Deposition Of Rocks Research Articles

ТЕХНОЛОГИЧЕСКИЕ РЕШЕНИЯ ПО ЭФФЕКТИВНОМУ ВОВЛЕЧЕНИЮ МИНЕРАЛЬНОГО СЫРЬЯ МЕСТОРОЖДЕНИЙ КАРБОНАТНЫХ ПОРОД

The article presents the results of studies of an effective technology for the development of elongated deposits of carbonate rocks, the novelty of which lies in the sequence of combined opening of the deposit, combined with the features of the separation of cargo flows of overburden rocks and minerals, as well as in the placement of primary processing facilities in the area of the worked-out space of the quarry and underground workings, together ensuring a reduction in the average coefficient of overburden and the earth capacity of open mining operations. It is proved that by varying the depth of the concentration horizon in the established technological corridor, depending on the deterministic group of the quarry, it is possible to achieve a reduction in the level of total operating costs up to 7.5%, which for large deposits amounts to tens of billions of rubles. The results of the research can be useful in substantiating the technology of the development of a deposit of carbonate rocks.

Study and valorization of a new bituminous concrete based on natural dune sand for hot and arid environments

The trans-desert road network is exposed to enormous degradation of asphalt concrete pavements due to the high temperatures of these arid regions, which considerably accelerate asphalt ageing. Common bituminous mixes generally use quarry sand fillers, the proportions of which are poorly controlled due to the diversity of rock deposits and their manufacturing conditions. This article responds to this problem by proposing dune sand as a source of filler by grinding it and then introducing it into pure bitumen to obtain the bitumen-filler mix. In this paper, two types of analysis were carried out, one thermal and the other mechanical to study the influence of the substitution of quarry sand filler by dune sand filler in asphalt concrete. In the thermal analysis, the study evaluates the stiffening power (?TBA) of three types of fillers incorporated into a pure bitumen, namely quarry sand, dune sand and standardized filler. The results of these analyses reveal that at a normative percentage of 57% filler with 43% pure bitumen, the stiffening power (?TBA) of dune sand filler and normalized filler comply with established standards (between 8 and 16°C), unlike quarry sand filler, which does not meet standards. The mechanical analysis carried out on quarry sand filler and dune sand filler revealed an improvement in mechanical performance when dune sand filler was used, with MARSHALL stability values indicating an average increase from 3.9 to 4.9, and better resistance to water with a greater than 99% ratio for the DURIEZ test well above the 75% threshold. These results offer the potential to optimize bituminous mixes by incorporating dune sand fillers, thereby enabling Saharan roads to be built more quickly, at lower cost and, above all, to extend their lifespan, making a positive contribution to the development of road infrastructure in hot, arid environments.

Mathematical substantiation and creation of information tools for optimal control of drilling and blasting in open-pit mine

Purpose. To establish the rationale for the informational infrastructure necessary for effectively managing drilling and blasting operations in open-pit mining of rock deposits. To define the distribution function of natural rock blocks within the mass they comprise. To ensure timely access to data regarding the strength, fracturing characteristics of geological formations in their initial state, as well as the particle size distribution of mined materials obtained post-explosion. Methodology. Statistical modeling techniques were employed to analyze the natural blockiness of rock masses. The approach involved utilizing the principle of measuring the dimensions of individual rock fragments through a transmitting television tube and differentiating the obtained results using electronic pulse circuits. Electronic circuits capable of implementing statistical dependencies derived for drilling machines and loading excavators were introduced. Findings. Electronic devices have been proposed for real-time determination of the dimensions of natural rock blocks along their visible surfaces, as well as for assessing the strength, fracturing characteristics of rocks within the mass, and the particle size distribution of the mined material obtained during drilling and blasting operations. Originality. The study has established the distribution function of natural rock fragments within a mass, serving as a prototype for the distribution function of visible rock fragments located on the sidewall of a slope. The theoretical developments of the proposed electronic devices are protected by patents. Practical value. The presented tools for obtaining real-time, objective information about the natural blockiness, strength, and fracturing characteristics of rock formations in their initial state (before blasting), as well as relationship of these indicators with the particle size distribution of mined material obtained through blasting. These a tangible opportunity to implement optimal management of the entire blasting process, which will enable the enhancement of the technical and economic performance of open-pit mining

Electrical Resistivity - Tomography Studies In Determining Shallow Aquifer Potential Zones a Case Study in Different Terrains

