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Jong-sub Lee - One of the best experts on this subject based on the ideXlab platform.
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effects of frozen water content and Silt Fraction on unconfined compressive behavior of fill materials
Construction and Building Materials, 2021Co-Authors: Sang Yeob Kim, Youngdae Kim, Jong-sub LeeAbstract:Abstract Characteristics of ice constituent and soil particles primarily determine the mechanical properties of fill materials in extreme regions. The objective of this study is to investigate the unconfined compressive behavior of sand-Silt mixed fill materials with various frozen water contents and Silt Fractions (SFs). Sand-Silt mixtures at a relative density of 60% and degrees of saturation of 15% to 25% are prepared at SFs of 0% to 70% in weight. The volumetric water contents are measured at ±5 °C in a freezing mold, and uniaxial compression tests are conducted after freezing. Test results show that the volumetric frozen water content is proportional to the void ratio because these values decrease equivalently when SF 30%. The unconfined compressive strength (UCS) and stress at maximum curvature point (MCP), except those of clean sand (SF = 0%), increase with the volumetric frozen water content and void ratio owing to ice-bonding and SF effects. The strength ratio (UCS/MCP) and visualized fracture mode present brittle-to-ductile transitional characteristics according to the SF. This study demonstrates that frozen water content, SF, and fracture mode should be considered when sand-Silt mixed materials are used for filling in extreme regions.
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Silt Fraction effects of frozen soils on frozen water content strength and stiffness
Construction and Building Materials, 2018Co-Authors: Sang Yeob Kim, Won Taek Hong, Jong-sub LeeAbstract:Abstract The strength and stiffness of soil mixtures vary with regard to the particle composition and the properties of soil mixtures that critically change when water, which is a component in soils, is frozen. The objective of this study is to evaluate Silt Fraction effects of frozen sand-Silt mixtures on the frozen water content, shear strength, and stiffness. The sand-Silt mixtures are prepared in a shear box at a fixed relative density of 60% and a fixed degree of saturation of 15% with various Silt Fractions ranging from 0 to 100% in weight (WSilt/Wsand × 100%). A time domain reflectometry (TDR) probe, bender elements, and thermocouple are installed in the shear box, and the direct shear apparatus is placed in the freezing chamber. After the sand-Silt mixtures are frozen at −5 °C, the direct shear tests are conducted. The TDR signals and shear waves are monitored before and after the freezing phases for the estimation of the volumetric water content and stiffness, respectively. Test results show that the void ratio, volumetric frozen water content, shear strength, and shear wave velocity are at a minimum near a Silt Fraction of 30%. As the relationships between the volumetric frozen water content and peak shear strength, as well as between the volumetric frozen water content and shear wave velocity after freezing, are linear, the peak shear strength correlates well with the shear wave velocity after freezing. Furthermore, as the residual shear strength and shear wave velocity before freezing are related to the Silt Fraction, the residual shear strength is bi-linearly proportional to the shear wave velocity before freezing. This study suggests that the void ratio and frozen water content of sand-Silt mixtures are affected by the Silt Fraction. Thus, the Silt Fraction effects should be considered for the characterization of the strength and stiffness of frozen soils.
Sang Yeob Kim - One of the best experts on this subject based on the ideXlab platform.
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effects of frozen water content and Silt Fraction on unconfined compressive behavior of fill materials
Construction and Building Materials, 2021Co-Authors: Sang Yeob Kim, Youngdae Kim, Jong-sub LeeAbstract:Abstract Characteristics of ice constituent and soil particles primarily determine the mechanical properties of fill materials in extreme regions. The objective of this study is to investigate the unconfined compressive behavior of sand-Silt mixed fill materials with various frozen water contents and Silt Fractions (SFs). Sand-Silt mixtures at a relative density of 60% and degrees of saturation of 15% to 25% are prepared at SFs of 0% to 70% in weight. The volumetric water contents are measured at ±5 °C in a freezing mold, and uniaxial compression tests are conducted after freezing. Test results show that the volumetric frozen water content is proportional to the void ratio because these values decrease equivalently when SF 30%. The unconfined compressive strength (UCS) and stress at maximum curvature point (MCP), except those of clean sand (SF = 0%), increase with the volumetric frozen water content and void ratio owing to ice-bonding and SF effects. The strength ratio (UCS/MCP) and visualized fracture mode present brittle-to-ductile transitional characteristics according to the SF. This study demonstrates that frozen water content, SF, and fracture mode should be considered when sand-Silt mixed materials are used for filling in extreme regions.
