scholarly journals Study on Particle-Size Process on Internal Erosion of Grap-Graded Soil--Rock Mixtures of Different Fine Contents

2021 ◽  
Author(s):  
Zhilin Cao ◽  
Weichen Sun ◽  
qiang xie ◽  
Zhihui Wu ◽  
Xiang Fu ◽  
...  
Keyword(s):  
Fine Particle ◽  
Fine Particles ◽  
Numerical Test ◽  
Coupling Model ◽  
Particle Migration ◽  
Test Method ◽  
Internal Erosion ◽  
Coarse Particles ◽  
Permeability Evolution ◽  
Fine Content

Soil–rock mixtures are widely encountered in geotechnical engineering projects. The instability and failure mechanism of grap-graded soil–rock mixtures under rainfall conditions has always been the focus of geological disaster research. To deeply explore the mechanism of seepage deformation of soil–rock mixtures, an indoor physical permeability test that considers soil–rock mixtures with different fine contents was conducted, and a particle-scale numerical simulation test of the permeability evolution was carried out using the coupling model of PFC3D and ABAQUS. The test results showed that the spatial distribution of fine particle loss along the height direction could be divided into three areas: top loss, middle uniform, and bottom loss area. The “island” effect of coarse particles, which is caused by excessive fine content and makes the fine particles bear more load, was eliminated with the loss of fine particles. In this preset working condition of coarse and fine particle diameters, setting FC to 35% may be the best way to fill the voids between the coarse particles. Particle migration leads to a change in the load-bearing skeleton structure, thereby causing seepage deformation. Therefore, the particle-scale numerical test method can better reproduce the seepage deformation process of grap-graded soil–rock mixtures.

scholarly journals Evidence for Asian dust effects from aerosol plume measurements during INTEX-B 2006 near Whistler, BC

2009 ◽  
Vol 9 (11) ◽  
pp. 3523-3546 ◽  
Author(s):  
W. R. Leaitch ◽  
A. M. Macdonald ◽  
K. G. Anlauf ◽  
P. S. K. Liu ◽  
D. Toom-Sauntry ◽  
...  
Keyword(s):  
Organic Material ◽  
Fine Particle ◽  
Radiative Forcing ◽  
Fine Particles ◽  
Anthropogenic Sources ◽  
Dust Particles ◽  
Coarse Particles ◽  
Organic Mass ◽  
Ion Chemistry ◽  
Scanning Transmission

Abstract. Several cases of aerosol plumes resulting from trans-Pacific transport were observed between 2 km and 5.3 km at Whistler, BC from 22 April 2006 to 15 May 2006. The fine particle (<1 μm) chemical composition of most of the plumes was dominated by sulphate that ranged from 1–5 μg m−3 as measured with a Quadrapole Aerosol Mass Spectrometer (Q-AMS). Coarse particles (>1 μm) were enhanced in all sulphate plumes. Fine particle organic mass concentrations were relatively low in most plumes and were nominally anti-correlated with the increases in the number concentrations of coarse particles. The ion chemistry of coarse particles sampled at Whistler Peak was dominated by calcium, sodium, nitrate, sulphate and formate. Scanning transmission X-ray microscopy of coarse particles sampled from the NCAR C-130 aircraft relatively close to Whistler indicated carbonate, potassium and organic functional groups, in particular the carboxyl group. Asian plumes reaching Whistler, BC during the INTEX-B study were not only significantly reduced of fine particle organic material, but organic compounds were attached to coarse particles in significant quantities. Suspension of dust with deposited organic material and scavenging of organic materials by dust near anthropogenic sources are suggested, and if any secondary organic aerosol (SOA) was formed during transport from Asian source regions across the Pacific it was principally associated with the coarse particles. An average of profiles indicates that trans-Pacific transport between 2 and 5 km during this period increased ozone by about 10 ppbv and fine particle sulphate by 0.2–0.5 μg m−3. The mean sizes of the fine particles in the sulphate plumes were larger when dust particles were present and smaller when the fine particle organic mass concentration was larger and dust was absent. The coarse particles of dust act to accumulate sulphate, nitrate and organic material in larger particles, diminishing the role of these compounds in indirect radiative forcing, but potentially enhancing their roles in direct radiative forcing.

scholarly journals Evidence for Asian dust effects from aerosol plume measurements during INTEX-B 2006 near Whistler, BC

