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Cohesive sediments
Published in Arved J. Raudkivi, Loose Boundary Hydraulics, 2020
The cohesion C in Table 10.2 is a value calculated form a test analogous to Brinell test, by pressing a spherical ball of diameter Ds under load P into the saturated clay sample. The cohesion is calculated from C=0.18MPπDsSwhere S is depth of depression in clay and M is a coefficient accounting for internal friction ϕ. The M- values according to Mirtskhoulava are The grain size in non-cohesive soils has a dominant influence on erosion since the weight is proportional to diameter cubed. In cohesive soils, in contrast, the grain size (if it can be defined at all) and its weight are quite insignificant in comparison to the electrochemical forces. Studies relating to aerosols indicate that the critical shear stress for incipient motion is proportional to d−1 to d−4/3 power. Figure 10.10 by Croad (1981) shows these tendencies, which are also in keeping with the plot by Sundborg (1956), Figure 10.11.
Ocean Disposal
Published in Stephen M. Testa, Geological Aspects of Hazardous Waste Management, 2020
Abyssal plains are characterized as large, nearly flat areas of the deep ocean floor adjacent to the outer margins of the continental rise. Sedimentary deposits are comprised of varying amounts of pelagic clays, hemipelagic muds, calcareous oozes, and turbidite deposits, depending upon proximity to the continental margin sediment sources (Table 13-5). Stratification is quite variable. Pelagic zones of relatively low permeability occur interstratified with turbidite layers which generally grade from coarse at the base to relatively fine at the top of the sequence. Thus, permeability varies with grain size. Depositional patterns are also complex. Deep-seated faults or other structural elements also exist, reflecting tectonic related activities or differential consolidation.
Weathering and Soils
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
The sizes of mineral grains in a soil define its texture. Grain size depends primarily on grain mineralogy and on the origin and history of soil parent material. Grain size is important because it affects many soil properties, including compressibility, strength, porosity and permeability, and water content.
The correlation between structure, multifunctional properties and applications of PVD MAX phase coatings. Part II. Texture and high-temperature properties
Published in Surface Engineering, 2020
Franco et al. [221] have found that the erosion rate of bulk polycrystalline alumina is strongly dependent on impact angle, being three to four times greater for impacts at 90° than for 45°impacts. The established erosion damage appears to be due to a brittle mechanism via an interaction of the cracks from adjacent impacts. Furthermore, the erosion rate varied strongly with grain size; the coarse grained material had erosion rates about six times greater than those of the finest grained material. The variation of erosion rates with impact angle for all grain sizes showed a power law dependence on velocity of normal impact, with an exponent of ∼3.9 [221].
Effect of feedstock bimodal powder mixture and infiltration process on mechanical behaviour of binder jetting processed 316L stainless steel
Published in Powder Metallurgy, 2023
Xuhao Liang, Xiaoyan Meng, Peishen Ni, Zhe Zhao, Xin Deng, Guanqiao Chen, Yongxuan Chen, Shidi Li, Shanghua Wu, Jinyang Liu, Zhi Qu, Feng Jin
The EBSD maps and Austenite grain size distribution of solid-phase sintered and infiltrated 9:1 powder mixture and solid-phase sintered pure coarse powder are shown in Figure 11. The average grain size of the solid-phase sintered pure coarse powder is 19.967 μm, while that of the solid-phase sintered 9:1 powder mixture is 26.838 μm. The significant porosity of solid-phase sintered pure coarse powder is the main reason for its smaller grain size. The existence of pore can effectively reduce the movement of grain boundary, resulting in the finer grain size. Figure 11 also shows that after infiltration, the average grain size of the 9:1 powder mixture is 19.996 μm, which is 25% less than that of solid-phase sintered 9:1 powder mixture. The penetration of Cu-Sn10 liquid phase in-between 316L stainless steel particles can form the effective obstacle for Austenite grain growth similar to the effect of porosity. Figure 11 evinces that during solid-phase sintering, the bimodal powder mixture promotes the grain growth of 316L stainless steel matrix more significantly than the unimodal powder system does. Usually the decrease of grain boundary area is the main factor contributing to the grain growth of polycrystalline materials. For powder materials, the grain size and grain boundary area is closely related to the initial particle size. Smaller particles usually have smaller grain size and hence larger grain boundary area. For bimodal powder system, the larger grains in larger particles prefer to grow even larger by consuming smaller grains in small particles to effectively reduce the overall grain boundary area. Compared with the unimodal powder system, the bimodal powder system prefer to have more significant grain growth, especially during solid-phase sintering.
Prediction of fluvial erosion rate in Jamuna River, Bangladesh
Published in International Journal of River Basin Management, 2022
Md. Shahidul Islam, Md. Abdul Matin
In May 2018, fieldwork was carried out to investigate the composition and characteristics of riverbank soil (FRERMIP, 2018). Geotechnical laboratory tests were performed to classify soil and determine its engineering properties. Grain size distribution was determined through sieving, hydrometer test, or both. By sieving through 4, 8, 16, 30, 50,1 00, and 200 no. sieves, the proportion of the weight of the different particle sizes above 74 µm was calculated. The hydrometer test was done when there were a significant number of particles smaller than 74 µm. This test was performed per ASTM D422.