International Journal of Minerals, Metallurgy, and Materials最新文献

Mining is the foundation of modern industrial development. In the context of the “carbon peaking and carbon neutrality” era, countries have put forward the development strategy of “adhering to the harmonious coexistence of humans and nature.” The ongoing progress and improvement of filling mining technology have provided significant advantages, such as “green mining, safe, efficient, and low-carbon emission,” which is crucial to the comprehensive utilization of mining solid waste, environmental protection, and safety of re-mining. This review paper describes the development history of metal mine filling mining in China and the characteristics of each stage. The excitation mechanism and current research status of producing cementitious materials from blast furnace slag and other industrial wastes are then presented, and the concept of developing cementitious materials for backfill based on the whole solid waste is proposed. The advances in the mechanical characteristics of cemented backfill are elaborated on four typical levels: static mechanics, dynamic mechanics, mechanical influencing factors, and multi-scale mechanics. The working/rheological characteristics of the filling slurry are presented, given the importance of the filling materials conveying process. Finally, the future perspectives of mining with backfill are discussed based on the features of modern filling concepts to provide the necessary theoretical research value for filling mining.

The development of industry is inseparable from the support of mining. However, mining processes consume a large amount of energy, and increased tailing emissions can have a significant impact on the environment. In the past few decades, the mining industry developed many technologies that are related to mineral energy management, of which cemented paste backfill (CPB) is one of the representative technologies. CPB has been successfully applied to mine ground control and tailings management. In CPB technology, the mixing process is the key to achieving materials with good final quality and controlled properties. However, in the preparation process, the mixed homogeneity of the CPB is difficult to achieve because of fine tailings, high solid volume fraction, and high viscosity. Most research focused on the effect of mixing ingredients on CPB properties rather than on the preparation process of the CPB. Therefore, improving the performance and reducing the production cost of CPB by optimizing the mixing process are important. This review summarizes the current studies on the mixing technology of CPB and its application status in China. Then, it compares the advantages and disadvantages of multiple mixing equipment and discusses the latest results and research hotspots in paste preparation. Finally, it concludes the challenges and development trends of mixing technology on the basis of the relevant application cases in China to promoting cement-based material mixing technology development.

The great challenge of cemented tailings backfill (CTB) is difficult simultaneously maintaining its excellent mechanical properties and low cost. Fly ash (FA) can potentially address this problem and further replace cement in favor of low carbon development. However, its mechanism on CTB with low cement dosage and low Ca system remains unclear. Consequently, this study conducted uniaxial compression, X-ray diffraction (XRD), and scanning electron microscopy (SEM)–energy dispersive spectrometer (EDS) tests to investigate the effect of FA dosage on the mechanical property and microstructure of CTB. A molecular model of FA-CSH was constructed to reproduce the molecular structure evolution of CTB with FA based on the test results. The influences of FA dosage and calcium/silica molar ratio (Ca/Si ratio) on the matrix strength and failure model were analyzed to reveal the mechanism of FA on calcium silicate hydrated (C–S–H). The results show that the strength of CTB increases initially and then decreases with FA dosage, and the FA supplement leads to a decrease in Ca(OH)₂ diffraction intensity and Ca/Si ratio around the FA particles. XRD and SEM–EDS findings show that the Ca/Si ratio of C–S–H decreases with the progression of hydration. The FA-CSH model indicates that FA can reinforce the silica chain of C–S–H to increase the matrix strength. However, this enhancement is weakened by supplementing excessive FA dosage. In addition, the hydrogen bonds among water molecules deteriorate, reducing the matrix strength. A low Ca/Si ratio results in an increase in water molecules and a decrease in the ionic bonds combined with Ca²⁺. The hydrogen bonds among water molecules cannot withstand high stresses, resulting in a reduction in strength. The water absorption of the FA-CSH model is negatively correlated with the FA dosage and Ca/Si ratio. The use of optimal FA dosage and Ca/Si ratio leads to suitable water absorption, which further affects the failure mode of FA-CSH.

Paste flow patterns and microscopic particle structures were studied in a pressurized environment generated by a pulse pump. Complex loop-pipe experiments and fluid–solid coupling-based simulations were conducted. The scanning electron microscopy technique was also applied. Results revealed that flow resistance is closely related to pipeline curvature and angle in a complex pipe network. The vertical downward–straight pipe–inclined downward combination was adopted to effectively reduce the loss in resistance along with reducing the number of bends or increasing the radius of bend curvature. The maximum velocity ratio and velocity offset values could quantitatively characterize the influences of different pipeline layouts on the resistance. The correlation reached 96%. Particle distribution and interparticle forces affected flow resistance. Uniform particle states and weak interparticle forces were conducive to steady transport. Pulse pump pressure led to high flow resistance. It could improve pipe flow stability by increasing flow uniformity and particle motion stability. These results can contribute to safe and efficient paste filling.

