Mining Subsidence Area Research Articles

AHP-EWM Based Model Selection System for Subsidence Area Research

Coal mining can create a variety of environmental, ecological, and land-use problems. Subsidence areas resulting from coal mining are a common and particularly difficult problem to manage. Despite much discussion in the academic literature as well as among local and international stakeholders, there is neither a uniform standard nor a universally accepted approach for selecting an appropriate governance model for a subsidence area. In particular, the lack of quantitative evaluation methods and excessive subjectivity represent key obstacles to the effective selection of governance models for subsidence areas. This paper proposes a selection framework for a coal mining subsidence governance model that integrates the analytic hierarchy process (AHP) and entropy weight method (EWM). The model comprehensively considers the settlement characteristics of the subsidence area, its geographic location, the water index, as well as the vegetation index. These variables are used as indicators to develop an evaluation framework upon which different subsidence zones can be quantitatively analyzed. The selection framework is demonstrated using examples from three subsidence areas in the Huainan and Huaibei mining areas in China, for which relevant data were collected and processed with the help of field surveys, remote sensing images, and subsidence prediction software. Applying the novel selection framework, the most suitable governance model for each subsidence area was obtained and determined to be consistent with the recommendations of an academic panel composed of multiple experts. The novel selection framework has high efficacy and potential to overcome the problem of subjectivity in the selection of governance models for coal mining subsidence areas. It is also envisaged that future incorporation of the selection framework into a user-friendly software package will significantly improve the efficiency with which suitable governance models for coal mining subsidence areas are selected.

Study on the law of residual deformation in mining subsidence area and its influence on the safety of ground buildings

After the mining subsidence area reaches the stable state of surface movement, due to the continuous existence of the mutual extrusion and activation state between rock strata, the movement of particles, rock creep, and soil compression will affect the surface movement in the long-term stability, thereby threatening the safety and stability of the above ground buildings. In order to study the deformation law of rock strata movement and surface displacement after the mining subsidence area is stabilized, establish a ground deformation model caused by mining, explore the characteristics of ground movement and deformation under the action of building loads, design a similar material simulation experiment, record the ground movement changes within 378 days after the mining is completed, after the settlement is stabilized, apply equivalent loads of 10–30 floors to the model at different locations, and study various surface deformation data, Analyze the change rule. In order to quantitatively analyze the impact of residual deformation of goaf on buildings under building load, the D5 gate area of Tangshan World Horticultural Exposition in mining subsidence area is taken as an example to calculate the ground settlement value and other deformation data using probability analysis method, and the Kelvin model in rock mechanics is introduced in terms of the duration of residual deformation. The calculation results are close to the actual measured values, and the impact of residual deformation on the proposed building is analyzed.

Ecological Stoichiometry of Soil Carbon, Nitrogen and Phosphorus in Reclaimed Farmland in Coal Mining Subsidence Area

Ecological Stoichiometry of Soil Carbon, Nitrogen and Phosphorus in Reclaimed Farmland in Coal Mining Subsidence Area

Multi-Scale Integration and Distribution of Soil Organic Matter Spatial Variation in a Coal–Grain Compound Area

Soil organic matter (SOM) scale effects are critical for crop growth and food security, especially in coal–grain complexes. However, few studies describe the spatial variation in SOM and its influencing factors at different sampling scales. Here, geostatistical theory and mathematical statistical methods were adopted to analyze the spatial variation characteristics of and structural differences in SOM in the coal mining subsidence area at Zhaogu No. 2 Mine at different sampling scales. The results showed that SOM varied spatially at large, medium, and small scales, and the coefficients of variation were 28.07%, 14.93%, and 14.31%, respectively, which are moderate values. The characteristic functions of the SOM content at different sampling scales differed, and the spatial structure scale effect was obvious. The spatial distribution of the SOM content fitted by the multiscale fitting model method was generally the same as the spatial distribution law of the SOM content fitted by the single scale kriging interpolation method; however, in terms of the detailed expression and spatial distribution of small-scale SOM content, the fitting model method was more accurate, and the accuracy increased by 36%. At the different sampling scales, sample size and soil type had specific effects on the SOM spatial distribution. These results provide research concepts and technical countermeasures for improving food security and the ecological environment in the coal–grain complex and help ensure sustainable agricultural lands.