The study documents the effectiveness of 2 D (Two Dimensional Electrical Resistivity Survey (Tomography) to map shallow subsurface geological formations namely recent Alluvium, Gondwana deposits and hard rock deposits. 2 dimensional Electrical Resistivity Survey (or tomography) was conducted at 2 locations at Valarpuram and one location Madurantakam areas. Gondwana deposits mask Valarpuram Thandalam, villages (at Kancheepuram District, Tamilnadu). To the east of Valarpuram alluvium thickness increases at shallow depths. Weathered and hard granitic gneiss and hard charnockite rocks overlie topsoil in Madurantakam areas (Chengalpettu District, Tamilandu). The survey was conducted to 12 m depth to decipher shallow permeable zones. Gondwana formations consisting of clays, siltstones are predominant in Valarpuram Thandalam and surrounding areas. Hard rock formations are found in Madurantakam areas. 2 Dimensional Resistivity Survey results indicate 2-D sections with very low resistivity values in the range of 2 to 4 ohm-m in Valarpuram Thandalam areas indicating predominant clay deposits with poor ground water potential. To the east of Valarpuram Thandalam resistivity data is of moderately higher value indicating sand deposits at shallow depths. These are ideal locations for dug wells. Low to moderate values at shallow depths indicating weathered thickness up to 12 m are observed at Madurantakam location. From 12m depth steep rise in resistivity values are observed in hard indicating presence of massive rock from 12m depth and below areas. Thus, 2 D Resistivity Imaging Technique are helpful in delineating shallow aquifer potential and this in turn helps in deciding the depth of open wells with high precision.

History of the study and the principal features of the MVT-type lead-zinc massive sulfide deposits of the Priargunsk minerogenic zone

Two types of ore deposits are distinguished within the Priargunsk minerogenic zone: the lead-zinc massive sulfide ore deposits in the Vendian-Cambrian carbonate sedimentary rocks (MVT type) and the polymetallic massive sulfide ones in the Mesozoic volcanogenic rocks (VMS type). The MVT-type deposits are confined to the volcanogenic-carbonate–terrigenous formation and comprise two genetic types of the ore bodies, the stratiform (stratified) beds and the stockwork-shaped hydrothermal-metasomatic zones in the feeding channels. The stratiform ore bodies occur concordantly with stratification of the host rocks in gentle paleodepressions; they are confined to the contacts of limestones with dolomites and carbonaceous siltstones or are controlled by interlayer tectonic deformations. Ore deposits of this type formed synchronously with sedimentation. At the same time, the mechanism of formation of stratiform or stratified ore bodies could be fundamentally different.

The uncertain future of mountaintop-removal-mined landscapes 1: How mining changes erosion processes and variables

Surface mining may be humanity's most tangible impact on Earth's surface and will become more prevalent as the energy transition progresses. Prediction of post-mining landscape change can help mitigate environmental damage, but requires understanding how mining changes geomorphic processes and variables. Here we investigate surface mining's complex influence on surface processes in a case study of mountaintop removal/valley fill (MTR/VF) coal mining in the Appalachian Coalfields, USA. The future of MTR/VF landscapes is unclear because mining's effects on geomorphic processes are poorly understood. We use geospatial analysis—leveraging the existence of pre- and post-MTR/VF elevation models—and synthesis of literature to ask how MTR/VF alters topography, hydrology, and land-surface erodibility and how these changes could be incorporated into numerical models of post-MTR/VF landscape evolution.MTR/VF reduces slope and area–slope product, and rearranges drainage divides. Creation of closed depressions alters flow routing and casts doubt on the utility of models that assume steady flow. MTR/VF creates two contrasting hydrologic domains, one in which overland flow is generated efficiently due to a lack of infiltration capacity, and one in which waste rock deposits act as extensive subsurface reservoirs. This dichotomy creates localized hotspots of overland flow and erosion. Loss of forest cover probably reduces cohesion in near-surface soils for at least the timescale of vegetation recovery, while waste rock fills and minesoils also likely experience reduced erosion resistance. Our analysis suggests three necessary ingredients for numerical modeling of post-MTR/VF landscape change: 1) accurate routing and accumulation of unsteady overland flow and accompanying sediment across low-gradient, depression-rich, engineered landscapes, 2) separation of the landscape into cut, filled, and unmined regions, and 3) incorporation of vegetation recovery trajectories. Improved modeling of post-mining landscape evolution will mitigate environmental degradation from past mining and reduce the impacts of future mining that supports the energy transition.

