scholarly journals Numerical approach to the top coal caving process under different coal seam thicknesses

2015 ◽  
Vol 19 (4) ◽  
pp. 1423-1428 ◽  
Author(s):  
Bin Yu ◽  
Ru Zhang ◽  
Ming-Zhong Gao ◽  
Guo Li ◽  
Ze-Tian Zhang ◽  
...  
Keyword(s):  
Coal Seam ◽  
Numerical Study ◽  
Numerical Approach ◽  
Extraction Process ◽  
Thin Layers ◽  
Stress Evolution ◽  
Stress Monitoring ◽  
Coal Quality ◽  
Coal Layer ◽  
Internal Fracture

Numerical study of mining-induced stress evolution of coal during the top coal caving process under different coal seam thicknesses is carried out, and the numerical prediction agrees well with the field test data. Main characters on stress distribution and dangerous area are elucidated. For the same coal quality, coal layers under 7 m thick fail earlier than thicker coal layers; correspondingly, the internal fracture networks of thin layers are more easily developed. During the mining of a coal layer less than 7 m thick, stress monitoring of the ?dangerous area? in the middle of the top coal should be emphasized, whereas during the mining of coal layers less than 11 m thick, stress monitoring of the ?dangerous area? at the bottom of the top coal should be highlighted. The research is to optimize caving technique and extraction process.

scholarly journals Modes of Occurrence and Origin of Minerals in Permian Coals from the Huainan Coalfield, Anhui, China

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 399
Author(s):  
Yuan Li ◽  
Wenhui Huang ◽  
Bo Jiu ◽  
Qilong Sun ◽  
Qingsong Che
Keyword(s):  
Coal Seam ◽  
Sedimentary Environment ◽  
Thin Layers ◽  
Hydrothermal Fluids ◽  
Low Rank ◽  
Coal Quality ◽  
Peat Accumulation ◽  
Modes Of Occurrence ◽  
Huainan Coalfield ◽  
Geological Evolution

Minerals in coal provide useful information for not only paleo-environments of peat accumulation, but also for geological evolution during later diagenesis and/or epigenesis. This paper reports new data on coal quality and the mineralogical and geochemical compositions of 17 unaltered (by intrusion) coal samples collected from the Huainan coalfield, providing new insight into the origins and modes of occurrence of the minerals in coal and their geological evolution. The results showed that the studied coal samples were low rank bituminous coal, with low ash yield (11.92–38.31%, average 24.80%) and high volatile content (25.13–43.43%, average 37.29%). Minerals in the coal mainly included kaolinite and quartz; varying proportions of calcite, siderite, ankerite, and pyrite; and traces of chlorite, zircon, strontianite, apatite, and gorceixite. Typical modes of mineral occurrence could be used to determine the formation stage of minerals. The detrital mineral, occurring as sub-angular to rounded discrete fragments or thin layers intimately admixed with organic matter at particular horizons, was of terrigenous origin, deposited during peat accumulation. Cell infillings, as well as nodule siderites and polycrystalline aggregates of pyrite, precipitated during the syngenetic to early diagenetic stages. Cleat infillings, compressed cell infillings, and fracture infillings precipitated in the epigenetic stage. However, the stage of mineral formation of the pore infilling was difficult to determine. Combined with coal quality, mineralogy, and geochemical analysis, the sedimentary environment of Shanxi Formation was affected by seawater, and Fe-rich hydrothermal fluids filled into the No. 3 coal seam in the epigenetic stage. The sedimentary environment of the No. 8 coal seam had widespread reduction and acid conditions due to basin subsidence, and sulfate-rich hydrothermal fluids may have been formed during the peat deposition stage. In contrast, the peat accumulation environment of the Upper Shihezi Formation was oxidized with a low pH condition. Alkaline fluid then flowed into the No. 13-1 coal seam in the epigenetic stage.

PARALLEL SOLVER FOR THE SIMULATIONS OF DETONATION WAVES ON UNSTRUCTURED GRIDS

2020 ◽  
Author(s):  
A. I. Lopato ◽  
◽  
A. G. Eremenko ◽  
Keyword(s):  
Chemical Kinetics ◽  
Numerical Scheme ◽  
Unstructured Grids ◽  
Numerical Study ◽  
Numerical Approach ◽  
Detonation Waves ◽  
Detailed Chemical Kinetics ◽  
Parallel Solver ◽  
Further Development ◽  
Detailed Chemical

Recently, we developed a numerical approach for the simulation of detonation waves on fully unstructured grids and applied it to the numerical study of the mechanisms of detonation initiation in multifocusing systems. Current work is devoted to further development of our numerical approach, namely, parallelization of the numerical scheme and introduction of more comprehensive detailed chemical kinetics scheme.

