Search Results (79)

To study hydrogeological characteristics after the occurrence of abnormal water bursts from the weak water-rich (permeable) aquifer of the Changxing Formation limestone overlying deep working faces during production in Guizhou karst landform mining areas, hydrogeological data covering the exploration and production periods of the Xinhua mining region in Jinsha County, Guizhou Province, were collected. On the basis of surface and underground drilling, geophysical exploration techniques, empirical equations, and indoor material simulation methods, the hydrogeological evolution characteristics of the Changxing Formation limestone in the mining region after mining damage to coalbed 9 were studied. The research results indicated that the ratio of the height of the roof failure fracture zone (as obtained via numerical simulation and ground borehole detection) to the mining height exceeded 25.78, which is far greater than the empirical model calculation values (from 13.0 to 15.8). After mining the underlying coalbed 9, an abnormal water-rich area developed in the Changxing Formation limestone, and mining damage fractures led to the connection of the original dissolution fissures and karst caves within the limestone, resulting in the weak water-rich (permeable) aquifer of the Changxing Formation limestone becoming a strong water-rich (permeable) aquifer, which served as the water source for mine water bursts. Over time, after mining damage occurrence, the voids in the Changxing Formation limestone were gradually filled with various substances, yielding water storage space and connectivity decreases. The specific yield decreased with an increasing water burst time and interval after the cessation of mining in the supply area, and the correlation coefficient R was 0.964, indicating a high degree of correlation between the two parameters. Full article

The formation of acidic goaf water in abandoned coal mines poses significant environmental threats, especially in karst regions where the risk of groundwater contamination is heightened. This study investigates the geochemical processes responsible for the generation of acidic water through batch and column leaching experiments using coal mine surrounding rocks (CMSR) from Yangquan, China. The coal-bearing strata, primarily composed of sandstone, mudstone, shale, and limestone, contain high concentrations of pyrite (up to 12.26 wt%), which oxidizes to produce sulfuric acid, leading to a drastic reduction in pH (approximately 2.5) and the mobilization of toxic elements. The CMSR samples exhibit elevated levels of arsenic (11.0 mg/kg to 18.1 mg/kg), lead (69.5 mg/kg to 113.5 mg/kg), and cadmium (0.6 mg/kg to 2.6 mg/kg), all of which exceed natural crustal averages and present significant contamination risks. The fluorine content varies widely (106.1 mg/kg to 1885 mg/kg), with the highest concentrations found in sandstone. Sequential extraction analyses indicate that over 80% of fluorine is bound in residual phases, which limits its immediate release but poses long-term leaching hazards. The leaching experiments reveal a three-stage release mechanism: first, the initial oxidation of sulfides rapidly lowers the pH (to between 2.35 and 2.80), dissolving heavy metals and fluorides; second, slower weathering of aluminosilicates and adsorption by iron and aluminum hydroxides reduce the concentrations of dissolved elements; and third, concentrations stabilize as adsorption and slow silicate weathering regulate the long-term release of contaminants. The resulting acidic goaf water contains extremely high levels of metals (with aluminum at 191.4 mg/L and iron at 412.0 mg/L), which severely threaten groundwater, particularly in karst areas where rapid cross-layer contamination can occur. These findings provide crucial insights into the processes that drive the acidity of goaf water and the release of contaminants, which can aid in the development of effective mitigation strategies for abandoned mines. Targeted management is essential to safeguard water resources and ecological health in regions affected by mining activities. Full article

Mine water treatment and emissions have become important factors that restrict the comprehensive benefits of coal enterprises and local economic development, and the use of the deep well recharge method can address the specific conditions of mine surge water. This paper takes the actual situation of coal mine water treatment as an example and innovatively carries out dynamic tests for the Ordovician limestone aquifers deep in the mine. Intermittent reinjection test shows that under the same reinjection time, the water level recovery rate during the intermittent period is fast at first and then slow. Moreover, the recovery speed of the water level buried depth slows down with the increase in the reinjection time, which reveals the characteristics of the water level rising rapidly and recovering quickly during the reinjection of the reservoir. The average formation water absorption index is 420.81 m³/h·MPa. The water level buried depth of the long-term reinjection test showed three stages (rapid rise, slow rise, and stable stages), and the water level buried depth was raised to 1.52 m at its highest. Monitoring data from the surrounding 5 km area showed that reinjection did not affect aquifer water levels, verifying the excellent storage capacity of the deep Ordovician fissure-karst aquifer. The variability of well loss under pumping and injection conditions was comparatively analyzed, and the well loss produced by the recharge test was 4.06 times higher than that of the pumping test, which provided theoretical support for the calculation of hydrogeological parameters to eliminate the influence of well loss. This study deepens the understanding of Ordovician limestone aquifers in deep mine water, providing a reference for cheap mine water treatment and sustainable groundwater management in similar mine areas. Full article

