Mechanisms of microbial diversity modulation of mineral black clay to achieve ecological restoration of open-pit mine dump.

The harsh climatic conditions and severe scarcity of surface soil present significant challenges to ecological restoration in open-pit mine dumps within China's type II plant cold resistance zone. To address the topsoil shortage, mineral black clay was used to create synthetic soil. This study explored the application of an ecological restoration bacteria (ERB) consortium to accelerate the ecological restoration of synthetic soil-covered areas by enhancing soil ecosystem construction. The results demonstrated that ERB significantly influenced the native bacterial community structure in mixed black clay. Specifically, ERB disrupted the inhibitory effects of the Actinobacterota phylum on the development of native bacterial diversity, leading to an increase in unclassified_o_Solirubrobacterales sp., norank_f_norank_o_norank_c_KD4-96 sp., Sphingomonas sp., Luteitalea sp., norank_f_Vicinamibacteraceae sp., and other aerobic and anaerobic bacteria. These alterations in soil microbial structure directly impacted soil composition and vegetation diversity. The plant diversity survey and metabolomics analysis revealed that the reduction of harmful substances, such as HPED, HODE, and HOME, in black clay soil improved the growth and distribution of Salsola collina Pall. and Medicago sativa L. This increase facilitated the cycling of key nutrients, such as nitrogen (N) and phosphorus (P), and promoted the establishment of symbiotic relationships between plants, microorganisms, and soil. Ultimately, the ecological remediation of the synthetic soil was achieved through the synergistic effects of ERB, which included the degradation of inhibitory soil components, enhanced nutrient consumption by microbiota and plants, and the overall promotion of ecosystem stability in the reclamation area.

Hydrogeochemical evolution patterns of diverse water bodies in mining area driven by large-scale open-pit combined underground mining-taking Pingshuo Mining Area as an example.

Large-scale open-pit combined underground mining activities (OUM) not only reshape the original topography, geomorphology, and hydrogeochemical environment of the mining area, but also alter the regional water cycle conditions. However, due to the complexity arising from the coexistence of two coal mining technologies (open-pit and underground mining), the hydrological environmental effects remain unclear. Here, we selected the Pingshuo Mining Area in China, one of the most modernized open-pit combined underground mining regions, as the focus of our research. We comprehensively employed mathematical statistics, Piper diagram, Gibbs model, ion combination ratio, principal component analysis and other methods to compare the hydrochemistry and isotope data of different water bodies before (2006) and after (2021) large-scale mining. The changing patterns of hydrochemical characteristics of different water bodies and their main controlling factors in mining area driven by OUM were analyzed and identified, revealing the water circulation mechanism under the background of long-term coal mining. The results showed that: (1) The chemical composition of water has changed greatly due to large-scale coal mining. The hydrochemical types of Quaternary and Permian-Carboniferous aquifers shifted from predominantly HCO3-Ca·Mg before intensive mining to primarily HCO3·SO4-Ca·Mg, HCO3-Na, HCO3·SO4-Na·Mg, and HCO3·SO4-Ca·Mg, HCO3-Ca·Na, HCO3·SO4-Mg·Ca post-mining. Variations in the hydrochemical types of surface water were found to be complex and diverse. (2) Coal mining activities promote the dissolution of silicate rock and sodium-bearing evaporites, enhancing the strength and scale of positive alternating adsorption of cations. The oxidation of pyrite, dissolution of silicate weathering, and the leaching of coal gangue were identified as the main reasons for the significant increase of SO42-, while decarbonation in confined aquifers led to a decrease in HCO3-. (3) Results from the principal component analysis and stable isotopes demonstrated the hydraulic connection among surface water, Quaternary aquifers, and Permian-Carboniferous aquifers induced by long-term OUM. The research findings provide a reference basis for the coordinated development of coal and water in the Pingshuo Mining Area and other open-pit combined underground mining areas.

Root traits drive the recovery of soil nematodes during restoration of open mines in a tropical rainforest.