Prehistoric pigment production on Rapa Nui (Easter Island), c. AD 1200–1650: New insights from Vaipú and Poike based on phytoliths, diatoms and 14C dating

The Holocene ◽  
2020 ◽  
pp. 095968362098167
Author(s):  
Welmoed A Out ◽  
Andreas Mieth ◽  
Sergi Pla-Rabés ◽  
Marco Madella ◽  
Svetlana Khamnueva-Wendt ◽  
...  
Keyword(s):  
Extraction Process ◽  
Thin Layers ◽  
Pigment Production ◽  
Cultural Continuity ◽  
Formation Processes ◽  
Rapa Nui ◽  
14C Dating ◽  
Crucial Information ◽  
Prehistoric Culture ◽  
And Storage

Although Rapa Nui has been proposed as a classic example of cultural collapse, this hypothesis has been repeatedly questioned. This paper investigates cultural continuity on Rapa Nui following the onset of deforestation through a study of red ochre pits. Red ochre pigments are well-known from various contexts on Rapa Nui, but until recently its origin and the extraction process involved in their production were not precisely understood. New excavations have revealed the presence of multiple pits used for pigment production and storage by the island’s prehistoric culture. Previous geoarchaeological studies, including geomorphological, pedological, geochemical and micromorphological analyses, have shown that the pits contain fine layers of reddish iron oxides (ochre), which result from repeated intentional burning. The oxide layers alternate with thin layers of phytoliths, interpreted as the remains of plant material used as fuel, and diatoms. This paper presents new phytolith and diatom data from the previously described site of Vaipú East, complemented with data from similar pits at the new sites of Vaipú West and Poike. New 14C dates are also presented from these sites. The phytolith and diatom data provide crucial information about the chaîne opératoire of the ochre production and the formation processes associated with the pits. The evidence of pigment production and storage at Vaipú East shows that labour-intensive ochre production took place on Rapa Nui during at least two separate phases after deforestation, while the pits discovered at other sites indicate that Vaipú East did not stand alone. This provides a further line of evidence in favour of cultural continuity rather than collapse following deforestation in the island’s late prehistory.

Thermal jet drilling of granite rock: a numerical 3D finite-element study

2021 ◽  
Vol 379 (2196) ◽  
pp. 20200128
Author(s):  
Timo Saksala ◽  
Reijo Kouhia ◽  
Ahmad Mardoukhi ◽  
Mikko Hokka
Keyword(s):  
Finite Elements ◽  
Numerical Study ◽  
Thermal Flux ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Mass Scaling ◽  
Granite Rock ◽  
Fracture Dynamics ◽  
Rock Heterogeneity ◽  
Thermal Drilling

This paper presents a numerical study on thermal jet drilling of granite rock that is based on a thermal spallation phenomenon. For this end, a numerical method based on finite elements and a damage–viscoplasticity model are developed for solving the underlying coupled thermo-mechanical problem. An explicit time-stepping scheme is applied in solving the global problem, which in the present case is amenable to extreme mass scaling. Rock heterogeneity is accounted for as random clusters of finite elements representing rock constituent minerals. The numerical approach is validated based on experiments on thermal shock weakening effect of granite in a dynamic Brazilian disc test. The validated model is applied in three-dimensional simulations of thermal jet drilling with a short duration (0.2 s) and high intensity (approx. 3 MW m −2 ) thermal flux. The present numerical approach predicts the spalling as highly (tensile) damaged rock. Finally, it was shown that thermal drilling exploiting heating-forced cooling cycles is a viable method when drilling in hot rock mass. This article is part of the theme issue ‘Fracture dynamics of solid materials: from particles to the globe’.

scholarly journals Comparison between Two Solid-Liquid Extraction Methods for the Recovery of Steviol Glycosides from Dried Stevia Leaves Applying a Numerical Approach

Processes ◽  
2018 ◽  
Vol 6 (8) ◽  
pp. 105 ◽  
Author(s):  
Monica Gallo ◽  
Andrea Formato ◽  
Gaetano Formato ◽  
Daniele Naviglio
Keyword(s):  
Stevia Rebaudiana ◽  
Value Added ◽  
Numerical Approach ◽  
Extraction Process ◽  
Extraction Methods ◽  
Liquid Extraction ◽  
Steviol Glycosides ◽  
Stevia Rebaudiana Bertoni ◽  
Solid Liquid Extraction ◽  
Solid Liquid

Abstract: Stevia rebaudiana Bertoni is a perennial shrub belonging to the Asteraceae family. The leaves contain a mixture of steviol glycosides with extraordinary sweetening properties, among which the most important are stevioside and rebaudioside A. These components have a high sweetening power, which is about 300 times that of sucrose, and a negligible calorie content. However, their extraction and purification are not easy. In this paper, the extraction technique under cyclic pressure, known as rapid solid-liquid dynamic extraction (RSLDE), was compared using a Naviglio extractor (NE) with conventional maceration. The aim was to identify an efficient and economically viable method for obtaining high amounts of steviol glycosides in a short time. Furthermore, a numerical model was set up for the solid-liquid extraction process of value-added compounds from natural sources. Several parameters must be evaluated in relation to the characteristics of the parts of the plant subjected to extraction. Therefore, since diffusion and osmosis are highly dependent on temperature, it is necessary to control the temperature of the extraction system. On the other hand, the final aim of this work was to provide a scientific and quantitative basis for RSLDE. Therefore, the results obtained from stevia extracts using the corresponding mathematical model allowed hypothesizing the application of this model to the extraction processes of other vegetable matrices.

