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15 pages, 2550 KiB

Open AccessArticle

Discussion on the Relationship between Debris Flow Provenance Particle Characteristics, Gully Slope, and Debris Flow Types along the Karakoram Highway

by Zhiquan Yang, Lai Wei, Yuqing Liu, Na He, Jie Zhang and Hanhua Xu

Sustainability 2023, 15(7), 5998; https://doi.org/10.3390/su15075998 - 30 Mar 2023

Cited by 16 | Viewed by 1652

Abstract

Debris flow, the most extensive and most severe geological hazard along the Karakoram Highway, frequently blocks the Karakoram Highway. Based on the methods of field measurement, indoor statistical analysis and theoretical research, this paper discusses the relationship between the four types of debris [...] Read more.

Debris flow, the most extensive and most severe geological hazard along the Karakoram Highway, frequently blocks the Karakoram Highway. Based on the methods of field measurement, indoor statistical analysis and theoretical research, this paper discusses the relationship between the four types of debris flow along the Karakoram Highway. The four types are the rain type, the rain glacier type, the glacier ice lake break type and the freeze–thaw type, and their particle characteristics and gully slope are also considered in the discussion. The results are as follows: (1) The provenance particle size of debris flow is controlled by the type of debris flow. Generally, the provenance average particle equivalent diameter of the debris flow induced by the glacier ice lake type is relatively small, followed by the freeze–thaw type and glacier ice lake break type, and the equivalent diameter of the debris flow induced by the rain type is relatively large; (2) The gully slope coefficient of the debris flow

C

along the Karakoram Highway is greater than 1, and it increases with the increase in gully slope

α

, that is, the larger

C

is, the steeper the gully slope will be; (3) The gully slope coefficient

C

and the average particle equivalent diameter

D

of the four types of debris flow are distributed in the ellipse with them as the axis. This ellipse quantitatively describes the relationship between the gully slope of the four types of debris flow and the corresponding provenance particle characteristics. This paper analyzes the formation and causes of debris flow along the Karakoram Highway. It accurately understands the scientific connotation of debris flow formation in the surface matrix layer and improves the diversity, stability, and sustainability of the ecosystem. The paper also proposes ideas and suggestions for promoting the ecological protection and restoration of the Karakoram Highway. Therefore, the research has a certain theoretical significance and practical application value for the appropriate selection and rational design of the debris flow prevention projects along the China–Pakistan Highway. Full article

(This article belongs to the Special Issue Sustainable and Responsible Development of Minerals, Safety-Driven Mining Operations, Digital Mining, Critical Minerals)

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16 pages, 8898 KiB

Open AccessArticle

Analysis and Prediction of the Meteorological Characteristics of Dust Concentrations in Open-Pit Mines

by Zhigao Liu, Ruixin Zhang, Jiayi Ma, Wenyu Zhang and Lin Li

Sustainability 2023, 15(6), 4837; https://doi.org/10.3390/su15064837 - 9 Mar 2023

Cited by 2 | Viewed by 1567

Abstract

Based on the dust concentration data and meteorological environment data monitored at the open-pit mine site, the characteristics of dust concentration and the influence of temperature, humidity, wind speed, air pressure and other meteorological conditions on dust concentration were analyzed, and the causes [...] Read more.

Based on the dust concentration data and meteorological environment data monitored at the open-pit mine site, the characteristics of dust concentration and the influence of temperature, humidity, wind speed, air pressure and other meteorological conditions on dust concentration were analyzed, and the causes of the change of dust concentration were clarified. Meanwhile, a dust concentration prediction model based on LSTM neural network is established. The results show that the dust concentration of the open-pit mine is high in March, November and the whole winter, and it is low in summer and autumn. The daily variation of humidity and temperature in different seasons showed the trend of “herringbone” and “inverted herringbone”, respectively. In addition, the wind speed was the highest in spring and the air pressure distribution was uniform, which basically maintained at 86–88 kPa. The peak humidity gradually deviates with each month and is obviously affected by seasonality. The higher the humidity, the lower the temperature and the higher the concentration of dust. In different seasons, the wind speed is the highest around 20:00 at night, and the dust is easy to disperse. The R² values of PM2.5, PM10 and TSP concentrations predicted by LSTM model are 0.88, 0.87 and 0.87, respectively, which were smaller than the MAE, MAPE and RMSE values of other prediction models, and the prediction effect was better with lower error. The research results can provide a theoretical basis for dust distribution law, concentration prediction and dust removal measures of main dust sources in open-pit mines. Full article

(This article belongs to the Special Issue Sustainable and Responsible Development of Minerals, Safety-Driven Mining Operations, Digital Mining, Critical Minerals)

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17 pages, 6042 KiB

Open AccessArticle

Ground Response of Non-Coal Pillar Mining Panel

by Hengzhong Zhu and Huajun Wang

Sustainability 2023, 15(4), 3164; https://doi.org/10.3390/su15043164 - 9 Feb 2023

Viewed by 1020

Abstract

The mining-induced ground response (MIGR) has a critical impact on safety management, the mining plan, and entry support. A clear understanding of the characteristics is the foundation of the MIGRs scientific control. This study is the result of the MIGRs development of the [...] Read more.