Mining is a major threat to vegetation and soil in the tropical forests. Reforestation of degraded surface mines is critically dependent on the recovery of soil health, where the nematodes play an important role. However, the key determinants of community assembly of soil nematodes during mine-restoration remain unknown in the tropical rainforests. Here, the recovery of taxonomic diversity of nematode communities and their trophic groups during reforestation of an extremely degraded tropical open-mining area is studied. The factors that may impact their recovery, such as root traits (length, area and tissue density), soil properties (pH and soil organic matter content (SOM)), and taxonomic diversities of soil bacterial and fungal communities are investigated. Differences in these parameters were evaluated in the three soil types: (i) mined soil - the erstwhile soil that was removed during mining and stock-piled for 10 years at the foot of an extremely degraded open-mining area; (ii) reforested soil, sampled from a 10-year successful restoration, which used the mined soil for reforestation; and (iii) undisturbed soil, collected from an adjacent undisturbed/not-mined tropical rainforest. A total of 11, 34 and 29 nematode-genera were identified in mined-, undisturbed-, and reforested soils, respectively. The taxonomic diversities of the 5 nematode groups in the mined soil were 1.5-5.2 times lower than in the undisturbed soil, but were similar in the restored and undisturbed soils. Taxonomic diversities of phytophagous and predator nematodes were correlated to restored root traits; whereas of bacterivores, fungivores, and omnivores were correlated to pH, SOM, soil bacterial and fungal communities. Consequently, complete loss of roots during mining likely severely reduced the nematodes, but their recovery after reforestation led to the restoration of taxonomic diversity of nematode communities. The mix-planting fast-growing tree species may be appropriate for recovering soil health, including nematode diversity, during reforestation of open tropical mines.

Research on controlled mining of end slope fire-burned area in open-pit mine.

To solve the problem of controlling mining in the open-pit mine end slope fire-burned area, applying multivariate function fitting to the roof and floor modeling of multi-coal seam open pit mines, introducing the factor of coal quality changes in the fire-burned area, determining coal quality information at each location through proximate analysis of coal, to establish the net profit model of the mining area, it is determined the net profit of each mining position by numerical integration, the final mining position was determined without failure by calculating the slope stability based on the numerical simulation of strength reduction. Taking the Dananhu No. 2 open-pit mine in Hami, Xinjiang, China as the engineering background, the fire-burned area III within the southern end slope boundary of the first mining area is 240 m. It was finally determined that the optimal mining position is when the advancement degree is 182 m, the ultimate pit slope angle is 25°, the three-dimensional slope stability is 1.305, the profit is 671.96 million yuan, The deep boundary of the southern end slope fire-burned area of the slope is reduced by 58 m. This paper solves the problem of end slope mining in Dananhu No. 2 mine, and maximizes its net profit under the condition of ensuring safe production.

The study on the relationship between perceived value, satisfaction, and tourist loyalty at industrial heritage sites.

The legacy of industry reflects a city's journey and marks its cultural essence, highlighting the significance of preserving and promoting such historical assets. There is a noticeable gap in the discourse surrounding the intrinsic value of industrial heritage attractions and their impact on the fidelity of tourists. In light of this, the present investigation, rooted in the ABC attitude framework, examines the linkage between the perceived value, contentment, and allegiance of initial visitors to these sites. The study delves into the intermediary function of contentment and the variable influence of gender. Focusing on the Maoming Open-pit Ecological Park as a case in point, this research gathered and scrutinized 320 valid questionnaires. The outcomes demonstrate that the perceived value exerts a positive effect on both the satisfaction and the steadfastness of tourists. Satisfaction is identified as an intermediary between perceived value and tourist steadfastness. Additionally, gender plays a notable role in moderating specific aspects of the model. This inquiry aids in harnessing the potential of industrial heritage sites for the advancement of tourism, fostering economic prosperity and the rebirth of cultural practices. Furthermore, it lays down essential theoretical and practical building blocks for the evolution of industrial heritage as a tourism asset.

Research on upper bound limit analysis of slope stability in open-pit mine based on least square principle.