2008 ◽  
Vol 8 (5) ◽  
pp. 18531-18589 ◽  
Author(s):  
W. R. Leaitch ◽  
A. M. Macdonald ◽  
K. G. Anlauf ◽  
P. S. K. Liu ◽  
D. Toom-Sauntry ◽  
...  
Keyword(s):  
Organic Material ◽  
Fine Particle ◽  
Radiative Forcing ◽  
Fine Particles ◽  
Organic Aerosol ◽  
Dust Particles ◽  
Coarse Particles ◽  
Organic Mass ◽  
Source Regions ◽  
Scanning Transmission

Abstract. Several cases of aerosol plumes resulting from trans-Pacific transport were observed between 2 km and 5.3 km at Whistler, BC from 22 April 2006 to 15 May 2006. The fine particle (<1 μm) chemical composition of most of the plumes was dominated by sulphate that ranged from 1–5 μg m−3 as measured with a Quadrapole Aerosol Mass Spectrometer (Q-AMS). Coarse particles (>1 μm) were enhanced in all sulphate plumes. Fine particle organic mass concentrations were relatively low in most plumes and anti-correlated with the increases in the coarse particles. The chemistry of coarse particles sampled at Whistler Peak was dominated by calcium, sodium, nitrate, sulphate and formate. Scanning transmission X-ray microscopy of coarse particles sampled from the NCAR C-130 aircraft relatively close to Whistler indicated carbonate, potassium and organic functional groups, in particular the carboxyl group. Asian plumes reaching Whistler, BC during the INTEX-B study were not only significantly reduced of fine particle organic material, but organic compounds were attached to coarse particles in significant quantities. Scavenging of organic aerosol precursors by dust near source regions is suggested, and any formation of secondary organic aerosol (SOA) during transport from Asian source regions across the Pacific was principally associated with the coarse particles. An average of profiles indicates that trans-Pacific transport between 2 and 5 km during this period increased ozone by about 10 ppbv and fine particle sulphate by 0.2–0.5 μg m−3. The mean sizes of the fine particles in the sulphate plumes were larger when dust particles were present and smaller when the fine particle organic mass concentration was larger and dust was absent. The coarse particles of dust act to accumulate sulphate, nitrate and organic material in larger particles, diminishing the role of these compounds in indirect radiative forcing, but potentially enhancing their roles in direct radiative forcing.

Impact Evaluation to Human Body Skin of Titania Photocatalyst Fine Particles

2006 ◽  
Vol 510-511 ◽  
pp. 38-41
Author(s):  
Eiji Watanabe ◽  
Mitsuharu Fukaya ◽  
Hiroshi Taoda
Keyword(s):  
Carbon Dioxide ◽  
Human Body ◽  
Impact Evaluation ◽  
Fine Particle ◽  
Fine Particles ◽  
Test Method ◽  
Artificial Skin ◽  
Evaluation Test ◽  
The Difference ◽  
Titania Photocatalyst

The establishment of evaluation test method of the titania photocatalyst fine particle impact to human body skin was attempted. In this method, the amount of emergence of carbon dioxide, which was expected one of the generation products from the artificial skin according to the titania photocatalyst fine particles activity, was identified and measured by the gas analyzer. It was found that the amount of the carbon dioxide evolution from the artificial skin was different according to the difference of the particle size of the titania photocatalyst fine particle.

Microstructure Control Using Precipitate Phases for the Development of Heat Resistant Fe3Al-based Alloys

2006 ◽  
Vol 980 ◽  
Author(s):  
Satoru Kobayashi ◽  
Stefan Zaefferer
Keyword(s):  
Grain Size ◽  
Carbide Phase ◽  
Fine Particle ◽  
Fine Particles ◽  
Composition Range ◽  
Particle Density ◽  
Coarse Particles ◽  
Thermomechanical Process ◽  
Fine Grained ◽  
Special Composition

AbstractA thermomechanical process (TMP) was performed to create a fine grained and recovered structure with densely formed fine particles in Fe3Al-Cr-Mo-C alloys. The TMP consists of two parts; the first part is to obtain fine recrystallised grains using coarse particles and the second to produce deformed/recovered structure using fine particles. It was found that k-Fe3AlC (E21) carbide phase tends to precipitate coarsely, which is effective to refine grain size in the first process. In a special composition range, the k carbide phase is thermo- dynamically stable in the Fe3Al matrix only at higher temperatures and fine M(Mo,Cr,Fe)2C (B81) carbide phase precipitates at lower temperatures. This fine M2C particles stabilize recovered structure by inhibiting the migration of subboundaries in the second process. This result suggests that if the fine particle density remains high, recovered structure can be maintained at 700°C.

scholarly journals Effect of Clay on Internal Erosion of Clay-Sand-Gravel Mixture