The mining-induced ground response (MIGR) has a critical impact on safety management, the mining plan, and entry support. A clear understanding of the characteristics is the foundation of the MIGRs scientific control. This study is the result of the MIGRs development of the non-pillar mining panel with gob-side entry by roof cutting (GSERC). Comprehensive research of the in situ measurements, numerical simulation, and theoretical analysis to determine the ground response characteristics, including mining panel and GSERC, were implemented. The results indicate that the MIGR presents the characteristic of asymmetric development and that the ground response near the non-roof cutting side is more significant than that near the roof cutting side. The development stage of the entry convergence of GESRC can be divided into seven stages; the primary rapid development stage should be paid more attention to in the support process. The entry convergence rapidly increases to 275 mm, 380 mm, 410 mm, and 525 mm, respectively, for the roof cutting rib to the virgin coal rib, the roof near the virgin coal side, the roof of the middle section, and the roof near the cutting side. The hydraulic support end cycle resistance at the roof cutting side and the middle section of the mining panel with the value of more than 30.8 MPa is greater than that at the non-roof cutting side with the value of less than 26 MPa, which presents the asymmetric feature. The numerical simulation results regarding vertical stress development, vertical displacement, and horizontal displacement also presents the asymmetric feature. The MIGR division is divided into five divisions. Division II (the middle section of the panel) and division IV (the entry range near the roof cutting side) should be paid more attention to in the panel mining process. The results of this study can provide technical guidance and theoretical reference for similar engineering practices. Full article

(This article belongs to the Special Issue Sustainable and Responsible Development of Minerals, Safety-Driven Mining Operations, Digital Mining, Critical Minerals)

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15 pages, 5136 KiB

Open AccessArticle

Effect of Loading Rate on the Mechanical Properties of Weakly Cemented Sandstone

by Lihui Sun, Yaxin Long, Xing Li, Zhixin Jiang, Yu Fan, Zongze Wang and Xiangang Han

Sustainability 2023, 15(3), 2750; https://doi.org/10.3390/su15032750 - 2 Feb 2023

Cited by 6 | Viewed by 1504

Abstract

Weakly cemented rocks are characterized by low strength, loose structure, and easy disintegration. High-intensity mining activities can damage and rupture such rock bodies and induce damage, such as flaking and roofing on roadways. To reveal the mining intensity influence on the weakly cemented [...] Read more.

Weakly cemented rocks are characterized by low strength, loose structure, and easy disintegration. High-intensity mining activities can damage and rupture such rock bodies and induce damage, such as flaking and roofing on roadways. To reveal the mining intensity influence on the weakly cemented rocks’ deformation and damage, a numerical particle flow model of weakly cemented sandstone was established based on particle flow theory. Uniaxial compression simulation tests were conducted at four loading rates of 0.01, 0.1, 0.5, and 1 mm/min to study the weakly cemented sandstone’s stress–strain relationship, damage rupture, acoustic emission, and energy evolution. The results show that, with an increased loading rate, the uniaxial compressive strength of weakly cemented sandstone increases exponentially, and the rupture mode transforms from brittle damage to ductile damage; the greater the loading rate, the greater the degree of damage and crushing range of the rock. Further, with an increased loading rate, the peak hysteresis of rock acoustic emission events decreases, and the number of events increases; the energy accumulated in the rock increases, thus intensifying the degree of rock damage. Therefore, the possibility of engineering disasters should be considered when conducting high-speed underground mining activities. Full article

(This article belongs to the Special Issue Sustainable and Responsible Development of Minerals, Safety-Driven Mining Operations, Digital Mining, Critical Minerals)

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12 pages, 3004 KiB

Open AccessArticle

Effects of High Temperature Treatments on Strength and Failure Behavior of Sandstone under Dynamic Impact Loads

by Jinping Guo, Yanzi Lei, Yanguang Yang, Ping Cheng, Zhao Wang and Saisai Wu

Sustainability 2023, 15(1), 794; https://doi.org/10.3390/su15010794 - 1 Jan 2023

Cited by 1 | Viewed by 1500

Abstract

With the increasing demand for resource consumption, the mining depths gradually increase, resulting in increases of temperature at tens or even hundreds of degrees. High temperature could damage to interior structures and alter the mechanical properties of rock mass. Therefore, studying the effects [...] Read more.