So as to extend the application of upper bound limit analysis for slope stability in open-pit mine, this paper analyzed failure mechanism of rock mass when shear failure occurred based on plastic mechanics principles, and combined with discrete mathematical theory and least square principle to propose a visualization method of logarithmic spiral. At the same time, the visualization method was applied to engineering practice for slope stability in open-pit mine, and cycle algorithm of stability analysis for open-pit mine slope was proposed through energy balance conditions, then stability analysis results were evaluated reasonably through uniting with limit equilibrium method. The results show that visualization method of logarithmic spiral proposed in this paper is highly consistent with original curve, and can ensure correlation coefficient square is greater than 0.9995. What is more, upper bound limit analysis method has a superhigh accuracy in slope engineering. At the same time, the most dangerous sliding surface obtained by this method can satisfy the requirements of velocity separation, which solved velocity problems during the process of slope evolution. Therefore, the method proposed in this paper has a stronger application in the field of open-pit mining.

Dynamic optimization design of open-pit mine full-boundary slope considering uncertainty of rock mass strength.

Rock and soil strength profoundly influences the stability of open-pit mine slopes. Traditional slope design, based on limited drilling data, often disregards inherent uncertainties. Effectively utilizing new sample information from mining operations poses a challenge, hindering dynamic and differentiated design for the entire perimeter slope. To address this, we propose a dynamic optimization method considering rock mass strength uncertainty for the entire perimeter slope. Our approach involves designing slope angles separately in different zones, while thoroughly considering decision-makers' preferences. Furthermore, we delegate the final adjustment authority of slope angles within the safety permissible range to on-site decision-makers. Compared to traditional methods, our dynamic design method incorporates rock mass strength uncertainty into slope evaluation while also accounting for decision-makers' safety and economic preferences. Through a case study of a specific open-pit mine, our proposed dynamic design method increases the overall slope angle by approximately 2.5°, fully accommodating the influence of on-site decision-making preferences on slope design. This article introduces a new method of dynamic optimization of open-pit mine slope based on simplified observation method, which improves the flexibility of decision-making and realizes the differential design of the whole surrounding slope.

Study on preparation and properties of antifreeze compound road dust suppressant.

Open-pit mine pavement dust dries and breaks easily. As such, a composite pavement dust suppressant with good wettability, moisturizing, coagulation, and antifreezing properties in winter was investigated. Monomer screening and orthogonal experiments were conducted, using evaporation rate, permeability rate, viscosity, and freezing point as evaluation indexes. Consequently, a dust suppressant solution is a mixture of glycerol (GLY), sodium dodecylbenzene sulfonate (SDBS), polyacrylamide (PAM), compound propylene glycol (PG), and potassium acetate (PA). The characteristics of the dust suppressant and its interaction mechanism with road dust were measured and analyzed. The results showed that the optimal ratio of the antifreeze-type composite dust suppressant is 3%GLY, 0.30%SDBS, 0.07% PAM, and 50%PG + 10%PA; the contact angle is 27.62°, which can effectively wet coal dust. Moreover, it easily forms hydrogen bonds with water molecules to release free -OH, which increases the oxygen-containing functional groups in the dust. The maximum viscosity is 25.4 mPa·s, and the hydrophobic groups adsorbed on the surface of the dust can condense and agglomerate the dust to form large particles, and effectively inhibit the occurrence of dust. It freezes at - 34.2 â„ƒ, resists a temperature of - 30 â„ƒ without freezing, and improves dust suppression efficiency and antifreezing effect in cold areas.

Stability evaluation of open-pit mine slope based on Bayesian optimization 1D-CNN.

As mechanized open-pit coal mining intensifies, assessing and predicting slope stability has become increasingly important. To address the limitations of traditional mechanical calculations, numerical simulations, and physical experiments, this paper identifies the key factors impacting slope stability in open-pit mines and develops a multi-parameter sample data set. The study employs hyperparameters optimized using a Bayesian algorithm, introduces additional convolutional layers, and combines the Adam optimizer with dropout techniques to enhance the feature extraction and performance of one-dimensional convolutional neural networks (1D-CNN). This leads to a Bayesian-optimized one-dimensional convolutional neural network (B-1D MCNN) model for predicting slope stability.The study evaluates the classification performance and accuracy of various models for slope stability, including BP neural networks, genetic algorithm-optimized convolutional neural networks, 1D-CNN, and B-1D MCNN, using accuracy, precision, and F1-score as metrics. The analysis also examines the influence of factor indicators and training set length on the model's output to assess its generalization capabilities.The research findings suggest that: (1) the B-1D MCNN model for evaluating slope stability demonstrates the capability to accurately depict the nonlinear correlation between influencing factors and slope stability. (2) Compared with other models, the B-1D MCNN model has shown enhancements of 10.96% to 27.85%, 10.26% to 28.55%, and 8.98% to 25.05% in terms of Accuracy, F1-Score, and Precision, respectively. (3) As the length of the training dataset increases, the performance of the model improves accordingly. (4) The B-1D MCNN model shows a generalization power of 87.5%.