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Silt Fraction effects of frozen soils on frozen water content strength and stiffness
Construction and Building Materials, 2018Co-Authors: Sang Yeob Kim, Won Taek Hong, Jong-sub LeeAbstract:Abstract The strength and stiffness of soil mixtures vary with regard to the particle composition and the properties of soil mixtures that critically change when water, which is a component in soils, is frozen. The objective of this study is to evaluate Silt Fraction effects of frozen sand-Silt mixtures on the frozen water content, shear strength, and stiffness. The sand-Silt mixtures are prepared in a shear box at a fixed relative density of 60% and a fixed degree of saturation of 15% with various Silt Fractions ranging from 0 to 100% in weight (WSilt/Wsand × 100%). A time domain reflectometry (TDR) probe, bender elements, and thermocouple are installed in the shear box, and the direct shear apparatus is placed in the freezing chamber. After the sand-Silt mixtures are frozen at −5 °C, the direct shear tests are conducted. The TDR signals and shear waves are monitored before and after the freezing phases for the estimation of the volumetric water content and stiffness, respectively. Test results show that the void ratio, volumetric frozen water content, shear strength, and shear wave velocity are at a minimum near a Silt Fraction of 30%. As the relationships between the volumetric frozen water content and peak shear strength, as well as between the volumetric frozen water content and shear wave velocity after freezing, are linear, the peak shear strength correlates well with the shear wave velocity after freezing. Furthermore, as the residual shear strength and shear wave velocity before freezing are related to the Silt Fraction, the residual shear strength is bi-linearly proportional to the shear wave velocity before freezing. This study suggests that the void ratio and frozen water content of sand-Silt mixtures are affected by the Silt Fraction. Thus, the Silt Fraction effects should be considered for the characterization of the strength and stiffness of frozen soils.
Jef Vandenberghe - One of the best experts on this subject based on the ideXlab platform.
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linking coarse Silt production in asian sand deserts and quaternary accretion of the chinese loess plateau
Geology, 2014Co-Authors: Rivka Amit, Yehouda Enzel, Amit Mushkin, Alan R Gillespie, Jigjidsurengiin Batbaatar, Onn Crouvi, Jef VandenbergheAbstract:The Chinese Loess Plateau (CLP) is a large, spatially well defined and persistent zone of loess accumulation developed near the fluctuating northwest margin of the East Asian monsoon. Many studies have analyzed its loess sediments to provide insights into paleoclimatic conditions. Although spatial and temporal variations in the grain sizes of CLP sediments are fundamental to this effort, controversy over the origin of the dominant coarse quartz Silt has limited interpretations. Reexamination of the spatial pattern of grain-size distribution across the CLP and a field-scale experiment conducted in the Gobi Desert revealed a genetic association between the coarse Silt Fraction of the loess and primary production of coarse Silt through eolian abrasion of sand in the proximal Mu-Us, Tengger, and Badain Jaran sandy deserts. Our results demonstrate the effectiveness of eolian abrasion of quartz sand in primary coarse Silt production in Central Asia and identify this process as the most consistent with the well-recognized systematic northwest-southeast depositional pattern of the CLP. We suggest that only abraded coarse quartz grains transported short distances by long-term persistent eolian activity can build up thick loess sequences to form a massive and spatially well defined loess plateau. These results decouple the production and transport of coarse Silt and finer Silt and clay particles, which have a more distant and wider provenance, changing the constraints on previous paleoclimatic reconstructions.
Emilia Bocanegra - One of the best experts on this subject based on the ideXlab platform.
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hydrogeochemistry and cation exchange processes in the coastal aquifer of mar del plata argentina
Hydrogeology Journal, 2002Co-Authors: Daniel Emilio Martinez, Emilia BocanegraAbstract:The aquifer of Mar del Plata is unconfined and composed of Silt and fine sand. The sand Fraction is mainly quartz, potassium feldspars, chalcedony, and gypsum. Volcanic-glass shards (40–60%) dominate the Silt Fraction, and the clays are of the smectite and illite groups. Calcium carbonate, in caliche form, constitutes about 10–20% of the sediment.
Cristiano Mazur Chiessi - One of the best experts on this subject based on the ideXlab platform.
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a submarine canyon as a climate archive interaction of the antarctic intermediate water with the mar del plata canyon southwest atlantic
Marine Geology, 2013Co-Authors: Ines Voigt, Alberto R. Piola, Ruediger Henrich, Benedict Preu, Till J J Hanebuth, Tilmann Schwenk, Cristiano Mazur ChiessiAbstract:Abstract The Mar del Plata Canyon is located at the continental margin off northern Argentina in a key intermediate and deep-water oceanographic setting. In this region, strong contour currents shape the continental margin by eroding, transporting and depositing sediments. These currents generate various depositional and erosive features which together are described as a Contourite Depositional System (CDS). The Mar del Plata Canyon intersects the CDS, and does not have any obvious connection to the shelf or to an onshore sediment source. Here we present the sedimentary processes that act in the canyon and show that continuous Holocene sedimentation is related to intermediate-water current activity. The Holocene deposits in the canyon are strongly bioturbated and consist mainly of the terrigenous “sortable Silt” Fraction (10–63 μm) without primary structures, similarly to drift deposits. We propose that the Mar del Plata Canyon interacts with an intermediate-depth nepheloid layer generated by the northward-flowing Antarctic Intermediate Water (AAIW). This interaction results in rapid and continuous deposition of coarse Silt sediments inside the canyon with an average sedimentation rate of 160 cm/kyr during the Holocene. We conclude that the presence of the Mar del Plata Canyon decreases the transport capacity of AAIW, in particular of its deepest portion that is associated with the nepheloid layer, which in turn generates a change in the contourite deposition pattern around the canyon. Since sedimentation processes in the Mar del Plata Canyon indicate a response to changes of AAIW contour-current strength related to Late Glacial/Holocene variability, the sediments deposited within the canyon are a great climate archive for paleoceanographic reconstructions. Moreover, an additional involvement of (hemi) pelagic sediments indicates episodic productivity events in response to changes in upper ocean circulation possibly associated with Holocene changes in intensity of El Nino/Southern Oscillation.