Search Results (317)

Caves and other subterranean ecosystems are characterized by stable, low temperatures, high humidity, and limited nutrient input, creating unique environments for extremophilic microorganisms. Among them, fungi play key roles in organic matter degradation, mineral interactions, and biogeochemical cycling, yet the diversity and adaptations of cold-adapted fungi in cave habitats remain insufficiently explored. This study investigated psychrophilic and psychrotolerant fungi inhabiting the stone surfaces of Ravništarka Cave in Eastern Serbia. Biofilm samples were collected from nine sites and analyzed using culture-based isolation on both nutrient-rich and diluted media, followed by incubation at 10 °C, 25 °C, and 37 °C. Fungal identification combined morphological characteristics with molecular analyses of the ITS region and BenA gene, while ecological roles were assigned using FUNGuild. A total of 41 fungal species were documented, spanning Ascomycota (53.1%), Basidiomycota (43.7%), and Mortierellomycota (3.1%) phyla. The genus Penicillium exhibited the greatest species richness, with 14 taxa documented, including P. chrysogenum, P. glandicola, and P. solitum, all previously associated with cold or oligotrophic environments. The psychrotolerant species Mortierella alpina was the only representative of Mortierellomycota. Ecological guild assignment revealed fungi functioning at different trophic levels, highlighting their multifunctional ecological roles in extreme subterranean habitats. Full article

Drawing on archaeological evidence, early ethnographic accounts, and historical documents, this article offers initial reflections on the possible past uses and meanings of a set of black drawings found deep within a cave in what is now known as the Sierra Mixe of Oaxaca, Mexico. Following this investigative approach, it explores the role of rock art as an interface between orality, imagery, and text in the context of ancient Mesoamerica. To understand the possible ontological perceptions of the creators of these images in the past, it is suggested that this imagery functioned as inscriptions in a dialogue with spatially related unfired figures modelled in clay, which are exceptionally well-preserved in this subterranean space. An interplay of media on various supports is proposed, wherein two-dimensional images and three-dimensional figures may have been used as a combined system for transmitting and circulating intergenerational cultural knowledge, serving as an anchor for collective memory. In this context, rock imagery played a role in a broader communication system in Mesoamerica. Full article

This paper reviews the apparent impact of how changes in nitrate, sulphate activities, and moisture affect the surface pH of rock art paintings at Cueva del Ratón, in the Sierra de San Francisco in Baja California Sur, Mexico. The data was collected after atypical weather events caused rain and mist in this normally arid area. The rock art paintings had been previously examined over several years and observed the unexpected formation of silica skins over some surfaces; such coatings are not often experienced in arid environments. The local geology of the cave and the availability of moisture can dramatically alter the microbiological activity on faecal material and development of surface acidity from such reactions which interacts with both the host rock and the pigments. Through a series of surface pH measurements and localised measurements on chloride, sulphate and nitrate it appears that both nitrate and sulphate concentrations have a significant impact on the surface pH, which is controlled by a diffusion-based movement of moisture from the closed to the open end of the shelter. The exfoliation of the rock surface and formation of the silica skins involves chemical reactions as contrasted with diffusion-controlled reactions which distribute the metabolites of the yeasts, moulds and bacteria, which are dominated by the availability of water through drip lines. The results are particularly relevant due to changing weather patterns in the last decade, caused by climate change, with an increase in hurricanes directly affecting the Baja California peninsula. The use of disposable test strips for semi-quantitative assessment of how these major anions impact on the decay mechanisms was a novel response to budget constraints and the remoteness of the location. Full article