Research on prediction of PPV in open-pit mine used RUN-XGBoost model.

The drill-blasting method is a commonly used mining technique in open-pit mines, and the peak particle velocity (PPV) caused by blasting vibrations is an important indicator for evaluating the rationality of blasting mining design parameters. To develop an effective PPV prediction model, a parameter self-optimizing RUN-XGBoost prediction model is implemented using the Runge-Kutta optimization algorithm (RUN) combined with extreme gradient boosting (XGBoost). The factors affecting the prediction of PPV, including maximum explosive (ME), total explosive (TE), blast center distance (BCD), blast hole depth (BHD), and height difference between the measurement location and the blast location (DH), are selected as the influencing indicators. 188 pieces of blasting operation data were measured at the RK open pit copper-cobalt mine. Then, the RUN-XGBoost prediction model for PPV is studied and compared with the Sadovsky empirical formula, traditional XGBoost model, PSO-XGBoost model, and some traditional machine learning models (Ridge, LASSO, SVM, and SVR) using R2, RMSE, VAF, MAE, and MBE as evaluation indicators for model prediction results. Finally, the Shapley Additive Explanations (SHAP) method is used to evaluate the contribution of different influencing indicators to the PPV prediction results. The results show that the RUN-XGBoost prediction model is significantly better than other machine learning models and the Sadovsky empirical formula in the prediction of PPV, further demonstrating that the RUN-XGBoost prediction model can handle the nonlinear features of multiple factors and provide a reliable, simple, and effective PPV prediction model, forming a rapid prediction and evaluation method for blasting vibrations in open-pit mining.

Comparison of the monitoring of surface deformations in open-pit mines with Sentinel-1A and TerraSAR-X satellite radar data.

In case necessary precautions are not taken in surface mines, serious accidents and loss of life may occur, particularly due to large mass displacements. It is extremely important to identify the early warning signs of these displacements and take the necessary precautions. In this study, free medium-resolution satellite radar images from the European Space Agency's (ESA) C-band Sentinel-1A satellite and commercial high-resolution satellite radar images (SAR, Synthetic Aperture Radar) from the Deutsches Zentrum für Luft- und Raumfahrt's (DLR) X-band TerraSAR-X satellite were obtained, and it was attempted to reveal the traceability and adequacy of monitoring of deformations and possible mass displacements in the dump site of an open-pit coal mine. The compatibility of the results obtained from the satellite radar data with two devices of Global Positioning System (GPS) which were installed in the field was evaluated. Furthermore, the velocity results in the Line Of Sight (LOS) direction and vertical deformation velocity results obtained with all three approaches (GPS/Sentinel-1A, GPS/TerraSAR-X, and Sentinel-1A/TerraSAR-X) were compared. It was observed that the results were statistically equal and the directions of movement were similar/compatible. The result of this study showed that deformations at mine sites can be monitored with sufficient accuracy for early warning with free Sentinel-1A satellite data, although the TerraSAR-X satellite offers a higher resolution.

Self-reported exposure to dust and diesel exhaust, respiratory symptoms, and use of respiratory protective equipment among Arctic miners.

Arctic miners face significant risks from diesel exhaust and dust exposure, potentially leading to adverse respiratory health. Employers must limit harmful exposures, using personal protective equipment (PPE) as a last line of defense. This study explored the association between reported respiratory exposure and symptoms, and PPE training and usage. Data from the MineHealth study (2012-2014) included a total of 453 Arctic open pit miners in Norway, Sweden, and Finland. Participants answered questions on exposure to dust and diesel exhaust, respiratory symptoms, and PPE use, in addition to age, gender, BMI, smoking, and self-rated health. Estimated exposure to dust was common, reported by 91%, 80%, and 82% and that of diesel exhaust by 84%, 43%, and 47% of workers in Sweden, Finland, and Norway, respectively. Reported dust exposure was significantly related to respiratory symptoms (OR 2.2, 95% CI 1.3-3.7), diesel exposure increased the occurrence of wheezing (OR 2.6, 95% CI 1.3-5.4). PPE use varied between the studied mines. Non-use was common and related to reduced visibility, wetness, skin irritation and fogging of the respiratory PPE. Future research should employ more precise exposure assessment, respiratory function as well as explore the reasons behind the non-compliance of PPE use.