The use of trees to revegetate urban areas contaminated by mining activity is a low-cost, low-maintenance technique, of which the success will depend on the plant species, planting methods, and geochemical processes at the soil-plant interface. This study analyzed the evolution of mineral composition in the rooting soil, tree, and herbaceous vegetation on soils contaminated by As, Cd, Cu, Co, Pb, and Zn. An in-situ experiment was carried out in Lubumbashi (South-eastern DR Congo) with six tree species (Acacia auriculiformis, Albizia lebbeck, Delonix regia, Leucaena leucocephala, Mangifera indica, and Syzygium guineense), in 0.187 m³ pits amended with municipal compost and limestone. After planting in the amended and unamended (control) pits, soil samples were taken for chemical analysis. Eighteen months after planting, a floristic inventory was carried out to assess the spontaneous colonization of herbaceous species. The results show an increase in metal concentrations in the rooting soil between 2019 and 2023 (Cu: 725 ± 136 to 6141 ± 1853 mg kg⁻¹; As: 16.2 ± 1.4 to 95 ± 28.5 mg kg⁻¹; Cd: 2.7 ± 1.3 to 8.7 ± 2.0 mg kg⁻¹; Co: 151 ± 36.3 to 182 ± 113 mg kg⁻¹; Zn: 558 ± 418 to 1098 ± 1037 mg kg⁻¹), with a stable pH and a decrease in nutrients (P, K, Ca, and Fe). The trees planted in the amended pits showed better height and diameter growth and greater survival than the controls, reaching average heights of 8 m and a DBH of up to 22 cm four years after planting. A total of 13 spontaneous herbaceous species were recorded, with an increased abundance during the second inventory. These results confirm the effectiveness of pit amendment for the rapid revegetation of urban soils polluted by trace metals. Full article

Urban expansion in coastal areas involves infrastructure development, industrial growth, and mining activities. These coastal environments face various environmental and geological hazards that require geo-engineers to devise solutions. An integrated geophysical approach aims to address such complex challenges as sea level rise, sea water intrusion, shoreline erosion, landslides and previous anthropogenic activity in coastal settings. In this study, the proposed methodology involves the systematic application of geophysical methods (FDEM, 3D GPR, 3D ERT, seismic), starting with a broad-scale survey and then proceeding to a localized exploration, in order to identify lithostratigraphy, bedrock depth, sea water intrusion and detect anthropogenic buried features. The critical aspect is to leverage the unique strengths and limitations of each method within the coastal environment, so as to derive valuable insights for survey design (extension and orientation of measurements) and data interpretation. The coastal zone of Throrikos valley, Attica, Greece, serves as the test site of our geophysical investigation methodology. The planning of the geophysical survey included three phases: The application of frequency-domain electromagnetic (FDEM) and 3D ground penetrating radar (GPR) methods followed by a 3D electrical resistivity tomography (ERT) survey and finally, using the seismic refraction tomography (SRT) and multichannel analysis of surface waves (MASW). The FDEM method confirmed the geomorphological study findings by revealing the paleo-coastline, superficial layers of coarse material deposits and sea water preferential flow due to the presence of anthropogenic buried features. Subsequently, the 3D GPR survey was able to offer greater detail in detecting the remains of an old marble pier inland and top layer relief of coarse material deposits. The 3D ERT measurements, deployed in a U-shaped grid, successfully identified the anthropogenic feature, mapped sea water intrusion, and revealed possible impermeable formation connected to the bedrock. ERT results cannot clearly discriminate between limestone or deposits, as sea water intrusion lowers resistivity values in both formations. Finally, SRT, in combination with MASW, clearly resolves this dilemma identifying the lithostratigraphy and bedrock top relief. The findings provide critical input for engineering decisions related to foundation planning, construction feasibility, and preservation of coastal infrastructure. The methodology supports risk-informed design and sustainable development in areas with both natural and cultural heritage sensitivity. The applied approach aims to provide a complete information package to the modern engineer when faced with specific challenges in coastal settings. Full article

