scholarly journals Experimental Investigation of Wave Velocity-Permeability Model for Granite Subjected to Different Temperature Processing

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Guanghui Jiang ◽  
Jianping Zuo ◽  
Teng Ma ◽  
Xu Wei
Keyword(s):  
Particle Size ◽  
High Temperature ◽  
Wave Velocity ◽  
Pore Fluid ◽  
Rock Matrix ◽  
Permeability Model ◽  
Wave Velocities ◽  
Before And After ◽  
Different Temperatures ◽  
Increasing Temperature

Understanding the change of permeability of rocks before and after heating is of great significance for exploitation of hydrocarbon resources and disposal of nuclear waste. The rock permeability under high temperature cannot be measured with most of the existing methods. In this paper, quality, wave velocity, and permeability of granite specimen from Maluanshan tunnel are measured after high temperature processing. Quality and wave velocity of granite decrease and permeability of granite increases with increasing temperature. Using porosity as the medium, a new wave velocity-permeability model is established with modified wave velocity-porosity formula and Kozeny-Carman formula. Under some given wave velocities and corresponding permeabilities through experiment, the permeabilities at different temperatures and wave velocities can be obtained. By comparing the experimental and the theoretical results, the proposed formulas are verified. In addition, a sensitivity analysis is performed to examine the effect of particle size, wave velocities in rock matrix, and pore fluid on permeability: permeability increases with increasing particle size, wave velocities in rock matrix, and pore fluid; the higher the rock wave velocity, the lower the effect of wave velocities in rock matrix and pore fluid on permeability.

scholarly journals Investigation of the kinetics of spontaneous combustion of the major coal seam in Dahuangshan mining area of the Southern Junggar coalfield, Xinjiang, China

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Li Shen ◽  
Qiang Zeng
Keyword(s):  
Particle Size ◽  
High Temperature ◽  
Coal Seam ◽  
Spontaneous Combustion ◽  
Heating Temperature ◽  
Characteristic Temperature ◽  
Mining Area ◽  
Particle Sizes ◽  
Coal Oxidation ◽  
Increasing Temperature

AbstractIn the present paper, with using diverse methods (including the SEM, the XRD, the TPO, the FTIR, and the TGA) , the authors analysed samples of the major coal seam in Dahuangshan Mining area with different particle sizes and with different heated temperatures (from 50 to 800 °C at regular intervals of 50 °C). The results from SEM and XRD showed that high temperature and high number of pores, fissures, and hierarchical structures in the coal samples could facilitate oxidation reactions and spontaneous combustion. A higher degree of graphitization and much greater number of aromatic microcrystalline structures facilitated spontaneous combustion. The results from TPO showed that the oxygen consumption rate of the coal samples increased exponentially with increasing temperature. The generation rates of different gases indicated that temperatures of 90 °C or 130 °C could accelerate coal oxidation. With increasing temperature, the coal oxidation rate increased, and the release of gaseous products was accelerated. The FTIR results showed that the amount of hydroxide radicals and oxygen-containing functional groups increased with the decline in particle size, indicating that a smaller particle size may facilitate the oxidation reaction and spontaneous combustion of coal. The absorbance and the functional group areas at different particle sizes were consistent with those of the heated coal samples, which decreased as the temperature rose. The results from TGA showed that the characteristic temperature T3 declined with decreasing particle size. After the sample with 0.15–0.18 mm particle size was heated, its carbon content decreased, and its mineral content increased, inhibiting coal oxidation. This result also shows that the activation energy of the heated samples tended to increase at the stage of high-temperature combustion with increasing heating temperature.

scholarly journals Compressibility behavior of Boron (Tincal) added to sand-bentonite mixtures under different temperatures

2020 ◽  
Vol 205 ◽  
pp. 09007
Author(s):  
Sukran Gizem Alpaydin ◽  
Yeliz Yukselen-Aksoy
Keyword(s):  
High Temperature ◽  
Volume Deformation ◽  
Landfill Liners ◽  
Low Thermal Expansion ◽  
Boron Minerals ◽  
Different Temperatures ◽  
Increasing Temperature ◽  
Waste Repositories ◽  
Oedometer Tests ◽  
Soil Changes