Photovoltaics literature survey (No. 181)

Photovoltaics literature survey (No. 181)

Relationship between soil water content and vegetation distribution in a small area before and after coal seam mining: a case study of coal mining subsidence area in Northwest China

Relationship between soil water content and vegetation distribution in a small area before and after coal seam mining: a case study of coal mining subsidence area in Northwest China

Water chemistry and stable isotope characteristics of subsidence lakes in coal mining areas, Eastern China.

Many subsidence lakes have formed in eastern China as a result of underground coal mining. These coal mining-related subsidence lakes vary in their formation time and connectivity with rivers. These factors may influence the water chemistry and hydrogen and oxygen stable isotope characteristics of the lake water. This study collected and tested subsidence lake water, atmospheric precipitation, river water, and shallow groundwater in the study area. The results showed that the water chemical types of the subsidence lake water and river water are Cl-Na and HCO3·Cl-Na and that the water chemical types of the shallow groundwater are mainly HCO3·Cl-Na and HCO3·Cl-Ca. There are no significant differences in the water chemical characteristics of subsidence lakes with different subsidence ages and types. The major ions in each water body mainly come from evaporite dissolution and silicate weathering, and ion exchange occurs. Reverse ion exchange occurs in some shallow groundwater samples. The stable isotopes of hydrogen and oxygen in the subsidence lake water, river water, and shallow groundwater are distributed along a straight line with a slope less than that of the LMWL, indicating that these water bodies have a common source, namely, precipitation. With increases in the formation time of the subsidence lakes, the heavy isotopes in the lake water gradually become depleted, and the d value gradually increases, mainly driven by precipitation dilution, weakening evaporation, river recharge, and groundwater recharge. The isotopic values of different types of lakes with the same subsidence time differ little. The research results may provide scientific guidance for the rational development and utilization of water resources in coal mining subsidence areas, enrich the study of the hydrological cycle in the area, and are of great significance for the protection of the local water balance and water environment.

Effects of Underground Mining on Soil–Vegetation System: A Case Study of Different Subsidence Areas

The influence of coal mining subsidence on the surface ecological environment can be characterized as the evolution of a complex system. Examining the ecological damage caused by coal mining subsidence from the perspective of internal soil–vegetation system relationships is important for the ecological protection and restoration of mining areas. We investigated vegetation coverage, surface soil water and nutrient content, and vadose zone soil moisture in uniform and nonuniform areas of coal mining subsidence. Subsidence reduced vegetation coverage, surface soil moisture and nutrient content, and vadose zone soil moisture while increasing their spatial variability. These effects are more pronounced in areas with nonuniform subsidence. Subsidence also reduced the degree of soil–vegetation system correlation, which was also more pronounced in areas of nonuniform subsidence. Furthermore, a higher degree of soil–vegetation correlation was linked to decreased variability in soil moisture and nutrient content. Areas of nonuniform subsidence were characterized by greater preferential flow during rain infiltration, which contributed to the spatial variability of soil moisture and nutrient content and damage to vegetation growth. Our findings revealed that coal mining subsidence reduces both the quality of environmental factors and the degree of internal correlation between these factors, of which the preferential flow effect is an important underlying mechanism. These findings provide a theoretical basis for ecosystem management and the restoration of land damaged by coal mining subsidence.

Retracted: A Statistical Prediction Model for Healthcare and Landslide Sensitivity Evaluation in Coal Mining Subsidence Area.

[This retracts the article DOI: 10.1155/2022/1805689.].