With the increasing demand for resource consumption, the mining depths gradually increase, resulting in increases of temperature at tens or even hundreds of degrees. High temperature could damage to interior structures and alter the mechanical properties of rock mass. Therefore, studying the effects of temperature on dynamic mechanical properties and failure behaviors are of great significance for deep resources exploitation. In this study, to study the effects of high temperature treatment on the strength and failure behavior of typical sandstones, specimens were prepared and heated to different degrees. The longitudinal wave velocity, volume, and density of specimens before and after high-temperature treatment were examined. Then, the Thomas Hopkinson (SHPB) test was conducted on specimens with different air pressures and the dynamic stress-strain curve, peak stress, peak strain, and other dynamic characteristics were obtained. The variations regulations and failure behavior of sandstone under the effects of high-temperature treatments and different impact loads were analyzed and discussed from the aspects of stress-strain, peak strength, and peak strain. It was observed that with the increase of heating temperature, the average density, average wave velocity, peak strength, and average elastic modulus of the sandstone specimens all showed a decreasing trend and the highest decreasing rated occurred at the temperature between 600 °C and 800 °C. The obtained results provided a certain theoretical basis for deep mine exploitation, especially for mines with high temperature. Full article

(This article belongs to the Special Issue Sustainable and Responsible Development of Minerals, Safety-Driven Mining Operations, Digital Mining, Critical Minerals)

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17 pages, 5004 KiB

Open AccessArticle

Study on Excavation Damage Characteristics of Surrounding Rock in Deeply Buried Tunnels by Particle Flow Code Simulation

by Yanbin Zhang, Huazhong Yu, Huanchun Zhu and Yongsheng Zhu

Sustainability 2022, 14(24), 16632; https://doi.org/10.3390/su142416632 - 12 Dec 2022

Viewed by 1186

Abstract

This study is aimed at investigating the excavation damage characteristics of surrounding rock in Jinping deeply buried marble tunnels, China. According to the acoustic detection results of tunnel cross-sections under the condition of tunnel boring machine (TBM) obtained on site, the PFC microscopic [...] Read more.

This study is aimed at investigating the excavation damage characteristics of surrounding rock in Jinping deeply buried marble tunnels, China. According to the acoustic detection results of tunnel cross-sections under the condition of tunnel boring machine (TBM) obtained on site, the PFC microscopic parameters of Types II/III tunnel marble were simulated and calibrated through the PFC^2D program. In doing so, the excavation damage characteristics of surrounding rock of deeply-buried sections in Jinping diversion tunnels were simulated. The results reveal that the excavation damage zones (EDZ) of surrounding rock of Types II/III marble sections in Jinping tunnels are unevenly distributed around the tunnels; the largest zone is located from the top arch to the north arch shoulder. The EDZ depth and damage degree of surrounding rock rise with the increase in buried depth, and they also increase with the decrease in rock quality. Generally, the maximum damage depth of Type III surrounding rock is about 1.0 m larger than that of Type II surrounding rock under the same buried depth, which is basically consistent with the detection results of the relaxation depth of surrounding rock. The simulation well discloses the excavation damage characteristics of surrounding rock in Jinping deeply buried tunnels. Full article

(This article belongs to the Special Issue Sustainable and Responsible Development of Minerals, Safety-Driven Mining Operations, Digital Mining, Critical Minerals)

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14 pages, 4273 KiB

Open AccessArticle

Influence of Joint Characteristics on Crack Propagation during the Double-Hole High-Energy Gas Impact Permeability Enhancement Process

by Dong Duan, Xi Chen, Xiaojing Feng, Wenbo Liu, Hongzhi Zhang, Xiaoyu Chen, Shilei Gao, Xin Wang and Ao Wang

Sustainability 2022, 14(24), 16342; https://doi.org/10.3390/su142416342 - 7 Dec 2022

Viewed by 1054

Abstract

In view of current research on the cracking mechanism of high-energy gas on coal, little attention has been paid to imitating the law of explosive blasting and cracks propagation, and the influence of joint on cracks propagation in the process of high-energy gas [...] Read more.

In view of current research on the cracking mechanism of high-energy gas on coal, little attention has been paid to imitating the law of explosive blasting and cracks propagation, and the influence of joint on cracks propagation in the process of high-energy gas impact permeability enhancement has not been taken into account. In this paper, the effects of joint dip angles and joint lengths on cracks size propagation are studied by using a similar simulation test and RFPA2D-dynamic numerical simulation software. In the process of impact permeability enhancement of high-energy gas, the extension direction of the cracks is approximately parallel to the joint, and with the increase in the dip angle and length, the higher the number of cracks, the larger the extension range, and the closer it is to the permeability enhancement holes, the fracture network is formed. When the dip angle of the joint is 30°, the impact permeability enhancement effect results in an obvious zoning phenomenon. When the joint dip angle is 60° and 90°, there is a higher number of cracks and the cracks network is formed, and with the increase in the dip angle, the more the cracks develop and the better the impact permeability enhancement effect. Full article

(This article belongs to the Special Issue Sustainable and Responsible Development of Minerals, Safety-Driven Mining Operations, Digital Mining, Critical Minerals)

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14 pages, 9017 KiB

Open AccessArticle

Construction and Application of VR-AR Teaching System in Coal-Based Energy Education

by Cun Zhang, Xiaojie Wang, Shangxin Fang and Xutao Shi

Sustainability 2022, 14(23), 16033; https://doi.org/10.3390/su142316033 - 1 Dec 2022

Cited by 6 | Viewed by 1834

Abstract

Coal-based energy has provided strong support and made outstanding contributions in the process of China’s economic development. Coal mining in China has gradually developed into intelligent, refined and green mining. However, due to the lack of effective science popularization and propaganda in coal [...] Read more.