Expanding the metamorphic devolatilization model: Komatiites as a source for orogenic gold deposits in high-grade metamorphic rocks

Abstract Orogenic gold deposits contribute the largest proportion of the world’s gold reserves, and the source of their ore-forming components has been recognized as the metamorphic devolatilization of metapelites or metabasites across the greenschist- to amphibolite-facies transition. However, hypozonal orogenic gold deposits represent an enigma in this context. Some of these apparently formed in higher-grade metamorphic rocks when temperatures were beyond the wet solidus of quartz-feldspar–bearing rocks; it is therefore puzzling how these fluids were generated in the source and migrated through the crust without causing partial melting. Here, we show that devolatilization of hydrated komatiites, a volumetrically significant lithological unit in Precambrian greenstone belts, is a viable model that can plausibly lead to gold mineralization at amphibolite-facies conditions. Our thermodynamic simulations indicate that subsolidus metamorphic devolatilization of komatiites at ~700 °C (upper amphibolite facies) can unlock significant amounts of gold via dehydration of talc and chlorite. This genetic model is supported by the geochemical characteristics of, and estimated pressure-temperature (P-T) formation conditions of, hypozonal gold deposits and the intimate spatiotemporal association between hypozonal deposits and komatiites in greenstone belts. This work expands the P-T range of the metamorphic devolatilization model and enhances its robustness in explaining gold mineralization in metamorphic terranes.

Spatial distribution of the critical mineral resource element titanium in China and its influencing factors

In China, titanium is found in multi-metal symbiotic ore deposits that present sorting difficulties, low recovery rates, high production costs, and low overall resource utilization rates. The concentration and distribution of titanium in the pedosphere must be better understood to assess the potential titanium resources. The China Geochemical Baseline project obtained harmonized soil and rock geochemical data covering mainland China and provided reliable data for 76 elements (including titanium) from 3382 top (0–25 cm) and 3380 deep (>100 cm) sediment or alluvial soil samples and 12,201 rock samples. In this study, titanium concentrations were determined by X-ray fluorescence spectrometry under strict quality control. The median titanium concentration values in the top and deep samples, which were considered geochemical baseline values, were 3498 mg/kg and 3406 mg/kg, respectively, with mean values of 3661 mg/kg and 3585 mg/kg, respectively. The titanium concentrations ranged from 266 to 24,674 mg/kg and 324 to 25,504 mg/kg in the top and deep soil samples, respectively. The 75 % range (Q25–Q95) of titanium concentrations in the rock ranged from 978 to 8299 mg/kg. The median titanium concentration was 2555 mg/kg in the rock samples, while the mean concentration was 3089 mg/kg. The geochemical map of titanium indicated that low titanium concentrations below Q25 (<3498 and 3406 mg/kg in the top and deep samples, respectively) are primarily distributed in southern Xinjiang, Tibet, Qinghai, Gansu, and Inner Mongolia. The distribution of low titanium content in the soils is likely attributed to these regions being covered by deserts (e.g., Gobi) and glaciers. Soils with high titanium concentrations are widely distributed in the Emeishan large igneous province at the southwest margin of the Yangzi block, which is related to the large distribution of intermediate-basic rock in the area, as well as along the northeast-southwest direction of the Yangtze block, which extends for nearly 1600 km. Moreover, these soils are mainly associated with the black rock system and intermediate-basic dikes. Soil titanium concentrations are affected by various factors, including the occurrence of tectonic activity and distribution of the black rock system, intermediate-basic rock (especially basalt), and VTi magnetite deposits. In particular, the large igneous province area generated by a mantle column represents the main location of VTi magnetite deposit formation and the area with the highest titanium content. In addition to providing detailed information about the titanium distribution in the pedosphere and rock of mainland China, the project can also provide basic geochemical data for the development and utilization of titanium resources and the formulation of critical mineral industry policies.