Variation of Soil Carbon, Nitrogen and Phosphorus and Ecological Stoichiometric Characteristics During Land Degradation in Coal Mining Subsidence Area

In order to explore the effects of land degradation on soil carbon, nitrogen and phosphorus and ecological stoichiometry in semi-arid coal mining subsidence area, the spatial pattern of soil carbon, nitrogen and phosphorus content, reserves and ecological stoichiometric ratio in the process of land degradation was studied by space-time substitution method with the soil in three stages of non-degradation, mild degradation and severe degradation as the research object. The results showed that :(1)Land degradation caused an average decrease of soil moisture content and porosity by 50.8% and 22.4%, respectively, resulting in an increase of soil pH and bulk density by 16.0% and 23.8%, respectively.(2)The soil organic carbon content and storage decreased by 55.6% and 50.7%, respectively, due to land degradation. The carbon loss in the surface soil was significant, and the nitrogen content and storage decreased by 21.8% and 13.9%, respectively. The soil nitrogen damage in the middle layer was the largest, and the phosphorus content and storage decreased by 37.9% and 31.8%, respectively.(3)Soil C/N decreased by 18.9%, C/P and N/P increased by 7.9% and 35.4%, respectively, after mild land degradation. Soil C/N and C/P decreased by 68.2% and 64.4%, respectively, while N/P increased by 16.1% after severe land degradation. (4) Soil water content and other environmental factors have different degrees of influence on soil carbon, nitrogen and phosphorus content, C/N and C/P, but no significant correlation with soil N/P. In summary, land degradation caused by multi-dynamic erosion damage in coal mining subsidence areas will significantly reduce soil environmental quality, cause soil drought, barrenness and salinization, and reduce the storage and supply capacity of ecosystem carbon, nitrogen and phosphorus.

Effects of vegetation restoration on ecosystem carbon storage and distribution pattern in semi-arid mining area

In order to explore the effect of artificial planting to promote vegetation restoration on ecosystem carbon storage in coal mining subsidence area, the distribution pattern of ecosystem carbon storage in mining area during vegetation restoration was studied by space-time substitution method.The results showed that : (1) The biomass of vegetation layer increased gradually with vegetation restoration, and the biomass distribution ratio of each component was shrub layer (92.1%) > litter layer (5.5%) > herb layer (2.4%). The biomass of shrub and herb layer was mainly distributed in the aboveground part, the former accounted for 73.2 %, and the latter accounted for 83.4 %. (2) The carbon content of the vegetation layer was shrub (45.5%) > herb (43.6%) > litter (38.7%). The total carbon storage was in the early initial of vegetation restoration (1657.1 kg hm-2) < mid-term vegetation restoration (4830.6 kg hm-2) < mature stage of vegetation restoration (8446.4 kg hm-2), and shrub was still the main storage part of carbon storage in this layer. In summary, vegetation restoration can significantly increase the carbon storage of the ecosystem, the proportion of carbon storage in the vegetation layer gradually increases.

Study on Characteristics of Overburden Strata Structure above Abandoned Gob of Shallow Seams—A Case Study

To understand the change in overburden structure after coal seam group mining, we investigated the overburden characteristics and bearing capacity of abandoned coal mines in a coal seam group. We provide a theoretical basis for the construction and utilization of a coal mining subsidence area under a complex geological environment. This paper takes the construction project of Zhongtie Huizhi Square in Zhangqiu District, Jinan City, Shandong Province as the engineering background. According to the occurrence conditions of the study area, theoretical analysis, similar simulation, numerical simulation, and engineering practice verification are used. The overburden structure characteristics of abandoned mines in a shallow-buried coal seam group were studied. The results show that the development height of the water-carrying fractured zone after the mining of the 3#, 4#, and 9# coal seams is 17 m, 19.5 m, and 27.1 m, respectively, which shows that the height of water flow in the fractured zone is proportional to the buried depth of the coal seam after coal seam mining. After the model is set aside for three months, the degree of development of the residual fracture in the goaf is analyzed, and the distribution law of residual porosity in the longwall old goaf of a shallow-buried multiple coal seam is obtained. The development rate of residual fissures on both sides of the goaf is between 20.31% and 42.31%. The residual fracture development rate in the middle is relatively small, being between 8.21% and 18.53%. We comprehensively analyzed the characteristics of overlying strata in the abandoned mine under actual stratum conditions, and compared the empirical calculation results, theoretical research, similar simulation, and numerical simulation results in the specification with the engineering practice to prove the reliability of the research.