Coal-based energy has provided strong support and made outstanding contributions in the process of China’s economic development. Coal mining in China has gradually developed into intelligent, refined and green mining. However, due to the lack of effective science popularization and propaganda in coal mining for a long time, people’s understanding of coal mining often stays in the stereotype of dirty, messy and very dangerous. Based on this fact, this paper firstly discusses the difficulties and pain points of the popularization of science in coal mining based on the questionnaire survey. And then a VR-AR system for intelligent coal mining was developed. Finally, popular science teaching activities based on VR-AR system were carried out during the “Open Day” activity and “Entering Campus” activity. It is found that the long-term negative reports of coal mining and the complexity of coal mining system make the science popularization and propaganda in coal mining less effective. The proportion of primary and secondary school students with bad impression reached 85.0% and 90.3%, respectively, and 63.1% for college students. With our VR-AR system in coal-based energy education, the impression of the coal industry has increased significantly, the proportion of bad impression decreased to 23.4%. This helps to form the nationwide coal mining science popularization and justifies China’s coal mining. Full article

(This article belongs to the Special Issue Sustainable and Responsible Development of Minerals, Safety-Driven Mining Operations, Digital Mining, Critical Minerals)

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19 pages, 7734 KiB

Open AccessArticle

Research on the Control of Mining Instability and Disaster in Crisscross Roadways

by Xiangye Wu, Shuai Wang, Jingya Wang, Zhongchen Wang, Shankun Zhao and Qingwei Bu

Sustainability 2022, 14(23), 15821; https://doi.org/10.3390/su142315821 - 28 Nov 2022

Viewed by 896

Abstract

In order to solve the disaster caused by the instability of spatial crisscross roadways under the action of leading abutment pressure in the coal mine face, combined with a specific engineering example, the methods of theoretical analysis, numerical simulation and field measurement are [...] Read more.

In order to solve the disaster caused by the instability of spatial crisscross roadways under the action of leading abutment pressure in the coal mine face, combined with a specific engineering example, the methods of theoretical analysis, numerical simulation and field measurement are adopted to simulate and analyze the stress mutual disturbance intensity and influence range of spatial crisscross roadways. The evolution law of the plastic zone in spatial crisscross roadways under the influence of mining is explored, and the key to mining instability control is made clear. The roof of the return air roadway, the shoulder angle of the two sides and the coal wall are the key parts of surrounding rock stability control. On this basis, the cooperative control scheme of changing the roadway section shape (straight wall semicircular arch), supporting (anchor cable and “U” section steel) and modifying (grouting) is put forward. Through the field measurement, within the influence range of the return air roadway, the displacement deformation of the top and bottom is less than 200 mm, which achieves the goal of roadway safety and stability. Furthermore, based on the theory of “butterfly plastic zone”, the mechanical mechanism of the overall instability of the spatial crisscross roadway is revealed; that is, during the advance of the working face, the advance mining stress is superimposed with the surrounding rock stress of the crisscross roadway, and the peak value of the partial stress of the surrounding rock mass of the crisscross roadway is increased. The expansion of the plastic zone is intensified, and beyond 7 m from the crisscross position, the shoulder angle of the two sides and the leading plastic zone of the coal wall of the working face are connected with each other, which leads to the overall failure and instability of the surrounding rock between the roadways at the intersection. Full article

(This article belongs to the Special Issue Sustainable and Responsible Development of Minerals, Safety-Driven Mining Operations, Digital Mining, Critical Minerals)

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15 pages, 5781 KiB

Open AccessArticle

Influence of the Primary Key Stratum on Surface Subsidence during Longwall Mining

by Kang Wang, Jiazhen Li and Zhupeng Jin

Sustainability 2022, 14(22), 15027; https://doi.org/10.3390/su142215027 - 14 Nov 2022

Cited by 5 | Viewed by 1540

Abstract

The surface subsidence caused by mining influences the mine environment and construction safety. In this paper, strata movement and surface subsidence were combined. Based on elasticity and Winkler theory, a prediction method of surface subsidence was established with the primary key stratum as [...] Read more.

