Open-pit Coal Mine Research Articles

Responses of soil bacterial community structure to different artificially restored forests in open-pit coal mine dumps on the loess plateau, China.

Artificial vegetation restoration is an effective method for improving soil quality. In areas experiencing coal mine subsidence, the microbial community is essential for reconstructing the ecological balance of the soil. Studies are needed to examine how soil microbial community structure respond to different artificial forest restoration types and ages, especially over long-term periods. Therefore, in this study, 10, 20, and 30-year trials were chosen with two restoration types: Pinus tabuliformis (PT) and Ulmus pumila (UP). The objective was to determine how various types and ages of forest restoration affect the structure of soil bacterial communities, as well as the soil environmental factors driving these changes. The results showed that artificial 30-year restoration for both PT and UP can improve soil physical and chemical properties more than restoration after 10 and 20 years. The soil bacterial community structure remarkably differed among the different forest types and restoration ages. The bacterial diversity was higher in UP than in PT; the alpha diversity at longer restoration years (30 and 20) was significantly higher than at 10 years for both PT and UP. Moreover, soil nutrients and pH were the primary soil environmental factors driving bacterial community structure in the PT and UP. Finally, the integrated fertility index (IFI) at 30 years of restoration was considerably higher for PT and UP, and thus, is more beneficial to the restoration of soil after coal mining. Our findings are useful for studying improvement in soil quality and the restoration of the ecological environment in mining areas.

Restoration of Water Systems in Typical Open-Pit Coal Mines in the Arid Desert Area of Northwest China

Restoration of Water Systems in Typical Open-Pit Coal Mines in the Arid Desert Area of Northwest China

Limiting Factors and Countermeasures of the Ecological Restoration of the Dump of Open-Pit Coal Mine in the Helan Mountains

Limiting Factors and Countermeasures of the Ecological Restoration of the Dump of Open-Pit Coal Mine in the Helan Mountains

Site Type Classification and Ecological Restoration Technology Selection of Open-Pit Coal Mine Dumps in Grassland Mining Area

Site Type Classification and Ecological Restoration Technology Selection of Open-Pit Coal Mine Dumps in Grassland Mining Area

Preparation and performance of starch-based cross-linked network structured dust suppression foams for complex climatic conditions

In complex environmental applications such as rain erosion and high-low temperatures in open-pit coal mines, the curing layer after dust suppression foam treatment is relatively poorly tolerated, resulting in poor dust suppression. This study is aimed at a high-solidification strong weather-resistant cross-linked network structure. First, oxidized starch adhesive (OSTA) was prepared by the oxidative gelatinization method to reduce the effect of the high viscosity of starch on the foaming effect. Then, OSTA, polyvinyl alcohol (PVA) and glycerol (GLY), were copolymerized with the cross-linking agent sodium trimetaphosphate (STMP), and compounded with sodium aliphatic alcohol polyoxyethylene ether sulfate (AES) and alkyl glycosides (APG-0810), a new material for dust suppression in foam (OSPG/AA) was proposed and its wetting and bonding mechanism was revealed. The results show that OSPG/AA has a viscosity of 5.5 mPa·s, a 30-day degradation of 43.564 % and a film-forming hardness of 86HA; through simulated tests in open-pit coal mine environments, it was found that the water retention of OSPG/AA is 40.0 % higher than that of water, and the dust suppression rate of PM10 is 99.04 %. The cured layer can adapt to temperature changes from −18 °C to 60 °C and remains intact after rain erosion or 24 h immersion, exhibiting good weather resistance.

Changes in assembly processes and differential responses of soil microbial communities during mining disturbance in mining reclamation and surrounding grassland