Block caving is a cost-effective mining method that enables the highly efficient mining of thick and large ore bodies. During ore extraction in block caving operations, the ore-drawing roadways require especially high safety standards. However, the complex in situ stress conditions and cyclic loading from caved ore significantly deteriorate the stability of the surrounding rock. This makes rock mass control particularly challenging, such that it is crucial to study an effective method for maintaining the long-term stability of the roadways. This research proposes a comprehensive approach combining laboratory rock mechanics testing, numerical simulation, and field engineering validation to design effective support strategies for disturbance-affected roadways. Laboratory tests provide accurate mechanical parameters for the rock mass, the numerical simulations allow for the comprehensive analysis of deformation–failure mechanisms under disturbance conditions, and field validation ensures the reliability and practical applicability of the proposed support method. This study focuses on a −285 m ore-drawing roadway in the western section of the Yanqianshan Iron Mine. The in situ stress distribution was characterized through rock mechanics testing and acoustic emission monitoring. The propagation mechanisms of ore-drawing disturbance waves within the rock mass were analyzed, and numerical simulations revealed the deformation patterns and failure modes under dynamic disturbance, upon which the support scheme was designed. The results demonstrate that the designed bolt–mesh–shotcrete support scheme can effectively control surrounding rock deformation within 5 mm and resists the deformation induced by cyclic disturbances. This study provides valuable technical support for stability management in block caving mines with similar conditions. Full article

Coal mining disturbance induces progressive damage and fracturing in overlying rock (OLR), forming a complex fracture network. This process triggers groundwater depletion, ecological degradation, and severely compromises mine safety. Based on field drilling sampling and mechanical experiments, this paper reveals the occurrence properties and characteristics of weakly cemented overlying rock (WCOLR). At the same time, similar simulation experiments, DIC speckle analysis system, and fractal theory are used to explain the development and evolution mechanism of mining-induced fractures under this special geological condition. The OLR fracture is determined based on the grid fractal dimension (D) distribution. A stress arch-bed separation (BS) co-evolution model is established based on dynamic cyclic BS development and stress arch characteristics, enabling identification of BS horizons. The results show that the overlying weak and extremely weak rock accounts for more than 90%. During the process of longwall face (LF) advancing, the D undergoes oscillatory evolution through five distinct stages: rapid initial growth, constrained slow growth under thick, soft strata (TSS), dimension reduction induced by fracturing and compaction of TSS, secondary growth from newly generated fractures, and stabilization upon reaching full extraction. Grid-based D analysis further categorizes fracture zones, indicating a water conducting fracture zone (WCFZ) height of 160~180 m. Mining-induced fractures predominantly concentrate at dip angles of 0–10°, 40–50°, and 170–180°. Horizontally BS fractures account for 70.2% of the total fracture population, vertically penetrating fractures constitute 13.1% and transitional fractures make up the remaining 16.7%. The stress arch height is 314.4 m, and the stable BS horizon is 260 m away from the coal seam. Finally, an elastic foundation theory-based model was used to predict BS development under top-coal caving operations. This research provides scientific foundations for damage-reduced mining in ecologically vulnerable Western China coalfields. Full article

To reveal the fracture mechanism of overburden aquifers during mining under anticlinal structural zones in western mining areas, this study takes Panel 1309 of the Guojiahe Coal Mine as the engineering background and employs field investigations, physical similarity simulation, and numerical simulation methods to systematically investigate the overburden fracture and crack evolution laws during extra-thick coal seam mining in anticlinal zones. The research results demonstrate the following: (1) The large slope angle of the anticlinal zone and significant elevation difference between slope initiation points and the axis constitute the primary causes of water inrush-induced support failures in working face 1309. The conglomerate of the Yijun Formation serves as the critical aquifer responsible for water inrush, while the coarse sandstone in the Anding Formation acts as the key aquiclude. (2) Influenced by the slope angle, both overburden fractures and maximum bed separation zones during rise mining predominantly develop toward the goaf side. The water-conducting fracture zone initially extends in the advance direction, when its width is greater than its height, and changes to a height greater than its width when the key aquifer fractures and connects to the main aquifer. (3) The height of the collapse zone of the working face is 65 m, and the distribution of broken rock blocks in the collapse zone is disordered; after the fracture of the water-insulating key layer, the upper rock layer is synchronously fractured and activated, and the water-conducting fissure leads to the water-conducting layer of the Yijun Formation. (4) Compared to the periodic ruptures of the main roof, the number of fractures and their propagation speed are greater during the initial ruptures of each stratum. Notably, the key aquiclude’s fracture triggers synchronous collapse of overlying strata, generating the most extensive and rapidly developing fracture networks. (5) The fracture surface on the mining face side and the overlying strata separation zone jointly form a “saddle-shaped” high-porosity area, whose distribution range shows a positive correlation with the working face advance distance. During the mining process, the porosity variation in the key aquiclude undergoes three distinct phases with advancing distance: first remaining stable, then increasing, and finally decreasing, with porosity reaching its peak when the key stratum fractures upon attaining its ultimate caving interval. Full article