This study determined the hydro-chemical properties of groundwater in a typical mining area and its associated human health risks, focusing on the Guangwang mining area. Groundwater samples were analyzed for toxic metals, after which analysis of principal components, the entropy-weighted water quality index, and Spearman analysis of correlation were applied to the collected data. The Environmental Protection Agency of the United States’s health hazard appraisal was utilized to assess the hazards of toxic metals in the local water supply to the health of both grownups and juveniles. HCO₃-Na and SO₄⋅Cl-Ca⋅Mg were found to be the predominant groundwater hydro-chemical types. The eastern section of the area of study showed the greatest average total dissolved solids (16,347.00 mg/L) and SO₄²⁻ (8980.00 mg/L) levels. It was determined that the groundwater hydro-chemical type was Ca-HCO₃ and that limestone leeching and the evaporative level in the coal seam aquifer were the predominant factors regulating groundwater hydrochemistry. Six of the ten assessed metals exceeded the World Health Organization’s safe water for drinking standards, with particularly high Al (66.97 mg/L) and Cd (194.53 μg/L). Spearman correlation analysis showed significant correlations between Mn, Al, Cu, and Zn, which could be attributed to bauxite minerals associated with the coal mine. Release of metal ions was attributed to the oxidation of metal sulfide minerals, which is driven by mining-induced water–rock interaction. The intake of water for drinking was shown to be the predominant route of hazard to human health. The hazard index decreased from east to west due to the level of abandoned coal mines in the eastern region, along with well-developed fissures. The total carcinogenic hazard for grownups exceeded that of juveniles due to the greater quantity of water for drinking consumed and higher surface area of skin amongst grownups. The results can guide groundwater pollution regulation activities in mining areas to minimize potential hazards of groundwater quality to the health of humans. Full article

As shallow coal resources in China become increasingly depleted, deep coal mining in complex geological areas has become an inevitable trend. However, the technical challenges associated with deep mining are becoming more significant, particularly the issues related to mine water hazards. This study utilized hydrogeological data from the III3 Mining Area in the Zhuxianzhuang Coal Mine, Anhui Province, and employed GMS (Groundwater Modeling System) software to construct a numerical karst water flow model under deep mining conditions. By simulating variations in the flow field, the study verified the drainage potential of the limestone water at the base of Seam 10 and assessed the water conductivity and connectivity of the F22 fault. The following conclusions were obtained: The simulation effectively captured the formation process of the karst water drawdown cone in the study area. The observed water level variations in different monitoring wells aligned well with the engineering reality after validation. The limestone water at the base of Seam 10 in the III3 Mining Area exhibited good transmissivity, weak recharge, and high drainage potential. Although the F22 fault is a normal fault with a maximum displacement of 550 m, offsetting formations from Seam 3 to the Ordovician limestone, its connectivity and water conductivity are poor, exhibiting significant water-blocking properties. The specific capacity (q) ranges from 1.40 × 10⁻⁴ to 3.26 × 10⁻³ m³/(s·m), and the hydraulic conductivity (K) ranges from 2.10 × 10⁻⁵ to 6.80 × 10⁻⁵. Under deep coal mining conditions, the extraction of coal disturbs the underlying limestone, generally resulting in an increase in its permeability coefficient compared to pre-mining conditions. The permeability coefficient (K) from the measured data before mining impact ranged from 0.000067 to 0.0022, while the simulated values after mining impact ranged from 0.0021 to 0.09. Additionally, mining activities affect the hydraulic head, flow rate, and flow paths of the karst water; the floor karst water is easily drainable, effectively reducing water pressure and the inrush coefficient, thus lowering water hazard risks. Although the mining area is affected by the large F22 fault, its water-resisting properties under sufficient drainage conditions prevent direct connectivity between the coal seam and the aquifer, avoiding water hazards. As global coal resources continue to be exploited, deep mining will inevitably become a common trend in coal extraction worldwide. This study develops a hydrogeological model tailored to deep mining under fault conditions, offering a solid theoretical foundation and practical reference for the prevention and management of mine water hazards on a global scale. This advancement contributes to the development of sustainable mining practices across the global industry. Full article

