Search Results (120)

Mining operations conducted beneath water-bearing strata pose significant risks associated with the development of water-conducting fracture zones in the overburden. The height criterion for this parameter is critical to ensuring the stability of underground mine workings and preventing the risk of water inrush incidents. The research is based on physical and numerical simulations and aims to forecast the development of the water-conducting fracture zone. The methodology is based on in situ hydrogeology data, geotechnical boreholes, physical 2D modeling of rock strata, discrete element modeling using UDEC, and finite–discrete element modeling using Prorock software. A physical model of layered rock mass is constructed to simulate unfilled excavation areas induced deformation under real polymetallic ore field conditions. Based on the results, relationships between vertical subsidence, layer curvature, inclination, and the height of the water-conducting fracture zone were obtained. Particular attention is given to the effects of tectonic discontinuities, chamber geometry, and backfilling on fracture development. A stepwise excavation sequence is simulated to reproduce field conditions and assess the evolution of stress and deformation fields in the overburden. The study reveals that the propagation of the fracture zone around a mine excavation adheres to a polynomial law, characterized by an increase in height concurrent with the expansion of the excavation. This approach enables the design of safe extraction strategies beneath aquifers or surface water bodies. The proposed framework is expected to enhance prediction accuracy and reduce uncertainties. Full article

With the increase in mining intensity and scale, the damage to groundwater resources and surface ecology caused by coal mining has become the main problem facing coal development. Coal mining can cause a redistribution of stress field and stress concentration in local areas of overlying rock, resulting in varying degrees of movement and damage to the overlying rock. Quantitative analysis of the degree of migration and damage in different areas of overlying rock and zoning control is crucial for achieving loss reduction and green mining. In this paper, the overburden damage is divided into regions according to the different causes of formation, regional characteristics of severity, and other factors, and the specific calculation method is given. UDEC7.0 numerical simulation software is used to simulate the overlying rock damage, and the best mining parameters are provided through the area changes in different zones. The research conclusions are as follows: according to the different damage states of overburden rock, the damage of overburden rock can be divided into four parts: I, caving fracture zone, II, fracture development zone, III, sliding failure zone, and IV, slight failure zone. In the four zones, the damage in zones II and IV is relatively light. During the mining process, attention should be given to controlling the development of Zone I to prevent it from abnormally enlarging; for Zone II, hydraulic fracturing can be used when there is a thick, hard key layer that poses a water inrush risk; for Zone III, the focus should be on preventing surface step fractures caused by it. For example, when a thick, hard key layer is present in Zone II, hydraulic fracturing can be applied to avoid large area hanging roofs and severe rock pressure. When the mining height is low, it mainly affects the proportion of regions I and III. With the increase in mining height, the main affected region becomes the II region. The larger the mining height is, the larger the proportion of the II region. With the increase in propulsion speed, the impact range on the surface increases, but the area with severe damage is relatively reduced. With the increase in mining width, the proportion of relatively seriously damaged areas increased. On-site measurements have shown that when the speeds of 120,401 and 22,207 working faces are slow, the rock layer pressure shows a dense state, the overburden fracture is more fully developed, and the area proportion of I and II zones is increased, which reflects the phenomenon of dense surface fracture development on the surface. When the advancing speed is large, the area proportions of zones III and IV increase, and the damage scope decreases. The on-site testing verified the conclusions drawn from theoretical analysis and numerical simulation, which can guide other mines under similar conditions to achieve safe and green production. Full article

This study aims to address the pronounced stress concentration in roadway-surrounding rock under conditions of multiple thick and hard roof strata at Xiao jihan coal mine, China. The work was carried out on the 13216 working mining face as the engineering background. A systematic investigation was conducted using a combination of theoretical analysis, numerical simulation, and field experiments. Under double mining disturbance, the lower thick hard roof behaves as a cantilever beam and the upper hard roof strata form a masonry beam structure, producing strong stress transfer to the roadway. The mechanical model indicates a peak stress of 28.90 MPa, 18.34 MPa higher than the in situ stress. Hydraulic roof cutting was designed at the upper thick hard roof horizon. UDEC simulations show that the vertical stress decreases from 26.10 MPa to 13.20 MPa. Field monitoring confirms pressure relief: the non-cutting zone shows a peak of 30.75 MPa, while the roof-cutting zone drops to 22.51 MPa, a 24.62% reduction. The findings of this study provide practical guidance for lateral structure regulation under similar geological and mining conditions. Full article