A framework for selecting and assessing soil quality indicators for sustainable soil management in waste dumps.

The primary objective of this study was to develop soil quality indexes (SQIs) to reveal the changes in SQ during the restoration of vegetation in the reclaimed waste dumps of the Hequ open-pit coal mine. The study built an SQI evaluation model for waste dumps based on the soil management assessment framework. The total data set (TDS) consisted of nine physicochemical property indicators. The selection of the minimum data set (MDS) involved the utilization of principal component analysis (PCA) and Norm values. The SQ was comprehensively evaluated for nine indicators, taking into account the non-linear membership function and the improved Nemerow index. The findings suggested a notable disparity in the SQ between the reclaimed area and the unreclaimed area, yet the overall SQ fell short. In the TDS index system, the organic matter has the highest weight and a greater contribution to the soil quality of the waste dumps. In the MDS indicator system, the weights of organic matter and total nitrogen are both 0.5. According to Nemerow index method, the average SQIN of 5 plots is calculated to be 0.4352 ± 0.194. The average value obtained from TDS is 0.581 ± 0.236, and the average value obtained from MDS is 0.602 ± 0.351. The weighted additive method was employed to compute three SQIs, all of which yielded satisfactory outcomes. And the above evaluation methods indicate that the overall soil quality level of the waste dumps is at a moderate level. The sequence of SQ in various waste dumps was as follows: No.4lower > No.1 > No.2 > No.3 > No.4upper. Specifically, the non-linear membership function indicated that pH, available nitrogen (AN), available phosphorus (AP), surface moisture content (SMC), and bulk density (BD) were crucial in limiting SQIs in total waste dumps. The crucial limiting SQIs in unreclaimed areas were total phosphorus (TP) and total nitrogen (TN). This analysis demonstrates its efficacy in formulating strategies for the SQ evaluation and targeted soil reclamation plans of waste dumps.

Research on the effect of water-cooling steel pipe on preventing spontaneous combustion of coal pile and its thermal migration behavior.

During the storage and transportation process after mining, coal piles are placed in open environments, making them prone to self-heating and spontaneous combustion due to the nature of coal and factors like natural wind flow. In recent years, there have been frequent spontaneous combustion incidents involving coal piles, posing significant safety risks. To effectively prevent and control spontaneous combustion disasters in open-air coal storage piles, we propose a method involving the arrangement of water-cooling steel pipes within the coal piles. This method applies theories of coal spontaneous combustion mechanisms, porous media heat transfer, and non-isothermal pipeline heat transfer. The multi-physics coupling model of COMSOL numerical simulation software is used to analyze the spontaneous ignition process and prevention effect of open pit coal pile. In the model, the thin material transfer of porous media is taken as the oxygen concentration field, the heat transfer of porous media is taken as the temperature field, and the free and porous media flow is taken as the air seepage velocity field. The simulation results of the spontaneous combustion process in the coal pile indicate that the high-temperature zone of spontaneous combustion is situated within the range of 0.5 ~ 1.5 m inside the wind-facing surface and extends 0.5 m above the ground level. These findings serve as a basis for determining the optimal placement of water-cooling steel pipes within the coal pile. The simulation results of a single water-cooling steel pipe demonstrate a positive correlation between the cooling effect on the coal pile and the water cool flow, and a negative correlation with the water cool temperature. Additionally, the cooling radius of the water-cooling steel pipe is determined by the circumference of the pipe and remains unaffected by the water cool flow. Finally, simulations were conducted to evaluate the cooling effect of multiple rows of steel pipes, and optimal arrangement parameters were determined: a center distance between steel pipes of 1 m and a water cool flow rate of 1500 L/min. As a result, the onset of the self-heating period in the coal pile was delayed by 11 days, and the spontaneous combustion period was extended by 56 days. The arrangement of water-cooling steel pipes in the coal pile has demonstrated significant efficacy in preventing and controlling spontaneous combustion.

