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4 pages, 175 KiB

Open AccessEditorial

Green Low-Carbon Technology for Metalliferous Minerals

by Lijie Guo

Metals 2022, 12(10), 1719; https://doi.org/10.3390/met12101719 - 14 Oct 2022

Viewed by 1035

Abstract

Metalliferous minerals play a central role in the global economy [...] Full article

(This article belongs to the Special Issue Green Low-Carbon Technology for Metalliferous Minerals)

Research

Jump to: Editorial

20 pages, 6336 KiB

Open AccessArticle

Experimental Study on Strength Development and Engineering Performance of Coal-Based Solid Waste Paste Filling Material

by Jiqiang Zhang, Ke Yang, Xiang He, Zhen Wei, Xinyuan Zhao and Juejing Fang

Metals 2022, 12(7), 1155; https://doi.org/10.3390/met12071155 - 6 Jul 2022

Cited by 23 | Viewed by 2025

Abstract

To explore the strength development characteristics and engineering performance of different coal-based solid waste filling materials cemented into filling body, coal gangue was used as coarse material, fly ash, desulfurization gypsum, gasification slag, and furnace bottom slag as fine material, and cement as [...] Read more.

To explore the strength development characteristics and engineering performance of different coal-based solid waste filling materials cemented into filling body, coal gangue was used as coarse material, fly ash, desulfurization gypsum, gasification slag, and furnace bottom slag as fine material, and cement as a gelling agent. The uniaxial compressive strength (UCS) and bleeding rate of coal-based solid waste cemented backfill (CBSWCB) were tested by an orthogonal experiment, and the influencing factors of mechanical properties and strength development were analyzed. The multiple generalized linear model of strength and bleeding rate was established, and the optimal filling material ratio was determined. The engineering performance index of CBSWCB with the optimal ratio was tested. The results show the following points: (1) the concentration and content of desulfurization gypsum had a great influence on the early compressive strength of CBSWCB, while fly ash, gasification slag, and furnace bottom slag had little influence on the early compressive strength. (2) High concentration, high content of fly ash and furnace bottom slag, low content of desulfurization gypsum, and gasification slag can significantly improve the early strength. High concentration and high content of fly ash, low content of gasification slag, furnace bottom slag, and desulfurization gypsum are beneficial to the later strength increase. (3) Under the optimal ratio scheme, the bleeding rate of CBSWCB was 1.6%, the slump was 16.6 cm, the cohesion was general, the segregation resistance was good, the initial setting time was 5.42 h, the final setting time was 7 h, and the early strength after curing for 8 h reached 0.24 MPa. Full article

(This article belongs to the Special Issue Green Low-Carbon Technology for Metalliferous Minerals)

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14 pages, 6749 KiB

Open AccessArticle

The Characteristics of Spiral Pipe Increasing Resistance and Reducing Pressure and the Amendment Equation of Stowing Gradient

by Weixiang Wang, Hongwei Mu, Guodong Mei, Lijie Guo, Xinqi Lu, Anhu Wang and Ran Sun

Metals 2022, 12(7), 1105; https://doi.org/10.3390/met12071105 - 28 Jun 2022

Cited by 2 | Viewed by 2070

Abstract

To solve the high slurry pressure and severe wear at some sections in backfilling pipelines, this study investigates the solution of using an auxiliary pipe to increase the resistance and reduce the pressure of the mine backfilling pipeline. Using computational fluid dynamics, three [...] Read more.

To solve the high slurry pressure and severe wear at some sections in backfilling pipelines, this study investigates the solution of using an auxiliary pipe to increase the resistance and reduce the pressure of the mine backfilling pipeline. Using computational fluid dynamics, three auxiliary pipe models, a Z-shaped pipe, a S-shaped pipe and a spiral pipe were constructed and the velocity and pressure distribution characteristics of the filling slurry in the auxiliary pipes were analyzed. The function of friction loss in spiral pipes with different pitches and spiral diameters was established, and the amendment equation for calculating the effective stowing gradient was studied when using spiral pipes to increase resistance and reduce pressure. The results show that, compared with the Z-shaped pipe and the S-shaped pipe, the velocity and pressure in the spiral pipe change continuously and steadily, and there is no obvious sudden change in the local velocity and pressure. Therefore, it is difficult to burst the pipe. When the velocity is 2.5 m/s and the vertical height of the pipe is 2.5 m, the friction loss of the filling slurry in the spiral pipe can reach 3.87~21.26 times that in the vertical pipe, indicating that the spiral pipe can effectively play the role of increasing resistance and reducing pressure. The relationship between the friction loss and spiral diameter is a linear function, and the relationship between the friction loss and pitch is a quadratic function. The three are binary quadratic function relationships. The equation for calculating the effective stowing gradient is obtained, which provides a convenient method for engineering applications and industrial design. Full article