The efficiency of coal deposit mining using the TPC (Top Coal Caving) method strongly depends on the detailed solutions of the mining method design, which significantly affect the degree of deposit utilization, the size of losses and dilution. In order to examine the most important factors of this technology, a physical model was built that reflects the conditions of the selected lignite mine, including models of the mechanized hydraulic support walking support used in this case. Based on the research, the relationships between the thickness of the rock shelf (lignite) in the range of 4 m, 6 m and 8 m and the formation of dilution and deposit waste during the exploitation of the deposit were determined. It was shown that the most effective method of releasing lignite from under the caving is the serial-regular method with a 1.2 m advance round. Detailed relationships between individual parameters, rock material granulation, round advance and the thickness of the deposit and the layer subject to caving were given. The developed physical model of the support allows for variant analyses of various combinations of deposit parameters for any deposits in order to achieve the best efficiency of the mining method. Full article

Since 1992, we have promoted the use of descriptions from ethnographic data, including ancient, surviving oral traditions, to aid in explaining the iconography portrayed in pictographs and petroglyphs found in Missouri, particularly those at Picture Cave. The literature to which we refer is from American Indian groups related linguistically and connected to the pre-Columbian inhabitants of Missouri. In addition, we have had on-going conversations with many elder tribal members of the Dhegiha Sioux language group (including the Osage, Quapaw, and Kansa (the Ponca and Omaha are also part of this cognate linguistic group)). With the copious collections of southern Siouan ethnographic accounts, we have been able to explain salient features in the iconography of several of the detailed rock art motifs and vignettes, and propose interpretations. This Midwest region is part of the Cahokia interaction sphere, an area that displays western Mississippian symbolism associated with that found in Missouri rock art as well as on pottery, shell, and copper. Full article

Empirical and numerical methodologies for the geomechanical assessment of underground excavations have evolved in recent years to adapt to the geotechnical and structural conditions of natural caves, enabling stability evaluation and ensuring safe conditions for speleological exploration. This study analyzes the evolution of the state of the art of these techniques worldwide, assessing their reliability and application context, and identifying the most suitable methodologies for determining the stability of the Al-Badia lava tube. The research was conducted through bibliographic analysis and rock mass characterization using empirical geomechanical classifications. Subsequently, the numerical boundary element method (BEM) was applied to compare the obtained results and model the stress–strain behavior of the cavity. The results allowed the classification of the Al-Badia lava tube into stable, transition, and unstable zones, using empirical support charts and determining the safety factors of the surrounding rock mass. The study site highlights that empirical methods are rather conservative, and numerical results align better with observed conditions. Full article

In this study, we examined the microclimates at eight entrances to a karst system distributed between an elevation of 812 and 906 m in Southern Spain. The karst system, characterised by subvertical open tectonic joints that form narrow shafts, developed on the slope of a mountainous area with a Mediterranean climate and strong chimney effect, resulting in an intense airflow throughout the year. The airflows modify the entrance temperatures, creating a distinctive pattern in each opening that changes with the seasons. The objective of this work is to characterise the outflows and find simple temperature-based parameters that provide information about the karst interior. The entrances were monitored for five years (2017–2022) with temperature–humidity dataloggers at different depths. Other data collected include discrete wind measurements and outside weather data. The most significant parameters identified were the characteristic temperature (T_y), recorded at the end of the outflow season, and the rate of cooling/warming, which ranges between 0.1 and 0.9 °C/month. These parameters allowed the entrances to be grouped based on the efficiency of heat exchange between the outside air and the cave walls, which depends on the rock-boundary geometry. This research demonstrates that simple temperature studies with data recorded at selected positions will allow us to understand geometric aspects of inaccessible karst systems. Dynamic high-airflow cave systems could become a natural source of evidence for climate change and its effects on the underground world. Full article