The surface subsidence caused by mining influences the mine environment and construction safety. In this paper, strata movement and surface subsidence were combined. Based on elasticity and Winkler theory, a prediction method of surface subsidence was established with the primary key stratum as the research object. Using the Tingnan Coal Mine as an example, the mining subsidence of the second panel was predicted. Comparing the predicted results with the measured results, the causes of errors were analyzed and the field of application of the model was clarified. Besides, the geological and mining factors affecting surface subsidence were also analyzed. The results show that the mining subsidence is the surface manifestation of the strata movement. Surface subsidence is affected by the mining area, load, and flexural rigidity of the primary key stratum, foundation modulus of the goaf, and the rock mass. The research results have significance for the planning of the coal resources and the prevention of geological disasters. Full article

(This article belongs to the Special Issue Sustainable and Responsible Development of Minerals, Safety-Driven Mining Operations, Digital Mining, Critical Minerals)

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17 pages, 6045 KiB

Open AccessArticle

Influence of Mesoscopic Parameters of Weakly Cemented Rocks on Macroscopic Mechanical Properties

by Lihui Sun, Zhixin Jiang, Yaxin Long, Quancai Ji, Zongze Wang, Yu Fan and Yingbin Hao

Sustainability 2022, 14(20), 13308; https://doi.org/10.3390/su142013308 - 16 Oct 2022

Cited by 4 | Viewed by 1448

Abstract

In weakly cemented rocks, the mesoscopic parameters have a great influence on the macroscopic mechanical properties. One example of a typical weakly cemented rock is the Cretaceous coarse sandstone in the Hongqinghe Coal Mine. In this study, rock samples were subjected to physical [...] Read more.

In weakly cemented rocks, the mesoscopic parameters have a great influence on the macroscopic mechanical properties. One example of a typical weakly cemented rock is the Cretaceous coarse sandstone in the Hongqinghe Coal Mine. In this study, rock samples were subjected to physical and mechanical experiments, from which a sample model was constructed based on particle flow theory. Uniaxial compression numerical simulation experiments and analyses were conducted, and sensitivity analyses of various microscopic parameters in relation to the macroscopic mechanical properties of the rock were performed via a control variable method. A response mechanism between the macroscopic and mesoscopic parameters was then inferred. On the microscopic scale, the rock is porous with a loose structure and extremely low average uniaxial compressive strength, indicating looseness and weakness. The mesoscopic parameters were then divided into three grades based on their degrees of influence from high to low on the peak strength, peak strain, and elastic modulus. Laboratory experiments revealed that the fracture form of weakly cemented coarse sandstone is typically due to single-section shear failure, whereas through simulation, cracks are caused mainly by tension failure. These two failure modes were inferred to be consistent with each other. Full article

(This article belongs to the Special Issue Sustainable and Responsible Development of Minerals, Safety-Driven Mining Operations, Digital Mining, Critical Minerals)

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17 pages, 5201 KiB

Open AccessArticle

Study on Evolution of Front Abutment Pressure at Working Face in Repeated Mining of Close-Distance Coal Seams

by Fulian He, Liang Li, Kai Lv, Binbin Qin, Xuhui Xu, Qing Ma and Yongqiang Chen

Sustainability 2022, 14(19), 12399; https://doi.org/10.3390/su141912399 - 29 Sep 2022

Cited by 7 | Viewed by 1345

Abstract

In order to determine the reasonable width of a stopping coal pillar in close-distance coal seams, the evolution law of front abutment pressure of the working face with repeated mining was studied. Based on the actual engineering project, we conducted field measurement, theoretical [...] Read more.

In order to determine the reasonable width of a stopping coal pillar in close-distance coal seams, the evolution law of front abutment pressure of the working face with repeated mining was studied. Based on the actual engineering project, we conducted field measurement, theoretical analyses, numerical simulations and a physical similarity simulation test to study. The results show that: (1) according to field measurement, the influence range of front abutment pressure increases from 60 m to 75 m with repeated mining; (2) according to theoretical analysis, the arch height and span are negatively and positively correlated with the influence range of front abutment pressure, respectively; (3) with repeated mining, the arch height increased to 165 m, the arch span to 235 m and the influence range to 83.5 m by 14.5 m relative to that before repeated mining; (4) if it is necessary to ensure that the main roadway is less affected by the mining stress, the width of the stopping coal pillar in 2214 working face should be greater than 80 m. The influence range of front abutment pressure increases obviously with repeated mining in close-distance coal seams. The study provides a reference for similar engineering projects. Full article

(This article belongs to the Special Issue Sustainable and Responsible Development of Minerals, Safety-Driven Mining Operations, Digital Mining, Critical Minerals)

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14 pages, 2325 KiB

Open AccessArticle

A Study on the Pore Structure and Fractal Characteristics of Briquettes with Different Compression Loads

by Lingling Qi, Xiaoqing Zhou, Xinshan Peng, Xiangjun Chen, Zhaofeng Wang and Juhua Dai

Sustainability 2022, 14(19), 12148; https://doi.org/10.3390/su141912148 - 26 Sep 2022

Cited by 3 | Viewed by 1334

Abstract

In order to study the effects of different compression loads on the pore characteristics of coal, taking remolded coal as the research object, the mercury intrusion method was used to determine the pore structures of the briquettes under the compression loads of 50, [...] Read more.