(This article belongs to the Special Issue Green Low-Carbon Technology for Metalliferous Minerals)

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19 pages, 7527 KiB

Open AccessArticle

Regional Distribution and Causes of Global Mine Tailings Dam Failures

by Shui-Quan Lin, Guang-Jin Wang, Wen-Lian Liu, Bing Zhao, Ying-Ming Shen, Meng-Lai Wang and Xiao-Shuan Li

Metals 2022, 12(6), 905; https://doi.org/10.3390/met12060905 - 26 May 2022

Cited by 38 | Viewed by 5461

Abstract

Tailings ponds are one of the three major production facilities in metal mines. The volume of tailings increases year by year, but the storage capacity of existing tailings ponds is limited. Therefore, tailings dams must become more fine-grained and larger. The potential hazard [...] Read more.

Tailings ponds are one of the three major production facilities in metal mines. The volume of tailings increases year by year, but the storage capacity of existing tailings ponds is limited. Therefore, tailings dams must become more fine-grained and larger. The potential hazard they represent should not be underestimated. This paper reveals the causes and regional distribution patterns of 342 tailings dam failures globally from 1915 to 2021 through statistical analysis. It was found that tailings pond failures occur almost every year, with an average of 4.4 accidents/year (1947–2021). The frequency has been gradually increasing in recent years, and most tailings pond failures are directly related to heavy rainfall or earthquakes. The frequency of tailings pond failures was significantly higher in Asia (21.3%) and the Americas (57.9%), especially in China (n = 43) and the United States (n = 107). Causes of tailings pond failures differed among regions. Most tailings pond failures in Asia and Europe were related to hydroclimate, while those in South America were mainly triggered by earthquakes. This study will provide theoretical data for the pre-design as well as the safe and stable operation of global tailings ponds, which will help to prevent global tailings pond failures. Full article

(This article belongs to the Special Issue Green Low-Carbon Technology for Metalliferous Minerals)

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11 pages, 1790 KiB

Open AccessArticle

A Particle Size Distribution Model for Tailings in Mine Backfill

by Zongnan Li, Lijie Guo, Yue Zhao, Xiaopeng Peng and Khavalbolot Kyegyenbai

Metals 2022, 12(4), 594; https://doi.org/10.3390/met12040594 - 30 Mar 2022

Cited by 9 | Viewed by 3173

Abstract

With the increasing awareness of sustainable mining, the cement tailings backfill (CTB) method has been developed rapidly over the past decades. In the CTB technique, the two main mechanical properties engineers were concerned with are the rheological properties of CTB slurry and the [...] Read more.

With the increasing awareness of sustainable mining, the cement tailings backfill (CTB) method has been developed rapidly over the past decades. In the CTB technique, the two main mechanical properties engineers were concerned with are the rheological properties of CTB slurry and the resulting CTB strength after curing. Particle size distribution (PSD) of tailings material or PSD of the slurry is a significant factor that highly influences the rheological of CTB slurry and the strength performance of CTB. However, the concentrically partial size distribution curve and existing mathematical model could not represent the PSD of tailings material. In this study, a mathematical model for the particle size distribution of mine tailings was established using three model coefficients A B and K, which mainly reflect the characteristics of particles from three aspects respectively, the average size of particles, the proportion of the coarse or the fine parts of particles, and the distribution width of particles; meanwhile, an optimal coefficient solution method based on error analysis is given. Twelve tailing materials sourced from metal mines around China were used for the model establishment and validation. The determination coefficient of error analysis (R²) for all twelve modeled PSD lognormal curves was more significant than 0.99, and the modeled PSD lognormal curves are highly consistent with the determined particle size distribution curve. Full article

