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Microwave energy is a promising application in future rock breakage operations in the civil, mining, processing, and space industries. Rock engineering projects frequently experience mechanical vibration and blasting impacts. Thus, understanding the dynamic fracturing behavior of microwave-treated rock is essential for its future application in microwave-assisted mechanical rock breakage. A customized industrial microwave system with a multimode resonant cavity was used to heat red sandstone at different microwave power levels (up to 4 kW) for a constant exposure time (4 min). The rock surface temperature distribution after microwave treatment was measured by an infrared camera. Dynamic splitting tests were conducted using a split Hopkinson pressure bar (SHPB) system in combination with a high-speed camera. Experimental results indicate that the rock dynamic splitting strength is negatively related to the microwave power, and the maximum reduction is 47.8%. Microwave treatment induced an obvious nonuniform temperature distribution and C-shaped surface cracks on disc specimens. During the dynamic splitting test, the crack induced by dynamic loading always initiates from the crack tip induced by microwave irradiation and then propagates along the loading diameter. The distribution of the inner high-temperature zone in the disc specimen is symmetric along the horizontal centerline of the disc specimen. Key words: microwave treatment, dynamic splitting behavior, infrared temperature, rock fracturing, dynamic nominal tensile strength. Le recours a l'energie micro-ondes represente un potentiel prometteur dans les futures operations de bris de roche dans les industries civiles, minieres, de transformation et spatiales. La vibration mecanique et les impacts des explosions sont frequents dans les projets d'ingenierie des roches. Il est donc essentiel de comprendre le comportement dynamique de fracturation de la roche traitee par micro-ondes pour son application future dans les operations de rupture mecanique de la roche assistee par micro-ondes. On a utilise un systeme micro-ondes industriel personnalise equipe d'une cavite resonnante multimode afin de chauffer du gres rouge a differents niveaux de puissance micro-ondes (jusqu'a 4 kW) durant un temps d'exposition constant (4 min). La distribution de la temperature de la surface de la roche apres le traitement par micro-ondes a ete mesuree par une camera infrarouge. Des essais de fendage dynamique ont ete realises a l'aide d'un systeme de barre de pression Hopkinson fendue (SHPB) associe a une camera a grande vitesse. Selon les resultats experimentaux, la limite de fendage dynamique de la roche est negativement liee a la puissance des micro-ondes, et la reduction maximale est de 47,8 %. Le processus de traitement par micro-ondes a provoque une distribution non uniforme de la temperature et des fissures superficielles en forme de C sur les specimens de disques. Pendant l'essai de fendage dynamique, la fissure induite par le chargement dynamique commence toujours a partir de la pointe de la fissure induite par l'irradiation par micro-ondes, puis se propage le long du diametre de chargement. La distribution de la zone interne a haute temperature du specimen de disque est symetrique le long de la ligne centrale horizontale du specimen de disque. [Traduit par la Redaction] Mots-cles: traitement par micro-ondes, comportement dynamique de fendage, temperature infrarouge, fracturation de la roche, resistance nominale dynamique a la traction., 1. Introduction Safe and efficient continuous rock breakage significantly affects the progress of rock engineering projects. As the most commonly used rock breakage technique, drilling and blasting have been widely [...]

Using metallurgical solid waste Titanium-extracted Residual Slag (TRS) as mine-filling cementitious material is crucial to reduce the filling cost and promote the utilization of solid waste resources. In this paper, taking the strength of the backfill at different curing ages as the response target, the Design-expert mixing design was used to optimize the proportioning experiment of titanium-extracted residual slag, titanium gypsum, silicate cement, and total tailings, to analyze the interactions and influences of the materials on the strength of the backfill, and to analyze the hydration mechanism of the titanium-extracted residual slag-based filling cementitious materials under the optimal proportioning. The results show that: (1) the order of the sensitivity of each component to the strength of backfill is: composite activator > cement > titanium gypsum > titanium-extracted residual slag, and there are different degrees of interaction between them; (2) the optimal ratio of titanium-extracted residual slag-based filling cementitious materials is TRS:titanium gypsum:cement:composite activator = 55:25:17:3; (3) early strength formation of backfill is mainly related to its hydration products ettringite and C-S-H, the rapid nucleation and cross-growth of ettringite in the early stage forms an effective physical filling effect, which is the main reason for the formation of high early strength, and the later strength of backfill benefited from the continuous accumulation of C-S-H encapsulation and bonding, which further densified its internal structure; (4) the use of titanium-extracted residual slag-based filling cementitious materials contributes to safe, green, and economic mining. [ABSTRACT FROM AUTHOR]

The study of the constitutive model under stress loading for rock after undergoing freeze-thaw weathering cycles (FTWCs) treatment has important theoretical significance for the site operation and numerical calculation of rock mass engineering in cold regions. In this work, a series of FTWCs treatment tests of sandstone were carried out, and the evolution characteristics of the T 2 spectrum distribution curve for sandstone before and after FTWCs treatment were analyzed utilizing nuclear magnetic resonance (NMR) technology. The schematic diagram of freeze-thaw damage evolution for sandstone was drawn, and the damage evolution mechanism was analyzed. Evolution laws of the stress-strain curves, peak and residual strength, peak and residual strain, and Young's modulus of sandstone under different FTWCs and confining pressures were analyzed by conventional triaxial compression tests. A piecewise constitutive model under triaxial stress loading for sandstone after undergoing FTWCs treatment was established, and the model considered the significant influence of FTWCs on the nonlinear deformation in the compaction stage and residual strength. By introducing error analysis indexes, the proposed model and published models were compared with the experimental data, it was found that the proposed model's performance is better than the published models, which indicated that the proposed model has good performance and strong universality. [ABSTRACT FROM AUTHOR]