The mechanical properties of cemented paste backfill (CPB) determine its control effect on the goaf roof. In this study, the mechanical strength of polymer-modified cemented paste backfill (PCPB) samples was tested by uniaxial compression tests, and the failure characteristics of PCPB under the compression were analyzed. Besides, acoustic emission (AE) technology was used to monitor and record the cracking process of the PCPB sample with a curing age of 28 d, and two AE indexes (rise angle and average frequency) were used to classify the failure modes of samples under different loading processes. The results show that waterborne epoxy resin can significantly enhance the mechanical strength of PCPB samples (when the mass ratio of polymer to powder material is 0.30, the strength of PCPB samples with a curing age of 28 d is increased by 102.6%); with the increase of polymer content, the mechanical strength of PCPB samples is improved significantly in the early and middle period of curing. Under uniaxial load, the macro cracks of PCPB samples are mostly generated along the axial direction, the main crack runs through the sample, and a large number of small cracks are distributed around the main crack. The AE response of PCPB samples during the whole loading process can be divided into four periods: quiet period, slow growth period, rapid growth period, and remission period, corresponding to the micro-pore compaction stage, elastic deformation stage, plastic deformation stage, and failure instability stage of the stress–strain curve. The AE events are mainly concentrated in the plastic deformation stage; both shear failure and tensile failure occur in the above four stages, while tensile failure is dominant for PCPB samples. This study provides a reference for the safety of coal pillar recovery in pillar goaf.

The technology of cemented paste backfill (CPB) is an effective method for green mining. In CPB, mixing is a vital process aiming to prepare a paste that meets the non-stratification, non-segregation, and non-bleeding requirements. As a multiscale granular system, homogenization is one of the challenges in the paste-mixing process. Due to the high shearing, high concentration, and multiscale characteristics, paste exhibits complex rheological properties in the mixing process. An overview of the mesomechanics and structural evolution is presented in this review. The effects of various influencing factors on the paste’s rheological properties were investigated, and the rheological models of the paste were outlined from the macroscopic and mesoscopic levels. The results show that the mechanical effects and structural evolution are the fundamental factors affecting the rheological properties of the paste. Existing problems and future development trends are presented to change the practice where the CPB process comes first and the theory lags.

Pipeline hydraulic transport is a highly efficient and low energy-consumption method for transporting solids and is commonly used for tailing slurry transport in the mining industry. Erosion wear (EW) remains the main cause of failure in tailings slurry pipeline systems, particularly at bends. EW is a complex phenomenon influenced by numerous factors, but research in this area has been limited. This study performs numerical simulations of slurry transport at the bend by combining computational fluid dynamics and fluid particle tracking using a wear model. Based on the validation of the feasibility of the model, this work focuses on the effects of coupled inlet velocity (IV) ranging from 1.5 to 3.0 m·s⁻¹, particle size (PS) ranging from 50 to 650 µm, and bend angle (BA) ranging from 45° to 90° on EW at the bend in terms of particle kinetic energy and incidence angle. The results show that the maximum EW rate of the slurry at the bend increases exponentially with IV and PS and first increases and then decreases with the increase in BA with the inflection point at 60° within these parameter ranges. Further comprehensive analysis reveals that the sensitivity level of the three factors to the maximum EW rate is PS > IV > BA, and when IV is 3.0 m/s, PS is 650 µm, and BA is 60°, the bend EW is the most severe, and the maximum EW rate is 5.68 × 10⁻⁶ kg·m⁻²·s⁻¹. In addition, When PS is below or equal to 450 µm, the maximum EW position is mainly at the outlet of the bend. When PS is greater than 450 µm, the maximum EW position shifts toward the center of the bend with the increase in BA. Therefore, EW at the bend can be reduced in practice by reducing IV as much as possible and using small particles.

The anisotropy of the structure and properties caused by the strong epitaxial growth of grains during laser powder bed fusion (L-PBF) significantly affects the mechanical performance of Inconel 718 alloy components such as turbine disks. The defects (lack-of-fusion, LoF) in components processed via L-PBF are detrimental to the strength of the alloy. The purpose of this study is to investigate the effect of laser scanning parameters on the epitaxial grain growth and LoF formation in order to obtain the parameter space in which the microstructure is refined and LoF defect is suppressed. The temperature field of the molten pool and the epitaxial grain growth are simulated using a multiscale model combining the finite element method with the phase-field method. The LoF model is proposed to predict the formation of LoF defects resulting from insufficient melting during L-PBF. Defect mitigation and grain-structure control during L-PBF can be realized simultaneously in the model. The simulation shows the input laser energy density for the as-deposited structure with fine grains and without LoF defects varied from 55.0–62.5 J·mm⁻³ when the interlayer rotation angle was 0°–90°. The optimized process parameters (laser power of 280 W, scanning speed of 1160 mm·s⁻¹, and rotation angle of 67°) were computationally screened. In these conditions, the average grain size was 7.0 µm, and the ultimate tensile strength and yield strength at room temperature were (1111 ± 3) MPa and (820 ± 7) MPa, respectively, which is 8.8% and 10.5% higher than those of reported. The results indicating the proposed multiscale computational approach for predicting grain growth and LoF defects could allow simultaneous grain-structure control and defect mitigation during L-PBF.