In-plane response of unreinforced masonry walls confined by reinforced concrete tie-columns and tie-beams

2017 ◽  
Vol 20 (11) ◽  
pp. 1632-1643 ◽  
Author(s):  
Masoud Amouzadeh Tabrizi ◽  
Masoud Soltani
Keyword(s):  
Numerical Study ◽  
Nonlinear Behavior ◽  
Numerical Approach ◽  
Masonry Wall ◽  
Masonry Walls ◽  
Lateral Loads ◽  
Confined Masonry ◽  
Smeared Crack ◽  
Modeling Strategy ◽  
Reversed Cyclic

This article focuses on the experimental and analytical investigations of masonry walls surrounded by tie-elements under in-plane loads. The experimental results of an unconfined and a confined masonry wall, tested under reversed cyclic lateral loads, are presented. For numerical study, a micro-modeling strategy, using smeared-crack-based approach, is adopted. In order to validate the numerical approach, experimental test results and data obtained from the literature are used, and through a systematic parametric study, the influence of adjoining walls and number of tie-columns on the seismic behavior of confined masonry panels is numerically assessed and a simple but rational method for predicting the nonlinear behavior of these structures is proposed.

Cyclic mechanical behavior of thin layers of copper: A theoretical and numerical study

2015 ◽  
Vol 51 (2) ◽  
pp. 161-169 ◽  
Author(s):  
Klaus Fellner ◽  
Thomas Antretter ◽  
Peter F Fuchs ◽  
Tiphaine Pélisset
Keyword(s):  
Mechanical Behavior ◽  
Numerical Study ◽  
Thin Layers

Numerical Investigation of the Identifiability of Elastomer Mechanical Properties by Nano-Indentation and Shape-Manifold Approach

2021 ◽  
Author(s):  
Oumaima Ezzaamari ◽  
Guénhaël Le Quilliec ◽  
Florian Lacroix ◽  
Stéphane Méo
Keyword(s):  
Numerical Study ◽  
Interpolation Method ◽  
Structural Characteristics ◽  
Numerical Approach ◽  
Kriging Interpolation ◽  
Nano Indentation ◽  
Kriging Interpolation Method ◽  
Elastomeric Materials ◽  
Hyper Elastic ◽  
Characterization Test

ABSTRACT Various research is covering instrumented nano-indentation in the literature. However, studies on this characterization test remain limited when it comes to the local mechanical behavior of elastomeric materials. The application of nano-indentation on these materials is a difficult task given their complex mechanical and structural characteristics. We try to overcome these experimental limitations and find an effective numerical approach for local mechanical characterization of hyper-elastic materials. For such needs, we carried out a numerical study based on model reduction and shape manifold approach to investigate the parameters identification of different hyper-elastic constitutive laws by using instrumented indentation. Similarly, we studied the influence of the indenter geometry, the friction coefficient variation, and finally the indented material height effect. To this end, we constructed a reduced order model through a design of experiments by proper orthogonal decomposition combined with the kriging interpolation method.

scholarly journals Evaluation of Electric Field and Space Charge Dynamics in Dielectric under DC Voltage with Superimposed Switching Impulse

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1836 ◽  
Author(s):  
Ik-Soo Kwon ◽  
Sun-Jin Kim ◽  
Mansoor Asif ◽  
Bang-Wook Lee
Keyword(s):  
Electric Field ◽  
Space Charge ◽  
Field Distribution ◽  
Electric Field Distribution ◽  
Numerical Study ◽  
Numerical Approach ◽  
Dc Voltage ◽  
Charge Dynamics ◽  
Electrical Stress ◽  
Dc Stress

The influx of a switching impulse during DC steady-state operations causes severe electrical stress on the insulation of HVDC cables. Thus, the insulation should be designed to withstand a superimposed switching impulse. All major manufacturers of DC cables perform superimposed switching impulse breakdown tests for prequalification. However, an experimental approach to study space charge dynamics in dielectrics under a switching impulse superposed on DC voltage has not been reported yet. This is because, unlike the DC stress, it is not possible to study the charge dynamics experimentally under complex stresses, such as switching impulse superposition. Hence, in order to predict and investigate the breakdown characteristics, it is necessary to obtain accurate electric field distribution considering space charge dynamics using a numerical approach. Therefore, in this paper, a numerical study on the switching impulse superposition was carried out. The space charge dynamics and its distribution within the dielectric under DC stress were compared with those under a superimposed switching impulse using a bipolar charge transport (BCT) model. In addition, we estimated the effect of a superimposed switching impulse on a DC electric field distribution. It was concluded that the temperature conditions of dielectrics have a significant influence on electric field and space charge dynamics.

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