Uranium isotopes in non-euxinic shale and carbonate reveal dynamic Katian marine redox conditions accompanying a decrease in biodiversity prior to the Late Ordovician Mass Extinction

The Late Ordovician mass extinction (LOME) is the first major mass extinction event in the Phanerozoic. However, global biodiversity started to decline during the Katian (prior to the LOME) and coeval global ocean redox conditions are not well understood. The deposition of Katian organic-rich sedimentary rocks, namely the calcareous Collingwood Member and overlying siliciclastic Rouge River Member, was triggered by the concurrent Taconic Orogeny in southern Ontario (Canada) near the interface between the epicratonic Appalachian and Michigan basins. In this study, we used geochemical elemental proxies and uranium isotope compositions (δ238U) to reconstruct local and global ocean redox states during deposition of both units at seven drill core localities throughout southern Ontario. Local redox conditions are revealed by several proxies (redox sensitive trace metals, Fe speciation, and Corg:P ratios). Collectively, these proxies suggest spatiotemporal redox variations for the Collingwood Member: O2-deficient conditions (non-euxinic) for the deep waters of the Appalachian and Michigan basins and mostly oxic-suboxic conditions for the shallow waters. In contrast, predominantly oxic-suboxic conditions are suggested for the Rouge River Member.Global ocean redox conditions are inferred from the δ238U of both units. The coeval seawater δ238U value during Collingwood Member deposition is estimated to be from ∼−0.87‰ to ∼−0.64‰, based on both carbonate δ238U (samples leached with 1 N HCl) and δ238Ubulk-non-detrital data (corrected from the bulk δ238U). Particularly, the δ238Ubulk-non-detrital data of the Collingwood Member from multiple cores (both shallow and deep waters) are positively correlated with elemental redox proxies, suggesting a local redox control on δ238U offsets between sediments and water columns. In contrast, the δ238Ubulk-non-detrital of the suboxic Rouge River Member (average = −0.32 ± 0.12‰) from several cores do not correlate with local redox proxies. The coeval seawater δ238U during Rouge River Member deposition is estimated between −0.62 ± 0.12‰ and −0.42 ± 0.12‰ assuming a δ238U offset of 0.1–0.3‰ as observed between modern suboxic sediments and seawater. For this range of seawater δ238U, a three-sink U isotope mass balance model suggests a contraction of global euxinic seafloor area from deposition of the Collingwood Member (0.5–31.6%; median = 1.0–14.2%) to the Rouge River Member (0.2–2.0%; median = 0.3–1.0%), which could have been associated with the concurrent Taconic Orogeny. Collectively, global marine redox proxy data (i.e., δ98Mo, δ238U) from this and previous studies imply dynamic Katian ocean redox conditions during the decrease of metazoan biodiversity prior to the LOME. As a similar extent of global ocean euxinia during the LOME2 also occurred episodically during the Katian but did not result in LOME2-like mass extinctions, it is suggested that other factors (e.g., climate), besides expanded ocean euxinia, could have contributed to the second phase of the LOME.

Integrated Development of Technogenic Resources

Overburden and host rock deposits typically contain by-products. If selective mining is not applied, these aggregates are moved to dumps and deposited haphazardly. To preserve mineral resources, it is necessary to create man-made technogenic deposits. This article explores the prospects of comprehensive mineral resource development. Examples of creating technogenic mineral deposits in exhausted quarry spaces are provided. We emphasize the need for the enactment of laws that promote the formation of technogenic deposits.

Multiple S-isotopic evidence for seawater incursions during the deposition of the upper Cretaceous source rocks in the Songliao Basin, northeastern China

The Songliao Basin, with an area of ∼260,000 km2 in northeast China, hosts the largest oilfield in China, which is one of the world's most productive oilfields. However, the origin of the organic-rich upper Cretaceous source rocks remains controversial. In this study, we report multiple S-isotopic compositions of pyrite (δ34S and Δ33S) from Member 1 (K2n1) and Member 2 (K2n2) of the Nenjiang Formation in the Songliao Basin. Our isotopic results reveal an extraordinarily large negative δ34S excursion of 50.54‰ (from +11.09‰ to −39.45‰), which is strong evidence for seawater incursions. The increasing positive Δ33S excursion coupled with the negative δ34S excursion strengthen the inference of a large influx of seawater to the Songliao Basin. We used a steady-state isotope box model to estimate the magnitude of the seawater incursions. Our modeling results show that the sulfate concentrations may have increased by 12–46 times when seawater invaded the Songliao Basin. We suggest that marine incursions may have facilitated the chemical stratification of the Songliao Basin and played an important role in the formation of the oil source rocks. Our findings potentially have important implications for understanding the formation of oilfields elsewhere.