The deep carbonate reservoirs in the Tarim Basin, Xinjiang, China, are widely developed with multi-scale complex reservoir spaces such as fractures, pores, and karst caves under the coupling of abnormal high pressure, diagenesis, karst, and tectonics and have strong heterogeneity. Among them, fracture–cavity carbonate reservoirs are one of the main reservoir types. Revealing the petrophysical characteristics of fracture–cavity carbonate reservoirs can provide a theoretical basis for the log interpretation and geophysical prediction of deep reservoirs, which holds significant implications for deep hydrocarbon exploration and production. In this study, based on the mineral composition and complex pore structure of carbonate rocks in the Tarim Basin, we comprehensively applied classical petrophysical models, including Voigt–Reuss–Hill, DEM (Differential Effective Medium), Hudson, Wood, and Gassmann, to establish a fracture–cavity petrophysical model tailored to the target block. This model effectively characterizes the complex pore structure of deep carbonate rocks and addresses the applicability limitations of conventional models in heterogeneous reservoirs. The discrepancies between the model-predicted elastic moduli, longitudinal and shear wave velocities (Vp and Vs), and laboratory measurements are within 4%, validating the model’s reliability. Petrophysical template analysis demonstrates that P-wave impedance (Ip) and the Vp/Vs ratio increase with water saturation but decrease with fracture density. A higher fracture density amplifies the fluid effect on the elastic properties of reservoir samples. The Vp/Vs ratio is more sensitive to pore fluids than to fractures, whereas Ip is more sensitive to fracture density. Regions with higher fracture and pore development exhibit greater hydrocarbon storage potential. Therefore, this petrophysical model and its quantitative templates can provide theoretical and technical support for predicting geological sweet spots in deep carbonate reservoirs. Full article

This study focuses on the monitoring and early warning of landslide hazards induced by blasting caving in the Shizhuyuan polymetallic mine. A 30-channel microseismic monitoring system was deployed to capture the spatiotemporal characteristics of rock mass fracturing during a large-scale directional stratified blasting operation (419 tons) conducted on 21 June 2012. A total of 85 microseismic events were recorded, revealing two distinct zones of intense rock failure: Zone I (below 630 m elevation, P1–P3, C6–C8) and Zone II (above 630 m elevation, P4–P5, C1–C6). The upper slope collapse occurred within 5 min post-blasting, as documented by real-time monitoring and video recordings. Principal component analysis (PCA) was applied to 54 microseismic events in Zone II to determine the kinematic characteristics of the slip surface, yielding a dip direction of 324.6° and a dip angle of 73.2°. Complementary moment tensor analysis further revealed that shear failure dominated the slope instability, with pronounced shear fracturing observed in the 645–700 m height range. This study innovatively integrates spatial microseismic event distribution with geomechanical mechanisms, elucidating the dynamic evolution of blasting-induced landslides. The proposed methodology provides a novel approach for monitoring and forecasting slope instability triggered by underground mining, offering significant implications for disaster prevention in similar mining contexts. Full article