Characteristics and Formation Mechanism of Surface Residual Deformation above Longwall Abandoned Goaf

With the rapid development of social economy in China, the contradiction between the wide distribution of abandoned goaf and the shortage of land for engineering construction is becoming increasingly prominent. The effective utilization of coal mining subsidence areas has become an effective measure to alleviate the poverty of construction land in mining areas and promote the green transformation of mining cities. The key to the scientific utilization of abandoned goaf is the prevention and control of surface residual deformation, which depends on the formation mechanism of surface residual deformation. Based on the regularity of mining-induced surface movement and deformation under different mining sizes, it is concluded that the full mining degree of working face is the primary condition for entering the surface recession period. The trapezoidal and periodic forward movement characteristics of mining-induced overburden destruction are analyzed. The regularity of upward transmission of mining-induced fissures with overburden destruction is clarified. The influencing factors of surface residual deformation are equivalent to the influencing factors of overburden structure and caved zone. The deformation characteristics of broken rock in the caved zone under different conditions (particle size, gradation, and water content) are analyzed. It is concluded that the surface residual subsidence near the boundary of the goaf is more significant than that in the middle of the goaf. It is revealed that the overburden structure at the boundary of the goaf and the re-compaction of the caved zone is the mechanism of surface residual deformation. The characteristics of surface residual deformation in abandoned goaf have been verified by field measurement, and it is pointed out that the surface residual deformation in abandoned goaf has long-term characteristics, which provides a theoretical basis for accurate prediction of surface residual deformation and rational utilization of abandoned goaf.

Yields of Buckwheat and Alfalfa in an Intercropping System Inoculated with Dark Septate Endophytes in a Coal Mining Subsidence Dryland Area

Coal mining subsidence areas in north Shaanxi province in north China are commonly low-fertility drylands, and intercropping is a popular method locally of maximizing crop yields. Inoculation with dark septate endophytes (DSE) can increase the yields of conventional crops grown in monoculture, but the effects of DSE on the growth and yield of intercropped plants are unknown. Here, a field experiment was conducted in a coal mining subsidence area on the loess plateau in 2020 and 2021. The two crops were buckwheat and alfalfa, with four treatments for each crop: sole cropping control, sole cropping with DSE inoculation, intercropping control, and intercropping with DSE inoculation. The yields, land equivalent ratios, DSE colonization rates, and yield components of buckwheat and alfalfa were compared in the different treatments. Stepwise regression and path analysis was conducted to identify the factors that determined crop yields. Yields of intercropped buckwheat and alfalfa with DSE inoculation increased in two consecutive years compared with sole cropping control, with yields increasing in 2020 by 117 and 86%, respectively. In 2021, the yield of buckwheat in intercropping with DSE inoculation did not increase significantly, but the yield of alfalfa increased by 120% compared with the sole cropping control. Buckwheat-alfalfa intercropping has the advantage of increasing the yield. DSE inoculation significantly increased the yield of buckwheat-alfalfa intercropping in 2020, but there was no yield advantage in 2021. The yield components of buckwheat and alfalfa showed inconsistent differences among experimental treatments. Stepwise regression and path analysis shows that the DSE colonization rate played an important role in the yield, which was an increased in buckwheat and alfalfa in 2020 and 2021. DSE affected the buckwheat yield indirectly by increasing the grain weight per plant, plant phosphorus uptake, and plant nitrogen content. DSE indirectly affected alfalfa yields by increasing plant nitrogen uptake and plant height. DSE may therefore have some potential to increase yields in buckwheat-alfalfa intercropping systems in coal mining subsidence areas.