Soil microbes play critical roles in regulating ecosystem-level functioning and responding to environmental changes after disturbance events. However, a systematic understanding of soil microbial community assembly processes and responses in the context of severe anthropogenic disturbance remains lacking. Here, microbial communities collected from the soil in the mining reclamation and surrounding grassland of the Baiyinhua #1 open-pit coal mine were profiled and compared by three-generation PacBio sequencing to identify the response characteristics of the soil microbial communities to mining-induced disturbance, microbial community assembly and their relevance to environmental variables. The results suggested that the five locations surveyed had heterogeneous microbial community structures, distribution patterns and network topological characteristics, especially exhibiting contrasting differences between the mining reclamation and the grassland surrounding the mine, and different survey sites supported the enrichment of different and adaptative bacterial and fungal taxa and biomarkers. In comparison to the bacterial community, the fungal community was more susceptible to the current mining disturbances, and the stability of the core fungal interaction network, fungal diversity and resistance index were relatively low. Redundancy analysis showed that the differences in microbial communities were driven by the joint impacts of soil alkaline phosphatase and total nitrogen, and differences in bacterial communities were also driven by pH. Stochastic processes dominated the microbial assemblies at the entire site across the mining reclamation and grasslands around the coal mine, and dispersal limitation and drift were the dominant processes of the bacterial and fungal assemblies, respectively, at most individual sites. The relative influences of deterministic and stochastic processes in terms of shaping microbial community assemblies shifted with soil enzyme activity and nutrients. These findings provide critical insights into the prediction of soil ecosystem recovery after disturbance and deepen our understanding of the responses and assembly rules associated with severe anthropogenic disturbance.

АЭРОДИНАМИЧЕСКАЯ ТРУБА 3-АТ-17,5/3 ФИРМЫ УНИКОН. ПОЛВЕКА В ЭКСПЛУАТАЦИИ

The wind tunnel with a long working part, designed for experimental solution of problems of energy, civil, industrial construction, as well as assessment of environmental indicators of projected and existing facilities, has been in operation for 50 years. The issues of wind pressure on the projected main buildings and auxiliary buildings, tower cooling towers, coal conveyor galleries of powerful thermal power plants, supports, phases and garlands of insulators of unique power transmission lines in dimensions of 1150 kilovolts (AC) and 1500 kilovolts (DC), issues of snow drifts of electric conversion complexes, warehouses of thermal coal have been resolved. It is shown that with certain wind directions relative to the studied object, the wind pressure in the local areas of the roof and facades can exceed 4 (four) or more times the values recommended by regulatory documents. The aerodynamic parameters of high-rise and unique buildings and complexes have been studied under the conditions of mutual influence of individual buildings in the complex, and recommendations have been developed for the purpose of wind and snow loads on buildings and structures. The results of model studies in the wind tunnel 3-AT-17.5/3 of the UNICON company are the basis for the Temporary Recommendations of the MDS 20-1.2006. Methods have been developed and proposed to reduce the volume of coal dust removal from the surface of open warehouses of thermal coal, as well as from the surface of rock dumps during open-pit coal mining. During the half-century period of technical operation, all non-metallic components of the wind tunnel have become physically obsolete, nodes with movable elements have worked out their resource, which required a deep modernization of the aerodynamic channel.

Study on the influences of the fractal dimension of the root system and slope degree on the slope stability

The problem of quantifying the effect of the alfalfa root morphology on the stability of the shallow surface layer of the slope of the Haizhou open-pit coal mine and the optimal slope degree in terms of the reinforcement of the shallow surface layer by the alfalfa root system was addressed. In this study, the mechanical parameters of plain soil and alfalfa root–soil composite samples were measured by indoor soil tests and triaxial compression tests, and a calculation model for the slope of the Haizhou open-pit coal mine was established in FLAC3D numerical simulation software to analyze the influence of the alfalfa root system on the maximum displacement of the shallow surface layer of the slope and the relationship with the fractal dimension of the alfalfa root system. The fractal dimension was applied to quantify the influence of the alfalfa root morphology to further investigate the relationship between the fractal dimension of the root system and the optimal slope of the shallow surface layer. The analysis showed that the fractal dimension of the alfalfa root system varied at different slope degrees, i.e., 40° > flat > 30° > 50°; the maximum soil displacement of the shallow surface layer of the slope increased with slope in nonlinear increments. Analysis of the fractal dimension of the alfalfa root system and the maximum displacement reduction rate at the different slope degrees revealed that the optimal slope degree of the shallow surface layer reinforced by alfalfa varied between 30° and 40°. The study results could provide a basis for further explaining the nature of the role of the alfalfa root morphology in reinforcing shallow surface soil and the optimal slope degree of the slope of the Haizhou open-pit coal mine reinforced by alfalfa roots.