Metallogenic Model for Pb-Zn Deposits in Clastic Rocks of the Dahai Mining Area, Northeast Yunnan: Evidence from H-O-S-Sr-Pb Isotopes

The Dahai Pb-Zn mining area is located in the northwestern Pb-Zn district in northeastern Yunnan Province in the Sichuan-Yunnan-Guizhou Pb-Zn metallogenic triangle (SYGT), east of the Xiaojiang fault. Numerous Pb-Zn deposits (spots) occur in clastic rocks in this area. In this study, the Maliping, Laoyingqing, and Jinniuchang Pb-Zn deposits, representative clastic rocks in the Dahai mining area, were selected as research objects. The results of H-O-S-Sr-Pb isotope analyses show that the three deposits mainly formed through the mixing of a basinal brine with a hydrothermal fluid derived from deep within the underlying (deformed) basement, and brines leached organic matter from wall rocks. The δ34S values range from −2.62–30.30‰. The S isotope results show two different sources of reduced S: one in the Laoyingqing deposit derived from the S reduction generated by the pyrolysis of sulfur-bearing organic matter in the carbonaceous slate of the Kunyang Group, and the second in the Maliping and Jinniuchang deposits derived from the S reduction generated by the thermochemical sulfur reduction (TSR) of seawater sulfate in the Lower Cambrian Yuhucun Formation and Sinian Dengying Formation. The Pb isotope results show that the Pb sources of the three deposits are derived from basement rocks (Kunyang Group) with a small portion derived from Devonian–Permian carbonate rocks and Dengying Formation dolomite, both of which have undergone homogenization during mineralization. The Sr content varied from 0.09629 to 0.2523 × 10−6, and the study shows that the main source of Sr is a mixture of ore-forming fluid flowing through basement rocks (Kunyang Group) and through sedimentary cover. However, most of the Sr in the Maliping deposit is derived from marine carbonate, and in the Laoyingqing deposit, it is provided by basement rocks (Kunyang Group). Based on a comparative study of the deposits, the Pb-Zn deposits in the clastic rocks of the Dahai mining area and the SYGT belong to the same metallogenic system and were formed under the same metallogenic geological background. Finally, a unified metallogenic model of the two types of fluid migration and mixed mineralization of the Pb-Zn deposit in clastic rocks of the Dahai mining area is proposed. The metallogenic model provides a basis for the study of the Pb-Zn metallogenic system and guidance for deep and peripheral prospecting in this area.

Palynology of the Upper Gondwana deposits from the Chintalapudi Sub-basin, South India: Insights into age and palaeodepositional settings

Palynological data were analyzed to determine the age and depositional settings of the Jangareddygudem area in Godavari Graben, South India. The abundance of coniferous pollen grains (Araucariacites spp., Podocarpidites spp., and Callialasporites spp.) as well as pteridophytic and bryophytic trilete spore characterizes the palynofloral assemblage. The First Occurrences (FOs) of biostratigraphically significant palynomorphs taxa have been identified, which allowed us to assign the studied stratigraphic sequence to the upper Aptian–lower Albian. Recovered palynoassemblages are compared with other contemporaneous assemblages from different Gondwana continents. Palynofacies research supports hetero-lithic shelf (proximal shelf) rock formation with gradual and continuous sediment input under dysoxic to anoxic conditions. The recovered palynomorphs consistently suggest cool and humid climates during rock deposition, favoring the formation and development of a dense canopy of luxurious coniferous forests near the coast.

Geological structure and reservoir productivity of Pre-Jurassic basement rocks of the Sredne-Nazymskoye oil field (Western Siberia): new data

he main tool for increasing of oil reserves are exploration works. Improving the scientific and technical support for exploration is a priority task for the oil industry. The article deals with the development of technology for prospecting and exploration of hydrocarbon deposits in the Pre-Jurassic basement rocks of Western Siberian oil and gas province, as well as approaches to improving the reliability of mapping prospective zones using seismic data. Using the example of the Sredne-Nazymskoye field, the seismogeological aspects of the forecast of oil and gas potential of the Pre-Jurassic complex and the main directions for reducing the uncertainties of the geological structure are shown.