(This article belongs to the Special Issue Green Low-Carbon Technology for Metalliferous Minerals)

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14 pages, 9195 KiB

Open AccessArticle

Numerical Modelling of Blasting Dust Concentration and Particle Size Distribution during Tunnel Construction by Drilling and Blasting

by Jianjun Shi, Wei Zhang, Shucheng Guo and Huaming An

Metals 2022, 12(4), 547; https://doi.org/10.3390/met12040547 - 23 Mar 2022

Cited by 16 | Viewed by 2866

Abstract

In order to reduce the blasting dust concentration in the tunnel during the drilling and blasting, accelerate the tunnel excavation process, and improve the working environment for the construction workers, a three-dimensional geometric model of dust transport was established based on the gas-solid [...] Read more.

In order to reduce the blasting dust concentration in the tunnel during the drilling and blasting, accelerate the tunnel excavation process, and improve the working environment for the construction workers, a three-dimensional geometric model of dust transport was established based on the gas-solid two-phase flow model using the DesginModeler software, and the discrete phase model (DPM) in the FLUENT software was used to simulate the variation of dust concentration and the distribution of dust particle size at different locations along the tunnel route within 1200 s after tunnel blasting. The results showed that the concentration of blasting dust gradually decreased over time, with the fastest decrease in the range of 2 s to 120 s, and after 900 s, the dust concentration stabilized. The overall spatial distribution of the dust concentration showed a trend of decreasing from the palm face to the tunnel entrance and from the bottom plate to the upper part. The distribution pattern of dust with different particle sizes was not the same along the length of the tunnel. The large particles settled in the area of 25 m from the palm face under the action of gravity. With the increases of distance, the mass flow rate decreased, and the dust particle size became smaller, but the proportion of small particles gradually increased, while the R-R distribution index increased. The results in this study were confirmed to be reliable by comparing the measured data to provide guidance for the dust reduction technology in tunnel blasting, so as to quickly remove the dust generated during the blasting process and improve the engineering construction efficiency. Full article

(This article belongs to the Special Issue Green Low-Carbon Technology for Metalliferous Minerals)

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19 pages, 10889 KiB

Open AccessArticle

A Numerical Model for the Compressive Behavior of Granular Backfill Based on Experimental Data and Application in Surface Subsidence

by Zhi-Hua Le, Qing-Lei Yu, Jiang-Yong Pu, Yong-Sheng Cao and Kai Liu

Metals 2022, 12(2), 202; https://doi.org/10.3390/met12020202 - 21 Jan 2022

Cited by 8 | Viewed by 3201

Abstract

Granular backfill is generally confined in stopes to bear underground pressure in metal mines. Its mechanical behavior under lateral confinement is vital for controlling stope wall behavior and estimating surface subsidence in backfill mining operations. In this paper, an experimental apparatus has been [...] Read more.

Granular backfill is generally confined in stopes to bear underground pressure in metal mines. Its mechanical behavior under lateral confinement is vital for controlling stope wall behavior and estimating surface subsidence in backfill mining operations. In this paper, an experimental apparatus has been developed to explore the bearing process of granular material. Pebbles were selected to model granular backfill. A series of compression experiments of pebble aggregation were performed under lateral confinement condition using the experimental apparatus. The bearing characteristics of the pebble aggregation with seven gradations were analyzed. Based on the experimental data, a constitutive model that takes the real physical characteristics of granular material into account was proposed with variable deformation modulus. The constitutive model was implemented into the FLAC^3D software and verified basically by comparison with experimental results. The surface subsidence in backfilling mines was studied using the proposed model. The effects of the particle size of the granular backfill and the height and buried depth of mined-out stopes on surface subsidence have been clarified. The research results are of great significance for guiding backfill mining and evaluating surface subsidence and movement. Full article

(This article belongs to the Special Issue Green Low-Carbon Technology for Metalliferous Minerals)

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12 pages, 1824 KiB

Open AccessArticle

Copper and Zinc Recovery from Sulfide Concentrate by Novel Artificial Microbial Community

by Xinglan Cui, Xuetao Yuan, Hongxia Li, Xiaokui Che, Juan Zhong, Lei Wang, Ying Liu, Xuewu Hu, Qidong Zhang, Rongzhen Jin and Qi Zheng

Metals 2022, 12(1), 45; https://doi.org/10.3390/met12010045 - 25 Dec 2021

Cited by 2 | Viewed by 2680

Abstract

Exploring efficient methods to enhance leaching efficiency is critical for bioleaching technology to deal with sulfide concentrate. In our study, a novel artificial microbial community was established to augment the bioleaching efficiency and recovery of copper (Cu) and zinc (Zn). The optimum parameters [...] Read more.