Open-pit mining often exposes weak rock layers, the strength of which significantly affects the stability of slopes. If these rock layers are also prone to disintegration and expansion, cyclic rainfall can exacerbate instability. Rainfall-induced changes in the seepage field also indirectly threaten the stability of slopes. Therefore, investigating the characteristics of mudstone limestone and the impact of the seepage field on slope instability under different wet–dry cycles is of great significance for the safe mining of open-pit mines. This paper takes the mudstone limestone slope of a certain open-pit mine in the southwest as the starting point and conducts experiments on saturated density, water absorption rate, permeability coefficient, compressive strength, and variable angle shear strength. Combined with scanning electron microscopy and phase analysis of X-ray diffraction analysis, the macroscopic and microscopic characteristics of the samples are comprehensively analyzed. FLAC3D software is used to explore the changes in the seepage field and the mechanism of instability. Our research found that for the preparation of mudstone limestone samples, a particle size of less than 1 mm and a drying temperature of 50 °C are optimal, with specific values for initial natural and saturated density, and natural water content. As the number of wet–dry cycles increases, the saturated density of mudstone limestone increases; the water absorption rate first rises sharply and then rises slowly; the permeability coefficient first rises sharply and then stabilizes, finally dropping sharply; the compressive and shear strength decreases slowly, and the internal friction angle changes little; frequent cycles also lead to mudification and seepage filtration. At the microscopic level, pores become larger and more regular, and the distribution is more concentrated; changes in mineral content weaken the strength. Combined with numerical simulation, the changes in the seepage field at the bottom of the slope exceed those at the slope surface and top, the transient saturated area expands, and the overall and local slope stability coefficients gradually decrease. During the third cycle, the local stability is lower than the overall stability, and the landslide trend shifts. In conclusion, wet–dry cycles change the pores and mineral content, affecting the physical and mechanical properties, leading to the deterioration of the transient saturated area, a decrease in matrix suction, and an increase in surface gravity, eventually causing slope instability. Full article

Acid mine drainage (AMD), which is primarily caused by the exposure of sulfidic minerals to oxygen and water during mining operations, remains a significant contributor to environmental pollution. Numerous technologies have been developed to prevent/control and treat AMD, including the isolation of waste from the atmosphere and treatment systems for AMD-impacted water. Many field studies on mine site reclamation have involved an individual AMD source and/or technology, with a limited number of studies looking at reclamation programs integrating multiple approaches to manage AMD stemming from both surface and underground sources. The former Franklin mine site in Nova Scotia, Canada, was impacted by the deposition of waste rock across the site and the discharge of mine water from underground workings, with the adjacent Sullivan’s Pond serving as the main environmental receptor. Site reclamation was completed in 2010 and involved the following: (1) excavation of the dispersed waste rock (117,000 m²) and backfilling with clean soil; (2) consolidation of the excavated waste rock into a covered, compact waste rock pile (WRP) (25,000 m²); and (3) construction of a passive treatment system for the discharging underground mine water. An extensive field sampling program was conducted between 2011 and 2018 to monitor a range of meteorological, cover material, waste rock, groundwater, and surface water quality parameters. The results confirm that the multi-layer, geomembrane-lined WRP cover system is an extremely effective barrier to air and water influx, thereby minimizing the rate of AMD generation and seepage into groundwater and eliminating all contaminated surface water runoff. A small AMD groundwater plume emanates from the base of the WRP, with 50% captured by the underground mine workings over the long term and 50% slowly migrating towards Sullivan’s Pond. Excavation of the former waste disposal area eliminated the AMD source from the previously dispersed waste, with only clean surface water runoff and a diminishing legacy groundwater plume remaining. Finally, the passive treatment system, which contains a series of treatment technologies such as a limestone leach bed and settling pond, successfully treats all mine water loading (~50 kg/day) discharging from the underground workings and surface runoff. Its additional treatment capacity (up to ~150 kg/day) ensures it will be able to manage any potential drop in treatment efficiency and/or increased AMD loading from long-term WRP seepage. This comprehensive study of mine site reclamation and AMD management at an abandoned mining site can be of great reference value for environmental management and policymakers in the mining sector. Full article