Mining Subsidence Monitoring Based on InSAR Method Fusing Multi-threshold Target

In view of the limitations of traditional InSAR technology in selecting stable target point for orbit refining and surface subsidence inversion in complicated mining area, this paper proposes a time-series InSAR mining area subsidence monitoring method based on the fusion of multi threshold targets. On the basis of the traditional technology, the deviation threshold parameters, the regional window threshold parameters and the coherence threshold parameters are set to extract the relatively stable target points on the ground. Applying this method and traditional InSAR method to practical cases, the monitoring results of surface subsidence in the study area are obtained and verified. The results show that: (1) there are three mining subsidence areas in the mining area, the maximum annual average subsidence rate is -156 mm/a, and the maximum subsidence is -376 mm. Compared with the optical image data, the location of the mining subsidence area is consistent with the mining work area of the coal mine; (2) The absolute average difference of subsidence in the mining area using the two methods shall not exceed 12 mm. It shows that the InSAR method of fusing multi threshold targets can not only effectively overcome the limitations of traditional InSAR, but also ensure high accuracy, and has more advantages in the monitoring of surface subsidence in mining areas.

Renew mineral resource-based cities: Assessment of PV potential in coal mining subsidence areas

Accurately assessing the photovoltaic (PV) power generation potential in coal mining subsiding regions is of great significance for the transformation of a resource-based city and the goal of carbon neutrality. In this paper, we proposed an assessment method for the PV power potential in coal mining subsidence areas. Both the environmental factors and ground deformation by interferometric synthetic aperture radar were fully considered. Furthermore, the levelized cost of PV electricity in subsidence areas and the benefits were predicted. Yangquan City, Shanxi province was selected as a study case. Results show that the optimal areas for PV power generation under the three-deformation rate ranges of (−40, −10), (−50, −10), and (−60, −10) mm/year in the Yangquan subsidence area are 32.13, 37.89 and 41.22 km2, respectively. The selected optimal PV construction regions agree well with the exiting PV facilities, indicating the effectiveness of the proposed method. The levelized cost of energy is estimated at 0.3934 RMB/kWh. The annual power generation can meet about 33 % of the electricity demand of Yangquan City. This work would guide the construction of PV power generation facilities in the coal mining subsidence areas for the transformation and upgrading of the mineral resource-based cities.

Assessing the impacts of ecological governance on carbon storage in an urban coal mining subsidence area

Carbon storage, which is considered one of the important service functions of ecosystems, plays an irreplaceable role in maintaining the regional carbon balance and regulating the climate. Regional carbon storage is closely related to regional land use and land cover (LULC). With the development and expansion of coal resource-based cities, the construction areas of cities have started to overlap with underground coal resources. Coal mining leads to regional LULC changes, such as large-scale surface subsidence and subsidence waterlogging, and LULC has changed and consequently affected carbon storage in urban coal mining subsidence areas. This study analyses the change trend of carbon storage and clarifies the effect of ecological governance being implemented in the urban coal mining subsidence area. First, the LULC change map of the ecological governance scenario was obtained via remote sensing technology. Then, the natural evolution scenario from 2000 to 2021 was simulated using the hybrid cellular automata and Markov chain, also named the CA–Markov model. Finally, combined with the subsidence waterlogging in the urban subsidence area, the InVEST model was used to analyse the spatial–temporal variation characteristics of carbon storage. The analysis results showed that LULC and carbon storage in small-scale urban coal mining subsidence areas changed dramatically between 2000 and 2021 due to coal mining and ecological governance. The subsidence waterlogging area increased by 1033.83 ha, resulting in total carbon storage decreasing by 37,560.21 t. Subsidence waterlogging is the key influencing factor in the decrease in carbon storage. The forest area increased by 1270.83 ha, resulting in a total carbon storage increase of 216,531.04 t. Forest is the crucial increasing factor in carbon storage. The changes in carbon storage in the urban coal mining subsidence area can be classified as follows: obvious improvement area, basically unchanged area, and significantly degraded area. As opposed to the natural evolution scenario, the ecological governance scenario increased the coverage of the “obvious improvement area” by 818.46 ha in the urban coal mining subsidence area. Overall, this study illustrates that ecological governance can effectively improve carbon sequestration and is conducive to the healthy development of coal resource-based cities.