Exploring efficient methods to enhance leaching efficiency is critical for bioleaching technology to deal with sulfide concentrate. In our study, a novel artificial microbial community was established to augment the bioleaching efficiency and recovery of copper (Cu) and zinc (Zn). The optimum parameters in bioleaching experiments were explored according to compare a series of conditions from gradient experiments: the pH value was 1.2, temperature was 45 °C, and rotation speed was 160 r/min, which were different with pure microorganism growth conditions. Under optimal conditions, the result of recovery for Cu and Zn indicated that the average leaching rate reached to 80% and 100% respectively, which almost increased 1.8 times and 1.2 times more than control (aseptic condition) group. Therefore, this method of Cu and Zn recovery using a new-type artificial microbial community is expected to be an environmentally-friendly and efficient bioleaching technology solution, which has the potential of large-field engineering application in the future. Full article

(This article belongs to the Special Issue Green Low-Carbon Technology for Metalliferous Minerals)

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14 pages, 3419 KiB

Open AccessArticle

Experimental Study on Factors Influencing the Strength Distribution of In Situ Cemented Tailings Backfill

by Xiaopeng Peng, Lijie Guo, Guangsheng Liu, Xiaocong Yang and Xinzheng Chen

Metals 2021, 11(12), 2059; https://doi.org/10.3390/met11122059 - 20 Dec 2021

Cited by 10 | Viewed by 2731

Abstract

Previous studies have found that the strength of in situ cemented tailings backfill usually presents an S-shaped distribution, which decreases first, then increases, and decreases thereafter along the direction of slurry flow. In this study, to explore the factors determining the distribution, a [...] Read more.

Previous studies have found that the strength of in situ cemented tailings backfill usually presents an S-shaped distribution, which decreases first, then increases, and decreases thereafter along the direction of slurry flow. In this study, to explore the factors determining the distribution, a similar model test of cemented tailings backfill was carried out. The distribution law of grain size composition and the cement content of backfill materials along the flow direction were experimentally studied, and the comprehensive factor influencing the strength distribution was analyzed. The results show that, firstly, near the feeding point, there are more coarse particles, whereas the content of fine particles is higher farther away. The measured maximum median particle size can be more than three times the minimum value. Secondly, the cement content increases gradually along the flow direction and reaches the peak at the end of the model, which can be more than twice the minimum value, indicating that the degree of segregation is significant. Thirdly, the strength distribution of cemented backfills is comprehensively determined by both the particle size distribution (PSD) and the cement content. The maximum value appears neither at the point with peak median particle size, nor at the point with the highest cement content. Lastly, there is a strong linear correlation between the strength of cemented backfills and the strength factor (SF), which is defined as the product of the uniformity coefficient and cement content of filling materials, indicating that the SF can be used to quantitatively reflect the comprehensive effects of PSD and cement content on the strength. As SF is a comprehensive quantitative index reflecting the distribution of strength, it will be further studied in later research to acquire more experimental results of the relationship between sample strength and SF, which will be meaningful for the quality evaluation of in situ cemented backfills, and the optimization of backfill system. Full article

(This article belongs to the Special Issue Green Low-Carbon Technology for Metalliferous Minerals)

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15 pages, 87158 KiB

Open AccessArticle

Response of Floc Networks in Cemented Paste Backfill to a Pumping Agent

by Jiaqi Zhu, Shunchuan Wu, Haiyong Cheng, Xiaojie Geng and Jin Liu

Metals 2021, 11(12), 1906; https://doi.org/10.3390/met11121906 - 26 Nov 2021

Cited by 4 | Viewed by 1695

Abstract

Cemented paste backfill is critical for the development of green mines, the safe exploitation of mineral resources deep underground, and the efficient disposal of solid wastes produced by mining. In this paper, the mechanism underpinning how the pumping agent works was studied. The [...] Read more.