This study presents a gravity survey conducted for mineral exploration in the Gerolekas overthrust area at a bauxite mining site in Central Greece. In the summer of 2018, a gravity survey, covering 28 km², was conducted, including confirmed and unexplored zones. By utilizing gravity data, we investigated the shallow subsurface geology and structural sequences, resulting in a high-resolution 3D density model. This model is generated through constrained gravity inversion by the exploitation of the boreholes available at mining sites, and the geological survey fills the areas with boreholes, which provides the stratigraphy to some depth. The suggested data-processing techniques provide information for the tectonism of the area, which is also important for mineral exploration, as well as mining design. The interface with density contrast between the flysch and the underlying limestone in the high-resolution 3D density model provides useful information on the geological status, but also, the slight density difference in limestone provides an interface where bauxite deposits can be. The inversion, conducted with EMIGMA software, incorporated high-resolution topography data and density constraints to produce a reliable 3D density model. The findings highlight the gravity method’s potential to enhance mineral exploration efficiency, offering a robust tool for further geological and mining considerations. Full article

During coal mining, sudden inrushes of water from the floor pose significant risks, seriously affecting mine safety. This study utilizes the 3602 working face of the Chenmanzhuang coal mine as a case study, and the original influencing factors were downscaled using principal component analysis (PCA) to obtain four key evaluation factors: water inflow, aquiclude thickness, water pressure, and exposed limestone thickness. The rough set theory (RST) was applied to determine the weights of the four main influencing factors as 0.2, 0.24, 0.36, and 0.2; furthermore, 19 groups of comprehensive values were calculated using the weighting method, and a water inrush risk assessment was conducted for several blocks within the working face. The results are presented as a contour map, highlighting various risk levels and identifying the water inrush danger zone on the coal seam floor. The study concludes that water inrush poses a threat in the western part of the working face, while the eastern area remains relatively safe. The accuracy and reliability of the model are demonstrated, providing a solid basis and guidance for predicting water inrush. Full article

Geological conditions or human activities will affect the hydrochemical characteristics and formation mechanism of mine groundwater to varying degrees. The northern part of the Beiyi mining area of Gubei Coal Mine is taken as the research area in this study. Based on the data of 52 groups of limestone water (Taihui water) samples in the primary environment, in the mining stage and after grouting, the spatial and temporal variation trend of the chemical characteristics of Taihui water was studied by means of constant index mathematical statistics, a Piper diagram, total ionic salinity, correlation analysis, the ion ratio method and the saturation index. The purpose of this study is to analyze the influence of special geological structures, mining activities and grouting treatment on the formation process of the chemical characteristics of Taihui water, and to provide a basis for the identification of water inrush sources and the resource utilization of deep mine water in this area. The results show that in the three stages, the order of cation concentration is Na⁺ + K⁺ > Ca²⁺ > Mg²⁺, and the order of anion concentration is changed from Cl⁻ > SO₄²⁻ > HCO₃⁻ to Cl⁻ > HCO₃⁻ > SO₄²⁻. The hydrochemical type is the most abundant in the mining stage, and tends to be unified after grouting. The dissolution of carbonate minerals, gypsum, rock salt and silicate minerals; cation exchange; pyrite oxidation; and the mixing of grouting precipitation liquid mainly occur in the limestone water. These effects are enhanced or weakened due to the influence of pumping and drainage and grouting precipitation liquid. The results of this study may be beneficial to the sustainable utilization of deep groundwater resources in other similar mines, and promote the establishment of data management and identification mechanisms of water inrush sources in deep coal seams. Full article