Stability analysis of pumped storage hydropower plant in abandoned open-pit mine affected by dynamic surface subsidence of combined mining.

The construction of a pumped storage hydropower plant (PSHP) in an abandoned open-pit mine is a potential alternative to green mining and energy storage, which can increase the utilization rate of renewable energy and develop residual resources of abandoned mines. Dynamic surface subsidence affected by combined underground and open-pit mining (CUOPM) seriously affects the construction and operation of the PSHP and is one of the critical scientific issues that needs to be solved immediately. The stability of the PSHP was analyzed and treatment scheme of the goafs was proposed based on on-site measurement, theoretical analysis, and numerical simulation. First, the distribution of goafs in the Haizhou open-pit mining area was investigated and surface subsidence value was obtained using InSAR technology and ground monitoring. Secondly, the surface subsidence mechanism affected by CUOPM is analyzed and indicates the subsidence maximum values and scope of influence are greater than those of single underground mining. A dynamic surface subsidence prediction model for combined mining is established based on the Knothe time function model. Thirdly, based on the CVISC model, the numerical calculation models were established by using FLAC3D, and the characteristics and laws of surface subsidence in different periods of CUOPM were studied. The comparative analysis of the observation results shows that the proposed model and numerical simulation calculation method have excellent applicability and accuracy. Finally, a stability evaluation method of PSHP was established, and the results of the evaluation show that the affected areas are the semi-ground powerhouse (SGPH) and the west side of the lower reservoir. The method of grouting filling was used to treat the goafs, and the results showed that it effectively alleviates the dynamic surface subsidence affected by CUOPM, and provides a safety guarantee for PSHP.

Recovery of small rodents from open-pit marble mining: effects on communities, populations, and individuals.

Mining can significantly alter landscapes, impacting wildlife and ecosystem functionality. Natural recovery in open-pit mines is vital for habitat restoration and ecosystem re-establishment, although few empirical studies have examined this process. Here, we assessed temporal and spatial responses of small rodents at the community, population, and individual levels during natural mine recovery. We examined the abundance, reproductive potential, and individual health of small rodents at active mines and at former mine sites left to recover naturally for approx. 10 and 20 years. We also assessed the effects of disturbance on rodent recovery processes at three distances from the mine boundary. Rodent numbers peaked after 10-13 years of recovery and exhibited the strongest male bias in the sex ratio. The Chinese white-bellied rat (Niviventer confucianus) was the most abundant species, achieving its highest population abundance at sites abandoned for 10-13 years and thriving at locations closer to the mine boundary. Only Chevrier's field mouse exhibited morphological responses to the mine recovery category. Ectoparasite load was unaffected by mine or distance-disturbance categories. Both Chevrier's field mouse (Apodemus chevrieri) and the South China field mouse (Apodemus draco) were affected significantly by vegetation layer cover during recovery succession. Our study highlights the complexities of ecological succession, with a peak in abundance as pioneer communities transition toward a climax seral stage. Careful prior planning and active site management are necessary to optimize abandoned mine recovery. Efforts to accelerate mine recovery through technical restoration should promote conditions that initiate and perpetuate the establishment and succession of wildlife assemblages.

Study on blasting fragmentation mechanism of burnt rock in open-pit coal mine.

A large number of burnt rocks in some open-pit mines in Xinjiang, Inner Mongolia and Ningxia have a great influence on the blasting effect. For this kind of rock, through the analysis of physical and chemical changes, combined with ANSYS/LS-DYNA and PFC 2D numerical simulation software, a burnt rock model with multiple joint cracks and irregular distribution is constructed to simulate the blasting process of burnt rock under the combined action of stress wave and detonation gas. The results show that the fracture of rock mass affects the propagation of blasting cracks in the fracture area, resulting in stress concentration and stress hindrance. The action time of stress wave is reduced, and the energy of blasting gas is partially absorbed by the fracture, resulting in uneven stress on the burnt rock bench and seriously affecting the bench blasting effect.

Creep characteristics and discharge optimization of overlying river inner dump: A case study of Yuanbaoshan open-pit coal mine in China.

