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Modelling of small-diameter rotary drilling tests on marbles
In order to optimise restoration strategies for the protection of natural building stones in historical monuments or to secure reliable numerical model estimations of the mechanical behaviour and collapse resistance of historical structures, it is necessary to know their mechanical properties, that is to say, deformability, uniaxial compressive and tensile strengths and fracture toughness among others, state of damage and effectiveness of possible consolidation treatments for restoration purposes. Continuum mechanics and discrete modelling are applied to investigate numerically rotary drill cutting experimental results on four marbles. Rock-cutting tests were performed by a new portable rotary microdrilling tool currently employed in practice for the quasi-non-destructive characterization of strength properties of rocks. The objectives of this research work were twofold, namely: to gain insight in the cutting mechanism of cohesive-frictional rocks, and to examine the comparability of numerical models predictions with experimental results by solving the forward problem. In the first type of model, a plane strain continuum calculation is done with a non-hardening, elastic-plastic, linear Mohr-Coulomb model with non-associative flow rule. In the second type of numerical model, discrete element calculations were done on a simulated plane strain sample of 540 discs. In both models, estimations are made on components of force applied to the cutting face of the bit and are compared with measurements taken with the data-acquisition system of the portable microdrilling tool during specially designed tests on marbles. It was found that the predictions of the continuum model are in full accordance with measured forces during drilling. It is also shown that the cohesion and internal friction angle are the most important parameters affecting the rock drilling resistance, as is depicted by the limit analysis theory of plasticity. Moreover, the calibration of the discrete element model on the experimental data permits the approximate estimation of the mode-I fracture toughness for each type of marble.
Modelling of small-diameter rotary drilling tests on marbles
In order to optimise restoration strategies for the protection of natural building stones in historical monuments or to secure reliable numerical model estimations of the mechanical behaviour and collapse resistance of historical structures, it is necessary to know their mechanical properties, that is to say, deformability, uniaxial compressive and tensile strengths and fracture toughness among others, state of damage and effectiveness of possible consolidation treatments for restoration purposes. Continuum mechanics and discrete modelling are applied to investigate numerically rotary drill cutting experimental results on four marbles. Rock-cutting tests were performed by a new portable rotary microdrilling tool currently employed in practice for the quasi-non-destructive characterization of strength properties of rocks. The objectives of this research work were twofold, namely: to gain insight in the cutting mechanism of cohesive-frictional rocks, and to examine the comparability of numerical models predictions with experimental results by solving the forward problem. In the first type of model, a plane strain continuum calculation is done with a non-hardening, elastic-plastic, linear Mohr-Coulomb model with non-associative flow rule. In the second type of numerical model, discrete element calculations were done on a simulated plane strain sample of 540 discs. In both models, estimations are made on components of force applied to the cutting face of the bit and are compared with measurements taken with the data-acquisition system of the portable microdrilling tool during specially designed tests on marbles. It was found that the predictions of the continuum model are in full accordance with measured forces during drilling. It is also shown that the cohesion and internal friction angle are the most important parameters affecting the rock drilling resistance, as is depicted by the limit analysis theory of plasticity. Moreover, the calibration of the discrete element model on the experimental data permits the approximate estimation of the mode-I fracture toughness for each type of marble.
Modelling of small-diameter rotary drilling tests on marbles
Modellierung von Rotationsbohrversuchen geringen Durchmessers an Marmoren
Stavropoulou, M. (author)
International Journal of Rock Mechanics and Mining Sciences ; 43 ; 1034-1051
2006
18 Seiten, 26 Bilder, 4 Tabellen, 18 Quellen
Article (Journal)
English
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