The importance of thermal behaviour of soils has increased significantly with increasing number of energy structures. There is a need for soils, which show design criteria (strength, permeability, etc.) performance during their life under high temperature or thermal cycles. In the literature studies, it was observed that the volumetric deformation of the soil changes with increasing temperature. Sand-bentonite mixtures generally act as impervious barrier in areas such as nuclear waste repositories, landfill liners etc. These mixtures will be exposed to high temperature; therefore, their engineering performance should not alter under high temperature. Boron is used in the industry for high temperature resistance, flexibility, lightness, power and ease of production. Boron minerals have very low thermal expansion and they are also resistant to thermal shocks. For that reason, the properties of sand-bentonite mixtures can be improved by boron additives at high temperatures. In this study, volume deformation behavior of sand-bentonite mixtures was determined in the presence of tincal. The oedometer tests were performed under room temperature and 80°C.

VELOCITY OF COMPRESSIONAL WAVES IN POROUS MEDIA AT PERMAFROST TEMPERATURES

Geophysics ◽  
1968 ◽  
Vol 33 (4) ◽  
pp. 584-595 ◽  
Author(s):  
A. Timur
Keyword(s):  
Porous Media ◽  
Wave Velocity ◽  
Compressional Wave ◽  
Freezing Process ◽  
Rock Matrix ◽  
Compressional Wave Velocity ◽  
Compressional Waves ◽  
Average Equation ◽  
Wave Velocities ◽  
Time Average

Measurements of velocity of compressional waves in consolidated porous media, conducted within a temperature range of 26 °C to −36 °C, indicate that: (1) compressional wave velocity in water‐saturated rocks increases with decreasing temperature whereas it is nearly independent of temperature in dry rocks; (2) the shapes of the velocity versus temperature curves are functions of lithology, pore structure, and the nature of the interstitial fluids. As a saturated rock sample is cooled below 0 °C, the liquid in pore spaces with smaller surface‐to‐volume ratios (larger pores) begins to freeze and the liquid salinity controls the freezing process. As the temperature is decreased further, a point is reached where the surface‐to‐volume ratio in the remaining pore spaces is large enough to affect the freezing process, which is completed at the cryohydric temperature of the salts‐water system. In the ice‐liquid‐rock matrix system, present during freezing, a three‐phase, time‐average equation may be used to estimate the compressional wave velocities. Below the cryohydric temperature, elastic wave propagation takes place in a solid‐solid system consisting of ice and rock matrix. In this frozen state, the compressional wave velocity remains constant, has its maximum value, and may be estimated through use of the two‐phase time average equation. Limited field data for compressional wave velocities in permafrost indicate that pore spaces in permafrost contain not only liquid and ice, but also gas. Therefore, before attempting to make velocity estimates through the time‐average equations, the natures and percentages of pore saturants should be investigated.

Strain Rate Sensitivity of Ultrafine Grained Aluminium Alloy AA6061

2008 ◽  
Vol 584-586 ◽  
pp. 741-747 ◽  
Author(s):  
Aferdita Vevecka-Priftaj ◽  
Andreas Böhner ◽  
Johannes May ◽  
Heinz Werner Höppel ◽  
Matthias Göken
Keyword(s):  
Strain Rate ◽  
Aluminium Alloy ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Grain Structure ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Before And After ◽  
Different Temperatures ◽  
Increasing Temperature

The strain rate sensitivity of the aluminium alloy AA6061 has been investigated in a conventional grain sized (CG) state and in two different ultrafine grained (UFG) conditions processed by Equal Channel Angular Pressing (ECAP) for 2 and 6 passes at 100o C. Strain rate jump tests in compression were performed at different temperatures and the strain-rate sensitivity exponent m was determined. The tests were accomplished by microstructural investigations before and after compression testing in CG and UFG conditions. It is shown that all UFG microstructures exhibit strongly increased strain-rate sensitivity (SRS) compared to the CG state. The SRS increases with increasing temperature and is more pronounced for the UFG material processed using 6 ECAP passes. The microstructural investigations show a rather high stability of the grain structure for the UFG conditions up to 250o C. The results are discussed with respect to the relevant deformation mechanisms.

scholarly journals A comparative study on properieties of hydroxyapatite prepared from bovine and dromedary bone