In order to study the effects of different compression loads on the pore characteristics of coal, taking remolded coal as the research object, the mercury intrusion method was used to determine the pore structures of the briquettes under the compression loads of 50, 70, 90 and 110 MPa, and the Menger sponge model was used to conduct fractal research on the measured parameters. The results show that the compression load has a significant effect on the pore structure parameters of the briquettes. The hysteresis loop generated by the mercury-intrusion and mercury-extrusion curves of raw coal is small, and the pore connectivity is better. After different loads are applied for briquettes, the hysteresis loop becomes larger, and the pore connectivity becomes worse. From the process of the raw coal to the briquettes loaded at 50 and 70 MPa, the pore-specific surface area reduced from 5.069 m²/g to 1.259 m²/g, the total pore volume increased from 0.0553 cm³/g to 0.1877 cm³/g, and the average pore size increased from 43.6 nm to 596.3 nm. When the compression load reached 70 MPa, the specific surface area, total pore volume, and average pore diameter of briquettes remained basically stable with the change in the compression load. The minipores and visible pores and fissures of raw coal contribute 78% of the pore volume, and the micropores and minipores contribute 99% of the specific surface area. After being pressed into briquettes, the volume of mesopores and macropores increases, the volume of visible pores and fractures decreases and the volume of minipores changes little; additionally, the pore surface area contributed by mesopores and macropores increases, and the pore surface area contributed by micropores decreases, indicating that the effect of compression load on pores of 10–100 nm is not obvious, mainly concentrated in the 100–10,000 nm region. The fractal curve of briquettes is fitted into three sections, which are defined as low-pressure sections 1 and 2 and high-pressure section 3, and the fractal dimensions are D₁, D₂ and D₃ respectively. The fractal dimension D₁ of briquettes with different compression loads is close to 2, D₂ is close to 3 and D₃ is greater than 3. The pore structures of briquettes have obvious fractal characteristics in the low-pressure sections 1 and 2 but do not conform to the fractal law in the high-pressure section. Furthermore, in the micropore stage of briquettes, the measured surface area and volume are both negative, indicating that the mercury intrusion method used to test the pore structure of the loaded briquette is more likely to cause the collapse of and damage to the pores in the micropore (<10 nm) stage. Full article

(This article belongs to the Special Issue Sustainable and Responsible Development of Minerals, Safety-Driven Mining Operations, Digital Mining, Critical Minerals)

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15 pages, 3697 KiB

Open AccessArticle

Study on Overburden Structure Characteristics and Induced Scour Mechanisms of Horizontal Sublevel Mining in Steep and Extra-Thick Coal Seams

by Shiguo Ge, Chongliang Yuan, Qingliang Chang, Yongzhong Wang and Biao Zhang

Sustainability 2022, 14(19), 11980; https://doi.org/10.3390/su141911980 - 22 Sep 2022

Cited by 1 | Viewed by 1494

Abstract

In order to study the space–time evolution law and the induced impact mechanism of overburden breaking in the tangential horizontal sublevel during the fully mechanized mining of extra-thick and steep coal seams, we took the Yaojie No. 3 mine as an example. Through [...] Read more.

In order to study the space–time evolution law and the induced impact mechanism of overburden breaking in the tangential horizontal sublevel during the fully mechanized mining of extra-thick and steep coal seams, we took the Yaojie No. 3 mine as an example. Through the establishment of an overburden breaking mechanical model, the structural characteristics of hinged rock beams after overburden breaking and the space–time evolution law of overburden structure instability were analyzed, the static and dynamic load conditions that induce rockbursts were analyzed, and the induced impact mechanism of dynamic and static load superposition was revealed. Our research showed that, due to the asymmetry of the roof and floor, the coal body in the working face is in the strong shear stress zone at the end of the air inlet roadway, which easily produces shear failure. The lateral support pressure and the shear stress of the coal body in the goaf are the static load sources of the rockburst in the steep coal seam; after the roof overburden is broken, a hinge-bearing structure is formed under the support of the sliding force of the fault block and the floating gangue in the goaf. When the coal is mined in the lower section, the strong dynamic load formed by the impact of the fault block on the topmost coal is the main dynamic load source of the impact on the working face. Under the superpositions of the dynamic load and static load, the coal and rock lose stability and release energy in a large range, generating dynamic and static superimposed rockbursts. Furthermore, the internal mechanism of the occurrence of rockbursts during the mining of steep and extra-thick coal seams in the Yaojie No. 3 coal mine was revealed. The static load of the coal body comes from the clamping actions of the roof and floor, and the dynamic impact load comes from the clamping structure’s instability. The reason for the occurrence of rockbursts in the mining of steep and extra-thick coal seams in the Yaojie No. 3 coal mine was reasonably explained. Full article

(This article belongs to the Special Issue Sustainable and Responsible Development of Minerals, Safety-Driven Mining Operations, Digital Mining, Critical Minerals)

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16 pages, 2880 KiB

Open AccessArticle

Study on Stability Discrimination Technology of Stope Arch Structure

by Quansheng Li, Yanjun Zhang, Yongqiang Zhao, Yuanhao Zhu and Yueguan Yan

Sustainability 2022, 14(17), 11082; https://doi.org/10.3390/su141711082 - 5 Sep 2022

Cited by 4 | Viewed by 1343

Abstract

The stress of rock strata changes under mining action, and the arch structure will be formed around the mining area. The stability study of the arch structure has crucial scientific value for solving the problems of stope pressure and surface subsidence. In this [...] Read more.