Cemented paste backfill is critical for the development of green mines, the safe exploitation of mineral resources deep underground, and the efficient disposal of solid wastes produced by mining. In this paper, the mechanism underpinning how the pumping agent works was studied. The number, area, and fractal dimension of pores in the microstructure of fresh paste were quantitatively analyzed using scanning electron microscopy (SEM), image processing, and fractal theory, and the response of flocs was investigated. The results show that floc networks disintegrated and the liquid network became the dominant structure under the action of the pumping agent, which enhanced the lubrication and promotion of multi-scale particles. In addition, the force chains became fragile and scattered, diminishing the yield stress of the paste. The pores had a more homogenized dimension and the porosity was 15.52% higher. The increase in the fractal dimension of the pores indicated that there was a higher self-similarity, in terms of microstructure, with a strengthened liquid network. The migration of floc structures contributed to the enhancement of the fluidity and rheology of the paste. This study provides insights into the effects of floc and liquid networks on the performance of paste, and it is of engineering significance in terms of realizing safe and efficient CPB operations. Full article

(This article belongs to the Special Issue Green Low-Carbon Technology for Metalliferous Minerals)

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12 pages, 18109 KiB

Open AccessArticle

Tailings Settlement Velocity Identification Based on Unsupervised Learning

by Jincheng Xie, Dengpan Qiao, Runsheng Han and Jun Wang

Metals 2021, 11(12), 1903; https://doi.org/10.3390/met11121903 - 26 Nov 2021

Cited by 2 | Viewed by 1327

Abstract

In order to reasonably and accurately acquire the settlement interface and velocity of tailings, an identification model of tailing settlement velocity, based on gray images of the settlement process and unsupervised learning, is constructed. Unsupervised learning is used to classify stabilized tailing mortar, [...] Read more.

In order to reasonably and accurately acquire the settlement interface and velocity of tailings, an identification model of tailing settlement velocity, based on gray images of the settlement process and unsupervised learning, is constructed. Unsupervised learning is used to classify stabilized tailing mortar, and the gray value range of overflow water is determined. Through the identification of overflow water in the settlement process, the interface can be determined, and the settlement velocity of tailings can be calculated. Taking the tailings from a copper mine as an example, the identification of tailings settling velocity was determined. The results show that the identification model of tailing settlement speed based on unsupervised learning can identify the settlement interface, which cannot be manually determined in the initial stage of settlement, effectively avoiding the subjectivity and randomness of manual identification, and provide a more scientific and accurate judgment. For interfaces that can be manually recognized, the model has high recognition accuracy, has a rapid and efficient recognition process, and the relative error can be controlled within 3%. It can be used as a new technology for measuring the settling velocity of tailings. Full article

(This article belongs to the Special Issue Green Low-Carbon Technology for Metalliferous Minerals)

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21 pages, 1733 KiB

Open AccessArticle

Dispatch Optimization Model for Haulage Equipment between Stopes Based on Mine Short-Term Resource Planning

by Ning Li, Shuzhao Feng, Haiwang Ye, Qizhou Wang, Mingtao Jia, Liguan Wang, Shugang Zhao and Dongfang Chen

Metals 2021, 11(11), 1848; https://doi.org/10.3390/met11111848 - 17 Nov 2021

Cited by 6 | Viewed by 2293

Abstract

The working environment of underground mines is complicated, making it difficult to construct an underground mine production plan. In response to the requirements for the preparation of a short-term production plan for underground mines, an optimization model for short-term resource planning was constructed, [...] Read more.