Enhancing predictions of blast-induced ground vibration in open-pit mines: Comparing swarm-based optimization algorithms to optimize self-organizing neural networks

The objective of this paper is to present a method for predicting blast-induced ground vibration in open-pit mines that is based on the use of self-organizing neural networks (SONIA) and metaheuristic algorithms. In order to improve the accuracy of the SONIA model, several metaheuristic algorithms were employed, including the Manta Ray Foraging Optimization (MRFO), Hunger Games Search (HGS), Aquila Optimization (AO), and Naked Mole-Rat Algorithm (NMRA). Additionally, the k-fold cross-validation technique was used to identify the best parameters for the algorithms, which were then used to retrain the models for predicting blast-induced ground vibration. The effectiveness of the proposed method was evaluated using a case study of an open-pit coal mine in Vietnam, which had 288 blasting events. The study found that SONIA was a suitable neural network for predicting blast-induced ground vibration due to its self-organizing structure, even with a small dataset containing complex relationships. However, the SONIA model could be further optimized using the metaheuristic algorithms to improve its accuracy. The study found that the MRFO-SONIA model was the most reliable and accurate, with the lowest error (MAE = 0.379, RMSE = 0.453, MAPE = 0.08) and the highest reliability (R2 = 0.896). Meanwhile, the HGS-SONIA, AO-SONIA, and NMRA-SONIA models provided lower performance, with MAE values of 0.455, 0.500, and 0.492, RMSE values of 0.552, 0.603, and 0.580, MAPE values of 0.100, 0.112, and 0.111, and R2 values of 0.845, 0.815, and 0.829, respectively. The results of this study demonstrated the potential of using metaheuristic-based SONIA models to enhance predictions of blast-induced ground vibration in open-pit mines. This approach could prove useful in other operations in open-pit mines where there is a need to predict vibrations or other disturbances/negative effects resulting from specific mining activities.

The Enhancement of Overall Performance of Lubricating Grease by Adding Layered Double Hydroxides

In this work, MgAl-layered double hydroxides (LDH) were synthesized by co-precipitation method using a colloid mill and characterized by XRD and SEM. It was found that the environmentally friendly LDHs had greater performance than the traditional antioxidant. By adding LDHs into large electric shovel grease (GRK-A) in open-pit coal mine, the service lifetime of grease was extended by 20%. With the increase in LDH addition, the grease sample attains greater activation energy, and the thermal oxidation and decomposition resistance become stronger. Comparing the energy storage modulus and flow transition index at different temperatures, adding the right amount of LDHs needs close attention for the system oxidation resistance and viscoelasticity. For the electric shovel grease, the best oxidation resistance and rheological properties can be achieved by adding 2% of LDHs. The rheological viscosity–temperature curves show that the grease samples with different ratios of solid LDHs have better low-temperature properties than the mine grease. This work outlines a simple method for creating an environmentally sustainable lubricant additive with the use of LDH. LDH serves as a novel inorganic antioxidant additive that is optimal for open gear lubrication and sliding friction.

TRANSITION FROM OPEN PIT COAL MINE TO THE UNDERGROUND MINE IN SOFT ROCKS

To achieve a successful and effective operation, the transition from open pit to underground mining requires accurate planning and analysis. Numerical modeling utilizing programs like FLAC3D has been an important tool for simulating and analyzing the complicated geomechanical behavior connected with this shift in recent years. The use of FLAC3D to develop a model for the switch from open pit coal mining to underground coal mining in soft rocks with using room and pillar mining method is explored in this abstract. It presents the development of model to analyze and simulate the complex dynamics of this transition. The significant considerations that went into developing the model, such as geotechnical characteristics, rock mass behavior, and mine design parameters, are highlighted in the abstract. It highlights how essential proper input data are to producing reliable simulations and forecasts in soft rocks. The usage of FLAC3D for tracking pit wall stability during the transition period, evaluating the influence on nearby infrastructure, and optimizing underground mine design are covered in the abstract. The models flexibility allows the investigation of various conditions and offers valuable insight about the transition process. The research emphasizes the potential of the FLAC3D model to lead decision-making during the transition from open pit to underground mining through detailed analysis like choosing appropriate width for main entrance and cross section stopes and their interpretation. It emphasizes how important it is to understand the geomechanical behavior of the coal deposit, optimize the mines design parameters, and ensure safety for employees. The room and pillar method is utilized to recover coal resources from deep underground mines, and the results from the model can help improve efficiency, sustainability, and risk prevention. KEYWORDS: Underground mining, Open pit mining, Room and Pillar mining method, FLAC3D, Coal mining, Soft rocks.