2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Chen Liang ◽  
Cai Guo-dong ◽  
Gu Jia-hui ◽  
Tan Ye-fei ◽  
Chen Cheng ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Fine Particle ◽  
Fine Particles ◽  
Fine Sand ◽  
Hydraulic Gradient ◽  
Internal Erosion ◽  
Engineering Project ◽  
Critical Flow Velocity ◽  
Critical Hydraulic Gradient ◽  
Mixture Samples

In this study, a one-dimensional seepage test apparatus was used to investigate the effect of clay on the critical hydraulic gradient, hydraulic conductivity, migration of fine particles in soil, and percentage of fine particle loss during the internal erosion of clay-sand-gravel mixture, compared with clean gravel. The critical hydraulic gradient and fine sand loss percentage of the clay-sand-gravel mixture decreased, and critical flow velocity and the hydraulic conductivity increased. Six clay-sand-gravel mixture samples with different clay contents were used to evaluate the effect of different clay contents on internal erosion. As the percentage of clay mass to fine particle mass increases from 0% to 25%, the critical hydraulic gradient of soil samples decreases by nearly half and the fine sand loss percentage decreases from 13.73% to 3.48%. Overall, clay has a significant effect on the development of internal erosion of clay-sand-gravel mixture. And attention should be paid in engineering project; clay-sand-gravel mixture with a small amount of clay is more likely to be damaged than clean gravel.

Effects of Well Cement Additive Particle Size and Density Towards Overall Blend Characterization

2021 ◽  
Author(s):  
Shameed Ashraf ◽  
Rahmad Haidzar Muhamad Husin ◽  
Fakhuma Ubaidillah Mohd Hafiz
Keyword(s):  
Particle Size ◽  
Fine Particle ◽  
Fine Particles ◽  
Glass Beads ◽  
High Density ◽  
Energy Requirements ◽  
Coarse Particles ◽  
Simple Formulation ◽  
Fine Material ◽  
Compaction Ratio

Abstract Well cementing has evolved tremendously since its first application in the early 1900s. In the past, cement was mixed with water at the optimal ratio and combined with silica, bentonite, and additives according to the conditions of use. This simple formulation cannot serve the full breadth of oilfield applications. As a result, cement blend composition has evolved with advanced materials such as lightweight glass beads, cenospheres, polymeric beads, hematite, silica, manganese tetroxide, and many more. The wide variety of material used combined with poor understanding of the modern blend has resulted in operational issues, causing failures in blend delivery and execution. There have been cases of unfavorable blend leading to operation failure after it got stuck within the silo, unable to be pneumatically transferred. Some blend has high segregation potential, causing components to separate out, leading to problems in terms of mixing and having stable density during execution. The focus of this study is to establish a comprehensive understanding of modern cement blend additives for seamless operational execution. Several commonly used materials have been selected to form a case study of powder additive behavior. These materials are grouped into three categories: light, medium, and heavy density, with specific gravity between 0.1 and 1.9, 2.0 and 3.9, and 4.0 and 6.0 g/cm3, respectively. Each group is further divided into subcategories based on the particle sizes of fine, medium, and coarse. These materials are then characterized in terms of flowability factor, aeration energy, and compaction ratio, which consists of the Carr index and Hausner ratio. These are typical physical flow characteristics of the bulk solids. Results show that particle size and density significantly influence the flowability factor, aeration energy, and compaction ratio of a powder blend. In general, materials with fine particle size tend to have higher resistance to flow when evaluated through the flowability factor. Both medium- and coarse-particle additives tend to have higher flowability factor than fine-particle blends, that results in easier blend movement. Aeration energy requirements are much higher for high-density and coarse particles compared to medium and fine particles. The compaction ratio evaluation shows that coarse materials have lower tendency to compact compared to the fine and medium materials. Based on the established understanding of individual components, mixtures are then formed with the intention of improving the overall blend character. The poor characteristics of a high-density fine material are significantly improved by combining the fine material with a lightweight cenosphere. The high aeration energy requirements of heavy coarse particles can be halved by adding lightweight glass beads. For improved behavior, a different particle size of silica materials can be mixed at optimized ratio. Combining materials to obtain optimal particle-size distribution and density is crucial to ensuring an overall blend with favorable characteristics. The behavior of individual components based on particle size and density has paved the way for effective optimization of blends for seamless operational deliverables

Computational Fluid Dynamics (CFD) Modeling of Fine Particle Spouting

2006 ◽  
Vol 4 (1) ◽  
Author(s):  
Wei Du ◽  
Weisheng Wei ◽  
Jian Xu ◽  
Yu Fan ◽  
Xiaojun Bao
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fine Particle ◽  
Cfd Simulation ◽  
Fine Particles ◽  
Coarse Particle ◽  
Frictional Stress ◽  
Coarse Particles ◽  
Spouted Bed ◽  
Computational Fluid Dynamics Cfd