During layered mining of extra-thick coal seams in deep rock-burst-prone mines, a thick bottom coal layer facilitates the accumulation of elastic strain energy in the floor strata. This stored energy may be released under mining-induced disturbances during retreat, thereby triggering rock-burst events. To mitigate floor energy accumulation at the lower-slice working face of extra-thick coal seams, previous studies have primarily adopted floor blasting for pressure relief. However, conventional blasting is often associated with poor energy utilization and limited controllability of the pressure-relief range, which hampers achieving the intended relief performance. Accordingly, this study proposes a shaped charge blasting scheme to reduce floor energy accumulation. ANSYS/LS-DYNA simulations and UDEC-based energy analyses, together with theoretical analysis and field validation, were conducted to clarify the mechanism of directional fracture propagation and the evolution of floor elastic energy before and after blasting. The results showed that the synergistic effects of the high-velocity jet and quasi-static pressure in shaped charge blasting generated a through-going fracture aligned with the maximum horizontal principal stress. This fracture effectively segmented the high-stress region in the floor and increased the maximum fracture length along the shaped charge direction to 10–13 times that achieved by conventional blasting. UDEC simulations and theoretical analysis indicated that the peak elastic energy in the floor was reduced by up to 54.08% after shaped charge blasting. Field measurements further showed that shaped charge blasting limited the maximum roadway floor heave to 300 mm and reduced floor deformation by 35–42% compared with the case without pressure relief. Overall, shaped charge blasting effectively blocks stress-transfer pathways and improves energy dissipation efficiency, providing theoretical support and a practical technical paradigm for safe and efficient mining of deep extra-thick coal seams. Full article

Thalassogenic diseases are human infections associated with exposure to marine environments. This review explores the occurrence of Cryptosporidium spp., Giardia duodenalis, and Blastocystis sp. in seawater and shellfish and their implications for public health. Between 2015 and 2026, multiple studies reported the presence of these parasites in shellfish and seawater. Cryptosporidium spp. was found at average concentrations of 5.5 × 10¹ oocysts/g in shellfish and up to 3.7 × 10¹ oocysts/L in seawater. Giardia duodenalis reached 9.1 × 10¹ cysts/g in shellfish, close to the infectious dose, and 3.5 × 10¹ cysts/L in seawater. Blastocystis sp. showed prevalence rates of 33.82% in shellfish and 17.3% in seawater. These findings highlight a potential infection risk for bathers and seafood consumers, emphasizing the need to determine the specific species (or subtypes) involved and assess their viability to accurately evaluate public health implications. The persistence of these parasites in the environment needs improved monitoring. Future strategies should integrate next-generation sequencing (NGS) or use of various fecal indicators to enhance environmental surveillance and reduce health risks in coastal regions. Full article

In recent years, the increasing frequency of intense rainfall events has led to a surge in landslide occurrences, posing severe threats to human safety and ecological integrity. This study utilizes the Universal Distinct Element Code (UDEC) for discrete element numerical simulations, combined with field observation-based mechanism analysis, to examine the primary drivers of landslide formation: rainfall and underground mining. Focusing on the Zengziyan landslide in Chongqing as a case study, the research investigates the underlying instability mechanisms. The findings indicate that mining activities primarily compromise slope stability by modifying rock structures, diminishing supporting forces, and creating goaf areas. Notably, these goaf zones generate an overhanging effect on the overlying rock mass, promoting crack initiation and the propagation of structural planes. Under rainfall conditions, groundwater infiltration and elevated pore water pressure exert a more substantial destabilizing influence, markedly accelerating rock mass sliding and collapse. The analysis reveals that rainfall predominantly governs landslide initiation and evolution, particularly during the triggering and rapid acceleration phases of slope instability. The outcomes of this research offer valuable insights for post-mining slope management and monitoring, as well as for developing landslide early warning systems in rainy conditions. Full article

Investigating the evolution mechanism of overlying strata fractures during mining and identifying the key factors that influence the development height of water-conducting fracture zones (WCFZs) are essential for preventing roof water inrush disasters, protecting mine water resources, and ensuring safe and sustainable mine development. To investigate the height of WCFZs and the evolution law of roof water inflow in a syncline structure working face under high-confined aquifer conditions, the 203 working face of Gaojiapu Coal Mine in Binchang Coalfield is selected as the engineering case. This paper analyzes the characteristics and control mechanisms of roof water inflow in a syncline structure mining area using UDEC 7.0 and COMSOL Multiphysics 6.0 multiphysics numerical simulation software. The results indicate that under different mining heights and advancing speeds, the height of the WCFZ in the overlying strata of a syncline structure working face continuously increases during the downward mining stage and in areas below the axis, and decreases thereafter, eventually stabilizing after reaching its maximum value at the initial stage of upward mining. When the WCFZ communicates with the strong aquifer of the Cretaceous Luohe Formation during the mining process, roof water inflow into the working face increases abruptly. The effectiveness of controlling water inflow by adjusting mining height is superior to that of controlling mining speed. Based on the response relationship between mining height, mining speed, and roof WCFZ, an on-site drainage prevention strategy was implemented involving reduced mining height and increased mining speed. Consequently, the roof water inflow at the working face has decreased from an initial rate of 950 m³/h to 360 m³/h. This study is of great significance for the safe and efficient extraction of coal seams under high-confined aquifers in the Binchang Coalfield, supporting the efficient development of coal resources while safeguarding regional water resources, thereby offering considerable engineering and practical value in promoting green mining and sustainable mining practices in large-scale coal production bases with similar geological conditions. Full article