The working environment of underground mines is complicated, making it difficult to construct an underground mine production plan. In response to the requirements for the preparation of a short-term production plan for underground mines, an optimization model for short-term resource planning was constructed, with the goal of maximizing the total revenue during the planning period. The artificial bee colony optimization algorithm is used to solve the model using MATLAB. According to the basic requirements of underground mine ore haulage and ore hoisting, a haulage equipment inter-stopes dispatch plan model was constructed, with the primary goal of minimizing the haulage equipment wait time. A non-dominated sorting genetic algorithm is used to solve the optimization model. An underground mine is examined using the two models, and the optimization results are compared and verified with the scheme obtained by using traditional optimization algorithms. Results show that based on the improved optimization algorithm, the use of short-term production planning schemes to guide mine production operations can increase the haulage equipment utilization rate, thereby increasing mine production revenue. Full article

(This article belongs to the Special Issue Green Low-Carbon Technology for Metalliferous Minerals)

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23 pages, 5360 KiB

Open AccessArticle

Propagation Laws of Reclamation Risk in Tailings Ponds Using Complex Network Theory

by Zhixin Zhen, Ying Zhang and Mengrong Hu

Metals 2021, 11(11), 1789; https://doi.org/10.3390/met11111789 - 6 Nov 2021

Cited by 6 | Viewed by 1909

Abstract

Accidents have occurred periodically in the tailings ponds where mine solid waste is stored in recent years, and thus their safety has become one of the constraints restricting the sustainable development of the mining industry. Reclamation is an important way to treat tailings [...] Read more.

Accidents have occurred periodically in the tailings ponds where mine solid waste is stored in recent years, and thus their safety has become one of the constraints restricting the sustainable development of the mining industry. Reclamation is an important way to treat tailings ponds, but improper reclamation methods and measures not only cannot reduce the accident risk of tailings ponds, but will further increase the pollution to the surrounding environment. The influencing factors of reclamation accidents in tailings ponds are complex, and the existing models cannot characterize them. In order to study the propagation process of tailings pond reclamation risk, this paper proposes a three-dimensional identification framework for accident hazards based on evidence (TDIFAHE) to identify all potential hazards that may occur during the reclamation stage, and obtain a list of hazards. Based on the complex network theory, this paper uses identified hazards as network nodes and the correlation between hazards as the edges of the network. Based on the identified hazard data, the evolution network of reclamation risk in tailings ponds (ENRRTP) is constructed. By analyzing the statistical characteristics of ENRRTP, it can be found that ENRRTP has small world and scale-free characteristics. The above characteristics show that the reclamation risk of tailings ponds is coupled with multiple factors and the disaster path is short. Giving priority to those hub hazards that have a dominant impact on the reclamation risk can significantly reduce the reclamation risk of the tailings pond. Full article

(This article belongs to the Special Issue Green Low-Carbon Technology for Metalliferous Minerals)

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17 pages, 30490 KiB

Open AccessArticle

Study and Analysis on the Influence Degree of Particle Settlement Factors in Pipe Transportation of Backfill Slurry

by Chonghao Wang and Deqing Gan

Metals 2021, 11(11), 1780; https://doi.org/10.3390/met11111780 - 5 Nov 2021

Cited by 10 | Viewed by 2297

Abstract

In this study, we developed a pipeline transport model to investigate the influence of particle sedimentation factors on slurry transportation through pipelines. The particle tracking module of the software was used to simulate the transport process, and the influences on the sedimentation rate [...] Read more.

In this study, we developed a pipeline transport model to investigate the influence of particle sedimentation factors on slurry transportation through pipelines. The particle tracking module of the software was used to simulate the transport process, and the influences on the sedimentation rate were analyzed considering the slurry concentration, particle size, and flow velocity. The established model exhibited small calculation errors. In addition, the results revealed that the proposed model is reliable for calculating the degree of influence of various factors on particle sedimentation. The effect of the particle sedimentation rate on the pipeline slurry was explored considering the particle size, slurry concentration, and flow velocity. The sedimentation rate was positively related to particle size and adversely related to the slurry concentration and flow velocity. Indeed, study on the sedimentation rate requires considering a reasonable range of particle sizes, preparing a slurry with an appropriate concentration, and adjusting an appropriate flow velocity. Numerical simulations were performed using the filling data as the background for a sample mining area. The experimental results showed optimal slurry concentration and particle size of 60% and 25.25 µm, respectively. Full article

(This article belongs to the Special Issue Green Low-Carbon Technology for Metalliferous Minerals)

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16 pages, 14528 KiB

Open AccessArticle

Monitoring and Analysis of Dynamic Response for Open-Pit Mine with Inside Inclined Shafts under Train Loading

by Yong Wang, Song-Tao Ni, Fa-Wu Yang, Zhong-Xin Wang, Hong Zhang, Ke Ma and Xiao-Jun Li

Metals 2021, 11(11), 1681; https://doi.org/10.3390/met11111681 - 22 Oct 2021

Cited by 2 | Viewed by 2058

Abstract

The stability of open-pit mining is a hot issue in geotechnical engineering. A mining railroad is in operation on the slope where the east exhaust inclined shaft and the east sand injection inclined shaft on the Laohutai Mine are located, and it was [...] Read more.

