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The response characteristics of the mesostructure and macro-characteristics of the soil–rock mixture under repeated freeze–thaw action have an important influence on the safety and stability of the dump slope in low-temperature environments. In order to further understand the multi-scale response behavior of a soil–rock mixture under freeze–thaw cycles, this paper carried out indoor freeze–thaw cycles, uniaxial compression, and electrochemical impedance spectroscopy tests on a soil–rock mixture taken from a graphite mine dump in Jixi City, Heilongjiang Province, China. Combined with the simulation calculation of discrete element numerical software (PFC2D 7.0), the effects of freeze–thaw cycling on electrochemical impedance spectrometry (EIS) mesoscopic parameters, uniaxial compressive strength, and crack propagation of soil–rock mixtures were analyzed. The intrinsic relationship between mesoparameters and macroscopic mechanical properties was established. The results showed that as the number of freeze–thaw cycles increases from 0 to 15, the mesopores inside the soil–rock mixture gradually increase, and the angular similarity of distribution characteristics increases by 5.25%. The uniaxial compressive strength and the peak secant modulus increase exponentially with the increase in the number of freeze–thaw cycles, the uniaxial compressive strength decreases by 47.62%, and the peak secant modulus decreases by 75.87%. The peak strain and pore compaction stage showed an exponential increase and an increasing trend, respectively, and the peak strain increased from 2.115% to 4.608%. The failure mode was basically similar in different cycles; the failure cracks extended from the corners to the middle and lower parts before the failure finally occurred. The types of failure cracks were mainly tensile cracks, followed by tensile shear cracks and the fewest compression shear cracks. The similarity and uniaxial compressive strength conformed to a good linear relationship with the number of freeze–thaw cycles, with the uniaxial compressive strength decreasing linearly with the increase in similarity. [ABSTRACT FROM AUTHOR]

Tungsten, essential in the industrial, military, and civilian domains and deemed a strategic resource by various nations, necessitates careful consideration in room and pillar mines due to the potential instability and safety hazards posed by untouched mine pillars, making tungsten recovery crucial for worker safety and economic gain. This research aims to provide guidance for recovering tungsten from mine pillars and making mining operations safer for workers in the Xianglushan mine. Numerical simulations are conducted to study the mechanical response of a preformed roadway in a backfill body subjected to static and dynamic loads with various explosive distances and positions. Blasting vibration velocity and blasting-induced damage in the backfill body are extracted to evaluate the mechanical response of the backfill body. The numerical results indicate that the steel frame and preformed roadway remain stable under the influence of both gravity and the impact from blasting, using a charge of 3.00 kg per blasthole. By analyzing these indicators, potential safety hazards in the backfill body and preformed roadway are identified, and the numerical results provide guidance for mine pillar recovery practices. [ABSTRACT FROM AUTHOR]

Carbonyl iron powder–polymer coating is one of the effective microwave absorption systems, which can be widely used as medium temperature structural materials in the aerospace industry. However, the significant mismatch of the coefficient of thermal expansion (CTE) between coatings and the titanium alloy substrates will cause serious cracking and peeling problems in practical applications. Thus, we designed to introduce Y2Mo3O12 (YMO) with negative CET into the carbonyl iron powder–boron-modified phenolic (BP) resin coating to reduce the CET of coating. The result showed that the CTE of the coatings is significantly decreased by the addition of Y2Mo3O12. The YMO/CIP/BP coating of 8 wt% YMO - 67 wt% CIP - 25 wt% BP shows a CTE of 21.1 × 10–6 ℃−1, which is 68% smaller than that of CIP/BP coating. The minimum RL (maximum of microwave absorption) of 8 wt% YMO - 67 wt% CIP - 25 wt% BP is – 12.3 dB at the thickness of 1.4 mm, which makes it an excellent candidate for the microwave absorptions applied on the titanium alloy surfaces. [ABSTRACT FROM AUTHOR]