The stress of rock strata changes under mining action, and the arch structure will be formed around the mining area. The stability study of the arch structure has crucial scientific value for solving the problems of stope pressure and surface subsidence. In this paper, the development process of rock strata arch structure is studied by theoretical analysis and particle flow numerical simulation, and the stability of the arch structure is analyzed. At the same time, based on the rock strata breaking theory, the calculation formulas of the development height and the critical width of the instability of the arch structure are obtained, and the correctness of the formula is verified by numerical simulation. The results show that during the mining stage of the working face, the rock strata arch structure has experienced the process of arching-arch breaking, and the instability of the arch structure is the root cause of increasing surface subsidence damage. The arch structure development height h is the sum of rock strata breaking height H_i and unbroken rock strata arch development height H_ig. The theoretical calculation shows that when the width:depth ratio of the working face is 1.60, the height of the arch structure exceeds the bedrock top, which is consistent with the numerical simulation results and verifies the correctness of the formula. By defining the instability coefficient C of rock strata arch structure, a method to judge the stability of the arch structure is provided. The theoretical calculation shows that the critical width L₀ of the arch structure instability is 134 m, which is not much different from the numerical simulation results of 136 m, and the correctness of the formula is proved. The research results have particular reference value for preventing ground disasters caused by underground coal mining and controlling ground subsidence and provide a reference for the application of the particle flow method in studying rock strata movement. Full article

(This article belongs to the Special Issue Sustainable and Responsible Development of Minerals, Safety-Driven Mining Operations, Digital Mining, Critical Minerals)

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13 pages, 3329 KiB

Open AccessArticle

Numerical Simulation to Determine the Largest Confining Stress in Longitudinal Tests of Cable Bolts

by Qingliang Chang, Qiang Leng, Xingjie Yao, Sihua Shao, Jianzhuang Qin, Xianyuan Shi and Biao Zhang

Sustainability 2022, 14(17), 10871; https://doi.org/10.3390/su141710871 - 31 Aug 2022

Viewed by 1200

Abstract

Bolt support is an economic method of roadway support. However, due to the influence of mining disturbance, the stress of roadway-surrounding rock changes, thus resulting in varying degrees of confining pressure in the radial direction of bolt. In this manuscript, a numerical solution [...] Read more.

Bolt support is an economic method of roadway support. However, due to the influence of mining disturbance, the stress of roadway-surrounding rock changes, thus resulting in varying degrees of confining pressure in the radial direction of bolt. In this manuscript, a numerical solution was proposed to determine the largest confining stress in longitudinal tests of cable tendons. FLAC3D was selected to simulate the longitudinal process of cable tendons. The structural pile element was selected to simulate the cable tendon. The loading behavior of the cable was controlled by the cohesive and the frictional behavior of the cable/grout surface. To confirm the credibility of this numerical solution, the loading behavior of a normal cable and an improved cable was simulated. Experimental longitudinal tests were selected to validate the numerical results, showing that there was a satisfactory agreement between numerical and experimental results. The loading behavior of normal cables and improved cables was numerically simulated. Under the same test conditions, when the improved cable was used, the confining medium can generate much higher confining stress compared with normal cable tendons. Consequently, higher confining stress can result in a larger loading capacity of cable tendons. Full article

(This article belongs to the Special Issue Sustainable and Responsible Development of Minerals, Safety-Driven Mining Operations, Digital Mining, Critical Minerals)

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19 pages, 5637 KiB

Open AccessArticle

Comprehensive Utilization of Mineral Resources: Optimal Blending of Polymetallic Ore Using an Improved NSGA-III Algorithm

by Lu Chen, Qinghua Gu, Rui Wang, Zhidong Feng and Chao Zhang

Sustainability 2022, 14(17), 10766; https://doi.org/10.3390/su141710766 - 29 Aug 2022

Cited by 4 | Viewed by 1999

Abstract

A serious problem faced by the metal mineral mining industry is the challenge to the sustainable development of resource mining due to the continuous decline of ore geological grade. In the case of producing concentrates of the same quality, compared with using only [...] Read more.