The stability of open-pit mining is a hot issue in geotechnical engineering. A mining railroad is in operation on the slope where the east exhaust inclined shaft and the east sand injection inclined shaft on the Laohutai Mine are located, and it was necessary to determine whether railroad vibration would have an impact on the safety of the inclined shafts. With this project as the background, the dynamic response of the slope with inside two inclined shafts was conducted under train loading. A three-dimensional numerical model by using PLAXIS 3D was established to analyze the stability of the slope. The results show that the dynamic reaction caused by the full-loaded train is significantly greater than the no-load train. The safety factor of the slope under the dynamic load is 1.201, and the maximum displacement of the slope which occurred in the gravel layer directly beneath the train track is about 5 mm. The acceleration responses of the two inclined shafts are almost consistent. The maximum horizontal and vertical acceleration occur at the epidote weak layer. The acceleration directly below the load increases significantly. Therefore, it can be considered that the slopes are stable under the action of train vibration, and the influence on the two inclined shafts is small and negligible. Full article

(This article belongs to the Special Issue Green Low-Carbon Technology for Metalliferous Minerals)

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14 pages, 3147 KiB

Open AccessArticle

Experimental SHPB Study of Limestone Damage under Confining Pressures after Exposure to Elevated Temperatures

by Lei Liu, Rui Li, Hao Qin and Wei Sun

Metals 2021, 11(10), 1663; https://doi.org/10.3390/met11101663 - 19 Oct 2021

Cited by 8 | Viewed by 2164

Abstract

Studying the dynamic performance of rocks affected by high temperatures is a crucial theoretical foundation of mining engineering design and the construction of deep metallic mineral resources. More importantly, such studies can provide technical support for the green and low-carbon mining of these [...] Read more.

Studying the dynamic performance of rocks affected by high temperatures is a crucial theoretical foundation of mining engineering design and the construction of deep metallic mineral resources. More importantly, such studies can provide technical support for the green and low-carbon mining of these resources. However, systematic studies on the dynamic mechanical properties of rocks affected by both confining pressure and temperature during the mining of deep metallic mineral resources are lacking. Therefore, systematic research was conducted on the dynamic mechanical properties of limestone under confining pressure after high-temperature treatment, and a corresponding constitutive model was established. In this study, limestones were heated to 200 °C, 400 °C, 600 °C, and 800 °C, and the Split Hopkinson Pressure Bar impact test was conducted with confining pressures of 0.0 MPa, 0.5 MPa, 1.5 MPa, and 2.5 MPa. The test results show that the temperature has a significant effect on the dynamic compressive strength of limestone, and as the temperature rises, the strength tends to first increase and then decrease, reaching the turning point at a temperature of 400 °C. The dynamic compressive strength increases as the confining pressure increases. The constitutive equation of the dynamic damage to limestone under confining pressure after high-temperature treatment is consistent with the test results. Therefore, the established constitutive model can represent the dynamic behavior of limestone, providing a reference for evaluating the dynamic performance of this material, and serving as a theoretical basis for the green and low-carbon mining of deep metallic mineral resources. Full article

(This article belongs to the Special Issue Green Low-Carbon Technology for Metalliferous Minerals)

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16 pages, 4425 KiB

Open AccessArticle

Structural Parameter Optimization for Large Spacing Sublevel Caving in Chengchao Iron Mine

by Yuye Tan, Mochuan Guo, Yimin Hao, Chi Zhang and Weidong Song

Metals 2021, 11(10), 1619; https://doi.org/10.3390/met11101619 - 12 Oct 2021

Cited by 8 | Viewed by 2069

Abstract

Non-pillar sublevel caving is beginning to use large structural parameters in China. Appropriate structural parameters can effectively control the loss and dilution of stope and improve ore drawing efficiency. In this study, taking Chengchao Iron Mine as the engineering background, a theoretical calculation, [...] Read more.