Open-pit coal mining exacerbates urban heat island in Bontang City, Indonesia

Global energy demand has surged, especially on coal commodities. To accommodate the demand, open-pit coal mining became a faster and cheaper solution, but left a land-use change and degradation. This research tried to examine the impact of open-pit coal mining on urban heat island (UHI) in Bontang city. The study used multitemporal Landsat images (2002 and 2019) to assess land surface temperature. Then, the UHI and non UHI area were calculated and excluded the sea for the calculation. As a result, UHI was only distributed in the centre of Bontang city. In 2019, UHI intensity distributed in the city centre and also occurred in the open-pit coal mining area with the UHI intensity >5°C distributed equally. The UHI intensity in coal mining is higher than the city. The impact was causing discomfort for the people and could lead to health problems due to interaction with air pollution from mining activities. This study concludes mining should be accompanied with restoration to enhance quality of life and other environmental benefits.

Numerical Investigation of the Evolution Process of an Open-Pit Mine Landslide Using Discrete-Element Method

Because of the complexity of geological conditions and disturbance of external factors, the process of instability of open-pit landslides is very complicated. To illustrate this complex process, taking an open-pit coal mine landslide as an example, an accurate landslide geological section was established via detailed field investigation, remote sensing image interpretation, and field borehole data, in this study. A two-dimensional discrete-element model was established by the Fast CPU Matrix Computing of Discrete-Element Method (MatDEM, Version 1.60). The failure evolution of the landslide was investigated; then, the deformation behavior and dynamic characteristics of the landslide were systematically studied. The analyses of the failure process, velocity, displacement, and heat showed that the evolution of the landslide could be divided into the stages of initial deformation, accelerated deformation, and deceleration and stabilization. During the movement of the landslide, the gravitational potential energy of the landslide gradually converted into kinetic energy, heat, and elastic potential energy. The kinetic energy in the initial stage was small but rapidly increased and occupied the dominant position in the second stage. The kinetic energy gradually decreased and tended to be stable in the third stage. The final geometry and accumulation characteristics of the landslide obtained by numerical simulation were consistent with the corresponding field investigation and remote sensing interpretation. This work can provide a reference for the study of the evolution and prevention of open-pit mine landslides.

Rehabilitation plan for coal pit revegetation area East Kalimantan

The degraded mining area, especially the disposal area, must be reclaimed to preserve the possibility of its subsequent use in the future. The open pit rehabilition must ensure post-mining contributes powerfully to the ecosystem by restoring the production capacity and stability of the area. The exercise was applied to a nearly 0.5 Ha of open-pit coal mine conducted in cooperation between Korea and Indonesia to create a production forest that can ultimately support the environment. The objective of this work was to design mine pit reclamation plan through characterization physically and chemically the location by regenerating, checking the drainage system, analyzing soil fertility and the possibility of soil contamination and discovering fast growing local crop and forest plant species. The main focus is more on analyzing the soil condition affected by the acid mine drainage problem. The results showed that the northern restoration target site had the steep slope, characterized as acidic soil (pH was 4.2 – 4.6) with low exchangeable cation and low phosphate availability. The heavy metals did not exceed the contamination limit, so separate processing to prevent leaching of heavy metals is not required. Routine monitoring of the drainage system is important because it will affect the watering frequency and leaching control. Understanding the step by step mine rehabilitation can assist in designing reclamation efforts especially for revegetation purpose.

Research on production capacity planning method of open-pit coal mine

Reasonable production capacity is related to the economic benefits of an open-pit coal mine. This study analyzes the relationship between the working face length, the annual advancing speed and the production capacity. It constructs a production capacity function relationship model. Take the Baorixile open-pit coal mine as an example. The remaining unmined parts are divided into four regions, and the range of production capacity in each region is analyzed by the established model and the determined respectively. On this basis, three mining district division plans are proposed. By analyzing and comparing the stripping ratio, mining life of the district, fault influence, difficulty of transition connection in the mining districts, the convenience of transportation system layout and other indexes of each plan, Plan 3 is determined to be the optimal plan. The production capacity planning results of each mining district in this plan are as follows: the production capacity of the 3rd mining district is 30–35 Mt/a; the production capacity of the 4th mining district in Region 1 is 20–31 Mt/a, and the production capacity in Region 2 is 24–33 Mt/a; the production capacity of the 5th mining district is 20–27 Mt/a.