Analysis of Formation Mechanism of Slightly Inclined Bedding Mudstone Landslide in Coal Mining Subsidence Area Based on Finite–Discrete Element Method

In this paper, the formation mechanism of a slightly inclined bedding mudstone landslide in the overlying mountain of the coal mining subsidence area of the Tanshan Coal Mine in Ningxia, China, is studied. By means of geotechnical investigation, indoor geotechnical tests, theoretical analysis and other technical means, we find the geological environment background of the study area and obtain the physical and mechanical property indexes of the mining landslide in the Tanshan Coal Mine. By combining the numerical simulation of discrete elements and finite elements, the macro deformation and failure law of the mining mudstone landslide and the displacement and stress nephogram of the failure process are discussed. The results show that the slightly inclined bedding mudstone landslide in the Tanshan Coal Mine is 850 m long from east to west, 500 m wide from north to south and 10,875,000 m3 in volume. It is composed of Jurassic mudstone and is a traction landslide caused by the coal mining subsidence area. The formation of the landslide is affected by internal factors and inducing factors. The internal factors are mainly geotechnical types and engineering geological properties, and the inducing factors are mainly coal mining activities and rainfall. By analyzing and summarizing the calculation process of the slope model prior to the landslide in 2D-Block and GeoStudio numerical simulation software, the sliding process of the slightly inclined bedding mudstone landslide in the Tanshan Coal Mine is divided into four stages: slope creep, slope deformation, landslide movement and landslide accumulation. GeoStudio software is used to calculate the stability of the Tanshan Coal Mine landslide under natural and rainfall conditions. The landslide is in a stable state under natural conditions and is basically stable under rainfall conditions. By comparing the calculation results of the limit equilibrium method and the finite element limit equilibrium method, we find that the calculated stability coefficient is more accurate when the appropriate constitutive model is selected. The research results have important reference significance for the prevention and control of the gently inclined bedding mudstone landslide of the overlying mountain in the coal mining subsidence area of the Loess Plateau.

Hydrogeochemical characterization and suitability assessment of groundwater in a typical coal mining subsidence area in China using self-organizing feature map

Hydrogeochemical characterization and suitability assessment of groundwater in a typical coal mining subsidence area in China using self-organizing feature map

Differential Response of Soil Microbial Community Structure in Coal Mining Areas during Different Ecological Restoration Processes

Micro-organisms play important roles in promoting soil ecosystem restoration, but much of the current research has been limited to changes in microbial community structure in general, and little is known regarding the more sensitive and indicative microbial structures or the responses of microbial diversity to environmental change. In this study, based on high-throughput sequencing and molecular ecological network analyses, the structural characteristics of bacterial communities were investigated in response to four different ecological restoration modes in a coal mining subsidence area located in northwest China. The results showed that among soil nutrients, nitrate-nitrogen and fast-acting potassium were the most strongly associated with microbial community structure under different ecological restoration types. Proteobacteria, Actinobacteria, and Acidobacteria were identified as important phyla regarding network connectivity and structural composition. The central natural recovery zone was found to have the smallest network size and low complexity, but high modularity and good microbial community stability. Contrastingly, a highly complex molecular ecological network of soils in the photovoltaic economic zone existed beneath the photovoltaic modules, although no key species, strong bacterial competition, poor resistance to disturbance, and a significant increase in the relative abundance of Gemmatimonadetes were found. Furthermore, the reclamation zone had the highest soil nutrient content, the most complex network structure, and the most key and indicator species; however, the ecological network was less stable and readily disturbed.