with experimental results in order to provide a reliable mean of investigation into the cuttability of aggressive rocks for tunnelling purposes.

Stage 2 is in situ and laboratory testing.
The in situ testing device includes a cutting model, capable of supporting picks or disc cutters (classical or assisted) and will test the rock in realistic working conditions. This device will have most of the classical laboratory testing advantages, such as variable cutting speed, advance speed, thrust, etc. For the specifications of the in situ cutting device, ARMINES will provide advice and will supervise the tests. For the design, the realization and the testing of the data acquisition system, SILIUS will be jointed by University of Cagliari. This system will measure and record the stresses and strains of the picks, the rotation and translation speeds of the cutting head, and the thrust and torque on the disc (for disc cutters). The data will be collected in a systematic way for future treatments.
The cutting tools tests mentioned below will also be realised with the in situ device in the Silius Mine. The design and realization of picks and disc cutters will be in the charge of ARMINES and CGES.
The laboratory tests will first provide a rock characterization. They will be conducted with the 10 rocks selected in the previous CCE project and the mineral Silius Mine. They will then be dedicated to full and reduced scales cutting tests. The experimental rigs available for the project consist of 2 full scale rigs and 2 reduced scale rigs. The testing programme aims to compare the dynamic performances of different types of cutting tools, to compare the lifetime of different tools, and to measure forces and torque with scaled cutting heads. The various tools to be compared are the classical tools (pick and disc cutter) and new tools such as water jet assisted cutting tools, diamond tipped tools and vibration assisted tools.

Stage 3 is the technical and economical evaluation. From the quantification of the incidence of wear of different cutting tools on the working costs of the cutting machine, the profitability of assisted tools will be analyzed. In the same way, a realistic choice between picks and disc cutters will be done with economical considerations. Such an evaluation of the mechanized mining costs could allow general applications to metallic mines and to other underground excavations, comparing the results with classical drilling and blasting methods. Finally, this analysis will be applied to the Silius Mine, and the technical characteristics of a cutting machine, economically viable, will be given.

Stage 4 is the final joint report.

Coordinator

Association pour la Recherche et le Développement des Méthodes et Processus Industriels - ARMINES
Address
Rue Saint-honoré 35
77305 Fontainebleau
France

Participants (1)

Nuova Mineraria Silius SpA
Italy
Address
Viale Merello 14
09123 Cagliari