Non-pillar sublevel caving is beginning to use large structural parameters in China. Appropriate structural parameters can effectively control the loss and dilution of stope and improve ore drawing efficiency. In this study, taking Chengchao Iron Mine as the engineering background, a theoretical calculation, a numerical simulation, and physical similarity experiments were combined to optimize sublevel height, production drift spacing, and drawing space. The optimal structural parameter range, based on the ellipsoid ore drawing theory, was obtained as a theoretical reference for subsequent studies. A “two-step” strategy was used, in which PFC2D software (Itasca Consulting Group, Minneapolis, MN, USA) was used to numerically simulate 20 groups of different sublevel heights and production drift spacing parameters were used to determine the appropriate sublevel height and production drift spacing for the project. Subsequently, the optimization of the ore drawing space was studied using PFC3D (Itasca Consulting Group, Minneapolis, MN, USA) particle unit software, numerical simulation analysis, and similar physical experiments. The results showed that safe and efficient mining can be achieved when the structural parameters of the stope are 17.5 m sublevel height, 20 m production drift spacing, and 6 m drawing space. The findings of this study can further the goal of green and efficient mining, and provide a theoretical reference for the popularization and application of pillarless sublevel caving with large structural parameters at home and abroad. It is an effective measure for the green mining of caving mines. Full article

(This article belongs to the Special Issue Green Low-Carbon Technology for Metalliferous Minerals)

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13 pages, 5555 KiB

Open AccessArticle

Enhancing Arsenic Solidification/Stabilisation Efficiency of Metallurgical Slag-Based Green Mining Fill and Its Structure Analysis

by Wei Gao, Zifu Li, Siqi Zhang, Yuying Zhang, Pingfeng Fu, Huifen Yang and Wen Ni

Metals 2021, 11(9), 1389; https://doi.org/10.3390/met11091389 - 1 Sep 2021

Cited by 6 | Viewed by 1943

Abstract

To dispose of arsenic-containing tailings with low carbon and high efficiency, sodium sulphate (Na₂SO₄), sodium hydroxide (NaOH), calcium nitrate Ca(NO₃)₂ and calcium hydroxide Ca(OH)₂ were independently added to metallurgical slag-based binder (MSB) solidification/stabilisation (S/S)-treated tailings [...] Read more.

To dispose of arsenic-containing tailings with low carbon and high efficiency, sodium sulphate (Na₂SO₄), sodium hydroxide (NaOH), calcium nitrate Ca(NO₃)₂ and calcium hydroxide Ca(OH)₂ were independently added to metallurgical slag-based binder (MSB) solidification/stabilisation (S/S)-treated tailings (MSTs) to enhance the MST arsenic S/S performance. Results showed that only Ca(OH)₂ could increase the unconfined compressive strength of MST from 16.3 to 20.49 MPa and decrease the leachate As concentration from 31 μg/L to below 10 μg/L. Na₃AsO₄·12H₂O and NaAsO₂ were used to prepare pure MSB paste for mechanism analysis. The results of microstructure analyses showed the high specific surface area and amorphous properties of calcium–sodium aluminosilicate hydrate facilitated the adsorption or solid-solution formation of As(V) and As(III). As(V) formed an inner-sphere complex in ettringite, whereas As(III) formed an outer-sphere complex, and the relatively larger size and charge of As(V) compared with SO₄²⁻ restrict substitution inside channels without affecting the ettringite structure under high loading of As(V). The added Ca(OH)₂ promoted the hydration reaction of MSBs and facilitated the formation of a Ca–As(V) precipitate with low solubility, from Ca₄(OH)₂(AsO₄)₂·4H₂O (K_sp = 10^−27.49) to Ca₅(AsO₄)₃(OH) (K_sp = 10^−40.12). This work is beneficial for the application of cement-free MSB in the S/S process. Full article

(This article belongs to the Special Issue Green Low-Carbon Technology for Metalliferous Minerals)

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