Analysis of thermo-mechanical damage around tunnel and deposition boreholes of an underground nuclear waste disposal facility at the Forsmark site (Sweden) by 3D coupled FDEM simulations

This study focuses on rock damage potentially developing in the near-field of a planned underground nuclear waste repository at the Forsmark site (Sweden). In hard, crystalline rocks, mechanical damage in the form of spalling may be induced during construction by overstressing of the excavation periphery. During operation, thermal damage may develop due to additional thermo-elastic stresses forming in response to the increasing rock temperatures induced by the heat-emitting spent nuclear fuel. Prediction of damage occurrence, location, and extent is critical for an effective repository design and long-term safety assessment as it may negatively affect the long-term isolation properties of the host rock. In this paper, the response of underground structures was studied using a novel 3D coupled thermo-mechanical simulator based on the finite-discrete element method (FDEM). It is the first numerical study to date that explicitly captures both mechanical and thermal fracturing processes while using the latest repository design and site-specific geomechanical input data. A sensitivity study is performed to investigate different combinations of rock mechanical properties, in-situ stresses, and deposition tunnel geometry on the host rock behaviour. Rock mass deconfinement is shown to promote the development of tensile damage in the tunnel sidewalls and floor with fracture surfaces growing parallel to the excavation boundaries. The negative effects deriving from the adoption of a relatively narrower tunnel cross-section and from an increase of horizontal in-situ stresses are highlighted. Thermo-mechanical analyses capture the rock mass behaviour following an increase of borehole surface temperature to 100 °C. Numerical results indicate that the temperature evolution is affected by the shape of the underground cavities and their distance from the heated boreholes. The coupled thermal expansion of the rock induces additional stresses which, in turn, promotes further damage. Despite this increase, however, the total amount of induced rock damage at final conditions remains relatively low.

Detrital zircon and apatite U-Pb provenance and drainage evolution of the Newark Basin during progressive rifting and continental breakup along the Eastern North American Margin, USA

Abstract Mesozoic rift basins of the Eastern North American Margin (ENAM) span from Florida in the United States to the Grand Banks of Canada and formed during progressive extension prior to continental breakup and the opening of the north-central Atlantic. The syn-rift strata from all the individual basins, lumped along the entire margin into the Newark Supergroup, are dominated by fluvial conglomerate and sandstone, lacustrine siltstone, mudstone, and abundant alluvial conglomerate and sandstone lithofacies. Deposition of these syn-rift sedimentary rocks was accommodated in a series of half grabens and subsidiary full grabens situated within the Permo-Carboniferous Appalachian orogen. The Mesozoic ENAM is commonly depicted as a magma-rich continental rift margin, with magmatism (Central Atlantic magmatic province [CAMP]) driving continental breakup. However, the southern portion of the ENAM shows evidence of magmatic breakup (e.g., seaward-dipping reflectors), and rifting and crustal thinning appeared to start ~30 m.y. prior to CAMP emplacement in the Jurassic. This study provides extensive new detrital zircon and apatite U-Pb provenance data to determine the provenance and reconstruct the paleodrainages of the Newark Basin during progressive rifting and magmatic breakup and the implications for the overall rift configuration and asymmetry during progressive rifting along the ENAM rift margin. Detailed new detrital zircon (N = 21; n = 3093) and apatite (N = 4; n = 559) U-Pb results from sandstone outcrop and core samples from the Newark Basin indicate a distinct provenance shift, with relatively older Carnian syn-rift strata predominately sourced from the hanging wall of the basin bounding fault in the east while relatively younger Norian strata were regionally sourced from both the hanging wall and footwall. The syn-rift strata at the Triassic-Jurassic boundary were sourced from the hanging wall before a transition to local footwall terranes. These results suggest two major provenance changes during progressive rifting—the first occurring during Carnian crustal necking and rift flank uplift as predicted by recent numerical models and the second occurring at the onset of the Jurassic due to regional and local thermal uplift during CAMP magmatism as seen along other magma-rich margins, such as the North Atlantic and the southern portion of the South Atlantic margin.

Bearing capacity of shallow foundations on Florida limestone: A study of single layer and rock-over-sand subsurface

This study investigated the bearing capacity of shallow foundations on Florida limestone using 3D finite element modeling (FEM) with a bilinear strength envelope based on rock formations and bulk dry unit weights. Most Florida limestones at shallow depths are highly porous and have a low density and strength, thereby resulting in a ductile stress–strain response and contractive volumetric behavior under service loads, both of which are not well characterized by conventional bearing capacity methodologies.In this study, a bilinear Mohr–Coulomb elastoplastic model with a non-associated flow rule (negative dilation angle) was integrated into a 3D FEM code from a series of laboratory triaxial strength test results. Numerical simulations were performed for different footing sizes, shapes, and embedment depths using homogeneous rock and rock-over-sand subsurface. Beginning with the numerical results from a strip footing on a homogeneous rock deposit, a bearing capacity equation was developed for bilinear strength conditions. Further, the width, shape, and embedment factors were developed, and a reduction factor was developed based on the rock layer thickness and moduli of rock and sand for the rock-over-sand condition often encountered in South Florida. The study concludes with a comparison between developed equations and conventional bearing capacity methodologies.