Active vegetation restoration plays an important role in the improvement in soil organic matter (SOM), including the carbon (C), nitrogen (N) and phosphorus (P) sequestration of degraded mining ecosystems. However, there is still a lack of understanding of the key drivers of SOM pool size and dynamics in active vegetation restoration. For this study, soil was collected from five different sites (Xiaoxian, Dingyuan, Chaohu, Tongling and Dongzhi), four habitats (platforms, slopes, steps and native areas) and two soil layers (0–20 cm and 20–40 cm) in limestone mines of Anhui province to quantify the spatial distribution of SOM contents and their stoichiometric characteristics and influential factors. It was found that the top soil in Chaohu had the highest significant C, N and P contents in the ranges of 14.95–17.97, 1.74–2.21 and 0.80–1.24 g/kg, respectively. Comparing the stoichiometric ratios of the different sites revealed significant differences in C:N and N:P ratios, but C:P ratios were relatively consistent. In particular, the C:N and C:P ratios in deep soil were higher than those in top soil, whereas the N:P ratio in deep soil was lower than that in top soil, suggesting that soil N is a major limiting factor in the top soil. The SOM content did not differ significantly between the three reclaimed habitats, but was significantly higher than that in the native habitat, suggesting that mine restoration has significantly enhanced SOM accumulation. Further analysis showed that nutrient availability and enzyme activity are important factors affecting soil C, N and P content in top soil, while the relationship gradually weakens in deep soil. This was attributed to active anthropogenic management and conservation measures during the early stages of reclamation. This study shows that the ecological recovery of the mining area can be enhanced by implementing differentiated vegetation planting strategies and anthropogenic management on different habitats in the mining area. Full article

Sustainable economic development serves society but requires taking over space, often at the expense of areas occupied by single trees or even parts of forest areas. Techniques for transplanting adult trees used in various conflict situations at the interface of economy and nature work as a tool for sustainable management of urbanized and industrial areas, as well as, in certain circumstances, forest or naturally valuable areas. This study aimed to evaluate the effectiveness of ground-penetrating radar (GPR) in determining the horizontal and vertical extent of tree root systems before transplantation. Employing this non-invasive method to map root system architecture aids in the appropriate equipment selection and helps define the dimensions and depth of trenches to minimize root damage during excavation. This study specifically focused on the root systems of wild service trees (Sorbus torminalis (L.) Crantz) found in a limestone mine area, where some specimens were planned to be transplanted, as the species is protected under law in Poland. The root systems were scanned with a ground-penetrating radar equipped with a 750 MHz antenna. Then, the root balls were dug out, and the root parameters and other dendrometric parameters were measured. The GPR survey and manual root analyses provided rich comparative graphic material. The number of the main roots detected by the GPR was comparable to those inventoried after extracting the stump. The research was carried out in problematic soil, causing non-standard deformations of the root systems. Especially in such conditions, identifying unusually arranged roots using the GPR method is valuable because it helps in a detailed planning of the transplanting process, minimizing root breakage during the activities carried out, which increases the survival chances of the transplanted tree in a new location. Full article

Laboratory-scale experiments were conducted on Carboniferous Limestone gravels from the Mendip Hills area, England; sandstones from the Pirambóia and Botucatu formations, Paraná sedimentary basin, Brazil; samples of schist and quartzite from Caldas Novas Hydrothermal Complex, Brazil; and the minerals tantalite, cassiterite, and columbite from mining areas at Rio Grande do Norte State, Brazil, with the purpose of evaluating the release of ²²²Rn to the water phase. The specific surface area of the samples corresponded to 1.69–81.36 cm²g⁻¹, which provided values of 0.001–1.68 dpm/g and 3.18 × 10⁻⁶ to 0.59 for the radon released and radon emanation coefficient, respectively. These results allowed us to calculate the radon flux with respect to the radon leakage, which corresponded to values of 0.00016–0.00158 Bq/m²/d for the denser materials and 0.018–0.43 Bq/m²/d for limestones and sandstones. They also permitted us to find an inverse, significant relationship between the radon generated by the minerals/rocks and the radon flux into the water phase, which was tested for sediments in coastal and inland Brazilian areas, demonstrating utility for evaluating the diffusive radon flux from the sediments, which is an important parameter to monitor submarine groundwater discharge (SGD) by means of radon as a natural tracer. Full article