2021 ◽  
Author(s):  
amina ghedjemis ◽  
Riad ayech ◽  
Ali BENOUADAH
Keyword(s):  
Particle Size ◽  
Research Work ◽  
Chemical Properties ◽  
Bovine Bone ◽  
Physico Chemical ◽  
Particle Size Analyzer ◽  
Different Temperatures ◽  
Chemical Techniques ◽  
Increasing Temperature ◽  
Additional Phase

Abstract The recovery of agro-food waste is at the heart of the challenges of the 21st century, in this context that this research work comes. A biomaterial is prepared from a significant resource such as dromedary bone and bovine bone by heat treatment at different temperatures and characterized by physico-chemical techniques in order to have the effect of bone type on the physico-chemical properties of hydroxyapatite. The results of FTIR and DRX show the removal of all organic matter and the production of pure hydroxyapatite without any additional phase for both bone types. Analyzes by SEM and laser particle size analyzer show that the particle size of hydroxyapatite is increased with increasing temperature. From the results of XRF, bone type is a direct effect on the concentration of hydroxyapatite compounds in hydroxyapatite prepared from dromedary bone compared to hydroxyapatite prepared from bovine bone.

scholarly journals High-temperature Fe oxidation coupled with redistribution of framework cations in lobanovite, K2Na(Fe2+ 4Mg2Na)Ti2(Si4O12)2O2(OH)4 – the first titanosilicate case

2019 ◽  
Vol 75 (4) ◽  
pp. 578-590 ◽  
Author(s):  
Elena S. Zhitova ◽  
Andrey A. Zolotarev ◽  
Frank C. Hawthorne ◽  
Sergey V. Krivovichev ◽  
Viktor N. Yakovenchuk ◽  
...  
Keyword(s):  
High Temperature ◽  
Elevated Temperatures ◽  
Iron Oxidation ◽  
Ex Situ ◽  
X Ray Diffraction ◽  
X Ray ◽  
Different Temperatures ◽  
Bond Strengths ◽  
Increasing Temperature

The high-temperature (HT) behaviour of lobanovite, K2Na(Fe2+ 4Mg2Na)Ti2(Si4O12)2O2(OH)4, was studied using in situ powder X-ray diffraction in the temperature range 25–1000°C and ex situ single-crystal X-ray diffraction of 17 crystals quenched from different temperatures. HT iron oxidation associated with dehydroxylation starts at 450°C, similar to other ferrous-hydroxy-rich heterophyllosilicates such as astrophyllite and bafertisite. A prominent feature of lobanovite HT crystal chemistry is the redistribution of Fe and Mg+Mn cations over the M(2), M(3), M(4) sites of the octahedral (O) layer that accompanies iron oxidation and dehydroxylation. This HT redistribution of cations has not been observed in titanosilicates until now, and seems to be triggered by the need to maintain bond strengths at the apical oxygen atom of the TiO5 pyramid in the heteropolyhedral (H) layer during oxidation–dehydroxylation. Comparison of the HT behaviour of lobanovite with five-coordinated Ti and astrophyllite with six-coordinated Ti shows that the geometry of the Ti polyhedron plays a key role in the HT behaviour of heterophyllosilicates. The thermal expansion, geometrical changes and redistribution of site occupancies which occur in lobanovite under increasing temperature are reported. A brief discussion is given of minerals in which the cation ordering (usually for Fe and Mg) occurs together with iron oxidation–dehydroxylation at elevated temperatures: micas, amphiboles and tourmalines. Now this list is expanded by the inclusion of titanosilicate minerals.

Effect of Limestone Origin on the CaCO3 Decomposition Process and Subsequent Crystallization Process of CaO

2021 ◽  
Vol 321 ◽  
pp. 45-50
Author(s):  
Dorothea Sklenářová ◽  
Karel Dvořák ◽  
Diana Mária Koporcová
Keyword(s):  
High Temperature ◽  
Crystallization Process ◽  
Total Porosity ◽  
Xrd Analysis ◽  
Decomposition Process ◽  
Firing Process ◽  
Geological Age ◽  
Different Temperatures ◽  
Increasing Temperature ◽  
Multiple Samples

In this study, the process of decomposition of CaCO3 and crystallization of CaO has been analyzed. The aim of this work is to compare behavior and changes in microstructure between different limestone samples (as geological age and origin, total porosity, hardness category). Studied samples were analyzed in high temperature chamber during the firing process by XRD analysis. With the increasing temperature, the growth of crystallites was measured and computed. In multiple samples a different behavior in these properties was observed. Further analysis studied different temperatures of the end of decomposition of CaCO3 and the beginning of formation of CaO in soft-porous and hard-recrystallized limestones.