Bioaccumulation of Titanium in diatom Cyclotella atomus Hust.

Diatomaceous earth or diatomite is a fossil rock deposit of diatoms made up of silica and other minerals. A distinguishing feature of diatoms that placed them in the single class of microalgae Bacillariophyceae, is the frustule, a transparent, hard-shelled cell wall. It's interesting to note that the diatom has specific proteins and enzymes for heavy metal detoxification and can intake and store more heavy metals in its frustule. Consequently, an attempt has been made in this study to determine the bioaccumulation of metals in the frustules of the diatom. Hence, a centric diatom was isolated from the freshwater sample collected from the Adyar River, Chennai, Tamil Nadu. The diameter of the cell was 5-7.5µm and 20-23 striations with radial arrangement. A single, dark off-center fultoportula and marginal fultoportula on the striae are found in the diatom. Additionally, one rimoportula between two marginal fultoportula distributed on the striae between the costa was also seen. As a result, the isolated diatom was morphologically identified as Cyclotella atomus Hust. Simultaneously, the bioaccumulation study reveals that the Titanium (Ti) was found accumulated in the frustules of the diatom incubated in the Ti-supplemented culture medium based on the scanning electron microscope-energy-dispersive X-ray analysis (SEM-EDAX). Therefore, the biogenic accumulation and fabrication of Titanium frustules in diatom have advantages in enhancing the efficiency of solar cells.

Реализация принципов безопасности труда при подземной разработке сложноструктурных рудных месторождений

Most of the metal ores are mined from the rock deposits by technologies with natural control of the state of rock massifs. Rationalization of the methods for controlling the state of an ore-bearing massif, considering their geomechanics, is becoming a priority direction for improving technologies for the development of complex structure ore deposits. The purpose of the study is to substantiate the possibility of managing the state of massifs based on the combination of filling mixtures in the conditions of the Sadon ore belt deposit. The complex of studies includes the engineering division of the massif with the allocation of engineering structural sections. By modeling on equivalent materials, a mechanism for the development of stresses in the vicinity of a working was established. It is determined that the studied massif is discrete with a gravitational-tectonic-structural stress field. Based on the experimental data, a model of the intensity of the ore-bearing massif is built on the basis of the hypothesis of wedging of the rocks of the bearing layer. The role of expansion stresses and backfill strength in the input of the massif into the volumetric compression mode is determined. A stress control technique is proposed by dividing the massif into geomechanically safe areas. It was proven that backfilling systems ensure the recovery of reserves, improve the quality of ores and preserve the earth surface, protecting the region from the negative impact of mining. The complexity of exploitation of ore-bearing massifs determines the need to monitor the geomechanics of ore-bearing rocks. The combination of technologies is a real step in improving mining production, as it allows to reduce ore dilution, increase labor productivity, and also improve the safety conditions of workers by increasing the reliability of technology parameters.

Global phosphorus cycling: The impact of international commercial trading and the path towards sustainable phosphorus management

Phosphorus is vital for global food production, but its use in commercial fertilizers has led to significant changes in the global P cycle. This has resulted in the depletion of phosphate rock deposits and increased eutrophication in lakes and oceans. While attempts have been made to quantify phosphorus flow at a country or regional level, there is still a lack of comprehensive understanding of how international commercial trading affects global phosphorus cycling over time. Through substance flow analysis, this research has found that the total global P flows through the five major P trade products have increased by around 5.4 Tg P between 2000 and 2019, with agricultural products trade having the fastest growth rate. The net P budget in the global trade of products changed among countries throughout these twenty years and relates to local natural resources and policies. Overall the global P flow has shifted from phosphate rock dominated structure to phosphate fertilizers and phosphoric acid dominated structure from 2000 to 2019, with centralized production reducing P resource losses during manufacturing. However, there are risks associated with P redistribution, including P resource shortages in certain countries/regions (e.g. Japan) and P pollutant accumulations in others (e.g. Brazil). These results highlight the importance of trade on the global phosphorus cycle and the need for both consuming and supplying countries/regions to work together to propose effective solutions for sustainable management of P in the future.