A serious problem faced by the metal mineral mining industry is the challenge to the sustainable development of resource mining due to the continuous decline of ore geological grade. In the case of producing concentrates of the same quality, compared with using only high-grade raw ore, ore blending is a way to slow down the decline of ore geological grade by combining high- and low-grade raw ore. There are many ore blending models considering cost minimization or profit maximization as the target value, ignoring the fact that ore blending is intended to obtain a homogenized product. Moreover, the ore blending model cannot be solved by traditional operational research methods when blended grade stability of multiple elements is considered in the ore blending program. In this paper, a multi-objective ore blending optimization model is constructed for the comprehensive utilization of associated resources in ores. It minimizes the deviation of the grade of each metallic element in the blended associated ore from the beneficiation grade and the percentage of different types of rocks at the unloading point. To solve this multi-objective optimization model, an intelligent optimization method is proposed that is an improved multi-objective optimization algorithm based on the Non-dominated Sorting Genetic Algorithm III (NSGA-III). The case study shows that the proposed model and algorithm can effectively solve the mixing problem of polymetallic ores and obtain a satisfactory ore blending solution. Full article

(This article belongs to the Special Issue Sustainable and Responsible Development of Minerals, Safety-Driven Mining Operations, Digital Mining, Critical Minerals)

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13 pages, 4054 KiB

Open AccessArticle

Study on Overburden Movement Deformation and Roof Breakage Law of Under-Protective Steeply Inclined Coal Seam Mining

by Xinshan Peng, Lingling Qi, Zhaofeng Wang, Xiaoqing Zhou and Chunlei Hua

Sustainability 2022, 14(16), 10068; https://doi.org/10.3390/su141610068 - 14 Aug 2022

Cited by 2 | Viewed by 1406

Abstract

The occurrence of a steeply inclined coal seam is extraordinary, and the coal body is seriously damaged by extrusion. The most steeply inclined coal seam is a high-gas or -outburst coal seam, and protective layer mining is the safest and most effective measure [...] Read more.

The occurrence of a steeply inclined coal seam is extraordinary, and the coal body is seriously damaged by extrusion. The most steeply inclined coal seam is a high-gas or -outburst coal seam, and protective layer mining is the safest and most effective measure for regional prevention of coal and gas outburst. Based on considering the coefficient of lateral pressure and vertical height of the section, the deflection of the basic roof of the steeply inclined protective layer in a mine in western Henan, China, was calculated using the deflection calculation method of the thin-plate theory of elasticity. Using MATLAB to understand the deflection, the deflection curve was obtained. The law of rock movement and deformation in the mining process of the protective layer was studied by a similarity simulation experiment. The results show that, after mining, the roof mainly sinks slowly without large-scale collapse, and the largest rock strata movement is located in the upper part of the slope. Rock strata movement and fracture development can relieve the pressure of the protected layer and provide a channel for gas migration and drainage. The mining conditions of the protected layer will not be destroyed, and mining this type of protected layer in this mine has better safety and feasibility. The conclusions of this study have a guiding and scientific significance for the control of surrounding rock and the layout of gas drainage boreholes of under-protective steeply inclined coal seam mining. Full article

(This article belongs to the Special Issue Sustainable and Responsible Development of Minerals, Safety-Driven Mining Operations, Digital Mining, Critical Minerals)

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Review

Jump to: Research

20 pages, 2102 KiB

Open AccessReview

A Review of the Force-Transferring Mechanism of Entirely Grouted Cable Tendons Performed with Experimental Pull Tests

by Jianhang Chen, Baoyang Wu, Peng Li, Guojun Zhang and Yong Yuan

Sustainability 2022, 14(24), 16543; https://doi.org/10.3390/su142416543 - 9 Dec 2022

Viewed by 1434

Abstract

Entirely grouted cable tendons are commonly used in mining engineering. They have superior working ability in reinforcing the excavated rocks and soils. During the working process of cable tendons, the force-transferring ability and the corresponding mechanism are significant in guaranteeing the safety of [...] Read more.

Entirely grouted cable tendons are commonly used in mining engineering. They have superior working ability in reinforcing the excavated rocks and soils. During the working process of cable tendons, the force-transferring ability and the corresponding mechanism are significant in guaranteeing the safety of underground openings. To further understand the force-transferring mechanism of entirely grouted cable tendons, this paper provided a literature review on the force transfer of cable tendons. First, the force-transferring concept of entirely grouted cable tendons was summarised. The force-transferring process and failure modes of cable tendons were illustrated. Then, the experimental test program used in testing the entirely grouted cable tendons was summarised. The advantages and disadvantages of various test programs were illustrated. After that, the working ability of entirely grouted cable tendons was reviewed. The effect of various parameters on the working ability of cable tendons was summarised and compared. These parameters include the rock stiffness, embedment length, cement grout property, resin grout property, modified geometry, borehole size, rotation and pre-tensioning. Last, a discussion was provided to elaborate the working ability and force-transferring mechanism of entirely grouted cable bolts. This literature review is beneficial for researchers and engineers, furthering their understanding of the working ability of cable tendons. Full article

(This article belongs to the Special Issue Sustainable and Responsible Development of Minerals, Safety-Driven Mining Operations, Digital Mining, Critical Minerals)

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