Rockfalls from stratified unstable rock masses on cliffs present a significant geological hazard. This study investigates their seismic failure mechanisms and quantifies the influence of key controlling factors through an integrated approach of shaking table tests and UDEC numerical simulations. The introduction of a displacement angle precisely defined failure initiation, with tests revealing that the collapse angle exhibited a strong positive correlation with block size. Numerical simulations on seven factors showed that the collapse displacement angle ranged from 9° to 21°, primarily controlled by joint spacing. The Analytic Hierarchy Process (AHP) quantified the factor priorities, identifying the degree of rock mass fragmentation as the most influential factor with a weight of 0.278, followed by seismic amplitude (0.222) and cliff slope angle (0.167). The results provide a quantitative basis for designing early-warning systems using displacement angle thresholds and prioritize targeted mitigation strategies for the most critical factors in seismic-prone regions. Full article

Large-mining-height technology has been increasingly applied in thick seam mining to enhance productivity and resource recovery. However, it also intensifies strata pressure and complicates surrounding rock control, leading to greater overburden movement, stronger roof weighting, and severe coal wall spalling. Taking the 12306 working face of the Wangjialing Mine as a case, this study employs physical similarity experiments and UDEC numerical simulations to investigate the coupled mechanism of overburden migration and coal wall instability. Results show that abutment stress induces non-uniform deformation, while strata pressure changes directly govern spalling depth. Moreover, coal wall instability is strongly affected by multiple factors: greater burial depth intensifies crack propagation, larger mining height expands failure depth, larger mining step size extends the stress-affected zone, larger dip angle shifts failure upward, and lower support resistance weakens control capacity. These findings clarify the disaster mechanism of deep large-mining-height faces and provide theoretical and engineering guidance for optimizing support design and enhancing coal wall stability. Full article

Biological processes may generate CO₂, CH_4, and N₂O. Few studies have evaluated the impact of vermifilters (VFs) on the generation of these gases. The objective of this study was to evaluate the GHG emissions of a full-scale VF used for sewage treatment, as well as the effects of seasonality and operational condition. The study monitored the influent and effluent of a VF in a rural area. Emissions fluxes were measured using the static chamber method in fall–winter and spring–summer. The results showed that in terms of annual per capita emissions (kgCO₂eq/cap·y), VFs generated less GHGs than conventional and non-conventional wastewater treatment plants (WWTPs), with CO₂, CH₄, and N₂O emissions ranging between 0.8 and 7.5 kg/cap·y, 0.1–0.5 kgCO₂eq/cap·y, and 5.7–9.5 kgCO₂eq/cap·y, respectively. Regarding the effects of seasonality, CO₂ increased by 139% in spring–summer compared to fall–winter, while N₂O increased by 139% in fall–winter compared to spring–summer. A positive correlation between influent COD concentrations and CO₂ emissions (r = 0.7) was observed, whereas the influent carbon/nitrogen ratio (C/N) and N₂O emissions (r = −0.6) presented a negative correlation. These results evidenced that seasonality and sewage characteristics influenced GHG emissions in a full-scale VF. Full article

To investigate the distribution of coal seam stress ahead of the working face under hard-roof conditions and analyze its impact on gas flow, this study focused on the 16,021 working face in Wu Hua No. 1 Mine. First, we established a mining model using UDEC to analyze stress distribution at different coal seam extraction distances. Second, we used COMSOL Multiphysics 6.3 to simulate the influence of stress on the permeability and gas pressure of coal seams during extraction, thereby exploring how stress distribution affects gas flow. Finally, we deployed gas extraction boreholes to validate the gas flow characteristics associated with the stress zones. The results indicate that the coal seam stress ahead of the working face forms four distinct zones, influenced by the main roof hanging: stress reduction zone I, stress concentration zone, stress reduction zone II, and original stress zone. When extraction days are equal, under high-stress conditions, the extracted coal seam exhibits low permeability and a small decrease in gas pressure, making gas extraction difficult; in contrast, under low-stress conditions, it exhibits high permeability and a large decrease in gas pressure, making gas extraction relatively easier. Field measurements show that the gas extraction flow rate initially increases and then decreases with distance from the coal wall, exhibiting a noticeable rise within the 47–62 m range before stabilizing. This trend aligns well with the characteristics of stress zoning. Full article