Soil recovery in a chronosequence of revegetated coal mine spoils in Colombian drylands: a view from the assessment of physical-chemical and biological properties

Characterizing changes in soil properties is essential to understand the effect of land rehabilitation practices and the mechanisms that drive such changes. The objective of this study was to evaluate the recovery of physical-chemical and biological properties of Technosols with increasing rehabilitation age in a chronosequence of dry forests (7, 10, and 21 years) in the El Cerrejón open-pit coal mine (La Guajira, Colombia). Based on previous studies that demonstrated a greater effect of surface change on the physicochemical properties of soils, composite samples taken at two depth levels (0–3 cm and 3–20 cm) were analyzed for each site. The studied properties improved over time, increasing significantly with respect to non-rehabilitated sites, mainly near the surface (0–3 cm). Particularly, after seven years, the increases in soil N content and soil P solution were significant (32% and 71%, respectively). The increased structural and functional development of the vegetation over time led to increased inputs of organic materials via fine litterfall. Overall, soil organic matter (SOM) ranged from 63 to 89% in the rehabilitated sites compared with a reference mature dry forest. Increased SOM is a key indicator of recovery in degraded mine spoils, as it has an outsized ability to influence other soil properties. This represents a positive result for the revegetation/restoration strategy applied at the El Cerrejón mine.

Study on MICP dust suppression technology in open pit coal mine: Preparation and mechanism of microbial dust suppression material

With the recent increases in energy demands, the dust hazards of coal mining caused by transportation, loading and unloading and other processes are becoming increasingly serious. To control dust in open pit coal mines more environmentally friendly and efficiently, and to promote the use and development of non-in situ high-yield urease microorganisms for dust suppression in coal mines, Bacillus pasteurii was selected for dust suppression experiments in this article. Additionally, the growth of microorganisms in the coal dust microenvironment was simulated, and the effect of microbial mineralization products on the calorific value of upper coal dust was further studied. Our findings indicated that Bacillus pasteurii induced dust suppression by forming a calcite precipitate with non-uniform particle size to coal dust cementation. Moreover, after a single spray, the wind erosion resistance efficiency was 84% when the wind speed was set at 10 m/s. The growth of microorganisms and urease activity in the coal dust leachate were largely equal to those in the control group, reaching a peak at approximately 24 h, that the maximum growth quantity of OD600 was about 1.5, and the maximum urease activity was 11 mmol·L−1·min−1. The difference between the peak heat release rate of mixed coal dust and pure coal was only 4.82 kW/m2, which would not affect the value of coal products. Non in-situ Bacillus pasteurii can be growth metabolized normally in the microenvironment of coal dust. Finally, the mechanism of coal dust suppression by mineralization of microbial bacterial solution to form calcium carbonate was described by a reaction equation, which is important for further application and development of microbial dust suppressants.

Automatically identifying the vegetation destruction and restoration of various open-pit mines utilizing remotely sensed images: Auto-VDR