Effect of Sintering Temperature on Properties of Setiu Clay Sediments

2020 ◽  
Vol 1010 ◽  
pp. 206-210
Author(s):  
Mohd Al Amin Muhamad Nor ◽  
Noor Asliza Ismail Adnen ◽  
Mohamad Zaky Noh ◽  
A.R.M. Warikh ◽  
Julie Juliewatty Mohamed
Keyword(s):  
Sintering Temperature ◽  
Slip Casting ◽  
Casting Process ◽  
Production Costs ◽  
Ceramic Samples ◽  
Before And After ◽  
Different Temperatures ◽  
Clay Sediment ◽  
Quality Of Products ◽  
Increasing Temperature

The effect of sintering temperature on physical properties of Setiu clay sediment was studied. The ceramic samples were prepared via slip casting method, and sintered at different temperatures ranging from 900 to 1100°C, with 2 hours soaking time. Morphologies of ceramic samples were characterized using Tabletop Microscope. Shrinkage was determined from measurement of samples before and after sintering process. A good ceramic sample without warping or cracks obtained after casting process and after sintered at different temperatures. The results show that sintering temperatures greatly influence morphology of samples. As sintering temperature increased the grain boundaries between particles become smoother and compacted while pores shrunk due to the densification behavior. A considerable increased in shrinkage from 5 to 20% were observed with increasing temperature from 900 to 1100°C. As conclusion, Setiu clay sediment are suitable for production ceramic products and 1000°C can be consider the best sintering temperature in terms of quality of products and production costs.

Effects of temperature gradient on the granite’s mechanical properties

2021 ◽  
pp. 1-10
Author(s):  
Jinyong Pei ◽  
Huagang He ◽  
Dongtao Hu ◽  
Shanke Lv ◽  
Jing Wang ◽  
...  
Keyword(s):  
High Temperature ◽  
Temperature Gradient ◽  
Strain Curve ◽  
Peak Stress ◽  
Tangent Modulus ◽  
Peak Strain ◽  
Compression Tests ◽  
Different Temperatures ◽  
Effects Of Temperature ◽  
Increasing Temperature

Temperature gradient significantly affects the production of surrounding rock stress in mining engineering. The mechanics and deformation characteristics of the rock will change under the temperature gradient, thereby increasing the probability of accidents in the roadway. This paper conducts uniaxial compression tests on granite at different temperatures from room temperature to 250∘C, and analyzes in detail the changes in the stress-strain curve, peak stress, peak strain and tangent modulus of granite under high temperature and different temperature gradient conditions. The results of this study are as follows: (1) Under high temperature conditions, the granite’s peak stress and tangent elastic modulus increased with temperature from 17 to 100∘C, then decreased from 100∘C to 250∘C, whereas the granite’s peak strain increased steadily with increasing temperature; (2) under temperature gradient, the granite’s peak stress and tangent modulus first decreased and then increased with increasing temperature gradient, while the granite’s peak strain first decreased and then increased at 100∘C, but first increased and then decreased from 150∘C to 250∘C.

THE ELASTICITY OF THE LARGE ARTERIES IN HYPERTENSION

1952 ◽  
Vol 30 (2) ◽  
pp. 125-129
Author(s):  
J. P. Adamson ◽  
J. Doupe
Keyword(s):  
Blood Pressure ◽  
Pulse Wave Velocity ◽  
Wave Velocity ◽  
Pulse Wave ◽  
Diastolic Pressure ◽  
Arterial Elasticity ◽  
Large Arteries ◽  
Wave Velocities

Intra-arterial pressures and pulse wave velocities were measured in 18 subjects whose auscultatory diastolic pressures ranged from 45 to 120 mm. Hg. Various methods were used to lower the blood pressure in the hypertensive and to raise it in nonhypertensive subjects so that pulse wave velocities might be compared in all subjects at a common diastolic pressure. The pulse wave velocities were calculated for a diastolic pressure of 80 mm. Hg. No significant differences were found between hypertensive and nonhypertensive subjects. It was concluded that a defect of arterial elasticity as gauged by pulse wave velocity is not a factor in the pathogenesis of hypertension.

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