To further the understanding of fine particle spouting phenomenon that has not been fully experimentally investigated until now, this article discusses some fundamental aspects of the computational fluid dynamics (CFD) simulation of fine particle spouting. Using the two-fluid method (TFM) embedded in the commercial CFD simulation package Fluent (Version 6.1), the spouting hydrodynamics of fine particles in a cylindrical-conical spouted bed is simulated and compared with the experimental data of Chen [“Spouting of fine particles at elevated pressure”, (M. A. Thesis), Beijing, University of Petroleum, (1999)]. The results show that for the CFD simulation of fine particle spouting, the Gidaspow [“Multiphase flow and fluidization”, Academic Press, San Diego, (1994)] model gives the best predictions of the flow pattern and the minimum spouting velocity; the influence of frictional stress is much more significant than for the CFD simulation of coarse particle spouting; the influences of the coefficient of restitution of particles on the fine particle spouting cannot be neglected, identical with the case of coarse particle spouting. Then, some typical hydrodynamic properties of fine particle spouting are simulated using the related models with suitable parameters. The results reveal that the flow regime transition of fine particle spouting is very similar to that of coarse particle spouting, but fine particle spouting is less stable and is limited to a more restricted region; the McNab [“Prediction of spout diameter”, Brit. Chem. Eng. Proc. Tech., 17, 532-541, (1972)] spout diameter correlation derived from experiments of coarse particle spouting is also suitable for fine particle spouting; the denser zone surrounding the spout axis in the spouted bed of fine particles is more obvious than that in the spouted bed of coarse particles; the particles in the spouted bed of fine particles are much quickly accelerated to their maximum velocities than those in a spouted bed of coarse particles. These differences are mainly caused by the aggregating tendency of fine particles.

scholarly journals Post-erosion mechanical response of internally unstable soil of varying size and flow regime

2020 ◽  
Author(s):  
Amirhassan Mehdizadeh ◽  
Mahdi M Disfani ◽  
Thomas Shire
Keyword(s):  
Steady State ◽  
Mechanical Response ◽  
Fine Particles ◽  
Friction Angle ◽  
Sample Volume ◽  
Internal Erosion ◽  
Cohesionless Soil ◽  
Dam Failure ◽  
Fine Content ◽  
The Impact

One of the leading causes of dam failure is internal erosion. The impact of erosion of non-plastic fine particles, known as suffusion, on the soil structure and strength has been studied experimentally. However, influences including sample size have not been thoroughly investigated. Internally unstable gap-graded cohesionless soil samples with various sizes were investigated using an erosion-triaxial apparatus. Samples were subjected to downward inflows of different seepage velocities. The results indicated that the potential for clogging increased with an increase in specimen length, leading to less fine particle erosion. Internal erosion changed the mechanical soil behaviour even after the loss of fines equal to five percent of the overall sample volume. Eroded specimens with similar intergranular void ratios showed similar undrained post-erosion behaviour. However, the magnitude of the post-erosion initial undrained peak shear strength is a function of coarse particle interlocking, residual fine content and equivalent intergranular contact index. It was also found that the steady state line remained unchanged after erosion of fine particles and the mobilized friction angle at the steady state line is independent of the residual fine content.

Microstructure Control Using Recrystallisation in Particle-Containing Fe3Al Alloys

2007 ◽  
Vol 558-559 ◽  
pp. 235-240 ◽  
Author(s):  
Satoru Kobayashi ◽  
Stefan Zaefferer
Keyword(s):  
Grain Size ◽  
Fine Particle ◽  
Fine Particles ◽  
Particle Density ◽  
Al Alloys ◽  
Coarse Particles ◽  
Thermomechanical Process ◽  
Fine Grained ◽  
Type Carbide ◽  
Carbide Particles

A fine grained and recovered structure with densely formed fine particles has been created by means of a thermomechanical process (TMP) in Fe3Al (bcc derivative structure)-based alloys. The TMP consists of the following two parts; the first part is grain refinement and the second the creation of recovered structure stabilized by fine particles. It was found in the first part that coarse particles are required in the process of deformation to refine grain size by particle stimulated nucleation (PSN) mechanism. Fine M2C type carbide particles were densely precipitated in the second part. These particles were observed to inhibit the growth of subgrains formed around coarse particles during annealing at 700°C. This result suggests that if the fine particle density remains high, the recovered structure can be maintained at 700°C.

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