The Shendong mining area, a pivotal coal production base in China, faces considerable challenges due to extensive mining activities. The significant development of overlying rock fractures and the widespread occurrence of surface cracks present a major challenge to mining safety and ecological preservation in China and other mining nations. This study focuses on the Panel 12,401 fully mechanized longwall face at Shangwan Coal Mine to systematically investigate overburden movement and the evolution of surface fractures. By combining UDEC discrete element modeling with a computational framework that links subsurface strata subsidence and surface settlement, this research examines the spatial and mechanical properties of fracture propagation. Experimental results show that surface fractures continue to develop as the working face advances, with their horizontal apertures gradually decreasing and eventually closing after the face passes. Both the maximum surface subsidence and the maximum fracture aperture exhibit a strong positive correlation with mining height. In contrast, increased mining depth leads to reductions in maximum surface subsidence, the subsidence factor, and the size of surface fracture apertures. These findings provide a theoretical basis for reducing mining-induced damage and promoting ecological restoration in mining areas. Full article

To alleviate strong strata-pressure bursts during ultra-thick coal extraction, we selected the 26 m number five seam of the Chenjiagou Coal Mine as a full-scale prototype. Three objectives were pursued: (1) elucidate the initiation mechanism of high-energy roof failures under top-coal caving (TCC); (2) quantitatively link the failure sequence of key strata to burst intensity; and (3) deliver field-oriented prevention criteria. A 1:300 physical similarity model and UDEC plane-strain simulations were combined to monitor roof deformation, stress evolution and dynamic response during extraction. Results demonstrate that pressure bursts are driven by abrupt kinematics of the overburden, triggered by sequential breakage of key horizons: the secondary key stratum collapsed at 130 m face advance, followed by the main-key stratum at 360 m. Their combined rupture generated a violent energy release, with roof displacement accelerating markedly after the main horizon failed. We therefore propose two dimensionless indices—the dynamic load factor (DLF) and stress concentration factor (SCF)—to characterize burst severity; peak values reached 1.62 and 2.43, respectively, while pronounced stress accumulation was localized 6–15 m ahead of the face. These metrics furnish a theoretical basis for early warning systems and control strategies aimed at intense rock burst. Full article

Polyhydroxyalkanoate (PHA) bioplastics are produced from wastewater as a carbon recovery strategy. However, the tuneable characteristics of PHAs and wastewater biorefinery potential have not been comprehensively reviewed. The aim of this study is to review the main challenges and strategies for carbon recovery from wastewater feedstocks via PHA production, assessing potential target biopolymer applications. Diverse PHA-accumulating prokaryotes metabolize organic pollutants present in wastewater through different metabolic pathways, determining the biopolymer characteristics. The synthesis of PHAs using mixed microbial cultures with wastewater feedstocks derived from municipal, agro-industrial, food processing, lignocellulosic biomass processing and biofuel production activities are described. Acidogenic fermentation of wastewater feedstocks and mixed microbial culture enrichment are key steps in order to enhance PHA productivity and determine biopolymer properties towards customized bioplastics for specific applications. Biorefinery of PHA copolymers and extracellular polysaccharides (EPSs), including alginate-like polysaccharides, are alternatives to enhance the value-chain of carbon recovery from wastewater. PHAs and EPSs exhibit a wide repertoire of applications with distinct safety control requirements; hence, coupling biopolymer production demonstrations with target applications is crucial to move towards full-scale applications. This study discusses the relationship between the metabolic basis of PHA synthesis and composition, wastewater type, and target applications, describing the potential to maximize carbon resource valorisation. Full article

Coastal fecal contamination is a global public health concern, particularly due to waterborne protozoan parasites such as Giardia duodenalis and Blastocystis sp. Concepcion Bay (Chile) is an important recreational and productive area in Chile. Nevertheless, it is impacted by two submarine outfalls and a rural sewage treatment plant, which may contribute to fecal pollution. This study evaluated the presence of waterborne parasites in Aulacomya atra mussels intended for human consumption. The mussels were collected from three sectors of the bay: northern, central, and southern. A total of 600 mussels were analyzed as accumulators using PCR targeting SSU-rDNA and β-giardin genes for the detection of Blastocystis sp. and G. duodenalis, respectively. Additionally, thermotolerant coliforms were quantified using the most probable number (MPN) method. Both parasites and coliforms were detected in all sectors, with the southern zone showing the highest number of positive samples, indicating a localized public health concern. This is the first report of these protozoa in mussels from Concepción Bay. The findings highlight the need for regulatory frameworks to control protozoan discharge and reduce pathogen transmission risks in coastal ecosystems, especially in areas with high recreational and economic activity, both in Chile and worldwide. Full article