The stability of bottom structures in block caving mines is significantly challenged by impact loads generated from large rockfalls and ore collapses on slopes. This study aims to investigate the mechanical response and failure characteristics of bottom structures under such dynamic and cyclic loading conditions. Discrete element methods (DEMs) were employed to simulate the impact load amplitudes caused by large rockfalls on bottom structures. Specimens with identical mechanical properties to the bottom structure were fabricated at a 1:100 scale, based on the principle of similarity ratio tests. Three distinct types of impact loads were identified and analyzed: overall impact from large-scale slope collapses, localized impact from partial rock and soil mass collapses, and continuous multiple impacts from progressive slope failures. True triaxial tests were conducted to evaluate the mechanical response of the bottom structure under these loading scenarios. The results indicate that while overall and multiple impact loads from slope collapses do not lead to catastrophic failure of the bottom structure, severe damage occurs under a 100 m thickness of ore and large block impacts. Specifically, the inner walls of ore accumulation troughs peel off, and ore pillars between troughs fracture and fail. This study highlights the need for advanced experimental and numerical approaches to accurately predict the stability and failure modes of bottom structures under complex loading conditions. Full article

With the increasing depth of coal mining operations, the repeated extraction of multiple coal seams has led to serious safety threats to mines, including secondary roof fracturing, interlayer separation-induced water hazards, and intense mine pressure. Due to the limited research available on the roof failure laws of gently inclined coal seam groups, this study focuses on the Yindonggou Coal Mine and employs a comprehensive approach combining theoretical analysis, numerical simulation, and field measurement. Theoretical calculations indicate that after the mining of Seam 1, the caving zone height ranges from 6.69 to 11.09 m, and the height of the water-conducting fracture zone ranges from 29.59 to 40.79 m. After Coal Seam 2 is mined, the caving zone extends 24.05–33.47 m above the roof of Coal Seam 1, and the fracture zone develops for up to 74.10–94.94 m. Following the mining of Seam 4, the caving zone expands to 30.73–40.15 m above the roof of Coal Seam 1, and the fracture zone reaches 92.26–113.10 m. The numerical simulation results show that after mining Seam 1, the caving zone height is 8.4 m, and the fracture zone reaches 36 m. After Seam 2 is mined, the caving zone extends to 27 m above the roof of Coal Seam 1 and the fracture zone extends to 89 m. After Seam 4 is mined, the caving zone expands to 40 m above the roof of Coal Seam 1 and the fracture zone develops to 112.6 m. The field measurements validate the following findings: a loss of flushing fluid during drilling indicates that after Coal Seam 4 is mined, the fracture zone develops up to 110.5 m above the roof of Coal Seam 1, and the caving zone reaches 47.5 m. Optical imaging logging shows the fracture zone developing to 114.5 m and the caving zone extending to 48.1 m above the roof of Coal Seam 1. The results demonstrate good consistency among these theoretical calculations, numerical simulations, and field measurements. This study reveals a progressive development pattern of roof failure during the repeated mining of gently inclined coal seam groups, providing a theoretical foundation for water hazard prevention and mine pressure control in deep multi-seam mining operations. Full article

To address the stability control challenges of the “support-surrounding rock” system in fully mechanized top-coal caving faces within steeply dipping coal seams, this study employs an integrated approach combining theoretical analysis and numerical simulations, revealing the three-dimensional boundary morphology of the top-coal limit equilibrium zone and establishing a quantitative framework for boundary delineation. The results show that the boundary spatial morphology of the limit equilibrium zone in the fully mechanized caving stope in steeply dipping coal seams is an “asymmetric arc-shaped ribbon-like curved surface”. Along the inclined direction of the working face, the boundary distribution presents an “asymmetric circular-arc arch”, with the vault located in the middle-upper part of the working face. Along the strike direction of the working face, the distance from the boundary to the longwall face shows a gradually increasing pattern from top to bottom. Upon comparing the results from the numerical simulation, theoretical calculation, and field monitoring, a consistent overall pattern emerges. This consistency validates the rationality of the analytical representation of the boundary of the top-coal limit equilibrium zone. The research findings hold significant importance in predicting the stability of the “support-surrounding rock” system and the top-coal cavability. They can offer a scientific foundation for guiding the stability control practices of the support–surrounding rock within this type of mining stope. Full article