The spatio-temporal pattern of vegetation disturbance by open-pit mining activities such as the disturbance area and magnitude are important for coordinated development of surface mining and environmental protection. This paper proposes an automatic method (Auto-VDR) for identifying vegetation destruction and restoration of various open-pit mines. The proposed method consists of three steps: construction of the sample dataset, identification of disturbance types, and extraction of disturbance time and magnitude. First, a sample dataset with three types was constructed according to the interannual trends of Normalized Difference Vegetation Index (NDVI) in mining areas: “Restoration after destruction (RAD)”, “Destruction without restoration (DWR)” and “No destruction (ND)”. Second, in order to accommodate to various open-pit mines with different background conditions (original vegetation cover prior to mining, loss rate and magnitude of vegetation due to mining, etc.), the “Shape-based distance” was used to match the NDVI curves of each pixel to the three disturbance types. Third, the disturbance time and magnitude in the destroyed regions were extracted based on the vegetated/bare ground threshold (α). The Shendong coal base in China was selected as the study area consisting of 133 open-pit coal mines. Annual NDVI was generated using Landsat time-series data. The maps of vegetation destruction and restoration caused by surface mining during 1990–2021 were drawn with accuracies of 0.82 and 0.87, respectively. The identification accuracy of the Auto-VDR is higher than Landsat-based detection of Trends in Disturbance and Recovery (LandTrendr) and Continuous Change Detection and Classification (CCDC). The results show that from 1990 to 2021, a total of 400.08 km2 of vegetation has been destroyed, accounting for 35.93% of the study area. Furthermore, restoration activities mainly began in 2010, lagging mining activities by approximately three years. The accumulated area of restoration was 177.91 km2 and accounts for 15.98% of the study area. The vegetation destruction at the Shendong coal base has gone through four stages, with 2008, 2015 and 2018 as splits, corresponding to the developing stage of the China coal industry. In particular, the area of vegetation destruction per year reached the maximum of 61.16 km2 in 2008, which was 1.38 times the total area mined over the past 17 years. There were 14% of the 133 open-pit mines in Shendong coal base with a restoration rate of 0.8 and 59% of the mines with a restoration rate of 0.5. This method has been demonstrated to be able to extract vegetation destruction and restoration processes accurately and rapidly for various open-pit mines at a scale of coal base, which provides an important reference for supervising the impact of mining on the environment and assessing the effectiveness of ecological restoration.

Ground Surface Subsidence Monitoring Using Sentinel-1 in the “Kostolac” Open Pit Coal Mine

Open pit coal mining affects surrounding populated areas, resulting in terrain surface deformation. Surface deformation should be monitored as often as possible to control deformations and prevent potential incidents. This paper analyzes time series deformation estimated from the Sentinel-1 satellite images using the Persistent Scatterer Interferometry method to monitor subsidence rates caused by open pit mining activities. It is possible to measure deformations using classical geodetic methods, but those are rarely used in practice because they are time-consuming and expensive for application in large areas. Using the open access radar images from the Sentinel-1 mission, 513 images from the repository were downloaded between October 2016 and the end of December 2020. We present the processing steps in detail in order to establish a workflow for the automated processing of vertical displacement estimation using open source tools; a total of 402 images were processed: 215 images belonged to the ascending satellite orbit, 187 images belonged to the descending orbit, and 111 images were rejected because of adverse weather conditions. The PS InSAR technique has never been used for the mines of the Republic of Serbia or for land surveying practices related to deformation monitoring. The results based on the Sentinel-1 images were compared with results from geodetic leveling and with neotectonic uplift trends. The trend lines of vertical displacement obtained from PS and corresponding leveling are significantly similar (a Pearson correlation of 85% with a p-value of 0.015). The final evaluation reported results of vertical displacements at the leveling benchmark of −3.4 mm/year with the PS InSAR method and −2.7 mm/year with the leveling method. A comparison of the PS vertical displacements with a settlement model fits reasonably, suggesting that the measurements are valid. As four years of PS time series data is insufficient to establish undisputable conclusions on the neotectonics uplift, extending the time series (covering at least a decade) implies that this approach will become attractive in future neotectonic uplift trend estimations. This study illustrates not only the ability of Sentinel-1 data in mapping vertical deformations, but the obtained results could also be used for geohazard monitoring and land monitoring in general for the area of interest.

Boundary optimization of inclined coal seam open-pit mine based on the ISSA–LSSVR coal price prediction method

As an important link in the complex system engineering project of open pit mining, the quality of the boundary determines the performance of the project to a large extent. However, changes in economic indicators may raise doubts about the optimality of mining boundaries. In this article, a coal price time series forecasting model that considers some amount of redundancy is proposed, which combines an improved sparrow search algorithm (ISSA) and a least squares support vector regression machine regression (LSSVR) algorithm. The optimal values of the penalty factor and kernel function parameter of the LSSVR model are selected by ISSA, which improves the prediction accuracy and generalization performance of the forecasting model. A multistep decision optimization method under fluctuating coal price conditions is proposed, and the model prediction results are applied to the boundary optimization design process. Using the widely applied block model as the basis, a set of optimal production nested pits is obtained, allowing the realm design results to fit the coal price fluctuation trend and further enhance enterprise efficiency. The applicability and effectiveness of this method were verified by taking an ideal two-dimensional model and an inclined coal seam open-pit coal mine in Xinjiang as an example.