Overlying river can accelerate the creep of the inner dump, so to master the creep characteristics of the overlying river can provide a theoretical basis for mine safety and discharge optimization. Taking the overlying river inner dump of Yuanbaoshan open-pit coal Mine in China as the research object, a design scheme is proposed to divide it into rolling zone and non-rolling zone. Based on the creep model obtained by in-situ deformation monitoring and laboratory rheological test, the creep evolution law and deformation of overlying channel after soil discharge, slope morphology and advancing position are simulated and analyzed. The results showed that the creep variable in the (non-) rolling zone had a nonlinear upward trend with time, and the initial upward trend was large. The maximum vertical and horizontal creep in the rolling area was located in the middle and upper part of the rolling line, while the maximum vertical and horizontal creep in the dump was located in the middle and upper part of the non-rolling area, respectively. The post-construction settlement and horizontal discharging increased with the increase of the discharge height, and the convergence creep of the top ten years after construction increased approximately linearly with the decrease of the distance from the shoulder of the inner dump. The rolled sand and gravel backfill belonged to the foundation of uniform settlement deformation in general, and the change of slope shape had little effect on the deformation of the slope top in the rolled area. The geoglage elongation in the dam area met the requirements. On the premise of ensuring the stability of the dump, the slope angle of the inner dump can be appropriately increased to increase the capacity of the inner dump. The research results can provide guidance for the construction of inner dump in open pit.

Origin and stability of pit lake water in Baiyinhua, Inner Mongolia, based on hydrochemistry and stable isotopes.

Isotope technology is widely used in geochemical mechanisms analysis; however, studies on the origin of pit lake water by isotopes in coal concentration areas in grassland are rare. In this study, 20 groups of water samples were collected, which were subjected to chemical analysis to determine the hydrogeochemical characteristics of pit lake water. The mechanisms of pit lake water formation and recharge-evaporation were ascertained through principal component analysis and the Rayleigh fractionation model. The results indicate that the phreatic water is least affected by evaporation, followed by confined water, surface water and pit lake water. The ionic composition of surface water, phreatic water and most of the confined water is mainly affected by leaching, some confined water can be recharged by surface or phreatic water; while the ionic composition of pit lake water is dominantly affected by evaporation (69.4 %) and is less affected by groundwater recharge (17.1 %) and human activities (11.5 %). The pit lake water is recharged by precipitation, phreatic water and the lateral runoff of confined water; however, the proportion of phreatic and confined water recharge is small. The evaporative loss of the pit lake water is 40-61 % of the initial water body.

Spatio-temporal evolutionary analysis of surface ecological quality in Pingshuo open-cast mine area, China.

The open-pit mining area is highly affected by human activities, which aggravate soil erosion and disturb surface ecology, bringing many problems and challenges to its environmental management and restoration, which has received widespread attention. The establishment of an objective, timely and quantitative remote sensing monitoring, and evaluation system for the spatio-temporal evolution of the surface ecological environment in the open-pit mining area is of great significance for its environmental protection, management decisions, and sustainable social development. Based on the Google Earth Engine (GEE) platform, this paper uses Landsat images to construct and calculate the remote sensing ecological index (RSEI) of the Pingshuo open-cast mine area (POMA) from 1990 to 2020 and monitor and evaluate its surface ecological environment. Combined with the Theil-Sen median, Mann-Kendall test, and Hurst index, the spatio-temporal process was analyzed. The results showed that the ecological environmental quality of the mining area first decreased and then increased from 1990 to 2020. 1990-2000 was a period of serious ecological degradation, followed by improvement. The overall improvement area reached 87.03%, and the degradation was concentrated in the coal mining area. Between 1990 and 2020, the Hurst index of the mining area was 0.452, indicating that the region has a fragile ecological environment and has difficult maintaining its stability. The global Moran's I mean value of the RSEI of the study area is 0.92, which combined with Moran's scatter plot to indicate that there is a strong positive spatial correlation rather than a random distribution of its ecological environment. During the study period, the impact on the climate of the ecological environmental change of POMA was weak, and human factors such as coal mining, land reclamation, and social construction were the main driving forces for the change in ecological quality. The results of this study reveal the changing trend of surface ecology in the mining area over the past 30 years, which is helpful for understanding its impact mechanism on ecological quality and provides support for the management of the region.